Retroviral labeling of Schwann cells: In vitro characterization and in vivo transplantation to improve peripheral nerve regeneration

Transplantation of Schwann cells (SCs) is a promising treatment modality to improve neuronal regeneration. Identification of the transplanted cells is an important step when studying the development of this method. Genetic la beling is the most stable and reliable method of cell identification, but i t is still unclear whether it has deleterious effect on SC characteristics. Our aim was to achieve a stable population of SCs transduced with the lacZ gene at a high frequency using a retroviral vector in vitro, and to follow the labeled SC in vitro to assess their viability and phenotypic marker ex pression. Furthermore, we transplanted lacZ-labeled SCs in a conduit to rep air peripheral nerve to investigate their effect on nerve regeneration in v ivo. Rat and human SCs were cultured and transduced with an MFG lacZ nls ma rker gene, achieving a transduction rate of 80% and 70%, respectively. Rat SCs were kept in culture for 27 weeks and examined every 4 weeks for expres sion of lacZ, viability, and phenotypic marker expression of GFAP, p75, MHC I and II. Throughout this period, transduced rat SCs remained viable and c ontinued to proliferate. The proportion of cells expressing lacZ dropped on ly by 10% and the expression of phenotypic markers remained stable. Transdu ced human SCs were followed up for 4 weeks in culture. They proliferated an d continued to express the lacZ gene and phenotypic marker expression of GF AP and p75 was preserved. Primary culture of transduced rat SCs were transp lanted, syngeneically, in a conduit to bridge a 10 mm gap in sciatic nerve and the grafts were examined after 3 weeks for the presence and participati on of labeled SCs and for axonal regeneration distance. Transplanted transd uced rat SCs were clearly identified, taking part in the regeneration proce ss and enhancing the axonal regeneration rate by 100% (at the optimal conce ntration) compared to conduits without SCs. Thus, retroviral introduction o f lacZ gene has no deleterious effect on SCs in vitro and these SCs take pa rt and enhance nerve regeneration in vivo. (C) 2001 Wiley-Liss. Inc.