AXONAL REINNERVATION DOES NOT INFLUENCE SCHWANN-CELL PROLIFERATION AFTER RAT SCIATIC-NERVE TRANSECTION

We asked whether reinnervating axons are Schwann cell mitogens in vivo as they are in vitro. Left sciatic nerves of 50 Wistar rats were tran sected. In one-half of the animals, axonal reinnervation from the prox imal to the distal stump was allowed to take place, while in the other half, sutures were placed on the transected nerve ends to prevent rei nnervation. Samples were collected from 3 days up to 8 weeks after the transection proximally and distally from the point of transection. PC NA-immunostaining was performed on paraffin sections to determine the number of proliferating cells. Axonal reinnervation was followed by Bi elschowsky staining and Schwann cell number was determined by counting S-100-immunopositive cells from paraffin sections. In the distal stum p Schwann cell proliferation was similar in both experimental groups. There was no statistical evidence of S-100 negative cell proliferation during the study. Proximally to the site of transection the number of small initial axonal sprouts and also the number of Schwann cells inc reased if the nerve stump had been sutured. In conclusion, although ax ons may be mitogenic for Schwann cells, axonal reinnervation into the distal stump of the transected peripheral nerve does not influence the proliferation of Schwann cells to a greater extent than other potenti al effects associated with nerve transection.