AGI January 41/1

Sonoyama, Kei, Suriya Rutatip, and Takanori Kasai. Gene expression of activin, activin receptors, and follistatin in intestinal epithelial cells. Am. J. Physiol. Gastrointest. Liver Physiol. 278: G89–G97, 2000.—Gene expression of activin, activin receptors, and follistatin was investigated in vivo and in vitro using semiquantitative RT-PCR in intestinal epithelial cells. Rat jejunum and the intestinal epithelial cell line IEC-6 expressed mRNA encoding the bA-subunit of activin, a-subunit of inhibin, activin receptors IB and IIA, and follistatin. An epithelial cell isolation study focused along the crypt-villus axis in rat jejunum showed that bA mRNA levels were eightto 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 differentiation model of enterocytes. Fourto fivefold induction of bA mRNA was observed in postconfluent Caco-2 cells grown on filter but not in those cells 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-IV gene, a differentiation marker, in IEC-6 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.