- Email: [email protected]
Plastic surgery
Plastic Surgery William M Kuzon Jr, MD, PhD, FRCS(C), FACS
be via potentiation of the interleukin-4 (IL-4) mediated induction of the collagen I alpha 1 gene.2 Gibson and colleagues showed using a rat wound cylinder model, that vascular endothelial growth factor (VGEF) concentrations can be increased by administering hyperbaric oxygen, although the relative role of VGEF in hyperoxia-induced angiogenesis is still unclear.3 Direct mono-ADP ribosolation was shown to reversibly inhibit VGEF-induced angiogenesis in vivo.4 With this experiment, Feng and associates have demonstrated that posttranscriptional events can play a significant role in the regulation of cytokines during wound healing. The rapid upregulation of both IL-1a1 and the signal-transducing receptor IL1R1 was demonstrated in wounded mouse skin by Doyle and colleagues.5 The IL-1 pathway may be critical to the initiation of the inflammatory response after wounding. IL-10 inhibits the synthesis of many proinflammatory cytokines, and its presence in chronic compared with acute wounds has been postulated to contribute to delayed wound healing. Roth and colleagues provided direct, mechanistic evidence for this hypothesis by demonstrating that the antigen presenting function of B cells, a process critical to wound maturation, is inhibited by IL-10.6 In addition to cytokines, multiple factors contribute to the regulation of the wound healing response. Jang and colleagues observed delayed healing and diminished angiogenesis in excisional wounds in vitronectin knockout mice, reconfirming that matrix molecules play a pivotal role in successful wound healing.7 To further characterize the scarless healing in fetal wounds, Chin and colleagues studied tyrosine phosphorylation patterns in adult and fetal dermal fibroblasts.8 At least five phosphorylated proteins observed in fetal fibroblasts were absent in adult fibroblasts. These proteins may represent tyrosine kinase receptors, suggesting that the intracellular signaling cascade is inherently different in fetal compared with adult cells. Sayah and associates found that apoptosis-related genes were significantly under-expressed in tissue ex-
In the past year, research in plastic and reconstructive surgery has continued to exemplify the diversity, creativity, and innovation that characterize this surgical specialty. Basic research addressed critical questions relating to wound healing, craniofacial and bone biology, peripheral nerve injury and regeneration, ischemia-reperfusion injury and flap physiology, composite tissue transplantation, and a broad array of other topics. Significant activity in the applied areas of tissue engineering, gene therapy, and technology application highlighted the multidisciplinary nature of plastic surgery research. Clinical and outcomes research addressed a broad range of questions in all areas of plastic surgery. This work will ultimately contribute to the plastic surgeon’s goal of restoration of form and function for patients suffering consequences of trauma or disease. Of course, the summary that follows encompasses only a fraction of the overall research activity in plastic surgery today. WOUND HEALING Delayed wound healing has enormous clinical and economic consequences. In the past year, work in this area has focused on determining the critical, but complex, role of cytokines in the regulation of healing in normal, chronic, and fetal wounds, on other mechanisms contributing to delayed wound healing, and on the process of pathologic scarring. Lanning and colleagues studied the differential effects of transforming growth factor b (TGF b) isoforms on excisional wounds in a rabbit model.1 They found that, while TGF b1 preferentially upregulated procollagen type I, TGF b3 upregulated procollagen type III, suggesting that differential TGF isoform expression plays a significant role in regulating the degree of fibrosis in excisional wounds. Bauer and colleagues demonstrated that one mechanism by which TGF-b1 modulates collagen synthesis might Received November 23, 1998; Accepted November 23, 1998. From the Section of Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, MI. Correspondence address: William M Kuzon Jr, MD, PhD, 2130 Taubman Health Care Center, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0340. © 1999 by the American College of Surgeons Published by Elsevier Science Inc.
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cised from human keloids compared with tissue excised from normal, nonpathologic scars.9 This observation may account for the prolonged and excessive production of collagen by keloid fibroblasts, and may allow development of therapies to induce apoptosis in keloid fibroblasts. Smith and colleagues provided additional evidence that keloid fibroblasts are phenotypically abnormal.10 Using cultured fibroblasts from keloids, normal skin either adjacent to or distant from a keloid, and neonatal foreskins, they observed that only keloid fibroblasts preferentially increased cell proliferation, DNA synthesis, and procollagen synthesis in response to exogenous TGF-b2. Lee and colleagues also underscored the importance of TGF-b isoforms in the pathogenesis of abnormal scars.11 Although keloid fibroblasts were observed to produce almost twice as much total TGF-b when compared with normal human fibroblasts, the production of the “antiscarring” TGF-b3 isoform was lower in keloid than in normal cells. Tredget and colleagues observed alterations in circulating T-cell function that lead to a deficiency in interferon g and excessive IL-4 secretion in patients with hypertrophic scars.12 This may offer a basis for cytokine therapy to treat hypertrophic scars. Nath and associates demonstrated another potential therapy for pathologic scarring.13 Using an antisense oligonucleotide, they successfully reduced collagen I protein levels in cultured mouse fibroblasts, a strategy that could be applied to reduce fibrosis or pathologic scarring. CRANIOFACIAL AND BONE BIOLOGY In this area, research has focused on bone healing, suture biology and craniosynostosis, distraction osteogenesis, guided bone regeneration and osteoinduction, and cleft biology. Recognizing that angiogenesis is crucial to bone healing, Saadeh and colleagues examined mouse MC-3T3 cells in culture, demonstrating that TGF-b1 and bFGF can induce VGEF expression at both the mRNA and protein levels.14 Prolonged hypoxia also increased VGEF production by MC-3T3 cells concomitant with a change toward a more differentiated phenotype, indicating that both humeral and physical stimuli can modulate cell behavior during osteogenesis.15 Rosenthal and Buchman placed cortical and cancellous grafts of enchondral and membranous bone in an inlay position in the rabbit cranium.16 They observed identical changes in bone volume in enchondral and membranous grafts, concluding that microarchitecture and biomechanical
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forces, and not embryologic origin, are the critical factors in determining the fate of inlay bone grafts. The critical interaction between the dura mater and the cranial sutures has been recognized for some time. The proosteogenic nature of the dura was demonstrated in a study by Sagiroglu and associates.17 Using a mouse model, a calvarial strip containing the posterior frontal suture was oriented so that the ectocranial surface was in contact with the dura. In the flipped sutures, fusion began at the neoendocranial surface, a reversal of the normal pattern. This study strongly supports data indicating that the dura mater is proosteogenic, elaborating TGF-b, bFGF, IGF, and other cytokines that regulate osteogenesis. Gosain and colleagues also demonstrated the osteogenic potential of the dura using membranous bone grafts to the rabbit calvarium.18 They observed that grafts placed adjacent to living dura displayed enhanced bone deposition and total bone formation compared with grafts in the same location that were isolated from contact with the dura. Ting and associates examined clinical specimens from children undergoing surgery for unilateral coronal synostosis.19 They demonstrated that the NEL-2 gene is upregulated during unilateral coronal suture fusion, suggesting that NEL-2 may enhance bone induction in fusing sutures. Using a rabbit model of nonsyndromic coronal synostosis, Ozaki and colleagues demonstrated that normal rabbit coronal sutures have higher bone density, lower internal surface area, and fewer trabeculae when compared with synostotic sutures.20 They suggest that biomechanical forces have a significant role in the regulation of bony ultrastructure during suture fusion. Mehrara, Longaker and colleagues from New York University examined gene expression during distraction osteogenesis in a rat model.21,22 They found upregulation of TGF-b1 and downregulation of collagen I and osteocalcin genes during distraction. Collagen I and osteocalcin were upregulated during the consolidation period, indicating that the unique, sequential expression of osteogenic factors is critical to successful distraction osteogenesis. Turegun and associates developed a new method of biomechanical evaluation to demonstrate that a PTFE scaffold can effectively guide bone regeneration in a critical rabbit skull defect.23 Successful healing of critical rabbit skull defects was also achieved with a new, commercially available form of demineralized bone matrix. This study by Shermak and colleagues demonstrated that an off-the-shelf product has the potential to significantly augment bone heal-
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ing under clinical circumstances.24 Hydroxyapatite was shown to be capable of supporting osteoinduction in soft tissues in a study by Song and associates.25 In longterm experiments using a sheep model, they observed that osteoinduction was maximized by the porous architecture of ceramic forms of hydroxyapatite. Anabasine was used to induce cleft palates in fetal goats in a study by Weinzweig and colleagues.26 The authors went on to perform von Langenbeck cleft palate repairs on affected fetuses in utero. Despite scarless healing of the repaired clefts, they observed gross maxillary hypoplasia, midface retrusion, and class III malocclusion in affected animals. In addition to reporting the first in utero repair of a true congenital cleft, these data support the notion of an intrinsic facial dysmorphology in cleft palate patients. Another powerful tool for research in this area was provided by Koo and associates who demonstrated that 100% of homozyogous TGF-b3 knockout fetuses had cleft palates.27 This teratogen free model will complement existing animal models of cleft palate for future studies on the etiology of this complex deformity. PERIPHERAL NERVE INJURY Peripheral nerve lesions remain a significant challenge for reconstructive surgeons. Reduced sensation, reduced muscle force and power output, and altered motor pathways contribute to significant disability in affected patients. In the past year, research in this area has focused on end-to-side nerve coaptation, peripheral nerve allografting, and end organ dysfunction after nerve injury and repair. For end-to-side nerve coaptations, the role of the perineurium as a barrier to axonal regeneration and the source of regenerating axons remain active research questions. Andreopoulos and coauthors used a rat model of end-to-side coaptation to determine the anatomic origin of axons regenerating across the coaptation site and into a distal nerve graft.28 Using retrograde labeling, they observed that, at an early time point, axons in the graft arose from either injured axons in the donor nerve or from collateral sprouting of donor axons. They conclude that some form of axonal injury is likely necessary to induce collateral sprouting. Rovak and colleagues used a similar rat model to demonstrate that, after end-toside nerve coaptation in one limb, motor neurons regenerating through a long nerve graft can successfully reinnervate target muscles in the contralateral leg, but only by relinquishing their functional con-
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nections to their original target.29 Ting and associates used a rat model to demonstrate successful axonal regeneration after end-to-side coaptation of an autogenous vein nerve conduit to the tibial nerve.30 They were unable to observe differences in regeneration based on the presence or absence of a perineurial window at the coaptation site. Doolabh and colleagues induced longterm tolerance to a peripheral nerve allograft by pretreating Buffalo rat recipients with a single dose of live donor Lewis rat cells in combination with a nondepleting anti-CD4 antibody.31 This combination of donor antigen and monoclonal antibody pretreatment, which prevented rejection of a donor allograft, allowed successful axonal regeneration and target organ reinnervation in this rat model and may prove a clinically feasible strategy for nerve allotransplantation. Interestingly, this group also demonstrated that the immunosuppressive agents cyclosporin A and FK506 accelerated the rate of recovery from both axontmetic and neruotmetic tibial nerve lesions in a rat model.32 Not only do these results suggest that the requisite immunosuppressive regime may not be harmful to axonal regeneration in nerve allografts, but they also indicate the potential utility of these agents in high extremity nerve injuries where no nerve grafting is required. Cederna and associates studied motor unit organization after reinnervation in a rat model of neurovascular muscle transfer.33 They found that reinnervation of muscles by reduced numbers of motor axons produced an increase in mean motor unit forces. The relative motor unit force increase, which was similar for all physiologic motor unit types, could not fully compensate for reduced motor unit numbers, suggesting that limits to the expansion of innervation ratio by individual motor units may contribute to the reduced force production observed after muscle reinnervation. ISCHEMIA AND REPERFUSION INJURY AND FLAP PHYSIOLOGY Research in this area has focused on the mechanisms responsible for flap failure and ischemia and reperfusion injury, on ischemic preconditioning of skin and muscle, on factors influencing microcirculation, and on potential therapies to improve flap survival and mitigate ischemia and reperfusion injury. Khiabani and associates demonstrated that SIN-1, a nitric oxide donor, enhanced survival of both skin and myocutaneous flaps in a pig model.34
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Reduced neutrophil accumulation in treated flaps suggested an antiinflammatory mechanism of SIN-1. Partial thrombosis at the arterial anastomosis with subsequent, downstream microembolic showers can result in reduced capillary perfusion and other microcirculatory changes that may contribute to the failure of free tissue transfers. Using a rat model that delivered a controlled thrombogenic insult to skeletal muscle, Krapohl and colleagues found that intraarterial administration of tissue-plasminogen activator (t-PA) ameliorated these changes and increased muscle capillary perfusion by over threefold when compared with control animals.35 Lipa and associates examined the vasomotor response of human musculocutaneous perforators when challenged with norepinephrine, endothelin-1, and other vasoactive mediators.36 They concluded that sensitivity to the vasoconstrictor norepinephrine was greater in human veins than in arteries, thereby supporting the clinical impression that venous venospasm is more difficult to relieve during microvascular surgical procedures. Kim and coauthors37 studied ischemic preconditioning of skin flaps. They found that the surviving areas of rat skin flaps could be doubled by two or three 5-minute cycles of ischemia and reperfusion before a 6-hour, global ischemic insult. Ischemic preconditioning was also observed to improve the microcirculatory hemodynamics of rat muscle flaps in a study by Adanali and colleagues.38 Decreased rolling, adhering, and transmigration of leukocytes was observed in rat cremasteric muscles preconditioned before a 4-hour ischemic insult compared with muscles that underwent ischemia without preconditioning. Vedder and colleagues presented preliminary results of a pilot Phase 2 clinical trial of humanized CD11/CD18 monoclonal antibody in patients with hemorrhagic shock.39 They achieved high saturation of CD11/CD18 sites on neutrophils and observed a mortality rate in treated patients that was not significantly different from untreated patients. These data suggest that clinical use of monoclonal antibody blockade of CD11/CD18 receptors may be feasible; further clinical trials will be required to determine the efficacy and indications for this innovative therapy. COMPOSITE TISSUE TRANSPLANTATION The field of composite tissue allotransplantation was sensationalized this year as a group at Jewish Hospital
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in Louisville, KY made careful preparations to conduct the first appropriate clinical trial of human hand transplants. It was further sensationalized by news reports from Lyon, France of a cadeveric hand transplant to a 48-year-old, unilateral amputee. Although important scientific, technical, and ethical questions remain, it is clear that the age of composite tissue allotransplantation is upon us. Basic research in numerous plastic surgery laboratories has contributed to this effort. T-cell depleted bone marrow transplantation coupled with low dose irradiation and shortterm immunosupression was used to generate chimerism across a major histocompatibility complex barrier in a rat model in a study by Foster and associates.40 In animals that successfully achieved stable chimerism, hindlimb allotransplants survived without significant signs of rejection. Recovery of gross motor and sensory function was documented in these extremities. This demonstration of longterm survival of a composite tissue allograft without immunosupression may have significant clinical implications. Talmor and colleagues studied the role of dendritic cells in the induction of thymic chimerism.41 After microvascular limb allografting, donor dendritic cells were observed in the thymus of recipient animals, suggesting that intrathymic inoculation of donor dendritic cells may be a rational pretreatment strategy to induce tolerance in recipient animals. Cober and associates demonstrated longterm tolerance in 2 out of 5 vascularized limb allografts transplanted across a single haplotype barrier in a miniature swine model.42 This large animal model of composite tissue transplantation will be useful in future studies of the tolerance induction process. OTHER BASIC SCIENCE RESEARCH In a mouse 20% total body surface area (TBSA) burn model, Pellegrin and colleagues observed that IL-1ra, a naturally occurring inhibitor of IL-1 that is upregulated after burn injury, inhibited proliferation of bone marrow phagocyte progenitors and was associated with leukopenia 14 days postburn.43 These data suggest that endogenous overproduction of IL-1ra may contribute to postburn bone marrow suppression, leukopenia, and infection. Narini and coauthors described the kinetics of a lymphocyte mediated host response to silicone gel.44 The kinetics were consistent with those observed in a delayed type hypersensitivity response and further strengthen the hypothesis that silicone gel can, under
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appropriate circumstances, elicit a delayed immune reaction. TISSUE ENGINEERING, GENE THERAPY, TECHNOLOGY APPLICATION As in all fields of medicine, targeted gene therapy holds significant promise for the treatment of disease in plastic surgery patients. This year, significant research in this area has been directed at achieving expression of desired gene products in specific target tissues. Local gene delivery techniques are required to achieve this goal. Pomahac and colleagues used a modified tattoo device to microseed human epidermal growth factor (hEGF) plasmid DNA into tibial periosteum in a rat model.45 They subsequently observed nanogram concentrations of hEGF, demonstrating that this method could be used to modulate local expression of osteogenic factors to enhance clinical bone healing. Weinfeld and associates used an adenoviral construct to produce local over expression of tissue-type plasminogen activator (t-PA) in a rabbit model of microvascular thrombosis.46 They were able to demonstrate both a 300% increase in t-PA levels and prevention of arterial thrombosis in treated animals. The application of technology for cardiomyoplasty and dynamic sphincteroplasty continues to be an active area of investigation. Using a canine model of dynamic neosphincteroplasty, Zonnevijlle and colleagues found that closed loop feedback control with amplitude modulation may be a feasible method to regulate pressures in a neosphincter while minimizing muscle fatigue and injury.47 This same group demonstrated that multichannel, multisite electrical stimulation of the paralyzed dog obicularis oculi muscle could be effected with lower current intensities and could achieve more effective eye closure when compared with single channel stimulation.48 The combination of multichannel stimulation with amplitude modulation appears to be a promising strategy to allow functional reconstruction of sphincter function in a variety of clinical circumstances. Tissue engineering holds significant promise for the reconstructive surgeon. In particular, the potential to provide off-the-shelf replacement tissues without donor site morbidity has sparked significant activity in this research area. Acarturk and colleagues used UV photolithography to produce patterned biomaterials; the influence of pattern geometry on the attachment and orientation of cultured mouse
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C2C12 cells was then studied.49 They concluded that micropatterning of biomaterials with contrasting adhesive and nonadhesive regions significantly influenced the orientation of myoblasts in culture. In a companion study, myoblast differentiation and maturation could be influenced by the varying the properties of the surface.50 Their findings indicate that biomaterials can modulate myoblast differentiation and myotube orientation, providing a strategy to control myogenesis during skeletal muscle tissue engineering. Marler and colleagues used cultured chondrocytes in a hydrogel carrier to create a nipplelike mound in a pig model.51 Subdermal injections of this material in combination with a sutureless vacuum device allowed engineered nipples to maintain projection for at least 10 weeks. Longterm studies are in progress. Hydrogel may also be suitable as a matrix for preadipocyte transplantation, as reported by Won Rhie and associates.52 Despite these encouraging results, enthusiasm for strategies employing hydrogel injections was tempered by data collected by Ashiku and associates.53 They demonstrated that, compared with the longterm stability of hydrogel/chondrocyte suspensions injected into nude mice, similar constructs in immune competent rabbits underwent progressive ossification. Clearly, a more detailed understanding of the factors influencing stability of tissue engineered cartilage will be required before this technique can be applied clinically. CLINICAL AND OUTCOMES RESEARCH Clinical research continues to be vital to the practice of plastic surgery and, as in most surgical specialties, an emphasis on outcomes research promises to enhance both clinical outcomes and patient satisfaction. Ultrasonic assisted liposuction (UAL) is now one of the most commonly performed aesthetic procedures. Howard and associates found that UAL at supraclinical amplitudes could cause significant functional injury to peripheral nerves.54 In their rat model, nearly complete recovery of nerve function was observed after 30 days. The practical clinical extrapolations of this experiment are that adherence to recommended amplitudes should minimize the chances of peripheral nerve injury with UAL and also should an injury occur, a conservative course of management should be pursued. The use of endoscopeassisted limited access techniques continues to expand for both aesthetic and reconstructive procedures. Koger and colleagues used a pig model to
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compare placement of tissue expanders using conventional incisions with placement via an endoscopeassisted technique.55 They found that the combination of minimally invasive access and balloon dissection reduced the complication rate and yielded more expanded tissue than conventional tissue expander placement. Cederna and associates validated a method that used anthromorphic data collected from digitized photographs to objectify aesthetic outcomes of breast reconstructions.56 This approach could be applied to a wide variety of reconstructive and aesthetic procedures. Chung and associates studied patient satisfaction in an outpatient setting.57 Significant predictors of high patient satisfaction included efficient appointment scheduling, short appointment lead times, and high quality physician-patient interactions. Interestingly, physician technical skill was not a significant predictor, underscoring the discrepancy between physician and patient perceptions of important factors that lead to satisfactory outcomes. In summary, plastic and reconstructive surgery is a specialty with an enormous breadth of clinical practice, and research in this area reflects this diversity. In the past year, basic research has contributed to our understanding of the pathophysiology of wound healing, bone healing, microcirculatory failure, flap necrosis, cranial suture biology, nerve regeneration, and a variety of other phenomena. Basic research in these areas has served as a foundation for applied research in the areas of tissue engineering, gene transfer, and the application of novel technologies. Clinical research has examined the application of these technologies on the clinical outcomes of plastic surgery patients. Clearly, the thriving, healthy state of research in the field of plastic and reconstructive surgery will lead to continued improvements in these outcomes. References 1. Lanning DA, Nwomeh BC, Montante SJ, et al. Differential effects of transforming growth factor b1 and b3 on excisional fetal rabbit wounds. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:660–661. 2. Bauer J, Phillips L, Papaconstantinou, J. TGFB1 potentiates and IL4 mediated upregulation of the human fibroblast COL1A1 gene. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 3. Gibson JJ, Sheikh AY, Rollins MD, et al. Increased oxygen tension and wound fluid vascular endothelial growth factor levels. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:607–610. 4. Feng JJ, Ledger G, Constant JS, et al. ADP ribosylation controls vascular endothelial growth factor activity. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:604–605.
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5. Doyle JW, Smith RM, Roth TP, et al. Interleukin-1 alpha and its type 1 receptor are induced in human epidermal cells by wounding. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 6. Roth T, Doyle J, Smith R, Li Y, et al. Interleukin 10 inhibition of antigen-presenting cell function in cultured human monocytes. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:614–615. 7. Jang YC, Gibran NS, Isik F. Vitronectin regulates the plasminogen activator system during angiogenesis. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 8. Chin GS, Lee TY, Kim WJH, et al. A difference in signal transduction by tyrosine phosphorylation: fetal rat dermal fibroblasts compared with adult rat dermal fibroblasts. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:641–643. 9. Sayah DN, Shaw WW, Holmes EC, et al. Downregulation of apoptosis genes accounts for aberrant cellular growth in keloid tissue. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:596–598. 10. Smith PD, Siegler K, Wang X, Roberson MC. Transforming growth factor b2 increases DNA synthesis and collagen production in keloid fibroblasts. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:617–619. 11. Lee S, Chau D, Rowe NM, et al. Keloid fibroblasts produce a reduced amount of transforming growth factors b3 compared with transforming growth factor b1 and transforming growth factor b2 isoforms. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:645–646. 12. Tredget EE, Ji M, Taghi-Kilani R, et al. Polarized T helper 2 cell (th2) intracellular cytokine synthesis in burn patients with hypertrophic scarring. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 13. Nath RK, Jensen JN, Weinfeld AB. Collagen type I blockade with antisense oligonucleotide DNA. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:656– 657. 14. Saadeh P, Mehrara B, Steinbrech D, et al. TBF-b1 and basic FGF modulate the expression of vascular endothelial growth factor by osteoblasts in vitro. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 15. Steinbrech D, Mehrara B, Saadeh P, et al. Vascular endothelial growth factor gene expression is increased by osteoblasts in response to hypoxic conditions. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 16. Rosenthal AH, Buchman SR. Characterization of the biologic principles determining the fate of inlay bone grafts in the craniofacial skeleton. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 17. Sagiroglu J, Mehrara BJ, Rowe NM, et al. Studies in cranial suture biology: impact of dura mater on cranial suture fusion. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 18. Gossain AK, Song L, Amarante MTJ, Simmons DJ. Regulation of osteogenesis and survival within bone grafts to the calvarium: the effect of the dura vs. the pericranium. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 19. Ting K, Zhang X, Kuroda S, et al. NEL-2 gene is associated with bone formation in craniosynostosis. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49: 602–604. 20. Ozaki W, Buchman SR, Glessner CM, et al. A biomechanical and ultrastructural study of coronal synostosis. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:631–633. 21. Mehrara BJ, Steinbrech DS, Rowe N, et al. Expression of TGF-B1 and osteocalcin during rat mandibular distraction osteogenesis. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 22. Longaker MT, Mehrara BJ, Steinbrech D, et al. Gene expression during mandibular distraction osteogenesis. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:646–648.
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23. Tu¨regu¨n MC, Henderson J, Zins J, et al. Guided osteogenesis in split- and full-thickness cranial defects of rabbits and introduction of biomechanical evaluation by indentation testing. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:649–650. 24. Shermak MA, Wong L, Inoue N, et al. Biologic mechanisms of cranial healing with demineralized bone matrix. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 25. Song L, Gosain AK, Amarante MT, et al. Optimizing Osteoinduction within hydroxyapatite biomaterials. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:663–665. 26. Weinzweig J, Panter K, Pantaloni M, et al. The fetal cleft palate: characterization and in utero repair of a true congenital model. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 27. Koo SH, Arabshahi B, Cunningham MC, et al. The TGF beta-3 knockout mouse: an animal model for cleft palate. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 28. Andreopoulos G, Skoulis T, Terzis J. Double labeling technique to trace axonal sprouting after end-to-side neurorraphy. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 29. Rovak J, Macionis V, Cederna P, et al. Termino-lateral neurroraphy: The functional axonal anatomy. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 30. Ting J, Huo G, Marin V, et al. End-to-side neurorrhaphy using autogenous vein nerve conduits. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:637– 638. 31. Doolabh V, Motoyama K, Mackinnon S, Flye M. Long-term tolerance to peripheral nerve allografts with donor antigen and antiCD4 monoclonal antibody (RIB 5/2) pretreatment. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:633–635. 32. Doolabh V, Mackinnon S, Jost S, Lee M. Early functional recovery following FK506 and cyclosporin A administration in a rat model. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 33. Cederna P, Eguchi T, van der Meulen J, et al. Force deficits in neurovascular muscle transfers. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:627– 628. 34. Khiabani K, Kerrigan C. Attenuation of ischemia reperfusion injury with a NO donor: SIN-1. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 35. Krapohl B, Turegun M, Perez P, et al. T-PA restores muscle tissue perfusion at the micorocirculatory level following a thrombogenic insult. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 36. Lipa J, Neligan P, Mahoney J, et al. Vasospasm in the human musculocutaneous perforator artery and vein: Constriction and relaxation differences. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 37. Kim K, Omar A, Sayed S, et al. Ischemic preconditioning of skin flaps: Effects of ischemia cycle length and number of cycles. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 38. Adanali G, Ozer K, Yetman R, et al. Ischemic preconditioning improves microcirculatory hemodynamics of muscle flaps. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 39. Vedder N, Harlan J, Winn R, et al. Pilot phase 2 clinical trial of a humanized CD11/CD18 monoclonal antibody in generalized reperfusion. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 40. Foster RD, Fan L, Niepp M, et al. Mixed allogeneic chimeras as a model for tolerance induction in composite tissue allografts: chimeric stability and functional recovery. American College of Sur-
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geons Surgical Forum, 84th Annual Clinical Congress. 1998;49:605–607. Talmor M, Mathes D, Kinkhabwala M, et al. Thymic chimerism in nonirradiated immunosuppressed rats receiving microvascularized limb transplants. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:639–641. Cober S, Davenport T, Ierino F, et al. Prolonged survival of vascularized limb allografts using short-term cyclosporine in NIH minature swine with class I and single-haplotype MHC disparities. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Pellegrin K, Peterson V, Ketch L. Administration of interleukin 1 receptor antagonist, an antiinflammatory, counter-regulatory cytokine, promotes bone marrow failure after burn injury. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:610–612. Narini P, Semple J, Hay J. Kinetics of the delayed hypersensitivity response to silicone gel. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Pomahac B, Yao F, Svensjo¨ T, et al. Microseeding provides efficient in vivo gene transfer to the periosteum. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49: 590–600. Weinfeld A, Waugh J, Yuksel E, et al. Microvascular gene therapy: Prevention of arterial thrombosis using adenoviral mediated tPA overexpression in and in vivo rabbit model. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Zonnevijlle E, Abadia G, Somia N, et al. Feedback (closed loop) control of a urinary graciloplasty neosphincter. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:621–622. Somia N, Zonnevijlle E, Stremel R, et al. Electronic reanimation of the paralyzed orbicularis oculi: The feasibility of multichannel electrical stimulation. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Acarturk T, Petroski P, Peel M, et al. Skeletal muscle tissue engineering on micropatterned biomaterials. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. DiEdwardo C, Petrosko P, Elbourne V, et al. Characterizing the molecular dynamics of myoblast differentiation using RT-PCR for skeletal muscle tissue engineering. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Marler J, Zienowicz R, Borland K, et al. Tissue engineering of the nipple: Advances in techniques and hydrogel evaluation. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Won Rhie J, Klitzman B, Levin LS, Brown A. Preadipocyte viability in a biomatrix: Model for soft tissue augmentation. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Ashiku S, Randolph M, Vacanti C, et al. Tissue engineering using an injectable, thermosensitive hydrogel polymer in immune competent animals. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Howard B, Kenkel J, Beran S, Rohrich R. Effects of ultrasound assisted liposuction on peripheral nerves. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Koger K, Klitzman B, Levin LS. Balloon dissection accelerates tissue expansion and increases flap advancement. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Cederna P, Lowery J, Kuzon W, Wilkins E. Computerized assessment of aesthetic outcomes in breast reconstruction: Determination of breast volume. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. Chung K, Hamill J, Kim H, et al. Predictors of patient satisfaction in and outpatient plastic surgery clinic. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49: 545–546.
be via potentiation of the interleukin-4 (IL-4) mediated induction of the collagen I alpha 1 gene.2 Gibson and colleagues showed using a rat wound cylinder model, that vascular endothelial growth factor (VGEF) concentrations can be increased by administering hyperbaric oxygen, although the relative role of VGEF in hyperoxia-induced angiogenesis is still unclear.3 Direct mono-ADP ribosolation was shown to reversibly inhibit VGEF-induced angiogenesis in vivo.4 With this experiment, Feng and associates have demonstrated that posttranscriptional events can play a significant role in the regulation of cytokines during wound healing. The rapid upregulation of both IL-1a1 and the signal-transducing receptor IL1R1 was demonstrated in wounded mouse skin by Doyle and colleagues.5 The IL-1 pathway may be critical to the initiation of the inflammatory response after wounding. IL-10 inhibits the synthesis of many proinflammatory cytokines, and its presence in chronic compared with acute wounds has been postulated to contribute to delayed wound healing. Roth and colleagues provided direct, mechanistic evidence for this hypothesis by demonstrating that the antigen presenting function of B cells, a process critical to wound maturation, is inhibited by IL-10.6 In addition to cytokines, multiple factors contribute to the regulation of the wound healing response. Jang and colleagues observed delayed healing and diminished angiogenesis in excisional wounds in vitronectin knockout mice, reconfirming that matrix molecules play a pivotal role in successful wound healing.7 To further characterize the scarless healing in fetal wounds, Chin and colleagues studied tyrosine phosphorylation patterns in adult and fetal dermal fibroblasts.8 At least five phosphorylated proteins observed in fetal fibroblasts were absent in adult fibroblasts. These proteins may represent tyrosine kinase receptors, suggesting that the intracellular signaling cascade is inherently different in fetal compared with adult cells. Sayah and associates found that apoptosis-related genes were significantly under-expressed in tissue ex-
In the past year, research in plastic and reconstructive surgery has continued to exemplify the diversity, creativity, and innovation that characterize this surgical specialty. Basic research addressed critical questions relating to wound healing, craniofacial and bone biology, peripheral nerve injury and regeneration, ischemia-reperfusion injury and flap physiology, composite tissue transplantation, and a broad array of other topics. Significant activity in the applied areas of tissue engineering, gene therapy, and technology application highlighted the multidisciplinary nature of plastic surgery research. Clinical and outcomes research addressed a broad range of questions in all areas of plastic surgery. This work will ultimately contribute to the plastic surgeon’s goal of restoration of form and function for patients suffering consequences of trauma or disease. Of course, the summary that follows encompasses only a fraction of the overall research activity in plastic surgery today. WOUND HEALING Delayed wound healing has enormous clinical and economic consequences. In the past year, work in this area has focused on determining the critical, but complex, role of cytokines in the regulation of healing in normal, chronic, and fetal wounds, on other mechanisms contributing to delayed wound healing, and on the process of pathologic scarring. Lanning and colleagues studied the differential effects of transforming growth factor b (TGF b) isoforms on excisional wounds in a rabbit model.1 They found that, while TGF b1 preferentially upregulated procollagen type I, TGF b3 upregulated procollagen type III, suggesting that differential TGF isoform expression plays a significant role in regulating the degree of fibrosis in excisional wounds. Bauer and colleagues demonstrated that one mechanism by which TGF-b1 modulates collagen synthesis might Received November 23, 1998; Accepted November 23, 1998. From the Section of Plastic and Reconstructive Surgery, University of Michigan, Ann Arbor, MI. Correspondence address: William M Kuzon Jr, MD, PhD, 2130 Taubman Health Care Center, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0340. © 1999 by the American College of Surgeons Published by Elsevier Science Inc.
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cised from human keloids compared with tissue excised from normal, nonpathologic scars.9 This observation may account for the prolonged and excessive production of collagen by keloid fibroblasts, and may allow development of therapies to induce apoptosis in keloid fibroblasts. Smith and colleagues provided additional evidence that keloid fibroblasts are phenotypically abnormal.10 Using cultured fibroblasts from keloids, normal skin either adjacent to or distant from a keloid, and neonatal foreskins, they observed that only keloid fibroblasts preferentially increased cell proliferation, DNA synthesis, and procollagen synthesis in response to exogenous TGF-b2. Lee and colleagues also underscored the importance of TGF-b isoforms in the pathogenesis of abnormal scars.11 Although keloid fibroblasts were observed to produce almost twice as much total TGF-b when compared with normal human fibroblasts, the production of the “antiscarring” TGF-b3 isoform was lower in keloid than in normal cells. Tredget and colleagues observed alterations in circulating T-cell function that lead to a deficiency in interferon g and excessive IL-4 secretion in patients with hypertrophic scars.12 This may offer a basis for cytokine therapy to treat hypertrophic scars. Nath and associates demonstrated another potential therapy for pathologic scarring.13 Using an antisense oligonucleotide, they successfully reduced collagen I protein levels in cultured mouse fibroblasts, a strategy that could be applied to reduce fibrosis or pathologic scarring. CRANIOFACIAL AND BONE BIOLOGY In this area, research has focused on bone healing, suture biology and craniosynostosis, distraction osteogenesis, guided bone regeneration and osteoinduction, and cleft biology. Recognizing that angiogenesis is crucial to bone healing, Saadeh and colleagues examined mouse MC-3T3 cells in culture, demonstrating that TGF-b1 and bFGF can induce VGEF expression at both the mRNA and protein levels.14 Prolonged hypoxia also increased VGEF production by MC-3T3 cells concomitant with a change toward a more differentiated phenotype, indicating that both humeral and physical stimuli can modulate cell behavior during osteogenesis.15 Rosenthal and Buchman placed cortical and cancellous grafts of enchondral and membranous bone in an inlay position in the rabbit cranium.16 They observed identical changes in bone volume in enchondral and membranous grafts, concluding that microarchitecture and biomechanical
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forces, and not embryologic origin, are the critical factors in determining the fate of inlay bone grafts. The critical interaction between the dura mater and the cranial sutures has been recognized for some time. The proosteogenic nature of the dura was demonstrated in a study by Sagiroglu and associates.17 Using a mouse model, a calvarial strip containing the posterior frontal suture was oriented so that the ectocranial surface was in contact with the dura. In the flipped sutures, fusion began at the neoendocranial surface, a reversal of the normal pattern. This study strongly supports data indicating that the dura mater is proosteogenic, elaborating TGF-b, bFGF, IGF, and other cytokines that regulate osteogenesis. Gosain and colleagues also demonstrated the osteogenic potential of the dura using membranous bone grafts to the rabbit calvarium.18 They observed that grafts placed adjacent to living dura displayed enhanced bone deposition and total bone formation compared with grafts in the same location that were isolated from contact with the dura. Ting and associates examined clinical specimens from children undergoing surgery for unilateral coronal synostosis.19 They demonstrated that the NEL-2 gene is upregulated during unilateral coronal suture fusion, suggesting that NEL-2 may enhance bone induction in fusing sutures. Using a rabbit model of nonsyndromic coronal synostosis, Ozaki and colleagues demonstrated that normal rabbit coronal sutures have higher bone density, lower internal surface area, and fewer trabeculae when compared with synostotic sutures.20 They suggest that biomechanical forces have a significant role in the regulation of bony ultrastructure during suture fusion. Mehrara, Longaker and colleagues from New York University examined gene expression during distraction osteogenesis in a rat model.21,22 They found upregulation of TGF-b1 and downregulation of collagen I and osteocalcin genes during distraction. Collagen I and osteocalcin were upregulated during the consolidation period, indicating that the unique, sequential expression of osteogenic factors is critical to successful distraction osteogenesis. Turegun and associates developed a new method of biomechanical evaluation to demonstrate that a PTFE scaffold can effectively guide bone regeneration in a critical rabbit skull defect.23 Successful healing of critical rabbit skull defects was also achieved with a new, commercially available form of demineralized bone matrix. This study by Shermak and colleagues demonstrated that an off-the-shelf product has the potential to significantly augment bone heal-
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ing under clinical circumstances.24 Hydroxyapatite was shown to be capable of supporting osteoinduction in soft tissues in a study by Song and associates.25 In longterm experiments using a sheep model, they observed that osteoinduction was maximized by the porous architecture of ceramic forms of hydroxyapatite. Anabasine was used to induce cleft palates in fetal goats in a study by Weinzweig and colleagues.26 The authors went on to perform von Langenbeck cleft palate repairs on affected fetuses in utero. Despite scarless healing of the repaired clefts, they observed gross maxillary hypoplasia, midface retrusion, and class III malocclusion in affected animals. In addition to reporting the first in utero repair of a true congenital cleft, these data support the notion of an intrinsic facial dysmorphology in cleft palate patients. Another powerful tool for research in this area was provided by Koo and associates who demonstrated that 100% of homozyogous TGF-b3 knockout fetuses had cleft palates.27 This teratogen free model will complement existing animal models of cleft palate for future studies on the etiology of this complex deformity. PERIPHERAL NERVE INJURY Peripheral nerve lesions remain a significant challenge for reconstructive surgeons. Reduced sensation, reduced muscle force and power output, and altered motor pathways contribute to significant disability in affected patients. In the past year, research in this area has focused on end-to-side nerve coaptation, peripheral nerve allografting, and end organ dysfunction after nerve injury and repair. For end-to-side nerve coaptations, the role of the perineurium as a barrier to axonal regeneration and the source of regenerating axons remain active research questions. Andreopoulos and coauthors used a rat model of end-to-side coaptation to determine the anatomic origin of axons regenerating across the coaptation site and into a distal nerve graft.28 Using retrograde labeling, they observed that, at an early time point, axons in the graft arose from either injured axons in the donor nerve or from collateral sprouting of donor axons. They conclude that some form of axonal injury is likely necessary to induce collateral sprouting. Rovak and colleagues used a similar rat model to demonstrate that, after end-toside nerve coaptation in one limb, motor neurons regenerating through a long nerve graft can successfully reinnervate target muscles in the contralateral leg, but only by relinquishing their functional con-
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nections to their original target.29 Ting and associates used a rat model to demonstrate successful axonal regeneration after end-to-side coaptation of an autogenous vein nerve conduit to the tibial nerve.30 They were unable to observe differences in regeneration based on the presence or absence of a perineurial window at the coaptation site. Doolabh and colleagues induced longterm tolerance to a peripheral nerve allograft by pretreating Buffalo rat recipients with a single dose of live donor Lewis rat cells in combination with a nondepleting anti-CD4 antibody.31 This combination of donor antigen and monoclonal antibody pretreatment, which prevented rejection of a donor allograft, allowed successful axonal regeneration and target organ reinnervation in this rat model and may prove a clinically feasible strategy for nerve allotransplantation. Interestingly, this group also demonstrated that the immunosuppressive agents cyclosporin A and FK506 accelerated the rate of recovery from both axontmetic and neruotmetic tibial nerve lesions in a rat model.32 Not only do these results suggest that the requisite immunosuppressive regime may not be harmful to axonal regeneration in nerve allografts, but they also indicate the potential utility of these agents in high extremity nerve injuries where no nerve grafting is required. Cederna and associates studied motor unit organization after reinnervation in a rat model of neurovascular muscle transfer.33 They found that reinnervation of muscles by reduced numbers of motor axons produced an increase in mean motor unit forces. The relative motor unit force increase, which was similar for all physiologic motor unit types, could not fully compensate for reduced motor unit numbers, suggesting that limits to the expansion of innervation ratio by individual motor units may contribute to the reduced force production observed after muscle reinnervation. ISCHEMIA AND REPERFUSION INJURY AND FLAP PHYSIOLOGY Research in this area has focused on the mechanisms responsible for flap failure and ischemia and reperfusion injury, on ischemic preconditioning of skin and muscle, on factors influencing microcirculation, and on potential therapies to improve flap survival and mitigate ischemia and reperfusion injury. Khiabani and associates demonstrated that SIN-1, a nitric oxide donor, enhanced survival of both skin and myocutaneous flaps in a pig model.34
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Reduced neutrophil accumulation in treated flaps suggested an antiinflammatory mechanism of SIN-1. Partial thrombosis at the arterial anastomosis with subsequent, downstream microembolic showers can result in reduced capillary perfusion and other microcirculatory changes that may contribute to the failure of free tissue transfers. Using a rat model that delivered a controlled thrombogenic insult to skeletal muscle, Krapohl and colleagues found that intraarterial administration of tissue-plasminogen activator (t-PA) ameliorated these changes and increased muscle capillary perfusion by over threefold when compared with control animals.35 Lipa and associates examined the vasomotor response of human musculocutaneous perforators when challenged with norepinephrine, endothelin-1, and other vasoactive mediators.36 They concluded that sensitivity to the vasoconstrictor norepinephrine was greater in human veins than in arteries, thereby supporting the clinical impression that venous venospasm is more difficult to relieve during microvascular surgical procedures. Kim and coauthors37 studied ischemic preconditioning of skin flaps. They found that the surviving areas of rat skin flaps could be doubled by two or three 5-minute cycles of ischemia and reperfusion before a 6-hour, global ischemic insult. Ischemic preconditioning was also observed to improve the microcirculatory hemodynamics of rat muscle flaps in a study by Adanali and colleagues.38 Decreased rolling, adhering, and transmigration of leukocytes was observed in rat cremasteric muscles preconditioned before a 4-hour ischemic insult compared with muscles that underwent ischemia without preconditioning. Vedder and colleagues presented preliminary results of a pilot Phase 2 clinical trial of humanized CD11/CD18 monoclonal antibody in patients with hemorrhagic shock.39 They achieved high saturation of CD11/CD18 sites on neutrophils and observed a mortality rate in treated patients that was not significantly different from untreated patients. These data suggest that clinical use of monoclonal antibody blockade of CD11/CD18 receptors may be feasible; further clinical trials will be required to determine the efficacy and indications for this innovative therapy. COMPOSITE TISSUE TRANSPLANTATION The field of composite tissue allotransplantation was sensationalized this year as a group at Jewish Hospital
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in Louisville, KY made careful preparations to conduct the first appropriate clinical trial of human hand transplants. It was further sensationalized by news reports from Lyon, France of a cadeveric hand transplant to a 48-year-old, unilateral amputee. Although important scientific, technical, and ethical questions remain, it is clear that the age of composite tissue allotransplantation is upon us. Basic research in numerous plastic surgery laboratories has contributed to this effort. T-cell depleted bone marrow transplantation coupled with low dose irradiation and shortterm immunosupression was used to generate chimerism across a major histocompatibility complex barrier in a rat model in a study by Foster and associates.40 In animals that successfully achieved stable chimerism, hindlimb allotransplants survived without significant signs of rejection. Recovery of gross motor and sensory function was documented in these extremities. This demonstration of longterm survival of a composite tissue allograft without immunosupression may have significant clinical implications. Talmor and colleagues studied the role of dendritic cells in the induction of thymic chimerism.41 After microvascular limb allografting, donor dendritic cells were observed in the thymus of recipient animals, suggesting that intrathymic inoculation of donor dendritic cells may be a rational pretreatment strategy to induce tolerance in recipient animals. Cober and associates demonstrated longterm tolerance in 2 out of 5 vascularized limb allografts transplanted across a single haplotype barrier in a miniature swine model.42 This large animal model of composite tissue transplantation will be useful in future studies of the tolerance induction process. OTHER BASIC SCIENCE RESEARCH In a mouse 20% total body surface area (TBSA) burn model, Pellegrin and colleagues observed that IL-1ra, a naturally occurring inhibitor of IL-1 that is upregulated after burn injury, inhibited proliferation of bone marrow phagocyte progenitors and was associated with leukopenia 14 days postburn.43 These data suggest that endogenous overproduction of IL-1ra may contribute to postburn bone marrow suppression, leukopenia, and infection. Narini and coauthors described the kinetics of a lymphocyte mediated host response to silicone gel.44 The kinetics were consistent with those observed in a delayed type hypersensitivity response and further strengthen the hypothesis that silicone gel can, under
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appropriate circumstances, elicit a delayed immune reaction. TISSUE ENGINEERING, GENE THERAPY, TECHNOLOGY APPLICATION As in all fields of medicine, targeted gene therapy holds significant promise for the treatment of disease in plastic surgery patients. This year, significant research in this area has been directed at achieving expression of desired gene products in specific target tissues. Local gene delivery techniques are required to achieve this goal. Pomahac and colleagues used a modified tattoo device to microseed human epidermal growth factor (hEGF) plasmid DNA into tibial periosteum in a rat model.45 They subsequently observed nanogram concentrations of hEGF, demonstrating that this method could be used to modulate local expression of osteogenic factors to enhance clinical bone healing. Weinfeld and associates used an adenoviral construct to produce local over expression of tissue-type plasminogen activator (t-PA) in a rabbit model of microvascular thrombosis.46 They were able to demonstrate both a 300% increase in t-PA levels and prevention of arterial thrombosis in treated animals. The application of technology for cardiomyoplasty and dynamic sphincteroplasty continues to be an active area of investigation. Using a canine model of dynamic neosphincteroplasty, Zonnevijlle and colleagues found that closed loop feedback control with amplitude modulation may be a feasible method to regulate pressures in a neosphincter while minimizing muscle fatigue and injury.47 This same group demonstrated that multichannel, multisite electrical stimulation of the paralyzed dog obicularis oculi muscle could be effected with lower current intensities and could achieve more effective eye closure when compared with single channel stimulation.48 The combination of multichannel stimulation with amplitude modulation appears to be a promising strategy to allow functional reconstruction of sphincter function in a variety of clinical circumstances. Tissue engineering holds significant promise for the reconstructive surgeon. In particular, the potential to provide off-the-shelf replacement tissues without donor site morbidity has sparked significant activity in this research area. Acarturk and colleagues used UV photolithography to produce patterned biomaterials; the influence of pattern geometry on the attachment and orientation of cultured mouse
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C2C12 cells was then studied.49 They concluded that micropatterning of biomaterials with contrasting adhesive and nonadhesive regions significantly influenced the orientation of myoblasts in culture. In a companion study, myoblast differentiation and maturation could be influenced by the varying the properties of the surface.50 Their findings indicate that biomaterials can modulate myoblast differentiation and myotube orientation, providing a strategy to control myogenesis during skeletal muscle tissue engineering. Marler and colleagues used cultured chondrocytes in a hydrogel carrier to create a nipplelike mound in a pig model.51 Subdermal injections of this material in combination with a sutureless vacuum device allowed engineered nipples to maintain projection for at least 10 weeks. Longterm studies are in progress. Hydrogel may also be suitable as a matrix for preadipocyte transplantation, as reported by Won Rhie and associates.52 Despite these encouraging results, enthusiasm for strategies employing hydrogel injections was tempered by data collected by Ashiku and associates.53 They demonstrated that, compared with the longterm stability of hydrogel/chondrocyte suspensions injected into nude mice, similar constructs in immune competent rabbits underwent progressive ossification. Clearly, a more detailed understanding of the factors influencing stability of tissue engineered cartilage will be required before this technique can be applied clinically. CLINICAL AND OUTCOMES RESEARCH Clinical research continues to be vital to the practice of plastic surgery and, as in most surgical specialties, an emphasis on outcomes research promises to enhance both clinical outcomes and patient satisfaction. Ultrasonic assisted liposuction (UAL) is now one of the most commonly performed aesthetic procedures. Howard and associates found that UAL at supraclinical amplitudes could cause significant functional injury to peripheral nerves.54 In their rat model, nearly complete recovery of nerve function was observed after 30 days. The practical clinical extrapolations of this experiment are that adherence to recommended amplitudes should minimize the chances of peripheral nerve injury with UAL and also should an injury occur, a conservative course of management should be pursued. The use of endoscopeassisted limited access techniques continues to expand for both aesthetic and reconstructive procedures. Koger and colleagues used a pig model to
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compare placement of tissue expanders using conventional incisions with placement via an endoscopeassisted technique.55 They found that the combination of minimally invasive access and balloon dissection reduced the complication rate and yielded more expanded tissue than conventional tissue expander placement. Cederna and associates validated a method that used anthromorphic data collected from digitized photographs to objectify aesthetic outcomes of breast reconstructions.56 This approach could be applied to a wide variety of reconstructive and aesthetic procedures. Chung and associates studied patient satisfaction in an outpatient setting.57 Significant predictors of high patient satisfaction included efficient appointment scheduling, short appointment lead times, and high quality physician-patient interactions. Interestingly, physician technical skill was not a significant predictor, underscoring the discrepancy between physician and patient perceptions of important factors that lead to satisfactory outcomes. In summary, plastic and reconstructive surgery is a specialty with an enormous breadth of clinical practice, and research in this area reflects this diversity. In the past year, basic research has contributed to our understanding of the pathophysiology of wound healing, bone healing, microcirculatory failure, flap necrosis, cranial suture biology, nerve regeneration, and a variety of other phenomena. Basic research in these areas has served as a foundation for applied research in the areas of tissue engineering, gene transfer, and the application of novel technologies. Clinical research has examined the application of these technologies on the clinical outcomes of plastic surgery patients. Clearly, the thriving, healthy state of research in the field of plastic and reconstructive surgery will lead to continued improvements in these outcomes. References 1. Lanning DA, Nwomeh BC, Montante SJ, et al. Differential effects of transforming growth factor b1 and b3 on excisional fetal rabbit wounds. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:660–661. 2. Bauer J, Phillips L, Papaconstantinou, J. TGFB1 potentiates and IL4 mediated upregulation of the human fibroblast COL1A1 gene. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 3. Gibson JJ, Sheikh AY, Rollins MD, et al. Increased oxygen tension and wound fluid vascular endothelial growth factor levels. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:607–610. 4. Feng JJ, Ledger G, Constant JS, et al. ADP ribosylation controls vascular endothelial growth factor activity. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:604–605.
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5. Doyle JW, Smith RM, Roth TP, et al. Interleukin-1 alpha and its type 1 receptor are induced in human epidermal cells by wounding. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 6. Roth T, Doyle J, Smith R, Li Y, et al. Interleukin 10 inhibition of antigen-presenting cell function in cultured human monocytes. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:614–615. 7. Jang YC, Gibran NS, Isik F. Vitronectin regulates the plasminogen activator system during angiogenesis. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 8. Chin GS, Lee TY, Kim WJH, et al. A difference in signal transduction by tyrosine phosphorylation: fetal rat dermal fibroblasts compared with adult rat dermal fibroblasts. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:641–643. 9. Sayah DN, Shaw WW, Holmes EC, et al. Downregulation of apoptosis genes accounts for aberrant cellular growth in keloid tissue. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:596–598. 10. Smith PD, Siegler K, Wang X, Roberson MC. Transforming growth factor b2 increases DNA synthesis and collagen production in keloid fibroblasts. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:617–619. 11. Lee S, Chau D, Rowe NM, et al. Keloid fibroblasts produce a reduced amount of transforming growth factors b3 compared with transforming growth factor b1 and transforming growth factor b2 isoforms. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:645–646. 12. Tredget EE, Ji M, Taghi-Kilani R, et al. Polarized T helper 2 cell (th2) intracellular cytokine synthesis in burn patients with hypertrophic scarring. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 13. Nath RK, Jensen JN, Weinfeld AB. Collagen type I blockade with antisense oligonucleotide DNA. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:656– 657. 14. Saadeh P, Mehrara B, Steinbrech D, et al. TBF-b1 and basic FGF modulate the expression of vascular endothelial growth factor by osteoblasts in vitro. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 15. Steinbrech D, Mehrara B, Saadeh P, et al. Vascular endothelial growth factor gene expression is increased by osteoblasts in response to hypoxic conditions. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 16. Rosenthal AH, Buchman SR. Characterization of the biologic principles determining the fate of inlay bone grafts in the craniofacial skeleton. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 17. Sagiroglu J, Mehrara BJ, Rowe NM, et al. Studies in cranial suture biology: impact of dura mater on cranial suture fusion. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 18. Gossain AK, Song L, Amarante MTJ, Simmons DJ. Regulation of osteogenesis and survival within bone grafts to the calvarium: the effect of the dura vs. the pericranium. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 19. Ting K, Zhang X, Kuroda S, et al. NEL-2 gene is associated with bone formation in craniosynostosis. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49: 602–604. 20. Ozaki W, Buchman SR, Glessner CM, et al. A biomechanical and ultrastructural study of coronal synostosis. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:631–633. 21. Mehrara BJ, Steinbrech DS, Rowe N, et al. Expression of TGF-B1 and osteocalcin during rat mandibular distraction osteogenesis. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 22. Longaker MT, Mehrara BJ, Steinbrech D, et al. Gene expression during mandibular distraction osteogenesis. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:646–648.
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23. Tu¨regu¨n MC, Henderson J, Zins J, et al. Guided osteogenesis in split- and full-thickness cranial defects of rabbits and introduction of biomechanical evaluation by indentation testing. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:649–650. 24. Shermak MA, Wong L, Inoue N, et al. Biologic mechanisms of cranial healing with demineralized bone matrix. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 25. Song L, Gosain AK, Amarante MT, et al. Optimizing Osteoinduction within hydroxyapatite biomaterials. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:663–665. 26. Weinzweig J, Panter K, Pantaloni M, et al. The fetal cleft palate: characterization and in utero repair of a true congenital model. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 27. Koo SH, Arabshahi B, Cunningham MC, et al. The TGF beta-3 knockout mouse: an animal model for cleft palate. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 28. Andreopoulos G, Skoulis T, Terzis J. Double labeling technique to trace axonal sprouting after end-to-side neurorraphy. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 29. Rovak J, Macionis V, Cederna P, et al. Termino-lateral neurroraphy: The functional axonal anatomy. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 30. Ting J, Huo G, Marin V, et al. End-to-side neurorrhaphy using autogenous vein nerve conduits. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:637– 638. 31. Doolabh V, Motoyama K, Mackinnon S, Flye M. Long-term tolerance to peripheral nerve allografts with donor antigen and antiCD4 monoclonal antibody (RIB 5/2) pretreatment. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:633–635. 32. Doolabh V, Mackinnon S, Jost S, Lee M. Early functional recovery following FK506 and cyclosporin A administration in a rat model. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 33. Cederna P, Eguchi T, van der Meulen J, et al. Force deficits in neurovascular muscle transfers. American College of Surgeons Surgical Forum, 84th Annual Clinical Congress. 1998;49:627– 628. 34. Khiabani K, Kerrigan C. Attenuation of ischemia reperfusion injury with a NO donor: SIN-1. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 35. Krapohl B, Turegun M, Perez P, et al. T-PA restores muscle tissue perfusion at the micorocirculatory level following a thrombogenic insult. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 36. Lipa J, Neligan P, Mahoney J, et al. Vasospasm in the human musculocutaneous perforator artery and vein: Constriction and relaxation differences. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 37. Kim K, Omar A, Sayed S, et al. Ischemic preconditioning of skin flaps: Effects of ischemia cycle length and number of cycles. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 38. Adanali G, Ozer K, Yetman R, et al. Ischemic preconditioning improves microcirculatory hemodynamics of muscle flaps. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 39. Vedder N, Harlan J, Winn R, et al. Pilot phase 2 clinical trial of a humanized CD11/CD18 monoclonal antibody in generalized reperfusion. Plastic Surgery Research Council 43rd Annual Meeting, Loma Linda, CA, 1998. 40. Foster RD, Fan L, Niepp M, et al. Mixed allogeneic chimeras as a model for tolerance induction in composite tissue allografts: chimeric stability and functional recovery. American College of Sur-
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