PLATELET-DERIVED GROWTH-FACTOR B-CHAIN EXPRESSION IN THE RAT RETINA AND OPTIC-NERVE - DISTRIBUTION AND CHANGES AFTER TRANSECTION OF THE OPTIC-NERVE

To test the possible involvement of platelet-derived growth factor B-c hain (PDGF-B) in anterograde and retrograde degenerations of the CNS n eurons, we studied the changes of PDGF-B localization and its mRNA exp ression in the rat retina and optic nerve (ON) after unilateral ON tra nsection, using immunohistochemistry and in situ hybridization. In the control retinas immunoreactivity for PDGF-B and its mRNA expression w ere localized in the retinal ganglion cells (RGCs) and the nerve fiber layer. After ON transection PDGF-B immunoreactivity in the nerve fibe r layer started to decrease on post-injury day 3 or 4. Atrophic change s in the RGCs started on day 5 just after the decrease of PDGF express ion, and thereafter the RGC number decreased. In the longitudinal sect ion of the ON rostral to the transected site, swollen axons showed int ense PDGF-B immunoreactivity and macrophages, and some glial cells rev ealed a significant increase in both immunoreactivity and hybridizatio n signals. Based on these findings, we hypothesized that the decrease in PDGF-B in RGCs after axotomy causes the loss of RGCs, and that incr eased PDGF-B expression in the ON plays a role in the cascade of tissu e reactions following ON transection. (C) 1998 Elsevier Science Ltd. A ll rights reserved.