FIGURE 5.

Schematic representation of the role of IMD/ADM2 signaling in oocyte-cumulus cell interactions. The endocrine FSH from the pituitary stimulates follicular growth by acting on granulosa and cumulus cells. In parallel, GDF9, BMP15, and other OSFs from oocytes coordinate the folliculogenesis and final maturation process by stimulating cell proliferation and cumulus expansion. By contrast, the IMD/ADM2 signaling from oocytes may provide a stationary signal to maintain cumulus cell survival and cell-cell contacts in COCs prior to cumulus cell expansion.