BMP-6 and retinoic acid synergistically differentiate the IMR-32 human neuroblastoma cells

We studied the effects of all-trans retinoic acid (ATRA) and Bone morphogenetic protein-6 (BMP-60 on neuronal differentiation of IMR-32 cells.

Immunostaining, Western blotting and MTT assays were used to characterize the survival and neuronal phenotype of IMR-32 cells differentiated by ATRA +/- BMP-6.

ATRA, BMP-6 and ATRA + BMP-6 treatments each induced dopaminergic neuronal differentiation of the IMR-32 cells as judged by expression of GAP-43, tyrosine hydroxylase and microtubule-associated protein 2ab. ATRA alone induced strong biochemical differentiation, whereas ATRA + BMP-6 treatment synergistically enhanced neurite outgrowth and morphological maturation. When compared with undifferentiated controls, ATRA induced Bcl-2 expression, while loss of Bax expression was observed only in cells differentiated by ATRA + BMP-6. The high Bcl-2/Bax ratio in cells differentiated by ATRA and ATRA + BMP-6, respectively, correlated with the survival of these cells in serum-free media. Upon re-exposure to fresh serum lacking factors, only cells differentiated by ATRA + BMP-6 were unable to resume cell division. In concordance with their morphological maturation, these cells were terminally differentiated when compared with cells differentiated by separate treatment with ATRA or BMP-6.