Effect of oocytectomy on glycosaminoglycan composition during cumulus expansion of porcine cumulus-oocyte complexes cultured in vitro.

To investigate the role of oocytes in the accumulation of glycosaminoglycans during cumulus expansion, we analyzed the amount and composition of glycosaminoglycans in porcine intact and oocytectomized cumulus-oocyte complexes. Follicular fluid induced cumulus expansion in intact and oocytectomized cumulus-oocyte complexes cultured for over 24 h, but the degree of expansion in oocytectomized complexes reached only 76% of that in intact complexes after 24 h in culture. There were no differences in the amounts of [3H]glucosamine incorporated into each type of complex. Metabolic labeling studies on glycosaminoglycans with [3H]glucosamine and [35S]sulfate showed that the amounts of 3H- and 35S-labeled glycosaminoglycans increased, and rapidly so, from 16 h in culture. The 3H-labeled glycosaminoglycans at these high levels were digested by Streptomyces hyaluronidase or chondroitinase ABC, and the rate of increase in 3H-labeled glycosaminoglycans was reduced by oocytectomy. In contrast, the increased levels of 35S-labeled glycosaminoglycans were affected only by chondroitinase ABC, and oocytectomy was ineffective. In conclusion, follicular fluid promotes cumulus expansion, and the oocyte plays an essential role in the acute synthesis of hyaluronic acid, but not chondroitin sulfate, during cumulus expansion stimulated in vitro.