Transforming growth factor β in bovine placentas

Transforming growth factor βs (TGFβ) are a family of multifunctional growth factors that are important embryonic morphogens. Because TGFβs may regulate the development of epitheliochorial placentas, we investigated the location, expression, secretion, and effects of TGFβs in bovine placentomes and cell cultures derived from chorionic and endometrial epithelia. Placentomes from early second-trimester pregnancies were examined by immunohistochemistry for TGFβ1, TGFβ2, and TGFβ3, and for TGFβ expression in Northern slot-blots. Effects of TGFβs were assessed in trophoblastic and endometrial epithelial cell lines by DNA synthesis assays. Secretion of TGFβs by trophoblastic and endometrial epithelial cells was determined using bioassays. All forms of TGFβ were immunolocalized in bovine placentomes. TGFβ mRNA was expressed in chorioallantois, caruncles, and in cultured trophoblastic and endometrial epithelial cells. Endometrial and trophoblastic cells secreted active and latent TGFβs, and these cells had a transient proliferative response to all forms of TGFβ. These results indicate that TGFβs are present at the fetal-maternal interface of the bovine placentome and may promote endometrial and chorionic growth.