Haemopoietic biglycan produced by brain cells stimulates growth of microglial cells

We have recently found that soluble biglycan purified from rat thymic myoid cells had haemopoietic activity capable of inducing preferential growth an d differentiation of monocytic lineage cells from various haemopoietic sour ces, including brain microglial cells. In the present study, to understand developmental mechanisms of microglial/monocytic cells in the brain, we hav e attempted to identify haemopoietic activity of the brain biglycan. The mR NA and the immunological epitope of biglycan were detected in the rat brain homogenates and several rat glial cell lines. Immunohistochemical study sh owed that several different types of brain cells produced biglycan. During development biglycan synthesis in the brain appeared to be increased. The b rain haemopoietic biglycan was easily separated by DEAE-Sepharose chromatog raphy from the macrophage colony stimulating factor (M-CSF) which was conco mitantly produced from the brain cells. The brain haemopoietic biglycan, pu rified through immunoaffinity column, indeed stimulated growth of primarily cultured microglial cells. Taken together, these results suggest that the haemopoietic biglycan plays an important role in generating brain-specific circumstances for development of microglial/monocytic cells. (C) 2000 Elsev ier Science B.V. All rights reserved.