RESUMEN
This study was designed to investigate the effect of different concentrations of L-cysteine supplementation into the maturation medium on the oocyte nuclear maturation, cumulus cell expansion, ultrastructure of the oocytes and the expression of oocyte-derived growth factors BMP-15, GDF-9 and CB-1 genes. Cumulus oocyte complexes (COCs) were collected from cow's ovaries obtained from abattoir and incubated at 38.5°C in maturation media supplemented with 0, 0.6, 0.8 or 1 mM L-cysteine in 5% CO2 under humidified air for 24 hr. We found that a significantly higher percentage of oocytes progressed to metaphase II stage in the in vitro maturation (IVM) medium supplemented with L-cysteine, particularly 0.8 mM group, compared with untreated control oocytes. Additionally, L-cysteine treatment significantly increased the number of expanded COCs and the degree of expansion of individual COCs. Results of RT-qPCR showed significant increase in expression levels of BMP-15 and GDF-9 in L-cysteine-treated groups compared with control one. Electron microgram showed improvement of cytoplasmic maturation regarding ultrastructure of the oocytes and oocyte-cumulus cell gap junction communication in all L-cysteine-treated groups especially 0.8 mM L-cysteine-treated one. In conclusion, supplementation of IVM medium with a potential anti-oxidant, L-cysteine can effectively improve in vitro oocytes cytoplasmic and nuclear maturation via activation of oocyte maturation related BMP-15 and GDF-9 genes in bovine oocytes, benefiting the extended researches about the potential applications of L-cysteine in mammalian breeding technologies.
Asunto(s)
Proteína Morfogenética Ósea 15 , Factor 9 de Diferenciación de Crecimiento , Animales , Proteína Morfogenética Ósea 15/metabolismo , Proteína Morfogenética Ósea 15/farmacología , Bovinos , Células del Cúmulo/fisiología , Cisteína/farmacología , Femenino , Factor 9 de Diferenciación de Crecimiento/metabolismo , Factor 9 de Diferenciación de Crecimiento/farmacología , Técnicas de Maduración In Vitro de los Oocitos/métodos , Técnicas de Maduración In Vitro de los Oocitos/veterinaria , Mamíferos , Oocitos/fisiologíaRESUMEN
We investigated whether paracrine signalling between the bovine oocyte and cumulus cells is altered during the course of in vitro maturation (IVM). Bovine COCs were cocultured with denuded oocytes or treated with specific oocyte-secreted factors, namely recombinant bone morphogenetic protein (BMP)-15 or growth differentiation factor (GDF)-9, beginning from 0 or 9h IVM. To generate a 9-h denuded oocyte (DO) group, COCs were cultured intact for the first 9h of IVM and then denuded. Coculturing intact COCs with DOs denuded immediately after collection or following 9h of maturation did not affect cleavage rate, but improved blastocyst yield (P<0.05) on Day 8 (51 and 61%, respectively; P<0.05) and cell number compared with COCs cultured alone (41%). Significantly, we observed higher levels of endogenous GDF-9 and BMP-15 protein in oocytes of COCs matured for 9h compared with no incubation. The addition of 175 ng mL(-1) GDF-9 or 10%v/v BMP-15 from partially purified transfected 293H cell supernatant for 24h IVM significantly enhanced development to the blastocyst stage from 40% (control) to 51 and 47%, respectively (P<0.05). However, treatment of COCs with GDF-9 or BMP-15 between 9 and 24h of IVM did not increase blastocyst yield. These results provide evidence of quantitative and possibly qualitative temporal changes in oocyte paracrine factor production during IVM.