Pure Schwann cell suspension grafts promote regeneration of the lesioned septo-hippocampal cholinergic pathway.

Regeneration of central nervous system (CNS) axons has been studied in the cholinergic septo-hippocampal system using various 'bridges' able to support fiber growth. In this study, a pure Schwann cell (Sc) suspension labeled with bisbenzimide (Hoechst 33342) was grafted in the lesioned septo-hippocampal pathway. At 2 weeks post-grafting, acetyl-cholinesterase (AChE)-positive fibers invaded the graft and grew in association with the Hoechst-labeled Sc, some of which expressed the low-affinity nerve growth factor receptor (NGF-R). At 2 months and 4 months post-grafting, the dorsal hippocampus was reinnervated with an apparently normal innervation pattern. Analysis of fiber growth in the hippocampus at four months post-grafting revealed a significant increase of reinnervation in the grafted animals (2 mm) compared to the non-grafted ones. No difference was observed in the number of cholinergic septal neurons expressing the NGF-R. These results demonstrate that a Sc suspension grafted into the lesioned septo-hippocampal system, integrates well into the host tissue, and supports axonal CNS outgrowth, implying that Sc by themselves provide an adequate environment for regeneration to occur.