Advanced studies on ovary physiology in China in the past 30 years

Follicular development and differentiation are sequential events which are tightly regulated by endocrine hormones, intraovarian regulators and cell-cell interactions. Balanced cell proliferation and apoptosis play an important role in the selection of dominant follicle. Primordial germ cell migration and homing within the gonadal ridge requires regulation by integrated signals, such as the oocyte-secreted polypeptide growth factors, the growth and differentiation factor 9, the bone morphogenetic proteins, stem cell factor (SCF), basic fibroblast growth factor (bFGF), the transcription factor Wilms' tumour 1 (Wt1), and involves the contact of primordial germ cells with extra-cellular matrix proteins and cellular substrates and attraction by the developing gonads. Maturation of cumulus-oocyte complexes and ovulation are directly controlled by luteinizing hormone (LH) and require activation of mitogen-activated protein kinase in granulosa cells. In this review, the key molecules involved in the cell-cell interaction and signal transduction during follicular development, differentiation and ovulation will be summarized, mainly focusing on the signaling factors produced by oocyte and the somatic cells.