NG2+glial cells: A novel glial cell population in the adult brain

We describe a major glial cell population in the central nervcus system (CN S) that can be identified by the expression of 2 cell surface molecules, th e NG2 proteoglycan and the alpha receptor for platelet-derived growth facto r (PDGF alpha R). In vitro and in the developing brain in vivo, NG2 and PDG F alpha R are expressed on oligodendrocyte progenitor cells but are down-re gulated as the progenitor cells differentiate into mature oligoder drocytes . In the mature CNS, numerous NG2+/PDGF alpha R+ cells with extensive arbor ization of their cell processes are found ubiquitously long after oligodend rocytes are generated. NG2+ cells in the mature CNS do not express antigens specific to mature oligodendrocytes, astrocytes, microglia, or neurons, su ggesting that they are a novel population of glial cells. Recently NG2+ cel ls in the adult CNS have been shown to undergo proliferation and morphologi cal changes in response to a variety of stimuli, such as demyelination and inflammation, suggesting that they are dynamic cells capable of responding to changes in the environment. Furthermore, high levels of NG2+ and PDGF al pha R are expressed on oligodendroglioma cells, raising the possibility tha t the NG2+/PDGF alpha R+ cells in the mature CNS contribute to glial neopla sm.