G(D3)+ CELLS IN THE ADULT-RAT OPTIC-NERVE ARE RAMIFIED MICROGLIA RATHER THAN O-2A(ADULT) PROGENITOR CELLS

The adult central nervous system (CNS) contains a population of adult oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells (O-2A(adult) progenitor cells). These cells may provide a source of the new oligodendrocytes that are needed to repair demyelinated lesions. In order to examine the role of O-2A(Adult) progenitor cells in the regeneration of the oligodendrocyte population following demyelinating damage, it is essential to be able to identify such cells unambiguously in sections of adult CNS tissue. The present study examined whether antibodies to the ganglioside GD3 specifically label O-2A(adult) progenitor cells in cultures and sections of adult optic nerve, since previous studies on the developing CNS had suggested that O-2A(perinatal) progenitor cells were G(D3)+ in vitro and in vivo. Evidence is presented indicating that, although O-2A(adult) progenitor cells in vitro were labelled with the R24 mAb (an anti-GD3 mAb), all GD3+ cells in sections of adult optic nerve bound the OX-42 mAb and the B4 isolectin derived from Griffonia Simplicifolia, and thus were noto-2A(adult) progenitor cells, but ramified microglia. The data suggest that O-2A(adult) progenitor cells become GD3+ when placed in culture and that ramified microglia lose GD3-expression in vitro. (C) 1994 Wiley-Liss, Inc.