EMBRYONIC FIBRONECTINS ARE UP-REGULATED FOLLOWING PERIPHERAL-NERVE INJURY IN RATS

Fibronectin mRNAs that include the alternatively spliced exons EIIIA, EIIIB, and V are prevalent during embryogenesis, and EIIIA and EIIIB r eappear during wound healing, Using ribonuclease protection analyses, we found an up-regulation of V120 (containing the alpha(4) beta(1) int egrin binding site), as well as EIIIA, and EIIIB in fibronectin mRNAs in the crush-injured adult rat sciatic nerve. In situ hybridization us ing splice variant-specific probes revealed that cells within endoneur ial tubes of the injured nerve synthesize these embryonic forms of fib ronectin. Our results suggest that embryonic fibronectins synthesized within the nerve contribute to the permissiveness of the peripheral ne rvous system to axon regrowth and a mechanism by which alternative spl icing of the V region in fibronectin mRNA could enhance nervous system regeneration. (C) 1995 John Wiley and Sons, Inc.