Gene expression of activin, activin receptors, and follistatin in intestinal epithelial cells

Gene expression of activin, activin receptors, and follistatin was investig ated in vivo and in vitro using semiquantitative RT-PCR in intestinal epith elial cells. Rat jejunum and the intestinal epithelial cell line IEC-6 expr essed mRNA encoding the beta A-subunit of activin, alpha-subunit of inhibin , activin receptors IB and IIA, and follistatin. An epithelial cell isolati on study focused along the crypt-villus axis in rat jejunum showed that bet a A mRNA levels were eight- to tenfold higher in villus cells than in crypt cells. Immunohistochemistry revealed the expression of activin A in upper villus cells. The human intestinal cell line Caco-2 was used as a different iation model of enterocytes. Four- to fivefold induction of beta A mRNA was observed in postconfluent Caco-2 cells grown on filter but not in those ce lls grown on plastic. In contrast, follistatin mRNA was seen to be reduced after reaching confluence. Exogenous activin A dose-dependently suppressed the proliferation and stimulated the expression of apolipoprotein A-TV gene , a differentiation marker, in IEC-B cells. These results suggest that the activin system is involved in the regulation of such cellular functions as proliferation and differentiation in intestinal epithelial cells.