Figure 1.

Expression of growth-associated genes in axotomized motoneurons after loss of target connections and in chronically denervated Schwann cells (SCs) in the distal nerve stumps. An illustrated motoneuron showing expression of growth-associated genes in motoneurons and in Schwann cells in the distal nerve stumps after a nerve injury (A). Experiments were performed in which we cut the sciatic nerve and sutured both proximal and distal nerve stumps to innervated muscle to prevent regeneration (B). p75NTFR in situ hybridization showing an early rise in expression in the denervated SCs in the distal nerve stump that declined within 6 months (C). Immunocytochemical evidence of a concomitant decline in p75 protein in the chronically denervated Schwann cells. (D). In situ hybridization showing a progressive decline to baseline values in the upregulation of the mRNA of the cytoskeletal protein tubulin in axotomized motoneurons (E). Semi-quantitation of the gene expression of Glial derived neurotrophic factor (GDNF) in the denervated distal nerve stump with rt-PCR, showing an exponential decline (F). The parallel expression of p75 and infiltration of macrophages into the denervated distal nerve stump (G). The slow rate of Wallerian degeneration of the isolated nerve in the denervated distal nerve stump is illustrated in the longitudinal micrographs of the denervated distal nerve stump (H–J) leaving parallel endothelial tubes with immunologically stained p75 expressing SCs by 12 weeks (K) that declines within 6-months (L,M). Adapted from [19].