FIBROBLASTS THAT RESIDE IN MOUSE AND FROG INJURED PERIPHERAL-NERVES PRODUCE APOLIPOPROTEINS

Apolipoprotein synthesis and secretion is upregulated in wallerian deg enerating peripheral nerves. A commonly expressed view has been that m acrophages are solely responsible for their production. In the present study we provide evidence that (1) nerve-derived fibroblasts contribu te to apolipoprotein production, (2) apolipoprotein production is conf ined to regions where myelin destruction and phagocytosis occur, and ( 3) some experimental procedures are detrimental for the production of apolipoproteins. Apolipoprotein production was studied in C57BL/6/NHSD (N) and C57/BL/6-WLD/OLA/NHSD (W) mice that display, respectively, ra pid and slow progression of wallerian degeneration. In N nerves, apoli poprotein E (apo-E) is produced during in vitro and in vivo degenerati on, and in vivo after freeze damage. In W nerves, apo-E is produced at the injury region where degeneration occurs but not farther distally where degeneration fails to develop. Apo-E is also produced in W nerve s during in vitro degeneration and in vivo after freeze damage. In cul ture, N and W mice nerve-derived fibroblasts, but neither macrophages nor Schwann cells produced apo-E. Two apolipoproteins are produced in in vivo wallerian degenerating and freeze-damaged frog nerves, i.e., a po-39 and apo-29. Only apo-39 is produced in in vitro degenerating ner ves. Neither apo-39 nor apo-29 is produced during in vivo degeneration in diffusion chambers. In culture, apo-39 is produced by nerve-derive d fibroblasts and macrophages but not by Schwann cells.