Derivation of functional oocytes from granulosa cells

Limited oocyte and ovarian reserve in vivo or chemo-therapy leads to reproductive aging or premature aging and associated diseases including infertility. Excitingly, oocytes have been successfully derived from embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) by ectopic expression of transcription factors, showing great potential in fertility preservation or restoration. The accessible granulosa cells are a type of somatic cells that interact and evolve with oocyte development during folliculogenesis. Further, with stem cells-like property, granulosa cells are amenable to reprogramming to generate iPSCs and have been the first used for clone animals. These prompted us to explore the potential of granulosa cells in derivation of germ cells. Meanwhile, the strict genome fidelity required for germ cells inspired us to test reprograming by complete small chemicals, which avoids genetic manipulation, cell transfection and destruction of embryos. Here we show that somatic granulosa cells of adult mouse ovaries can be converted to germ cells and functional oocytes that reproduce fertile pups. We are able to consistently induce granulosa cells to pluripotent state (gPSCs) like ESCs in both developmental competence and molecular signatures. Notably, crotonic sodium-facilitated crotonylation is critical not only for pure small chemicals-based reprogramming of granulosa cells to gPSCs, but also confers the gPSCs with high germline capacity. Consequently, the gPSCs and the derived primordial germ-cell like cells hold longer telomeres and maintain high genomic stability which is critical for germ cells. Taken together, we efficiently generate high quality gPSCs and functional oocytes from adult granulosa cells by significantly improving chemical reprograming approach.