Interactions between different maturation states of oocytes and granulosa cells in human antral follicles identified by single-cell transcriptomics

Human ovarian folliculogenesis is an highly regulated and complex process. Characterization of follicular cell signatures during this dynamic process is important to understand follicle fate (to grow, become dominant or undergo atresia). The transcriptional signature of human oocytes and granulosa cells (GC) in early-growing and ovulatory follicles have been previously described, however that of oocytes with surrounding GCs in small antral follicles have not been studied yet. Here, we have generated a unique dataset of single-cell transcriptomics (SmartSeq2) consisting of the oocyte with surrounding GCs from several individual (non-dominant) small antral follicles isolated from adult human ovaries. We have identified two main types of (healthy) follicles, with a distinct oocyte and GC signature. Using the CellphoneDB algorithm, we then investigated the bi-directional ligand-receptor interactions regarding the TGFβ/BMP, WNT, NOTCH, and receptor tyrosine kinases (RTK) signaling pathways between oocyte and GCs within each antral follicle type. Our work not only revealed the diversity of small antral follicles but also contributes to fill the gap in mapping the molecular landscape of human folliculogenesis and oogenesis. 141 cells from 14 individual antral follicles from 3 donor ovaries