CELL VIABILITY AND MIGRATION IN NERVE ISOGRAFTS AND ALLOGRAFTS

Even though autogenous nerve grafts are used frequently, there is litt le information concerning cell survival rates and migration patterns, following peripheral nerve grafting. Labeling techniques with a vital fluorescent stain (PKH-26, Zynaxis Cell Science, Malvern, PA) allow ce ll migrations from both the nerve graft and host nerve to be tracked f or up to 45 days from the time of nerve transplantation. With this lab eling technique, two phases of nerve graft incorporation were identifi ed, early and late, in an animal model using inbred Lewis and Brown-No rway rats. In genetically identical Lewis rats, isografts were perform ed as a means of modeling the autografts used clinically. At approxima tely 3 days after isogeneic transplantation, with the proximal host ne rve end labeled, there was an early migration of host cells from the p roximal nerve end into the epineural tissue of the nerve graft. At 25 days, a late phase was evident, with fluorescent labeling of host cell s into the perineural and endoneural tissues. When the nerve grafts we re labeled, the label persisted for up to 45 days, indicating viabilit y of the graft. Cells migrated from the labeled nerve graft into the d istal host nerve segment. Cellular migration from peripheral nerve tis sue, following allograft transplantation, was initially similar to the isograft studies. But after 25 days, with the proximal host nerve end labeled, a significant decrease in the labeled host cells migrating i nto the graft was noted (p < 0.05). By 45 days after allograft transpl antation with the nerve graft labeled, there was a significant decreas e in the percentage of tissue with the fluorescent label, indicating a loss in viable cells within the graft tp < 0.05). Furthermore, the mi gration of labeled cells from the graft into the distal host nerve end was significantly decreased. Clinical Relevance. Autogenous nerve gra fts function as viable tissue grafts, and techniques to preserve this viability during surgery should be optimized. Allografts are incorpora ted by integration of host nerve cells until rejection occurs. This la beling technique with PKH-26 may provide a method of quantifying the e fficacy of techniques to delay or decrease allograft rejection through immunosuppression or tissue typing.