Developmental Changes in Progenitor Cell Responsiveness to Cytokines

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Abstract

Multipotent progenitor cells have been identified within periventricular generative zones of the developing and adult brain. To determine whether the environmental responsiveness of these cells changes during development, progenitor cells were cultured from embryonic, postnatal, and adult rat brain in the presence of either basic fibroblast growth factor (bFGF) or epidermal growth factor (EGF). Embryonic cells cultured as intact progenitor neurospheres proliferated more robustly in response to bFGF than to EGF, whereas proliferation of postnatal and adult progenitor cells was enhanced more by EGF than bFGF. Progenitor cells generated in the presence of either bFGF or EGF had the capacity to generate neurons, astrocytes, and oligodendrocytes at all developmental stages. Most embryonic and neonatal bFGF-generated cells differentiated predominantly into neurons, whereas late stage embryonic and neonatal EGF-generated progenitors largely remained in an undifferentiated state. However, later postnatal and adult progenitor species, irrespective of whether they were generated in the presence of bFGF or EGF, gave rise preferentially to astrocytes. Treatment with bone morphogenetic protein (BMP)2 or BMP7 enhanced astroglial differentiation and suppressed oligodendroglial differentiation of both EGF- and bFGF-generated progenitor species, suggesting that the effects of the BMPs are not dependent on EGF receptor activation. Thus, while central nervous system (CNS) progenitor cells retain multipotent capacity and responsiveness to the BMPs throughout development, they exhibit significant changes in other cellular response properties, perhaps reflecting differences in the requirements for specific generative versus regenerative events.

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