ADAPTIVE PLASTICITY OF XENOPUS GLIAL-CELLS IN-VITRO AND AFTER CNS FIBER TRACT LESIONS IN-VIVO

Xenopus oligodendrocytes and aspects of their differentiation were ana lyzed in vitro and in vivo using cell- and stage-specific antibodies. Undifferentiated oligodendrocytes were derived from optic nerves or sp inal cords. They divided in vitro, were of elongated shape, were glial fibrillary acidic protein and O4 positive, transiently exhibited seve ral antigens including HNK-1 and L1, and promoted axon growth as do Sc hwann cells. With forskolin they differentiated and, much like myelin- forming oligodendrocytes in the intact optic nerve and spinal cord, th ey expressed sets of advanced myelin markers. These advanced myelin ma rkers disappeared from the regenerating optic nerve 4 weeks after lesi on. The optic nerve instead was populated by cells with radial process es and somata in the center of the nerve; among them were cells and pr ocesses that were O4 positive and that are suspected to represent undi fferentiated oligodendrocytes. Where processes of these cells reached to the retinal axons in the nerve's periphery, advanced myelin markers typical of differentiated oligodendrocytes reappeared 8 weeks after l esion. These glial changes did not occur in the absence of retinal axo ns. Thus, the apparent capability of Xenopus oligodendrocytes to adapt to the transient absence, reappearance, and regenerative state of the axons enables them to contribute to central nervous system fiber trac t repair. This occurs in the lesioned optic nerve but not in the spina l cord, where no such glial changes were observed and where axons fail to regenerate. (C) 1996 Wiley-Liss, Inc.