Improving Cell Survival in Injected Embryos Allows Primed Pluripotent Stem Cells to Generate Chimeric Cynomolgus Monkeys

Monkeys are an optimal model species for developing stem cell therapies. We previously reported generating chimeric cynomolgus monkey fetuses using dome-shaped embryonic stem cells (dESCs). However, conventional primed pluripotent stem cells (pPSCs) lack chimera competency. Here, by altering the media in which injected morulae are cultured, we observed increased survival of cynomolgus monkey primed ESCs, induced PSCs, and somatic cell nuclear transfer-derived ESCs, thereby enabling chimeric contributions with 0.1%–4.5% chimerism into the embryonic and placental tissues, including germ cell progenitors in chimeric monkeys. Mechanically, dESCs and pPSCs belong to different cell types and similarly express epiblast ontogenic genes. The host embryonic microenvironment could reprogram injected PSCs to embryonic-like cells. However, the reprogramming level and chimerism were associated with the cell state of injected PSCs. Our findings provide a method to understand pluripotency and broaden the use of embryonic chimeras for basic developmental biology research and regenerative medicine. [Display omitted] •Optimizing culture media for injected morulae inhibits primed PSC apoptosis in embryos•Improved survival of pPSCs injected into embryos generates chimeric monkeys•Embryonic microenvironment reprograms injected PSCs to embryonic-like cells•Reprogramming level and chimerism are related to the cell state of injected PSCs Kang et al. show that inhibition of apoptosis enables conventional primed ESCs, iPSCs, and NT-ESCs to generate chimeric cynomolgus monkeys by optimizing culture conditions for injected morulae, confirming pluripotency and developmental potential of monkey PSCs. Chimera generation results from reprogramming injected PSCs to embryonic-like cells by the host embryonic microenvironment.