Smooth muscle expresses bone morphogenetic protein (Vgr-1/BMP-6) in human fetal intestine.

During human fetal development, autocrine TGF-beta1 regulates the synthesis of specific collagen types by intestinal smooth muscle cells in an age-dependent manner. Vgr-1/BMP6, a member of the TGF-beta superfamily, modulates epithelial, endochondral and neural tissue development in mice: a related peptide is essential to gut morphogenesis in Drosophila. This is the first study to detect vgr-1/BMP-6 during human intestinal organogenesis. Polyclonal antibodies to the precursor and mature fragments of vgr-1 were used in immunohistochemical studies of human intestine at 15, 19 and 24 weeks' gestation. Immunoreactivity was detected with the antibody directed against the precursor portion of vgr-1. Only smooth muscle structures stained for vgr-1 including muscularis propria, muscularis mucosa and vasculature. BMP-6 mRNA was detected by RNase protection assay in cultured muscle cells from 11, 17 and 22 weeks' gestation. This study demonstrates vgr-1/BMP 6 expression in the developing human fetal intestine, exclusively in muscle.