[Cytological localization of hPL, hCG, and mRNA in chorionic tissue using in situ hybridization]

The human trophoblast elaborates at least two major hormones, hPL and hCG(alpha, beta). To clarify the mechanism of biosynthesis and the gene expression of hPL and hCG(alpha, beta), the specific mRNA should be examined. We here studied the cytological distribution of these mRNAs in trophoblastic tissue of normal placenta, hydatidiform mole and choriocarcinoma by in situ hybridization using complementary DNAs(cDNA) corresponding to hPL and hCG alpha, beta-subunit. mRNAs for hPL and hCG alpha, beta were primarily observed on syncytiorophoblasts excepting some cytotrophoblasts which contain the signals for hCG alpha mRNA and probably beta mRNA. Therefore, we came to the conclusion that hPL and hCG were synthesized mainly in syncytiotrophoblasts. AT the same time, we believe that the gene expression of hCG alpha and probably hCG beta begins before transformation from cyto- to syncytiotrophoblast, while that of hPL appears later in well differentiated syncytiotrophoblasts. On the other hand, in choriocarcinoma hPL mRNA was not observed while many signals for hCG alpha, beta mRNA were localized in syncytiotrophoblastic cells. In other words, the hPL gene was not expressed in choriocarcinoma because of the blocking of trophoblastic differentiation. The data presented here show that the gene expression of hPL and hCG alpha, beta is closely related to trophoblastic differentiation and/or dedifferentiation (tumoregenesis).