Late preovulatory synthesis of proteoglycans by the human oocyte and cumulus cells and their secretion into the oocyte-cumulus-complex extracellular matrices

Light- and electron-microscope autoradiography using 3H-glucosamine and 3H-fucose as precursors was employed to investigate proteoglycan synthesis and secretion by late preovulatory human oocytes and cumulus cells. Both the oocyte and cumulus cells were found to be important cellular sources supplying proteoglycans to the oocyte-cumulus-complex extracellular matrices, i.e., the zona pellucida and the cumulus intercellular matrix. Both the oocyte and cumulus cells were shown to secrete labelled proteoglycans into the zona pellucida. Labelled proteoglycans were also detected in the cumulus intercellular matrix. Chase experiments revealed the labelled molecules to be relatively closely associated with both the zona pellucida and the cumulus intercellular matrix. Staining with chromic acid and phosphotungstic acid showed proteoglycan material to penetrate from the cumulus intercellular matrix into pores of the zona pellucida. This material is thought to be a structural equivalent of the newly synthesized proteoglycans secreted by cumulus cells and migrating into the zona pellucida (as detected by autoradiography). It is concluded that newly synthesized proteoglycans secreted by the oocyte and cumulus cells in the late preovulatory period are a component of the microenvironment in which fertilization takes place.