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Inhibition of Unfolded Protein Response Decreases Scar Formation
S98
Scientific Forum Abstracts
J Am Coll Surg
before the second treatment, indicating sustained vasodilitory effects. The time interval between the maximum rate of arterial inflow and venous outflow was shortened in response to cumulative HBO treatments, suggesting decreased overall time in the capillary bed. After prolonged treatments, all time points occurred significantly later, and overall intensity decreased as compared with baseline and the initial 2 HBO treatments, potentially indicating vascular redistribution via neoangiogenesis.
Investigation of the Use of Bone Marrow Stem Cells to Facilitate Pathologic Fracture Healing of the Mandible after Irradiation Alicia E Snider, MD*, Noah Nelson, BS, Russell Ettinger, MD, Alex Donneys, MD, Kavitha Ranganathan, MD, Steven Buchman, MD University of Michigan Ann Arbor, MI, University of South Carolina, Columbia, SC
CONCLUSIONS: HBOT immediately affects the microcirculation, both on an arterial and a venous level, and this appears to be cumulative and sustained. Long-term HBOT might change the architecture of the peri-wound microvasculature by inducing capillary neoangiogenesis. This work offers an insight into the potential mechanism of HBOT.
INTRODUCTION: Radiation therapy for head and neck cancer results in devastating morbidity for bone healing, including the complications of osteoradionecrosis and subsequent pathologic fractures. Our investigation sought to improve bone healing through the use of bone marrow stem cells (BMSCs) in a mandibular osteotomy defect after radiotherapy. Our hypothesis was that use of BMSCs would improve union rates and bone mineralization metrics, thereby improving clinical outcomes.
Inhibition of Unfolded Protein Response Decreases Scar Formation Tatiana V Boyko, MD, Dadi Jiang, PhD, Hongbin Cao, Albert C Koong, MD, PhD, Michael T Longaker, MD, MBA, FACS, George P Yang, MD, FACS Stanford University, Stanford, CA, University at Buffalo, Buffalo, NY INTRODUCTION: We previously demonstrated that IRE1, a major component of the unfolded protein response (UPR) was activated during wound healing and had increased activity in keloids, a disease of excessive wound healing. A major feature of keloids is excessive collagen deposition. Because the UPR is critical in cellular adaption to high protein synthesis rates, we hypothesized that inhibition of IRE1 could decrease scarring. METHODS: Primary fibroblasts were exposed to STF-57, a small molecule inhibitor of IRE1, and assayed for the active form of XBP1, the major transcription factor activated by IRE1. Excisional stented wounds were created on mice and treated with STF-57 or dimethyl sulfoxide (DMSO) as the control. Progress of wound healing was analyzed by daily photography, and scar thickness was determined by histology. RESULTS: In vitro, 5 mM STF-57 inhibited XBP1 splicing in primary fibroblasts. In vivo treatment of excisional stented wounds on mice showed that at 100 mM, it took 1 added day to complete wound closure (15.8 vs 14.8 days with control DMSO treatment). There was complete inhibition of wound healing at concentrations of 250 mM and higher. Wounds were harvested on the day of complete healing, and histologic analysis of wounds treated with 100 mM showed scar thickness to be halved when compared with control (30176 mm vs 583172 mm, p<0.0001). CONCLUSIONS: We showed that inhibition of IRE1 significantly decreased scar thickness formation in mice. Increasing concentrations actually prevented the scar from healing. Further investigation of this potential treatment for keloid scar formation is warranted.
METHODS: Lewis rats (n¼31) were divided into 3 groups: nonradiated fracture (Fx), radiated fracture (XFx), and radiated fracture with BMSCs (XFxBMSC). The groups receiving radiation were administered a human-equivalent dose of 35 Gy over 5 days. Two weeks later, the rats received a mandibular osteotomy and external fixation to 2.1 mm. The animals were euthanized at postoperative day 40, their mandibles were harvested, examined for bony union, and mCT scanned. Metrics of bone mineral content, bone mineral density, tissue mineral content, tissue mineral density, and bone volume fraction were ascertained. RESULTS: Although only 20% of the XFx group demonstrated unions, 66% of the XFxBMSC group had unions (Table). For all mineralization metrics, a significant decrease was observed between Fx and XFx, and significant remediation was imparted with BMSC therapy. Even more impressive was that no statistically significant differences were seen between the Fx and XFxBMSC groups. Table. Experimental group Fractured (FX)
Union rate, %
Bone mineral density
100
710
FX+ Radiation (XRT)
20
312
FX+XRT+ Bone Marrow Stem Cells (BMSC)
66
599
CONCLUSIONS: BMSCs significantly improve the clinically relevant metrics of bony union and mineralization in a model of irradiated mandibular fracture healing. Given our results, we are proponents of additional studies in order to translate this promising therapy to clinical investigation. Measuring Functional Recovery after Chronic Denervation of Peripheral Nerves: A Novel Rat Forelimb Model Amy Quan, MPH, Joseph Lopez, MD, MBA, Sami H Tuffaha, MD, Joshua D Budihardjo, Howard D Wang, MD, Ahmet Hoke, MD, PhD, WP Andrew Lee, MD, FACS, Gerald Brandacher, MD Johns Hopkins University School of Medicine, Baltimore, MD
Scientific Forum Abstracts
J Am Coll Surg
before the second treatment, indicating sustained vasodilitory effects. The time interval between the maximum rate of arterial inflow and venous outflow was shortened in response to cumulative HBO treatments, suggesting decreased overall time in the capillary bed. After prolonged treatments, all time points occurred significantly later, and overall intensity decreased as compared with baseline and the initial 2 HBO treatments, potentially indicating vascular redistribution via neoangiogenesis.
Investigation of the Use of Bone Marrow Stem Cells to Facilitate Pathologic Fracture Healing of the Mandible after Irradiation Alicia E Snider, MD*, Noah Nelson, BS, Russell Ettinger, MD, Alex Donneys, MD, Kavitha Ranganathan, MD, Steven Buchman, MD University of Michigan Ann Arbor, MI, University of South Carolina, Columbia, SC
CONCLUSIONS: HBOT immediately affects the microcirculation, both on an arterial and a venous level, and this appears to be cumulative and sustained. Long-term HBOT might change the architecture of the peri-wound microvasculature by inducing capillary neoangiogenesis. This work offers an insight into the potential mechanism of HBOT.
INTRODUCTION: Radiation therapy for head and neck cancer results in devastating morbidity for bone healing, including the complications of osteoradionecrosis and subsequent pathologic fractures. Our investigation sought to improve bone healing through the use of bone marrow stem cells (BMSCs) in a mandibular osteotomy defect after radiotherapy. Our hypothesis was that use of BMSCs would improve union rates and bone mineralization metrics, thereby improving clinical outcomes.
Inhibition of Unfolded Protein Response Decreases Scar Formation Tatiana V Boyko, MD, Dadi Jiang, PhD, Hongbin Cao, Albert C Koong, MD, PhD, Michael T Longaker, MD, MBA, FACS, George P Yang, MD, FACS Stanford University, Stanford, CA, University at Buffalo, Buffalo, NY INTRODUCTION: We previously demonstrated that IRE1, a major component of the unfolded protein response (UPR) was activated during wound healing and had increased activity in keloids, a disease of excessive wound healing. A major feature of keloids is excessive collagen deposition. Because the UPR is critical in cellular adaption to high protein synthesis rates, we hypothesized that inhibition of IRE1 could decrease scarring. METHODS: Primary fibroblasts were exposed to STF-57, a small molecule inhibitor of IRE1, and assayed for the active form of XBP1, the major transcription factor activated by IRE1. Excisional stented wounds were created on mice and treated with STF-57 or dimethyl sulfoxide (DMSO) as the control. Progress of wound healing was analyzed by daily photography, and scar thickness was determined by histology. RESULTS: In vitro, 5 mM STF-57 inhibited XBP1 splicing in primary fibroblasts. In vivo treatment of excisional stented wounds on mice showed that at 100 mM, it took 1 added day to complete wound closure (15.8 vs 14.8 days with control DMSO treatment). There was complete inhibition of wound healing at concentrations of 250 mM and higher. Wounds were harvested on the day of complete healing, and histologic analysis of wounds treated with 100 mM showed scar thickness to be halved when compared with control (30176 mm vs 583172 mm, p<0.0001). CONCLUSIONS: We showed that inhibition of IRE1 significantly decreased scar thickness formation in mice. Increasing concentrations actually prevented the scar from healing. Further investigation of this potential treatment for keloid scar formation is warranted.
METHODS: Lewis rats (n¼31) were divided into 3 groups: nonradiated fracture (Fx), radiated fracture (XFx), and radiated fracture with BMSCs (XFxBMSC). The groups receiving radiation were administered a human-equivalent dose of 35 Gy over 5 days. Two weeks later, the rats received a mandibular osteotomy and external fixation to 2.1 mm. The animals were euthanized at postoperative day 40, their mandibles were harvested, examined for bony union, and mCT scanned. Metrics of bone mineral content, bone mineral density, tissue mineral content, tissue mineral density, and bone volume fraction were ascertained. RESULTS: Although only 20% of the XFx group demonstrated unions, 66% of the XFxBMSC group had unions (Table). For all mineralization metrics, a significant decrease was observed between Fx and XFx, and significant remediation was imparted with BMSC therapy. Even more impressive was that no statistically significant differences were seen between the Fx and XFxBMSC groups. Table. Experimental group Fractured (FX)
Union rate, %
Bone mineral density
100
710
FX+ Radiation (XRT)
20
312
FX+XRT+ Bone Marrow Stem Cells (BMSC)
66
599
CONCLUSIONS: BMSCs significantly improve the clinically relevant metrics of bony union and mineralization in a model of irradiated mandibular fracture healing. Given our results, we are proponents of additional studies in order to translate this promising therapy to clinical investigation. Measuring Functional Recovery after Chronic Denervation of Peripheral Nerves: A Novel Rat Forelimb Model Amy Quan, MPH, Joseph Lopez, MD, MBA, Sami H Tuffaha, MD, Joshua D Budihardjo, Howard D Wang, MD, Ahmet Hoke, MD, PhD, WP Andrew Lee, MD, FACS, Gerald Brandacher, MD Johns Hopkins University School of Medicine, Baltimore, MD