Differential response of mature TrkA/p75(NTR) expressing human and pig oligodendrocytes: Aging, does it matter?

A differential morphological response of mature oligodendrocytes (OL) isola ted from human and pig brains to the phorbol ester 12-O-tetradecanoylphorbo l-13-acetate (TPA) and to the nerve growth factor (NGF) was observed. In bo th cases, OL regenerate their processes; however, the rate and the extensio n of the process formation of human OL were behind that of pig OL. Presumab ly, the advanced age of the human tissue in these experiments might have co ntributed to this decrease in process formation, an effect that was already observed for rat OL [Yong et al. (1991) J Neurosci Res 29:87-99]. The less effectivity of NGF via TrkA, which was immunocytochemically shown in human OL, and of TPA via the protein kinase C (PKC) pathway, may have its common focus on the mitogen-activated protein kinase (MAPK) cascade. In this cont ext, it was noted that only a few studies on aging of mature OL are availab le. It is conceivable that age-related changes in the properties of OL coul d be an important factor for their cellular responsiveness during longer la sting demyelinating diseases such as multiple sclerosis. Hence, this review would like to provide a basis for future investigations on the aging of ma ture OL. The data presently available suggest a preliminary classification of mature OL into three categories. (C) 2001 Wiley-Liss, Inc.