Production of colony-stimulating factor-1 (CSF-1) by mouse astroglia in vitro.

We investigated whether astroglia produce any of the known macrophage growth factors, CSF-1, GM-CSF, and IL-3, and if so, whether any of these cytokines stimulate the growth of CNS macrophages. In this work we used highly enriched cell cultures of C3H/HeJ mouse neopallium: cultures of astroglia and cultures of macrophage-like cells derived from nutritionally deprived astroglia cultures. We found that astroglia in cultures accumulate in the medium, an activity that stimulates the proliferation of macrophage-like cells. The activity has been identified as CSF-1 by using growth assays of cells dependent and nondependent on CSF-1, and by radioreceptor analysis which is highly specific for CSF-1. Northern blot analysis demonstrated the presence in astroglia of CSF-1 mRNA and the presence of CSF-1 receptor (c-fms) mRNA in macrophage-like cells but not in astroglia. The astroglia did not produce GM-CSF or IL-3. We concluded that a paracrine relationship exists between astroglia production of CSF-1 and the response of macrophage-like cells to the cytokine in culture.