Expression patterns of HMGA2 in the placenta during pregnancy

BackgroundHigh-mobility group AT-hook 2 (HMGA2) expression can be detected in many embryonic and fetal tissues but becomes down-regulated during postnatal life except for many benign and malignant tumors. In the latter case, its expression has been correlated with epithelial-mesenchymal transition and invasive growth. The placenta contributes essentially to proper development of the embryo and the fetus. In a tumor-like manner it shows rapid invasive growth during the first weeks of gestation. To address the possible role of HMGA2 during placental development, we have measured its expression throughout the prenatal period and in term placentae by mRNA quantification as well as by immunohistochemistry. MethodsExpression of HMGA2 and HPRT was measured on 89 fetal placentas, encompassing calendar gestational age of five to 41 weeks, using quantitative real time-PCR. In eleven cases in addition immunohistochemistry was used to determine the localization of HMGA2 and to compare with data obtained by quantitative real time-PCR. ResultsThe expression of HMGA2 was found to be inversely correlated with gestational age (p < 0.001). For the first part of the first trimester the level of HMGA2 is high. After that the expression shows a decline down to a baseline level where it remains until birth. HMGA2 protein was mainly detected in the nuclei of the stromal cells in the placental villi. ConclusionsDuring pregnancy, the expression of HMGA2 follows a non-linear pattern of decrease. In the first trimester, from two to three weeks after the implantation of the conceptus until the blood supply is established (hypoxic phase), the expression is high, indicating a critical role during early development and in the control of its invasive behavior, respectively.