Cumulus oophorus extracellular matrix in the human oocyte: a role for adhesive proteins

A viscous elastic matrix secreted by the cumulus oophorus cells represent the "extracellular matrix" surrounding the human mature oocyte obtained from assisted reproductive technology (ART). The cumulus matrix is involved in several reproductive processes, including the pick-up of the oocyte-cumulus complex by the oviduct, the final maturation of the ovum and sperm-egg interaction. As showed by some Authors, the cumulus matrix is rich in hyaluronan, as well as in other proteins including inter-alpha-trypsin inhibitor, a dermatan sulfate proteoglycan, and a pentraxin-3. Proteins and hyaluronan are linked together to form a meshwork comprised of granules and filaments. We found in human cumulus oocyte complexes the presence of specialized cells still capable of producing fibronectin and tenascin-c in the post-ovulatory period. Moreover, fibronectin and tenascin-c are present within the hyaluronan matrix at fertilization during the tubal sojourn of the ovum and the embryo. Since pentraxin3 is important in matrix stabilization and gamete interactions, a possible role for fibronectin and tenascin-c may be postulated in the final maturation of the ovum, in the tubal pick-up and in the complex dialogue with the tubal epithelium.