Local fetal signal is not required for maintaining IGFBP gene expression in the human decidua: evidence from extrauterine pregnancies.

Abstract

Insulin-like growth factor-II (IGF-II) from the invading extravillous cytotrophoblasts (EVTs) and insulin-like growth factor binding proteins (IGFBPs) from the maternal decidua interact at the feto-maternal interface and regulate implantation and placentation. To determine whether a local stimulus from the fetus is important in the regulation of IGFBP gene expression in the human decidua, we compared the expression of IGFBP genes in intra- and extrauterine (tubal) pregnancies. The expression of IGF-II and IGFBP-1 to IGFBP-6 mRNAs was determined by in-situ hybridization in the Fallopian tubes of extrauterine pregnancies and concurrent decidua (n = 6), and in the placentae and Fallopian tubes of intrauterine pregnancies (n = 6). All six IGFBP mRNAs were identified in the decidualized endometrium and decidualized Fallopian tubes of intra- and extrauterine pregnancies, with IGFBP-1 mRNA being the predominant mRNA. IGFBP-4 was the second most predominant mRNA and was slightly more abundant in the decidua of extrauterine pregnancies than of intrauterine pregnancies. IGF-II mRNA was expressed mainly in cells of fetal origin. The fact that the IGFBP mRNAs were expressed similarly in both intra- and extrauterine pregnancies indicates that the local physical stimulus from an implanting fetus is not necessary to induce or maintain decidual IGFBP gene expression.