Tiam Mana Saffari

190 CHAPTER 9 differentiated MSCs after implementation while undifferentiated MSCs require time to interact with the environment 14 . A comparative study focusing on functional outcomes can elucidate the effect of different cells and their different effective phases on motor nerve regeneration. The purpose of this study was to determine the effect of dynamically seeding undifferentiated and differentiated MSCs onto decellularized nerve allografts 7 with respect to functional and histologic outcomes in a rat sciatic defect model. MATERIALS AND METHODS Experimental design After IACUC institutional review committee and our Institutional Review Board approval (IACUC protocol A2464-00), a 10 mm segmental defect of the sciatic nerve of 80 male Lewis rats weighing 250-300 grams (Envigo, Madison, WI, USA) was repaired with a 10 mm (i) reversed autograft, (ii) decellularized allograft (iii) decellularized allograft seeded with undifferentiated MSCs, or (iv) decellularized allograft seeded with differentiated MSCs. The decellularized allografts originated from Sprague- Dawley rats and were specifically chosen for their histocompatibility mismatch to Lewis rats 29,30 . This simulates the clinical setting where an allogenic processed nerve graft is seeded with autologous MSCs. After 12 and 16 weeks, functional, histological and immunofluorescence outcomes were evaluated. Nerve allograft collection, processing and seeding Sixty sciatic nerve segments from 30 Sprague-Dawley rats (Envigo, Madison, WI, USA) weighing 250-350 grams served as nerve allografts. After anesthesia with isoflurane, rats were euthanized, shaved and sterilely prepped. The sciatic nerve was exposed, removed under an operating microscope (Zeiss OpMi6, Carl Zeiss Surgical GmbH, Oberkochen, Germany) and processed according to a previously published protocol 7 . After sterilization with g-irradiation, nerves were stored at 4°C in Phosphate Buffered Saline (PBS) until surgery.