Cell Viability and Migration in Nerve Isografts and Allografts

ABSTRACT

Even though autogenous nerve grafts are used frequently, there is little 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 cell migrations from both the nerve graft and host nerve to be tracked for up to 45 days from the time of nerve transplantation. With this labeling technique, two phases of nerve graft incorporation were identified, early and late, in an animal model using inbred Lewis and Brown-Norway rats. In genetically identical Lewis rats, isografts were performed as a means of modeling the autografts used clinically. At approximately 3 days after isogeneic transplantation, with the proximal host nerve end labeled, there was an early migration of host cells from the proximal nerve end into the epineural tissue of the nerve graft. At 25 days, a late phase was evident, with fluorescent labeling of host cells into the perineural and endoneural tissues. When the nerve grafts were labeled, the label persisted for up to 45 days, indicating viability of the graft. Cells migrated from the labeled nerve graft into the distal host nerve segment. Cellular migration from peripheral nerve tissue, 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 into the graft was noted (p < 0.05). By 45 days after allograft transplantation with the nerve graft labeled, there was a significant decrease in the percentage of tissue with the fluorescent label, indicating a loss in viable cells within the graft (p < 0.05). Furthermore, the migration of labeled cells from the graft into the distal host nerve end was significantly decreased.

Clinical Relevance. Autogenous nerve grafts function as viable tissue grafts, and techniques to preserve this viability during surgery should be optimized. Allografts are incorporated by integration of host nerve cells until rejection occurs. This labeling technique with PKH-26 may provide a method of quantifying the efficacy of techniques to delay or decrease allograft rejection through immunosuppression or tissue typing.