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Laminin B1 and Collagen Type IV Gene Expression in Transected Peripheral Nerve: Reinnervation Compared to Denervation

Abstract: The expression of B1 laminin and type IV collagen was followed in the microsurgically isolated endoneurium of transected rat sciatic nerves from 3 days until 8 weeks. Northern hybridizations revealed that after nerve transection the proximal stumps of denervated, as well as freely regenerating, nerves showed a markedly increased expression of laminin and type IV collagen which lasted from 3 days up to 8 weeks. In the distal stumps, close to the site of transection (2–7 mm), the expression of laminin, and to a certain extent that of type IV collagen, seemed to be enhanced if free axonal reinnervation was allowed. Further distally (10–15 mm), the patterns of B1 laminin and typeIV collagen expression were similar in both experimental groups, so that an increased expression was noticed during the first 2 weeks. The present results suggest that laminin and type IV collagen gene expression is markedly different in different parts of transected rat sciatic nerve. During peripheral nerve regeneration, there is a long‐lasting basement membrane gene expression in the proximal stump. In the distal part of the transected nerve, the axonal reinnervation possibly up‐regulates, but is not essential for, the expression of B1 laminin and type IV collagen.