Effects of ovarian morphology on oocyte quantity and quality, granulosa cells, in vitro maturation, and steroid hormone production in buffaloes

The present study was conducted to investigate the effects of ovarian morphology on oocyte quantity and quality, as well as the effect of preincubated granulosa cells (PGCs) on in vitro maturation of buffalo oocytes and steroid hormone production. A total of 52 ovarian pairs were grouped into 3 types: Type I (with functional corpus luteum), Type II (with regressed corpus luteum), or Type III (without corpus luteum). The number of follicles and oocytes per ovary were documented. The follicles were classified into 3 groups: <2 mm, 2 to 6 mm, and >6 mm. Oocytes were classified according to their morphology into one of 4 grades (A, B, C, or D) and according to their cumulus compactness into 4 groups (>3 layers of cumulus cells, 1 to 3 layers, partial remnants of cumulus cells, or no cumulus cells). Preincubated granulosa cells were used to investigate their steroidogenic potential with in vitro maturation. A greater number of vesicular follicles and aspirated oocytes were found in Type III than in Type II or Type I. The number of Grade A and Grade B oocytes was significantly higher (P < 0.01) in number in Type III ovaries compared to other types. Oocytes with >3 layers of cumulus cells had a higher maturation rate than oocytes with partial remnants or no cumulus cells, but had low maturation rate compared to oocytes with 1 to 3 layers of cumulus cells. Besides to the higher maturation rate in compact than denuded oocytes, there was a higher (P < 0.01) rate in compact or denuded oocytes when cultured in vitro with PGCs than the corresponding oocytes with no PGCs. These maturation rates coincided with a higher (P < 0.05) concentration of estradiol-17β when compact oocytes were cultured with or without PGCs compared to denuded oocytes and a higher (P < 0.05) concentration of progesterone after culture with PGCs for both compact and denuded oocytes compared to oocytes with no PGCs. In summary, buffalo ovaries with no corpus luteum may result in a higher number of follicles and good oocytes than those with a corpus luteum. Oocytes with an intact cumulus had better maturation than those with partial or denuded cumulus although the denuded oocytes improved their meiotic competence when cultured in vitro with PGCs.