In most mammals, the growth and development of the oocyte and its surrounding somatic cells occur in a highly coordinated and mutually dependent manner. The oocytes acquire their developmental competence sequentially during follicular growth, ultimately reaching the ability to undergo the complete meiotic and cytoplasmic maturation at the final stage of preovulatory follicle. Fully-grown immature oocytes are tightly surrounded by compact layers of specialized granulosa cells termed cumulus cells that form the cumulus-oocyte complex (COC). After a preovulatory surge of gonadotrophin, the cumulus cells organize a special muco-elastic extracellular matrix (ECM) that requires the synthesis and deposition of a large amount of hyaluronan (HA) and HA binding matrix glycoproteins. Many studies have reported that the formation of COC matrix mass plays important roles for a variety of reproductive aspects, oocyte meiotic maturation with changes of junctional communication and cytoskeletal modification in COC, ovulation, fertilization and early embryo development. Lately, we identified the expressions of HA synthases and HA receptor CD44 in porcine COC matrix. The interaction of HA-CD44 appears to be closely related to the gap junctional communication and meiotic resumption. This review points to the recent findings on the regulation and the presumptive mechanism of COC matrix molecules, and physiological features in COC expansion.
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