Expression of growth factor receptors in injured nervous tissue. II. Induction of specific platelet-derived growth factor binding in the injured PNS is associated with a breakdown in the blood-nerve barrier and endoneurial interstitial oedema.

We have studied the expression of the platelet-derived growth factor (PDGF) receptors in the injured chick PNS using [125I]-iodinated PDGF as a radioactive probe to map autoradiographically the in situ distribution of specific [125I]PDGF binding. Crush or transection of the sciatic nerve led to a rapid and massive induction of specific [125I]PDGF binding on fibroblast-like cells of the injured endoneurium, already observed 2 h postoperatively. It is initially characterized by a symmetrical appearance both below and above the site of injury, spreading throughout the distal part of the lesioned nerve 1 to 2 days postoperatively. Comparison with distribution of specific [125I]beta-nerve growth factor (beta-NGF) binding (see preceding paper) revealed a number of important differences: unlike the specific [125I]beta-NGF binding, which rapidly disappears after reinnervation of the distal nerve, this was not observed in the case of [125I]PDGF binding. [125I]PDGF binding also correlated poorly with the extent of axonal injury. The segmental removal of the perineurium, resulting in heavy interstitial oedema without widespread axonal injury, led to a strong, local induction of [125I]PDGF binding, while causing moderate beta-NGF binding to only the few degenerating nerve fibre tubes. These results suggest the existence of different pathophysiological mechanisms that regulate the expression of PDGF and beta-NGF receptors in the lesioned and regenerating PNS.