(T1274) IN VITRO HUMAN PLURIPOTENCY AT THE EXPANDED STATE HARBOURS BI-LINEAGE DIFFERENTIATION POTENTIAL INTO EXTRA-EMBRYONIC LINEAGES AND MOLECULAR CHARACTERISTICS DISTINCT FROM PRIMED PLURIPOTENCY
Abstract: The elucidation of the molecular machinery orchestrating human embryogenesis has been limited by both technical and ethical challenges. The establishment of human pluripotent stem cells (hPSCs) has offered valuable in vitro models for the scalable and perturbable dissection of the diverse genetic mechanisms underlying human embryo development. We have previously developed human expanded potential stem cells (hEPSCs), which exhibit molecular signatures resembling human pre-blastocyst embryos, and have the ability to differentiate into both embryonic as well as extra-embryonic cell types. In this study, we first validated the expanded developmental potency of hEPSCs for differentiation into the AME-like and trophoblastic lineages using single-cell transcriptomics. From this platform, we further identified the transposable element (TE) HERVE-int as a novel marker of AME cells. Furthermore, a systematic analysis of the molecular characteristics of hEPSCs was performed, which identified that hEPSCs were substantially different from primed hPSCs but share remarkably similarities with pre-implantation human embryos. These include but are not limited to their transcriptomic signatures like relatively higher HERVK-int/LTR5_Hs and DNA damage repair including homologous recombination gene expression; lower glycolytic activity; mitochondrial morphology as well as low H3K27me3 levels, which were also exclusively observed in morula-stage human embryos. Distinct from naïve hPSCs but similar to primed hPSCs, hEPSCs exhibited appropriate DNA methylation patterns and therefore maintained genomic imprinting. Additionally, the various molecular signatures of hEPSCs were evolutionarily conserved in porcine and bovine EPSCs. In conclusion, hEPSCs exhibit a distinctive dual extra-embryonic differentiation potential with certain molecular characteristics resembling those of the pre-blastocyst human embryos. Hence, hEPSCs hold the potential for investigating human cell fate commitment and developing stem cell-based therapies for regenerative medicine purposes.
Funding Source: This project is supported by Health@InnoHK, Innovation Technology Commission, HKSAR
