Chromosomal instability in human trophoblast stem cells and placenta

The human placenta, a unique tumor-like organ, is typically thought to exhibit rare aneuploidy associated with adverse pregnancy outcomes. Discrepancies in reported aneuploidy prevalence in placenta likely stem from limitations in modeling and the resolution of detection methods. Here, we used isogenic trophoblast stem cells (TSCs) derived from both naïve and primed human pluripotent stem cells (hPSCs) to reveal the spontaneous occurrence of aneuploidy, suggesting chromosomal instability (CIN) as an inherent feature of the trophoblast lineage. We identified potential pathways contributing to the occurrence and tolerance of CIN. These findings were further validated using single-cell multiome data from healthy human placentas, where we observed a high prevalence of heterogeneous aneuploidy across trophoblast cells. Despite extensive chromosomal abnormalities, TSCs maintained their proliferative and differentiation capacities, suggesting that CIN is a typical aspect of placental development. Our study challenges the traditional view of aneuploidy in the placenta and provides new insights into the role of CIN in normal placental function.