Single cell trajectory modeling identifies a primitive trophoblast state defined by BCAM enrichment

The establishment and function of the human placenta is dependent on specialized cells called trophoblasts. Unfortunately, little is known about the cellular and molecular processes controlling human trophoblast stem cell maintenance and differentiation into mature trophoblast sub-populations/cell states. To address this, we here report transcriptomic data from n=7 first trimester human placental tissues, n=3 regenerative human trophoblast stem cell (hTSC) derived trophoblast organoids, and n=3 EVT-differentiated hTSC derived organoid cultures at single-cell resolution. This study sought to identify the molecular programs and cell states important in trophoblast progenitor establishment, renewal, and differentiation. Placental tissues were collected following elective termination at the British Columbia Women’s Hospital CARE clinic. hTSC cultures were established as described and sequenced on either day 0 of culture (for regenerative organoid colonies), or day 7 of culture (for EVT-differentiated organoid colonies). Placental tissues: First trimester placental tissues were collected from consenting women at two gestational age timepoints: early first trimester (n=4, 6-7 weeks’ gestational age) or late first trimester (n=3, 11-12 weeks’ gestational age). Live cells were purified for mRNA sequencing using the 10X Genomics chromium single cell 3’ reagent v2 chemistry kit. Human trophoblast stem cell derived organoids: Trophoblast organoids were established from 3 hTSC cell lines using a modified version of previously described protocols and differentiated into EVT by removal of WNT signaling components. Live cells were purified for mRNA sequencing from n=3 regenerative cultures on culture day 0 and from n=3 EVT-differentiated cultures on culture day 7 using the 10X Genomics chromium single cell 3’ reagent v3 chemistry kit.