Placental trophoblasts are key determinants of in utero development. Mouse trophoblast stem cells (mTSCs), which were first derived over a decade ago, are a powerful cell culture model for studying their self-renewal or differentiation. Our attempts to isolate an equivalent population from the trophectoderm of human blastocysts generated colonies that quickly differentiated in vitro. This finding suggested that the human placenta has another progenitor niche. Here we show that the chorion is one such site. Initially, we immunolocalized pluripotency factors and trophoblast fate determinants in the early-gestation placenta, amnion and chorion. Immunoreactive cells were numerous in the chorion. We isolated these cells and plated them in medium containing FGF and an inhibitor of activin/nodal signaling, which is required for human embryonic SC self-renewal. Colonies of polarized cells with a limited lifespan emerged. Trypsin dissociation yielded continuously self-replicating monolayers. Colonies and monolayers formed the two major human trophoblast lineages—multinucleate syncytiotrophoblasts and invasive cytotrophoblasts (CTBs). Transcriptional profiling experiments revealed the factors associated with the self-renewal or differentiation of human chorionic trophoblast progenitor cells (TBPCs). They included imprinted genes, NR2F1/2, HMGA2 and adhesion molecules that were required for TBPC differentiation. Together, the results of these experiments suggested that the chorion is one source of epithelial CTB progenitors. These findings explain why CTBs of fully formed chorionic villi have a modest mitotic index and identify the chorionic mesoderm as a niche for TBPCs that support placental growth.

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Objective Investigate associations between serum BPA concentrations and follicular response to exogenous ovary stimulation. Design Fasting serum was prospectively collected on the day of oocyte retrieval and assessed for unconjugated BPA using high-performance liquid chromatography (HPLC) with Coularray detection. Multivariable linear regression and negative binomial regression were used to assess associations between concentrations of BPA and outcome measures. Models were adjusted for race/ethnicity, antral follicle count at baseline, and cigarette smoking. Setting A reproductive health center. Patients Forty-four women undergoing in vitro fertilization (IVF). Main outcome measures Peak-estradiol level (E2) and the number of oocytes retrieved during IVF. Results The median unconjugated serum BPA concentration is 2.53 ng/ml (range 0.3–67.36 ng/ml). Bisphenol A is inversely associated with E2 (β=−0.16; 95% confidence interval (CI) −0.32, 0.01), as well as with E2 normalized to the number of mature-sized follicles at the hCG trigger (β=−0.14; 95%CI −0.24, −0.03). No association is observed for BPA and the number of oocytes retrieved (adjusted risk ratio=0.95; 95%CI 0.82, 1.10). Conclusions Bisphenol A is associated with a reduced estradiol response during IVF. Although limited by the preliminary nature of this study, these results merit confirmation in a future comprehensive investigation.

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