Effect of tumor necrosis factor-α on developing optic nerve oligodendrocytes in culture

There is increasing evidence that proinflammatory cytokines are involved in the development of periventricular leukomalacia (PVL), a condition in which developing oliodendrocytes (01-s) are preferentially injured. In the present study, we utilized an in vitro assay to demonstrate that the A2B5(+) OL progenitors as well as the O4(+) prooligodendrocytes (pro-OLs) were more susceptible to tumor necrosis factor-alpha (TNF-alpha) cytotoxicity than the O4(+)/O1(+) immature O1-s. OL progenitors were isolated from optic nerves of 7-day-old rat pups and cultured in chemically defined medium supplemented with platelet-derived growth factor and basic fibroblast growth factor. OL progenitors were allowed to differentiate into pro-OLs and immature OLs under special cultural conditions. Cells at three different developmental stages were subjected to TNF-alpha treatment. Cell death, presumably by apoptosis as evidenced by TUNEL staining and caspase-3 activation, was observed following TNF-alpha treatment. Corresponding to TNF-alpha-induced apoptosis, cell survival rate decreased in a time- and dose-dependent manner. The sensitivity of different OL developmental stages to TNF-alpha decreased with the progression of cell maturation. However, this differential response was not related to differentially expressed TNF-alpha receptors. Consistent with reports that progenitor cells are preferentially injured in PVL, our results may further support the role of TNF-alpha as a potential mediator of PVL. (c) 2005 Wiley-Liss, Inc.