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Stem cell treatment for musculoskeletal disease
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ScienceDirect Stem cell treatment for musculoskeletal disease Alice Carstairs and Paul Genever Musculoskeletal disease is prevalent in society and with an ageing population, the incidence and impact on public health are set to rise. Severe long-term pain and mobility restriction impair the welfare and quality of life of patients with musculoskeletal disease. Current treatments are often restricted to the management of symptoms or temporary replacement with inert materials, rather than targeting prevention and cure. There is an urgent need for alternative biological approaches to musculoskeletal disease therapy. The rapid emergence of stem cell technologies, primarily using ‘mesenchymal stem cells’ (MSCs), has resulted in a number of pre-clinical and clinical studies in an effort to provide more effective treatment options. Challenges exist in bench-to-bedside translation, but they are not insurmountable. Addresses Department of Biology (Area 9), University of York, York YO10 5DD, UK Corresponding author: Genever, Paul ([email protected])
Current Opinion in Pharmacology 2014, 16:1–6 This review comes from a themed issue on Musculoskeletal Edited by Alison Gartland and Lynne J Hocking
1471-4892/$ – see front matter, # 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.coph.2014.01.005
Introduction Our understanding of stem cells has accelerated in recent years, and with it their potential use in regenerative medicine to treat a spectrum of human disorders. The World Health Organisation has described musculoskeletal disease as the most common cause of severe long-term pain and physical disability [1]. The classification of musculoskeletal disease is broad including both acute and chronic conditions; they can affect any part of the musculoskeletal system, namely bones, muscle, cartilage, tendons, ligaments, joints and nerves. With an increasingly ageing population, the incidence of musculoskeletal disease is rising and predicted to be a significant socio-economic burden on society, yet the complex nature of these diseases generally means that treatment options are limited to managing symptoms rather than prevention and cure [2]. This unmet need is driving rapid advances in stem cell technology with the potential of using regeneration therapy to aid these conditions. www.sciencedirect.com
Stem cells — embryonic stem cells and induced pluripotent stem cells Stem cells are defined by their ability to undergo asymmetric cell division to self-renew, maintaining a stem cell pool, and give rise to differentiated progeny. This inherent trait makes stem cells a very attractive choice for regenerative therapies. Stem cells can be broadly characterised into two groups; embryonic stem cells (ESCs) and adult stem cells. ESCs are derived from the inner cell mass of blastocyst-stage embryos and possess the ability to differentiate into all cell derivatives from the three primary germ layers, ectoderm, endoderm and mesoderm (from which skeletal tissues arise). The plasticity of ESCs makes them attractive therapeutic cells for many clinical applications including the treatment of musculoskeletal disease [3,4]. Despite this potential, the use of ESCs in regeneration therapy does require a number of issues to be resolved. The implantation of ESCs has been reported to result in hyperproliferation giving rise to teratomas; cancerous tumours possessing cells/ tissue from the three primary germ layers [5]. Additionally, the incompatibility of the host cells with the newly implanted ESCs can lead to immune rejection [6]. Finally, most reported protocols require ESCs to be partially differentiated before implantation in order to ensure their progression down the correct lineage. This typically uses animal products in culture medium generating a risk of xenobiotic transfer, which will need to be addressed before ESC technology can be used in a clinical setting. Induced pluripotent stem cells (iPSCs) can be generated by introducing factors (such as Oct4, Sox2, Klf4 and cMyc) into somatic cells to initiate reprogramming to an ESC-like state [7]. Consequently, iPSCs provide a primitive, patientspecific cell source for directed differentiation to new tissues in degenerative disorders, including musculoskeletal disease. Recent work has shown that iPSCs can be produced from osteoarthritic synovial cells [8] and chondrocytes [9] with subsequent re-differentiation to cartilage tissue, and improved outcome for the homogeneity and quality of chondrogenic differentiation [10]. iPSC technology could transform regenerative medicine strategy, but concerns associated with teratoma risk, use of (viral) gene delivery and low reprogramming efficiency remain. The technical challenges associated with the use of pluripotent stem cells in therapy are likely to be addressed in time; however, the current lead therapeutic cell for musculoskeletal disease is the ‘MSC’, which will be main focus of this review.
Stem cells — ‘MSCs’ The term ‘MSC’ has been given to mesenchymal stem cells, mesenchymal stromal cells and bone marrow stromal cells (as well as other related cell populations). In Current Opinion in Pharmacology 2014, 16:1–6
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truth, very few studies have employed authentic mesenchymal stem cells (i.e. that are homogenous, identifiable selfrenewing cells capable of differentiation into all mesenchymal tissues) and the vast majority of work is performed using heterogeneous stromal cultures. Still, the ‘MSC’ abbreviation has been widely adopted and will be used here with this caveat in mind. MSCs provide an attractive option for cell-based therapy as they remove some of the technical constraints (and ethical issues) associated with ESCs and iPSCs. MSCs hold great promise for musculoskeletal disease in particular, as they can be isolated from various tissues and induced to differentiate into relevant cell types such as osteoblasts (bone), adipocytes (fat) and chondrocytes (cartilage) (Figure 1a) [11,12]. The pathways governing lineage
specification are not entirely clear; however, there are two additional intrinsic properties of MSCs that aid tissue regeneration. First is their ability to secrete a wide range of growth factors, which have trophic effects on surrounding host cells [13,14]. Second, once administered these cells can coordinate differentiation in tandem with differentiated and undifferentiated resident host cells [15]. Combined with the relative ease of expanding these cells in culture, a partially differentiated start point and possible immunomodulatory properties [16], MSCs are an attractive source for clinical usage. There have been many clinical trials using MSCs, particularly targeting musculoskeletal diseases such as fracture nonunions, avascular/osteonecrosis and osteoarthritis.
Figure 1
(a)
(c)
MSCs
14
Number of Trials
12
Osteocytes
Other Lineages?
10 8 6 4 2 0
Chondrocytes
Adipocytes
Phase 0 Phase 1 Phase 1 | Phase 2 Phase 2 | Phase 3 Phase 2 Phase 3
Clinical Trial Phase
(b) Neurodegenerative, 13%
Other, 15%
Wounds and Injuries, 8%
Ankylosing Spondylitis, 6% Avascular/ Osteonecrosis, 12%
Nonunion, 18%
Lung, 4% Musculoskeletal, 19%
Osteoarthritis, 36%
Liver, 8%
Musculoskeletal Other, 21%
Immune Rejection/ Graft vs Host, 7%
Rheumatoid Arthritis, 6%
Gastro, 5%
Blood/Circulation/Heart, 17% Diabetes, 4% Current Opinion in Pharmacology
The value of MSCs in musculoskeletal disease therapy. (a) Schematic summary of the differentiation potential of MSCs. (b) Analysis of clinical trials by disease type registered at clinicaltrials.gov using MSCs. The database was searched using the search criteria ‘mesenchymal stem cells’ OR ‘mesenchymal stromal cells’ to find all relevant clinical trials. The clinical trials here have been registered since January 2011 and have a known status. (c) Clinical trials relevant to musculoskeletal conditions using MSCs listed by phase. Data accessed: 14th November 2013. Current Opinion in Pharmacology 2014, 16:1–6
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Stem cell treatment for musculoskeletal disease Carstairs and Genever 3
To determine recent activity in this area, we mined the clinical trials database using an approach similar to Trounson et al. [17]. A total of 173 clinical studies have commenced since January 2011, with nearly a fifth of these relevant to musculoskeletal disease (Figure 1b). The majority of trials examining MSCs in musculoskeletal disease are in Phase 2 (proof of concept in human patients) or a mixture of Phase 1 (safety)/Phase 2 (Figure 1c). This review will examine some of the preclinical and clinical trials data to determine the current treatment options for using MSCs in musculoskeletal disease.
MSC therapy in cartilage repair The nature of cartilage tissue, being both avascular and hypocellular, leaves a limited capacity for self-repair and regeneration. It also makes it difficult for native MSCs to migrate to the damaged tissue in order to (re)generate functional chondrocytes. Cartilage damage and defects are therefore slow to repair without appropriate intervention. Osteoarthritis (OA) is a degenerative disease characterised by a loss of cartilage and bony overgrowth in a joint inducing a local inflammatory reaction. Clinical symptoms present mainly as pain, stiffness and immobility. OA is the most common form of arthritis worldwide; approximately a third of all adults aged 45 and over has sought treatment for OA in the UK alone and the incidence of this musculoskeletal disease is rising [18]. OA can affect any joint within the body but is most prevalent in the knee and hip. There is no treatment available that improves or reverses the degeneration of OA and the healing process is extremely slow [19]. Where healing cannot occur, secondary fibrosis is likely, meaning that degeneration of these tissues continues. Surgical options are often associated with complications and/or failure, driving the need for new, permanent biological treatment options [19]. Since January 2011, 36% of all clinical trials relating to musculoskeletal disease using MSCs have focused on OA [20]. Autologous cell therapy generally consists of isolating cells from patients, expanding the cells in vitro before direct delivery of the expanded cells back into the diseased tissue of the patient. There are two suggested methods of approach when implanting MSCs into patients, either during surgery, where the use of cellsupportive scaffolds can be implemented, or through less invasive procedures such as intra-articular injection. The prevalence of MSC-like cells in various tissues can also reduce the invasiveness of MSC harvest, compared to isolation from bone marrow for example [21]. Intra-articular injection was first reported in 2008, where a 46 year old male patient was administered autologous MSCs, with no adverse effects and a positive outcome reported 6 months after treatment. The patient showed an increase in meniscus and cartilage volume in addition to an increased range of movement and decreased pain score [22]. Since then, similar findings have been reported. The majority of patients treated also showed a degree of improvement www.sciencedirect.com
both in subjective and physical parameters [23,24–26]. Results varied dependent on age and the progression of the OA, leading to the suggestion that intra-articular injections may only be suitable for patients with early onset OA when the defect is present in the cartilage alone [23,27].
MSC therapy in bone repair As normal bone development and remodelling relies on MSC activity, the rationale for using MSC therapy to aid bone regeneration in disease would seem clear. Currently, the preferred treatment is autologous bone grafting which involves removing a bone graft from the patient and transplanting it to the required site. This effectively transplants MSCs already present in the bone in an environment suitable to stimulate osteogenesis, however, there are issues with donor site morbidity and volume restrictions [28]. Another treatment option involves injecting bone marrow aspirate directly into the defect site, which has been used in both non-unions and cysts [29,30]. The success rate of this therapy is highly variable and depends on the number of colony-forming units fibroblastic (CFU-Fs, an indication of progenitor cell activity) present within the aspirate which is age-dependent and varies greatly between individuals [31]. Implantation of three-dimensional (3D) biomimetic scaffolds, seeded with MSCs expanded in vitro, can aid voidfilling and host tissue integration. Proof of concept has been demonstrated in pre-clinical studies using hydroxyapatite-based scaffolds implanted into mice, dogs and horses to name but a few [32–35]. In all cases, bone formation was observed. The use of biocompatible scaffolds is an improvement in comparison to traditional implant material such as titanium, as they can be engineered with interconnected porosity, appropriate resorption rates and allow for the creation of an osteoinductive environment [3]. Nevertheless, there are issues with the use of cell-seeded scaffolds; MSCs undergo replicative senescence and phenotypic drift during ex vivo culture. After a number of passages, cells demonstrate morphological abnormalities, changes in surface marker expression and ultimately growth arrest [36]. MSCs therefore cannot be grown for prolonged periods in vitro, restricting the numbers available for implantation and it is yet to be determined the precise number of MSCs required for treatment [37]. In situ techniques using cell-free scaffolds that elicit a response in the resident host cells may to some extent circumvent problems seen when loading scaffolds with cells [38,39]. Both synthetic and natural materials have been used to synthesise scaffolds which are engineered to provide stability to the regenerating bone. However, scaffolds are being increasingly developed to be both osteoconductive and osteoinductive thus not only providing mechanical stability but also an environment that Current Opinion in Pharmacology 2014, 16:1–6
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further stimulates osteogenesis, which can be achieved using various methods [40]. For example, the topography of scaffolds has been shown to influence growth, adhesion and differentiation of cells and a specific elasticity has been determined that induces an osteogenic effect [41,42]. In addition, growth factors can be covalently attached to the scaffold to promote osteogenesis and vascularisation (such as BMP-2 and VEGF) [43]. Cellfree scaffolds have already been successfully used to treat various complaints, including use in spinal and cranial surgery, but these scaffolds all utilise differing materials [44]. A comparative study of the various cell-free scaffolds in use does not appear to have been conducted and may well be required to progress this technology further.
MSC therapy in tendon repair Tendons, like many other tissues, degenerate with age leading to ruptures and cases of tendonitis [45]; tendon injuries are also commonplace in recreation/sport. Tendons are a connective tissue and, like cartilage, have poor vasculature resulting in a low healing capacity [46]. These problems with tendon self-regeneration have driven interest in tissue engineering and stem cell technology in order to improve repair rates, and stem cell tendon precursors have been identified in human tissue [47]. Since 2011, there has been only one clinical trial started in
humans examining MSC-augmented repair of lateral epicondylitis, more commonly known as ‘tennis elbow’ [20]. This study has been classified as Phase 0 indicating a first-in-human study; current research using MSCs for tendon repair has been limited mostly to studies in animal models. The use of synovial MSCs to aid repair of an anterior cruciate ligament rupture using the Achilles tendon demonstrated increased numbers of collagen fibres compared to a control group after just 7 days. However, by 4 weeks there was no significant difference [48]. Various studies have also reported that after a given period of time there was no significant improvement in MSC-treated injuries compared to controls, suggesting that MSCs may only be beneficial in early tendon repair [49]. Tendon damage is also common and often careerending in racehorses; several studies have therefore determined the effectiveness of MSC treatment for equine tendon repair in naturally occurring tendinitis. No adverse effects were noted in any of the studies undertaken with the majority of horses able to return to racing after MSC treatment [50,51,52]. This outcome compared favourably to horses treated with pin firing, a traditional alternative that involves stimulating inflammation via cauterisation [52]. Entheses connect a tendon or ligament to the bone and degenerate with age leading to ruptures. A study examining the Achilles tendon enthesis
Figure 2
Mesenchymal Stem Cells
Pros
Cons
Autologous Heterogeneity Allogeneic potential Limited expansion Ease of use Senescence Research and clinical experience Established differentiation protocols
Musculoskeletal Disease Therapy
Induced Pluripotent Stem Cells Autologous Pluripotent High cell yield Research experience
Teratoma risk Genetically modified Low efficiency Epigenetics
Pluripotent High cell yield Research experience
Allogeneic Teratoma risk Ethics
Embryonic Stem Cells
Current Opinion in Pharmacology
Schematic summary of stem cell therapy for musculoskeletal disease. Mesenchymal stem/stromal cells (MSCs) can be isolated from different tissues, though bone marrow is often the primary source. Induced pluripotent stem cells (iPSCs) can be generated from a range of somatic cell types, though most frequently studied using dermal fibroblasts. Embryonic stem cells (ESCs) are generated from the inner cell mass of the early embryo blastocyst. The use of MSCs, iPSCs and ESCs in musculoskeletal disease therapy has advantages and disadvantages; currently MSCs are the cells of choice. Current Opinion in Pharmacology 2014, 16:1–6
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Stem cell treatment for musculoskeletal disease Carstairs and Genever 5
in rats when grafted to the anterior cruciate ligament in the knee demonstrated that treatment with MSCs resulted in an organised enthisis regeneration resembling that of a native enthisis. This was in comparison to treatment with chondrocytes, which formed an enthisis but without an organised structure [53].
Acknowledgments We would like to thank The National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC/K001671/1) and Arthritis Research UK Tissue Engineering Centre (19429).
References and recommended reading Papers of particular interest, published within the period of review, have been highlighted as: of special interest of outstanding interest
Issues with MSC therapy The problem of MSC heterogeneity discussed earlier must be addressed. MSCs cannot be reproducibly isolated due to the lack of unique cell surface markers [54]. Commonly used defining criteria suggest that MSCs should be isolated by plastic adherence, express CD105, CD73 and CD90, and lack expression of CD45, CD34, CD14 or CD11b, CD79a or CD19 and HLA-DR surface molecules [11]. However, this definition does not describe a stem cell population and until this is achieved, clinical studies will continue to use mixed stromal cells with unclear or unpredictable differentiation capacity. Though some will argue the evidence of clinical benefit with heterogeneous MSCs, existing and future studies that indicate little, no or adverse effects through the use of undefined MSCs, will actually hold back clinical development, which could impact on other areas of cell-based therapy. The lack of unique markers may be biologically meaningful, reflecting the existence of different MSC subpopulations with specific in vivo (clinically relevant) functions. Tracking studies have failed to faithfully determine if MSCs integrate into the host tissue post-implantation, this information is needed to determine effect. Finally, it has been reported in several studies across various musculoskeletal diseases, that MSC therapy appears to be beneficial only in certain patient groups, for example, patients under the age of 55 in OA [23]. Patient stratification with predictive biomarkers and guidelines for individual suitability would need to be explored fully to improve outcome.
Conclusion Musculoskeletal disease is the most common cause of severe-long term pain and restricted mobility, and treatment of many of these diseases is limited to symptom management. MSCs differentiate into cell types relevant to musculoskeletal diseases and are able to secrete growth factors to stimulate a repair-appropriate environment. Various studies have been conducted in both animal models and clinical trials demonstrating the safety and clinical benefit of MSC therapy. Across different forms of musculoskeletal disease, MSC therapy has resulted in greater healing than is possible with conventional alternatives. However, issues with MSC heterogeneity, insufficient cell numbers and patient suitability need to be addressed to enable MSC treatments for musculoskeletal disease to be adopted on a wider scale (see Figure 2). www.sciencedirect.com
1.
Woolf AD, Pfleger B: Burden of major musculoskeletal conditions. Bull World Health Organ 2003, 81:646-656.
2.
Brooks P: The burden of musculoskeletal disease — a global perspective. Clin Rheumatol 2006, 25:778-781.
3.
Amini AR, Laurencin CT, Nukavarapu SP: Bone tissue engineering: recent advances and challenges. Crit Rev Biomed Eng 2012, 40:363-408.
4.
Cheng A, Hardingham TE, Kimber SJ: Generating cartilage repair from pluripotent stem cells. Tissue Eng Part B Rev 2013 http://dx.doi.org/10.1089/ten.TEB.2012.0757.
5.
Seminatore C, Polentes J, Ellman D, Kozubenko N, Itier V, Tine S, Tritschler L, Brenot M, Guidou E, Blondeau J et al.: The postischemic environment differentially impacts teratoma or tumor formation after transplantation of human embryonic stem cell-derived neural progenitors. Stroke J Cereb Circ 2010, 41:153-159.
6.
Nussbaum J, Minami E, Laflamme MA, Virag JAI, Ware CB, Masino A, Muskheli V, Pabon L, Reinecke H, Murry CE: Transplantation of undifferentiated murine embryonic stem cells in the heart: teratoma formation and immune response. FASEB J 2007, 21:1345-1357.
7.
Takahashi K, Tanabe K, Ohnuki M, Narita M, Ichisaka T, Tomoda K, Yamanaka S: Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell 2007, 131:861-872.
8.
Kim M-J, Son MJ, Son M-Y, Seol B, Kim J, Park J, Kim JH, Kim YH, Park SA, Lee C-H et al.: Generation of human induced pluripotent stem cells from osteoarthritis patient-derived synovial cells. Arthritis Rheum 2011, 63:3010-3021.
9.
Wei Y, Zeng W, Wan R, Wang J, Zhou Q, Qiu S, Singh SR: Chondrogenic differentiation of induced pluripotent stem cells from osteoarthritic chondrocytes in alginate matrix. Eur Cell Mater 2012, 23:1-12.
10. Diekman BO, Christoforou N, Willard VP, Sun H, SanchezAdams J, Leong KW, Guilak F: Cartilage tissue engineering using differentiated and purified induced pluripotent stem cells. Proc Natl Acad Sci U S A 2012, 109:19172-19177. 11. Dominici M, Le Blanc K, Mueller I, Slaper-Cortenbach I, Marini F, Krause D, Deans R, Keating A, Prockop D, Horwitz E: Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement. Cytotherapy 2006, 8:315-317. 12. Pittenger MF, Mackay AM, Beck SC, Jaiswal RK, Douglas R, Mosca JD, Moorman MA, Simonetti DW, Craig S, Marshak DR: Multilineage potential of adult human mesenchymal stem cells. Science 1999, 284:143-147. 13. Haynesworth SE, Baber MA, Caplan AI: Cytokine expression by human marrow-derived mesenchymal progenitor cells in vitro: effects of dexamethasone and IL-1 alpha. J Cell Physiol 1996, 166:585-592. 14. Caplan AI, Dennis JE: Mesenchymal stem cells as trophic mediators. J Cell Biochem 2006, 98:1076-1084. 15. Kolf CM, Cho E, Tuan RS: Mesenchymal stromal cells. Biology of adult mesenchymal stem cells: regulation of niche, selfrenewal and differentiation. Arthritis Res Ther 2007, 9:204. 16. English K: Mechanisms of mesenchymal stromal cell immunomodulation. Immunol Cell Biol 2013, 91:19-26. Current Opinion in Pharmacology 2014, 16:1–6
6 Musculoskeletal
17. Trounson A, Thakar RG, Lomax G, Gibbons D: Clinical trials for stem cell therapies. BMC Med 2011, 9:52. 18. Arthritis Research UK: Osteoarthritis in General Practice. 2013. thorough report exploring the impact of osteoarthritis in the UK and the A recommendations required to address the socio-economic impact of this musculoskeletal disease. 19. Sarzi-Puttini P, Cimmino MA, Scarpa R, Caporali R, Parazzini F, Zaninelli A, Atzeni F, Canesi B: Osteoarthritis: an overview of the disease and its treatment strategies. Semin Arthritis Rheum 2005, 35:1-10.
reconstruction of the mouse calvarium and mandible. Stem Cells 2006, 24:2140-2149. 36. Hayflick L: The limited in vitro lifetime of human diploid cell strains. Exp Cell Res 1965, 37:614-636. 37. Qi Y, Feng G, Yan W: Mesenchymal stem cell-based treatment for cartilage defects in osteoarthritis. Mol Biol Rep 2012, 39:5683-5689.
20. Home — ClinicalTrials.gov.; 2013.
38. Schneider U, Schmidt-Rohlfing B, Gavenis K, Maus U, MuellerRath R, Andereya S: A comparative study of 3 different cartilage repair techniques. Knee Surg Sports Traumatol Arthrosc 2011, 19:2145-2152.
21. Kern S, Eichler H, Stoeve J, Klu¨ter H, Bieback K: Comparative analysis of mesenchymal stem cells from bone marrow, umbilical cord blood, or adipose tissue. Stem Cells 2006, 24:1294-1301.
39. Schu¨ettler KF, Struewer J, Rominger MB, Rexin P, Efe T: Repair of a chondral defect using a cell free scaffold in a young patient — a case report of successful scaffold transformation and colonisation. BMC Surg 2013, 13:11.
22. Centeno CJ, Busse D, Kisiday J, Keohan C, Freeman M, Karli D: Increased knee cartilage volume in degenerative joint disease using percutaneously implanted, autologous mesenchymal stem cells. Pain Physician 2008, 11:343-353.
40. Bueno EM, Glowacki J: Cell-free and cell-based approaches for bone regeneration. Nat Rev Rheumatol 2009, 5:685-697.
23. Koh Y-G, Choi Y-J: Infrapatellar fat pad-derived mesenchymal stem cell therapy for knee osteoarthritis. Knee 2012, 19:902-907. A larger study involving 25 patients demonstrating the safety and efficacy of treating patients with MSCs isolated using a non-invasive extraction and treatment. 24. Davatchi F, Abdollahi BS, Mohyeddin M, Shahram F, Nikbin B: Mesenchymal stem cell therapy for knee osteoarthritis. Preliminary report of four patients. Int J Rheum Dis 2011, 14:211-215. 25. Koh Y-G, Jo S-B, Kwon O-R, Suh D-S, Lee S-W, Park S-H, Choi YJ: Mesenchymal stem cell injections improve symptoms of knee osteoarthritis. Arthroscopy 2013, 29:748-755. 26. Emadedin M, Aghdami N, Taghiyar L, Fazeli R, Moghadasali R, Jahangir S, Farjad R, Baghaban Eslaminejad M: Intra-articular injection of autologous mesenchymal stem cells in six patients with knee osteoarthritis. Arch Iran Med 2012, 15:422-428. 27. No¨th U, Steinert AF, Tuan RS: Technology insight: adult mesenchymal stem cells for osteoarthritis therapy. Nat Clin Pract Rheumatol 2008, 4:371-380. 28. Dawson JI, Kanczler J, Tare R, Kassem M, Oreffo RC: Bridging the gap: bone regeneration using skeletal stem cell-based strategies — where are we now? Stem Cells 2013 http:// dx.doi.org/10.1002/stem.1559. This review gives extensive coverage of the various therapeutic options in bone regeneration including scaffold technology. 29. Hernigou P, Poignard A, Manicom O, Mathieu G, Rouard H: The use of percutaneous autologous bone marrow transplantation in nonunion and avascular necrosis of bone. J Bone Joint Surg Br 2005, 87:896-902. 30. Docquier P-L, Delloye C: Treatment of simple bone cysts with aspiration and a single bone marrow injection. J Pediatr Orthop 2003, 23:766-773. 31. Hernigou P, Poignard A, Beaujean F, Rouard H: Percutaneous autologous bone-marrow grafting for nonunions. Influence of the number and concentration of progenitor cells. J Bone Joint Surg Am 2005, 87:1430-1437. 32. Liu G, Zhang Y, Liu B, Sun J, Li W, Cui L: Bone regeneration in a canine cranial model using allogeneic adipose derived stem cells and coral scaffold. Biomaterials 2013, 34:2655-2664. 33. Arinzeh TL, Peter SJ, Archambault MP, Van Den Bos C, Gordon S, Kraus K, Smith A, Kadiyala S: Allogeneic mesenchymal stem cells regenerate bone in a critical-sized canine segmental defect. J Bone Joint Surg Am 2003, 85:1927-1935.
41. Norman JJ, Desai TA: Methods for fabrication of nanoscale topography for tissue engineering scaffolds. Ann Biomed Eng 2006, 34:89-101. 42. Engler AJ, Sen S, Sweeney HL, Discher DE: Matrix elasticity directs stem cell lineage specification. Cell 2006, 126:677-689. 43. Blackwood KA, Bock N, Dargaville TR, Ann Woodruff M: Scaffolds for growth factor delivery as applied to bone tissue engineering. Int J Polym Sci 2012, 201:2 http://dx.doi.org/ 10.1155/2012/174942. 44. Billstro¨m GH, Blom AW, Larsson S, Beswick AD: Application of scaffolds for bone regeneration strategies: current trends and future directions. Injury 2013, 44(Suppl 1):S28-S33. 45. MacLean S, Khan WS, Malik AA, Snow M, Anand S: Tendon regeneration and repair with stem cells. Stem Cells Int 2011:2012 http://dx.doi.org/10.1155/2012/316281. 46. Fenwick SA, Hazleman BL, Riley GP: The vasculature and its role in the damaged and healing tendon. Arthritis Res 2002, 4:252260. 47. Tempfer H, Wagner A, Gehwolf R, Lehner C, Tauber M, Resch H, Bauer HC: Perivascular cells of the supraspinatus tendon express both tendon- and stem cell-related markers. Histochem Cell Biol 2009, 131:733-741. 48. Ju Y-J, Muneta T, Yoshimura H, Koga H, Sekiya I: Synovial mesenchymal stem cells accelerate early remodeling of tendon-bone healing. Cell Tissue Res 2008, 332:469-478. 49. Chong AKS, Chang J, Go JCH: Mesenchymal stem cells and tendon healing. Front Biosci 2009, 14:4598-4605. 50. Smith RKW, Werling NJ, Dakin SG, Alam R, Goodship AE, Dudhia J: Beneficial effects of autologous bone marrowderived mesenchymal stem cells in naturally occurring tendinopathy. PLoS ONE 2013, 8:e75697. 51. Lacitignola L, Crovace A, Rossi G, Francioso E: Cell therapy for tendinitis, experimental and clinical report. Vet Res Commun 2008, 32(Suppl 1):S33-S38. 52. Renzi S, Ricco` S, Dotti S, Sesso L, Grolli S, Cornali M, Carlin S, Patruno M, Cinotti S, Ferrari M: Autologous bone marrow mesenchymal stromal cells for regeneration of injured equine ligaments and tendons: a clinical report. Res Vet Sci 2013, 95:272-277. This study demonstrates the use of MSCs in equine orthopaedics and its success in comparison to traditional alternative treatments such as pin firing.
34. Krebsbach PH, Kuznetsov SA, Satomura K, Emmons RV, Rowe DW, Robey PG: Bone formation in vivo: comparison of osteogenesis by transplanted mouse and human marrow stromal fibroblasts. Transplantation 1997, 63:1059-1069.
53. Nourissat G, Diop A, Maurel N, Salvat C, Dumont S, Pigenet A, Gosset M, Houard X, Berenbaum F: Mesenchymal stem cell therapy regenerates the native bone–tendon junction after surgical repair in a degenerative rat model. PLoS ONE 2010, 5:e12248.
35. Mankani MH, Kuznetsov SA, Wolfe RM, Marshall GW, Robey PG: In vivo bone formation by human bone marrow stromal cells:
54. Wagner W, Ho AD: Mesenchymal stem cell preparations — comparing apples and oranges. Stem Cell Rev 2007, 3:239-248.
Current Opinion in Pharmacology 2014, 16:1–6
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ScienceDirect Stem cell treatment for musculoskeletal disease Alice Carstairs and Paul Genever Musculoskeletal disease is prevalent in society and with an ageing population, the incidence and impact on public health are set to rise. Severe long-term pain and mobility restriction impair the welfare and quality of life of patients with musculoskeletal disease. Current treatments are often restricted to the management of symptoms or temporary replacement with inert materials, rather than targeting prevention and cure. There is an urgent need for alternative biological approaches to musculoskeletal disease therapy. The rapid emergence of stem cell technologies, primarily using ‘mesenchymal stem cells’ (MSCs), has resulted in a number of pre-clinical and clinical studies in an effort to provide more effective treatment options. Challenges exist in bench-to-bedside translation, but they are not insurmountable. Addresses Department of Biology (Area 9), University of York, York YO10 5DD, UK Corresponding author: Genever, Paul ([email protected])
Current Opinion in Pharmacology 2014, 16:1–6 This review comes from a themed issue on Musculoskeletal Edited by Alison Gartland and Lynne J Hocking
1471-4892/$ – see front matter, # 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.coph.2014.01.005
Introduction Our understanding of stem cells has accelerated in recent years, and with it their potential use in regenerative medicine to treat a spectrum of human disorders. The World Health Organisation has described musculoskeletal disease as the most common cause of severe long-term pain and physical disability [1]. The classification of musculoskeletal disease is broad including both acute and chronic conditions; they can affect any part of the musculoskeletal system, namely bones, muscle, cartilage, tendons, ligaments, joints and nerves. With an increasingly ageing population, the incidence of musculoskeletal disease is rising and predicted to be a significant socio-economic burden on society, yet the complex nature of these diseases generally means that treatment options are limited to managing symptoms rather than prevention and cure [2]. This unmet need is driving rapid advances in stem cell technology with the potential of using regeneration therapy to aid these conditions. www.sciencedirect.com
Stem cells — embryonic stem cells and induced pluripotent stem cells Stem cells are defined by their ability to undergo asymmetric cell division to self-renew, maintaining a stem cell pool, and give rise to differentiated progeny. This inherent trait makes stem cells a very attractive choice for regenerative therapies. Stem cells can be broadly characterised into two groups; embryonic stem cells (ESCs) and adult stem cells. ESCs are derived from the inner cell mass of blastocyst-stage embryos and possess the ability to differentiate into all cell derivatives from the three primary germ layers, ectoderm, endoderm and mesoderm (from which skeletal tissues arise). The plasticity of ESCs makes them attractive therapeutic cells for many clinical applications including the treatment of musculoskeletal disease [3,4]. Despite this potential, the use of ESCs in regeneration therapy does require a number of issues to be resolved. The implantation of ESCs has been reported to result in hyperproliferation giving rise to teratomas; cancerous tumours possessing cells/ tissue from the three primary germ layers [5]. Additionally, the incompatibility of the host cells with the newly implanted ESCs can lead to immune rejection [6]. Finally, most reported protocols require ESCs to be partially differentiated before implantation in order to ensure their progression down the correct lineage. This typically uses animal products in culture medium generating a risk of xenobiotic transfer, which will need to be addressed before ESC technology can be used in a clinical setting. Induced pluripotent stem cells (iPSCs) can be generated by introducing factors (such as Oct4, Sox2, Klf4 and cMyc) into somatic cells to initiate reprogramming to an ESC-like state [7]. Consequently, iPSCs provide a primitive, patientspecific cell source for directed differentiation to new tissues in degenerative disorders, including musculoskeletal disease. Recent work has shown that iPSCs can be produced from osteoarthritic synovial cells [8] and chondrocytes [9] with subsequent re-differentiation to cartilage tissue, and improved outcome for the homogeneity and quality of chondrogenic differentiation [10]. iPSC technology could transform regenerative medicine strategy, but concerns associated with teratoma risk, use of (viral) gene delivery and low reprogramming efficiency remain. The technical challenges associated with the use of pluripotent stem cells in therapy are likely to be addressed in time; however, the current lead therapeutic cell for musculoskeletal disease is the ‘MSC’, which will be main focus of this review.
Stem cells — ‘MSCs’ The term ‘MSC’ has been given to mesenchymal stem cells, mesenchymal stromal cells and bone marrow stromal cells (as well as other related cell populations). In Current Opinion in Pharmacology 2014, 16:1–6
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truth, very few studies have employed authentic mesenchymal stem cells (i.e. that are homogenous, identifiable selfrenewing cells capable of differentiation into all mesenchymal tissues) and the vast majority of work is performed using heterogeneous stromal cultures. Still, the ‘MSC’ abbreviation has been widely adopted and will be used here with this caveat in mind. MSCs provide an attractive option for cell-based therapy as they remove some of the technical constraints (and ethical issues) associated with ESCs and iPSCs. MSCs hold great promise for musculoskeletal disease in particular, as they can be isolated from various tissues and induced to differentiate into relevant cell types such as osteoblasts (bone), adipocytes (fat) and chondrocytes (cartilage) (Figure 1a) [11,12]. The pathways governing lineage
specification are not entirely clear; however, there are two additional intrinsic properties of MSCs that aid tissue regeneration. First is their ability to secrete a wide range of growth factors, which have trophic effects on surrounding host cells [13,14]. Second, once administered these cells can coordinate differentiation in tandem with differentiated and undifferentiated resident host cells [15]. Combined with the relative ease of expanding these cells in culture, a partially differentiated start point and possible immunomodulatory properties [16], MSCs are an attractive source for clinical usage. There have been many clinical trials using MSCs, particularly targeting musculoskeletal diseases such as fracture nonunions, avascular/osteonecrosis and osteoarthritis.
Figure 1
(a)
(c)
MSCs
14
Number of Trials
12
Osteocytes
Other Lineages?
10 8 6 4 2 0
Chondrocytes
Adipocytes
Phase 0 Phase 1 Phase 1 | Phase 2 Phase 2 | Phase 3 Phase 2 Phase 3
Clinical Trial Phase
(b) Neurodegenerative, 13%
Other, 15%
Wounds and Injuries, 8%
Ankylosing Spondylitis, 6% Avascular/ Osteonecrosis, 12%
Nonunion, 18%
Lung, 4% Musculoskeletal, 19%
Osteoarthritis, 36%
Liver, 8%
Musculoskeletal Other, 21%
Immune Rejection/ Graft vs Host, 7%
Rheumatoid Arthritis, 6%
Gastro, 5%
Blood/Circulation/Heart, 17% Diabetes, 4% Current Opinion in Pharmacology
The value of MSCs in musculoskeletal disease therapy. (a) Schematic summary of the differentiation potential of MSCs. (b) Analysis of clinical trials by disease type registered at clinicaltrials.gov using MSCs. The database was searched using the search criteria ‘mesenchymal stem cells’ OR ‘mesenchymal stromal cells’ to find all relevant clinical trials. The clinical trials here have been registered since January 2011 and have a known status. (c) Clinical trials relevant to musculoskeletal conditions using MSCs listed by phase. Data accessed: 14th November 2013. Current Opinion in Pharmacology 2014, 16:1–6
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Stem cell treatment for musculoskeletal disease Carstairs and Genever 3
To determine recent activity in this area, we mined the clinical trials database using an approach similar to Trounson et al. [17]. A total of 173 clinical studies have commenced since January 2011, with nearly a fifth of these relevant to musculoskeletal disease (Figure 1b). The majority of trials examining MSCs in musculoskeletal disease are in Phase 2 (proof of concept in human patients) or a mixture of Phase 1 (safety)/Phase 2 (Figure 1c). This review will examine some of the preclinical and clinical trials data to determine the current treatment options for using MSCs in musculoskeletal disease.
MSC therapy in cartilage repair The nature of cartilage tissue, being both avascular and hypocellular, leaves a limited capacity for self-repair and regeneration. It also makes it difficult for native MSCs to migrate to the damaged tissue in order to (re)generate functional chondrocytes. Cartilage damage and defects are therefore slow to repair without appropriate intervention. Osteoarthritis (OA) is a degenerative disease characterised by a loss of cartilage and bony overgrowth in a joint inducing a local inflammatory reaction. Clinical symptoms present mainly as pain, stiffness and immobility. OA is the most common form of arthritis worldwide; approximately a third of all adults aged 45 and over has sought treatment for OA in the UK alone and the incidence of this musculoskeletal disease is rising [18]. OA can affect any joint within the body but is most prevalent in the knee and hip. There is no treatment available that improves or reverses the degeneration of OA and the healing process is extremely slow [19]. Where healing cannot occur, secondary fibrosis is likely, meaning that degeneration of these tissues continues. Surgical options are often associated with complications and/or failure, driving the need for new, permanent biological treatment options [19]. Since January 2011, 36% of all clinical trials relating to musculoskeletal disease using MSCs have focused on OA [20]. Autologous cell therapy generally consists of isolating cells from patients, expanding the cells in vitro before direct delivery of the expanded cells back into the diseased tissue of the patient. There are two suggested methods of approach when implanting MSCs into patients, either during surgery, where the use of cellsupportive scaffolds can be implemented, or through less invasive procedures such as intra-articular injection. The prevalence of MSC-like cells in various tissues can also reduce the invasiveness of MSC harvest, compared to isolation from bone marrow for example [21]. Intra-articular injection was first reported in 2008, where a 46 year old male patient was administered autologous MSCs, with no adverse effects and a positive outcome reported 6 months after treatment. The patient showed an increase in meniscus and cartilage volume in addition to an increased range of movement and decreased pain score [22]. Since then, similar findings have been reported. The majority of patients treated also showed a degree of improvement www.sciencedirect.com
both in subjective and physical parameters [23,24–26]. Results varied dependent on age and the progression of the OA, leading to the suggestion that intra-articular injections may only be suitable for patients with early onset OA when the defect is present in the cartilage alone [23,27].
MSC therapy in bone repair As normal bone development and remodelling relies on MSC activity, the rationale for using MSC therapy to aid bone regeneration in disease would seem clear. Currently, the preferred treatment is autologous bone grafting which involves removing a bone graft from the patient and transplanting it to the required site. This effectively transplants MSCs already present in the bone in an environment suitable to stimulate osteogenesis, however, there are issues with donor site morbidity and volume restrictions [28]. Another treatment option involves injecting bone marrow aspirate directly into the defect site, which has been used in both non-unions and cysts [29,30]. The success rate of this therapy is highly variable and depends on the number of colony-forming units fibroblastic (CFU-Fs, an indication of progenitor cell activity) present within the aspirate which is age-dependent and varies greatly between individuals [31]. Implantation of three-dimensional (3D) biomimetic scaffolds, seeded with MSCs expanded in vitro, can aid voidfilling and host tissue integration. Proof of concept has been demonstrated in pre-clinical studies using hydroxyapatite-based scaffolds implanted into mice, dogs and horses to name but a few [32–35]. In all cases, bone formation was observed. The use of biocompatible scaffolds is an improvement in comparison to traditional implant material such as titanium, as they can be engineered with interconnected porosity, appropriate resorption rates and allow for the creation of an osteoinductive environment [3]. Nevertheless, there are issues with the use of cell-seeded scaffolds; MSCs undergo replicative senescence and phenotypic drift during ex vivo culture. After a number of passages, cells demonstrate morphological abnormalities, changes in surface marker expression and ultimately growth arrest [36]. MSCs therefore cannot be grown for prolonged periods in vitro, restricting the numbers available for implantation and it is yet to be determined the precise number of MSCs required for treatment [37]. In situ techniques using cell-free scaffolds that elicit a response in the resident host cells may to some extent circumvent problems seen when loading scaffolds with cells [38,39]. Both synthetic and natural materials have been used to synthesise scaffolds which are engineered to provide stability to the regenerating bone. However, scaffolds are being increasingly developed to be both osteoconductive and osteoinductive thus not only providing mechanical stability but also an environment that Current Opinion in Pharmacology 2014, 16:1–6
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further stimulates osteogenesis, which can be achieved using various methods [40]. For example, the topography of scaffolds has been shown to influence growth, adhesion and differentiation of cells and a specific elasticity has been determined that induces an osteogenic effect [41,42]. In addition, growth factors can be covalently attached to the scaffold to promote osteogenesis and vascularisation (such as BMP-2 and VEGF) [43]. Cellfree scaffolds have already been successfully used to treat various complaints, including use in spinal and cranial surgery, but these scaffolds all utilise differing materials [44]. A comparative study of the various cell-free scaffolds in use does not appear to have been conducted and may well be required to progress this technology further.
MSC therapy in tendon repair Tendons, like many other tissues, degenerate with age leading to ruptures and cases of tendonitis [45]; tendon injuries are also commonplace in recreation/sport. Tendons are a connective tissue and, like cartilage, have poor vasculature resulting in a low healing capacity [46]. These problems with tendon self-regeneration have driven interest in tissue engineering and stem cell technology in order to improve repair rates, and stem cell tendon precursors have been identified in human tissue [47]. Since 2011, there has been only one clinical trial started in
humans examining MSC-augmented repair of lateral epicondylitis, more commonly known as ‘tennis elbow’ [20]. This study has been classified as Phase 0 indicating a first-in-human study; current research using MSCs for tendon repair has been limited mostly to studies in animal models. The use of synovial MSCs to aid repair of an anterior cruciate ligament rupture using the Achilles tendon demonstrated increased numbers of collagen fibres compared to a control group after just 7 days. However, by 4 weeks there was no significant difference [48]. Various studies have also reported that after a given period of time there was no significant improvement in MSC-treated injuries compared to controls, suggesting that MSCs may only be beneficial in early tendon repair [49]. Tendon damage is also common and often careerending in racehorses; several studies have therefore determined the effectiveness of MSC treatment for equine tendon repair in naturally occurring tendinitis. No adverse effects were noted in any of the studies undertaken with the majority of horses able to return to racing after MSC treatment [50,51,52]. This outcome compared favourably to horses treated with pin firing, a traditional alternative that involves stimulating inflammation via cauterisation [52]. Entheses connect a tendon or ligament to the bone and degenerate with age leading to ruptures. A study examining the Achilles tendon enthesis
Figure 2
Mesenchymal Stem Cells
Pros
Cons
Autologous Heterogeneity Allogeneic potential Limited expansion Ease of use Senescence Research and clinical experience Established differentiation protocols
Musculoskeletal Disease Therapy
Induced Pluripotent Stem Cells Autologous Pluripotent High cell yield Research experience
Teratoma risk Genetically modified Low efficiency Epigenetics
Pluripotent High cell yield Research experience
Allogeneic Teratoma risk Ethics
Embryonic Stem Cells
Current Opinion in Pharmacology
Schematic summary of stem cell therapy for musculoskeletal disease. Mesenchymal stem/stromal cells (MSCs) can be isolated from different tissues, though bone marrow is often the primary source. Induced pluripotent stem cells (iPSCs) can be generated from a range of somatic cell types, though most frequently studied using dermal fibroblasts. Embryonic stem cells (ESCs) are generated from the inner cell mass of the early embryo blastocyst. The use of MSCs, iPSCs and ESCs in musculoskeletal disease therapy has advantages and disadvantages; currently MSCs are the cells of choice. Current Opinion in Pharmacology 2014, 16:1–6
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Stem cell treatment for musculoskeletal disease Carstairs and Genever 5
in rats when grafted to the anterior cruciate ligament in the knee demonstrated that treatment with MSCs resulted in an organised enthisis regeneration resembling that of a native enthisis. This was in comparison to treatment with chondrocytes, which formed an enthisis but without an organised structure [53].
Acknowledgments We would like to thank The National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC/K001671/1) and Arthritis Research UK Tissue Engineering Centre (19429).
References and recommended reading Papers of particular interest, published within the period of review, have been highlighted as: of special interest of outstanding interest
Issues with MSC therapy The problem of MSC heterogeneity discussed earlier must be addressed. MSCs cannot be reproducibly isolated due to the lack of unique cell surface markers [54]. Commonly used defining criteria suggest that MSCs should be isolated by plastic adherence, express CD105, CD73 and CD90, and lack expression of CD45, CD34, CD14 or CD11b, CD79a or CD19 and HLA-DR surface molecules [11]. However, this definition does not describe a stem cell population and until this is achieved, clinical studies will continue to use mixed stromal cells with unclear or unpredictable differentiation capacity. Though some will argue the evidence of clinical benefit with heterogeneous MSCs, existing and future studies that indicate little, no or adverse effects through the use of undefined MSCs, will actually hold back clinical development, which could impact on other areas of cell-based therapy. The lack of unique markers may be biologically meaningful, reflecting the existence of different MSC subpopulations with specific in vivo (clinically relevant) functions. Tracking studies have failed to faithfully determine if MSCs integrate into the host tissue post-implantation, this information is needed to determine effect. Finally, it has been reported in several studies across various musculoskeletal diseases, that MSC therapy appears to be beneficial only in certain patient groups, for example, patients under the age of 55 in OA [23]. Patient stratification with predictive biomarkers and guidelines for individual suitability would need to be explored fully to improve outcome.
Conclusion Musculoskeletal disease is the most common cause of severe-long term pain and restricted mobility, and treatment of many of these diseases is limited to symptom management. MSCs differentiate into cell types relevant to musculoskeletal diseases and are able to secrete growth factors to stimulate a repair-appropriate environment. Various studies have been conducted in both animal models and clinical trials demonstrating the safety and clinical benefit of MSC therapy. Across different forms of musculoskeletal disease, MSC therapy has resulted in greater healing than is possible with conventional alternatives. However, issues with MSC heterogeneity, insufficient cell numbers and patient suitability need to be addressed to enable MSC treatments for musculoskeletal disease to be adopted on a wider scale (see Figure 2). www.sciencedirect.com
1.
Woolf AD, Pfleger B: Burden of major musculoskeletal conditions. Bull World Health Organ 2003, 81:646-656.
2.
Brooks P: The burden of musculoskeletal disease — a global perspective. Clin Rheumatol 2006, 25:778-781.
3.
Amini AR, Laurencin CT, Nukavarapu SP: Bone tissue engineering: recent advances and challenges. Crit Rev Biomed Eng 2012, 40:363-408.
4.
Cheng A, Hardingham TE, Kimber SJ: Generating cartilage repair from pluripotent stem cells. Tissue Eng Part B Rev 2013 http://dx.doi.org/10.1089/ten.TEB.2012.0757.
5.
Seminatore C, Polentes J, Ellman D, Kozubenko N, Itier V, Tine S, Tritschler L, Brenot M, Guidou E, Blondeau J et al.: The postischemic environment differentially impacts teratoma or tumor formation after transplantation of human embryonic stem cell-derived neural progenitors. Stroke J Cereb Circ 2010, 41:153-159.
6.
Nussbaum J, Minami E, Laflamme MA, Virag JAI, Ware CB, Masino A, Muskheli V, Pabon L, Reinecke H, Murry CE: Transplantation of undifferentiated murine embryonic stem cells in the heart: teratoma formation and immune response. FASEB J 2007, 21:1345-1357.
7.
Takahashi K, Tanabe K, Ohnuki M, Narita M, Ichisaka T, Tomoda K, Yamanaka S: Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell 2007, 131:861-872.
8.
Kim M-J, Son MJ, Son M-Y, Seol B, Kim J, Park J, Kim JH, Kim YH, Park SA, Lee C-H et al.: Generation of human induced pluripotent stem cells from osteoarthritis patient-derived synovial cells. Arthritis Rheum 2011, 63:3010-3021.
9.
Wei Y, Zeng W, Wan R, Wang J, Zhou Q, Qiu S, Singh SR: Chondrogenic differentiation of induced pluripotent stem cells from osteoarthritic chondrocytes in alginate matrix. Eur Cell Mater 2012, 23:1-12.
10. Diekman BO, Christoforou N, Willard VP, Sun H, SanchezAdams J, Leong KW, Guilak F: Cartilage tissue engineering using differentiated and purified induced pluripotent stem cells. Proc Natl Acad Sci U S A 2012, 109:19172-19177. 11. Dominici M, Le Blanc K, Mueller I, Slaper-Cortenbach I, Marini F, Krause D, Deans R, Keating A, Prockop D, Horwitz E: Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement. Cytotherapy 2006, 8:315-317. 12. Pittenger MF, Mackay AM, Beck SC, Jaiswal RK, Douglas R, Mosca JD, Moorman MA, Simonetti DW, Craig S, Marshak DR: Multilineage potential of adult human mesenchymal stem cells. Science 1999, 284:143-147. 13. Haynesworth SE, Baber MA, Caplan AI: Cytokine expression by human marrow-derived mesenchymal progenitor cells in vitro: effects of dexamethasone and IL-1 alpha. J Cell Physiol 1996, 166:585-592. 14. Caplan AI, Dennis JE: Mesenchymal stem cells as trophic mediators. J Cell Biochem 2006, 98:1076-1084. 15. Kolf CM, Cho E, Tuan RS: Mesenchymal stromal cells. Biology of adult mesenchymal stem cells: regulation of niche, selfrenewal and differentiation. Arthritis Res Ther 2007, 9:204. 16. English K: Mechanisms of mesenchymal stromal cell immunomodulation. Immunol Cell Biol 2013, 91:19-26. Current Opinion in Pharmacology 2014, 16:1–6
6 Musculoskeletal
17. Trounson A, Thakar RG, Lomax G, Gibbons D: Clinical trials for stem cell therapies. BMC Med 2011, 9:52. 18. Arthritis Research UK: Osteoarthritis in General Practice. 2013. thorough report exploring the impact of osteoarthritis in the UK and the A recommendations required to address the socio-economic impact of this musculoskeletal disease. 19. Sarzi-Puttini P, Cimmino MA, Scarpa R, Caporali R, Parazzini F, Zaninelli A, Atzeni F, Canesi B: Osteoarthritis: an overview of the disease and its treatment strategies. Semin Arthritis Rheum 2005, 35:1-10.
reconstruction of the mouse calvarium and mandible. Stem Cells 2006, 24:2140-2149. 36. Hayflick L: The limited in vitro lifetime of human diploid cell strains. Exp Cell Res 1965, 37:614-636. 37. Qi Y, Feng G, Yan W: Mesenchymal stem cell-based treatment for cartilage defects in osteoarthritis. Mol Biol Rep 2012, 39:5683-5689.
20. Home — ClinicalTrials.gov.; 2013.
38. Schneider U, Schmidt-Rohlfing B, Gavenis K, Maus U, MuellerRath R, Andereya S: A comparative study of 3 different cartilage repair techniques. Knee Surg Sports Traumatol Arthrosc 2011, 19:2145-2152.
21. Kern S, Eichler H, Stoeve J, Klu¨ter H, Bieback K: Comparative analysis of mesenchymal stem cells from bone marrow, umbilical cord blood, or adipose tissue. Stem Cells 2006, 24:1294-1301.
39. Schu¨ettler KF, Struewer J, Rominger MB, Rexin P, Efe T: Repair of a chondral defect using a cell free scaffold in a young patient — a case report of successful scaffold transformation and colonisation. BMC Surg 2013, 13:11.
22. Centeno CJ, Busse D, Kisiday J, Keohan C, Freeman M, Karli D: Increased knee cartilage volume in degenerative joint disease using percutaneously implanted, autologous mesenchymal stem cells. Pain Physician 2008, 11:343-353.
40. Bueno EM, Glowacki J: Cell-free and cell-based approaches for bone regeneration. Nat Rev Rheumatol 2009, 5:685-697.
23. Koh Y-G, Choi Y-J: Infrapatellar fat pad-derived mesenchymal stem cell therapy for knee osteoarthritis. Knee 2012, 19:902-907. A larger study involving 25 patients demonstrating the safety and efficacy of treating patients with MSCs isolated using a non-invasive extraction and treatment. 24. Davatchi F, Abdollahi BS, Mohyeddin M, Shahram F, Nikbin B: Mesenchymal stem cell therapy for knee osteoarthritis. Preliminary report of four patients. Int J Rheum Dis 2011, 14:211-215. 25. Koh Y-G, Jo S-B, Kwon O-R, Suh D-S, Lee S-W, Park S-H, Choi YJ: Mesenchymal stem cell injections improve symptoms of knee osteoarthritis. Arthroscopy 2013, 29:748-755. 26. Emadedin M, Aghdami N, Taghiyar L, Fazeli R, Moghadasali R, Jahangir S, Farjad R, Baghaban Eslaminejad M: Intra-articular injection of autologous mesenchymal stem cells in six patients with knee osteoarthritis. Arch Iran Med 2012, 15:422-428. 27. No¨th U, Steinert AF, Tuan RS: Technology insight: adult mesenchymal stem cells for osteoarthritis therapy. Nat Clin Pract Rheumatol 2008, 4:371-380. 28. Dawson JI, Kanczler J, Tare R, Kassem M, Oreffo RC: Bridging the gap: bone regeneration using skeletal stem cell-based strategies — where are we now? Stem Cells 2013 http:// dx.doi.org/10.1002/stem.1559. This review gives extensive coverage of the various therapeutic options in bone regeneration including scaffold technology. 29. Hernigou P, Poignard A, Manicom O, Mathieu G, Rouard H: The use of percutaneous autologous bone marrow transplantation in nonunion and avascular necrosis of bone. J Bone Joint Surg Br 2005, 87:896-902. 30. Docquier P-L, Delloye C: Treatment of simple bone cysts with aspiration and a single bone marrow injection. J Pediatr Orthop 2003, 23:766-773. 31. Hernigou P, Poignard A, Beaujean F, Rouard H: Percutaneous autologous bone-marrow grafting for nonunions. Influence of the number and concentration of progenitor cells. J Bone Joint Surg Am 2005, 87:1430-1437. 32. Liu G, Zhang Y, Liu B, Sun J, Li W, Cui L: Bone regeneration in a canine cranial model using allogeneic adipose derived stem cells and coral scaffold. Biomaterials 2013, 34:2655-2664. 33. Arinzeh TL, Peter SJ, Archambault MP, Van Den Bos C, Gordon S, Kraus K, Smith A, Kadiyala S: Allogeneic mesenchymal stem cells regenerate bone in a critical-sized canine segmental defect. J Bone Joint Surg Am 2003, 85:1927-1935.
41. Norman JJ, Desai TA: Methods for fabrication of nanoscale topography for tissue engineering scaffolds. Ann Biomed Eng 2006, 34:89-101. 42. Engler AJ, Sen S, Sweeney HL, Discher DE: Matrix elasticity directs stem cell lineage specification. Cell 2006, 126:677-689. 43. Blackwood KA, Bock N, Dargaville TR, Ann Woodruff M: Scaffolds for growth factor delivery as applied to bone tissue engineering. Int J Polym Sci 2012, 201:2 http://dx.doi.org/ 10.1155/2012/174942. 44. Billstro¨m GH, Blom AW, Larsson S, Beswick AD: Application of scaffolds for bone regeneration strategies: current trends and future directions. Injury 2013, 44(Suppl 1):S28-S33. 45. MacLean S, Khan WS, Malik AA, Snow M, Anand S: Tendon regeneration and repair with stem cells. Stem Cells Int 2011:2012 http://dx.doi.org/10.1155/2012/316281. 46. Fenwick SA, Hazleman BL, Riley GP: The vasculature and its role in the damaged and healing tendon. Arthritis Res 2002, 4:252260. 47. Tempfer H, Wagner A, Gehwolf R, Lehner C, Tauber M, Resch H, Bauer HC: Perivascular cells of the supraspinatus tendon express both tendon- and stem cell-related markers. Histochem Cell Biol 2009, 131:733-741. 48. Ju Y-J, Muneta T, Yoshimura H, Koga H, Sekiya I: Synovial mesenchymal stem cells accelerate early remodeling of tendon-bone healing. Cell Tissue Res 2008, 332:469-478. 49. Chong AKS, Chang J, Go JCH: Mesenchymal stem cells and tendon healing. Front Biosci 2009, 14:4598-4605. 50. Smith RKW, Werling NJ, Dakin SG, Alam R, Goodship AE, Dudhia J: Beneficial effects of autologous bone marrowderived mesenchymal stem cells in naturally occurring tendinopathy. PLoS ONE 2013, 8:e75697. 51. Lacitignola L, Crovace A, Rossi G, Francioso E: Cell therapy for tendinitis, experimental and clinical report. Vet Res Commun 2008, 32(Suppl 1):S33-S38. 52. Renzi S, Ricco` S, Dotti S, Sesso L, Grolli S, Cornali M, Carlin S, Patruno M, Cinotti S, Ferrari M: Autologous bone marrow mesenchymal stromal cells for regeneration of injured equine ligaments and tendons: a clinical report. Res Vet Sci 2013, 95:272-277. This study demonstrates the use of MSCs in equine orthopaedics and its success in comparison to traditional alternative treatments such as pin firing.
34. Krebsbach PH, Kuznetsov SA, Satomura K, Emmons RV, Rowe DW, Robey PG: Bone formation in vivo: comparison of osteogenesis by transplanted mouse and human marrow stromal fibroblasts. Transplantation 1997, 63:1059-1069.
53. Nourissat G, Diop A, Maurel N, Salvat C, Dumont S, Pigenet A, Gosset M, Houard X, Berenbaum F: Mesenchymal stem cell therapy regenerates the native bone–tendon junction after surgical repair in a degenerative rat model. PLoS ONE 2010, 5:e12248.
35. Mankani MH, Kuznetsov SA, Wolfe RM, Marshall GW, Robey PG: In vivo bone formation by human bone marrow stromal cells:
54. Wagner W, Ho AD: Mesenchymal stem cell preparations — comparing apples and oranges. Stem Cell Rev 2007, 3:239-248.
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