Transforming growth factor-beta 1 and -beta 2 promote neurite sprouting and elongation of cultured rat hippocampal neurons.

Transforming growth factor-beta (TGF-beta) is known as a potent regulator of cell proliferation and differentiation. In the present study, we investigated the effects of TGF-beta 1 and -beta 2 on the survival, neurite sprouting and process elongation of primary cultured hippocampal neurons obtained from rat embryos. Addition of TGF-beta 1 little affected the total number of surviving neurons, but clearly increased the number of neurons bearing processes, indicating that TGF-beta 1 promotes neurite sprouting rather than neuronal survival. Furthermore, TGF-beta 1 significantly promoted the elongation of axon-like processes, but did not affect the process branching and the number of dendrite-like processes. TGF-beta 2 also promoted the neurite sprouting and stimulated the elongation of axons without affecting the branching. The effects of TGF-beta 2 were very similar to those of TGF-beta 1 in terms of both effective concentrations (0.1-1 ng/ml) and maximal effects. It is possible that TGF-beta 1 and -beta 2 play roles in the formation of neuritic networks in the central nervous system.