Introduction
Artificial nerve grafts, such as acellular nerve allografts, can be used to repair nerve gaps following peripheral nerve injury. However, the regenerative potential of these grafts is limited by their inherent lack of cells. Supplementing these grafts with cells could further enhance regeneration, but techniques to transplant cells to grafts are underdeveloped. This study developed methods to transplant SCs to nerve grafts. Specifically, this study determined whether fibrin could be used to promote transplanted SC survival and facilitate SC transplantation to nerve grafts.

Material and Methods
To evaluate the ability of fibrin gels to effectively transplant cultured SCs, adult Lewis rat sciatic nerves were transected, resulting in a 5mm gap, and the gap repaired using acellular nerve grafts and fibrin gels with and without SCs. These repaired nerves were harvested at 1, 7, and 14 days to evaluate SC survival and nerve regeneration using standard immunohistochemistry techniques. SCs were injected into acellular nerve grafts, with and without fibrin, where transgenic SCs expressing fluorescent reporter were used to quantify SC repopulation of the grafts.

Results
Constructed fibrin gels promoted nerve regeneration across a 5mm gap in rat sciatic nerves. Axons were visualized within the fibrin by 7 days and crossing to the distal nerve by 14 days. Fibrin gels also served as a viable scaffold carrier to facilitate SC transplantation. One day following transplant, SC numbers within fibrin gels were estimated at ~20% of the original transplanted SC numbers. Furthermore, transplanted SCs were evident after 7 days within the fibrin gel and adjacent nerve stumps. These fibrin gels with SCs enhanced nerve regeneration across the short gap, where axons were visualized crossing the gap by 7 days. Acellular nerve grafts supplemented with fibrin containing SCs were able to achieve 50% of SC survival after repaired to injured nerves by 7 days and has better SC viability compared to the nerve grafts supplemented with SCs but without fibrin.

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