The interactions between cysteamine, cystine and cumulus cells increase the intracellular glutathione level and developmental capacity of goat cumulus-denuded oocytes

To improve in vitro maturation (IVM) of denuded oocytes (DOs), we observed the interactive effects of cysteamine, cystine and cumulus cells on the glutathione (L-gamma-glutamyl-L-Cysteinyl-glycine; GSH) level and developmental capacity of goat IVM oocytes. Cysteamine supplementation increased the GSH level and blastocyst rates of both cumulus-oocyte complexes (COCs) and DOs, while the addition of cystine increased the GSH level and blastulation only in the presence of cumulus cells (COCs or DOs co-cultured on a cumulus cell monolayer). Simultaneous supplementation of cysteamine and cystine increased the GSH content and blastulation of co-cultured DOs to a level similar to that of COCs matured without thiol supplementation. Co-culture without thiol supplementation improved DOs' GSH synthesis but not blastulation. The results suggest that DOs cannot utilize cystine for GSH synthesis unless exogenous cysteamine is supplied by either cumulus cells or supplementation. Thus, while the addition of cystine alone is enough to improve IVM of COCs, improvement of DOs requires supplementation of both cystine and cysteamine. Synergic actions between cysteamine, cystine and cumulus cells restore the GSH level and developmental capacity of goat DOs.