The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell, University of California, San Francisco, San Francisco, United States; Department of Urology, University of California, San Francisco, San Francisco, United States; Center for Reproductive Sciences, University of California, San Francisco, San Francisco, United States; Developmental and Stem Cell Biology Graduate Program, University of California, San Francisco, San Francisco, United States
Yan Zhou
The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell, University of California, San Francisco, San Francisco, United States; Center for Reproductive Sciences, University of California, San Francisco, San Francisco, United States; Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, United States
Mirhan Kapidzic
The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell, University of California, San Francisco, San Francisco, United States; Center for Reproductive Sciences, University of California, San Francisco, San Francisco, United States; Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, United States
Susan Fisher
The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell, University of California, San Francisco, San Francisco, United States; Center for Reproductive Sciences, University of California, San Francisco, San Francisco, United States; Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, San Francisco, United States
The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell, University of California, San Francisco, San Francisco, United States; Department of Urology, University of California, San Francisco, San Francisco, United States; Center for Reproductive Sciences, University of California, San Francisco, San Francisco, United States
The human placenta contains two specialized regions: the villous chorion where gases and nutrients are exchanged between maternal and fetal blood, and the smooth chorion (SC) which surrounds more than 70% of the developing fetus but whose cellular composition and function is poorly understood. Here, we use single cell RNA-sequencing to compare the cell types and molecular programs between these two regions in the second trimester human placenta. Each region consists of progenitor cytotrophoblasts (CTBs) and extravillous trophoblasts (EVTs) with similar gene expression programs. While CTBs in the villous chorion differentiate into syncytiotrophoblasts, they take an alternative trajectory in the SC producing a previously unknown CTB population which we term SC-specific CTBs (SC-CTBs). Marked by expression of region-specific cytokeratins, the SC-CTBs form a stratified epithelium above a basal layer of progenitor CTBs. They express epidermal and metabolic transcriptional programs consistent with a primary role in defense against physical stress and pathogens. Additionally, we show that SC-CTBs closely associate with EVTs and secrete factors that inhibit the migration of the EVTs. This restriction of EVT migration is in striking contrast to the villous region where EVTs migrate away from the chorion and invade deeply into the decidua. Together, these findings greatly expand our understanding of CTB differentiation in these distinct regions of the human placenta. This knowledge has broad implications for studies of the development, functions, and diseases of the human placenta.
