Stimulation of in vitro ovine oocyte maturation with a novel peptide isolated from follicular fluid of the buffalo (Bubalus bubalis)

Importance of Antioxidant Supplementation during In Vitro Maturation of Mammalian Oocytes

The in vitro embryo production (IVEP) technique is widely used in the field of reproductive biology. In vitro maturation (IVM) is the first and most critical step of IVEP, during which, the oocyte is matured in an artificial maturation medium under strict laboratory conditions. Despite all of the progress in the field of IVEP, the quality of in vitro matured oocytes remains inferior to that of those matured in vivo. The accumulation of substantial amounts of reactive oxygen species (ROS) within oocytes during IVM has been regarded as one of the main factors altering oocyte quality. One of the most promising approaches to overcome ROS accumulation within oocytes is the supplementation of oocyte IVM medium with antioxidants. In this article, we discuss recent advancements depicting the adverse effects of ROS on mammalian oocytes. We also discuss the potential use of antioxidants and their effect on both oocyte quality and IVM rate.

Using RT-PCR and glutathione level to study the effect of follicular fluid on in vitro maturation and gene expression of sheep oocytes

The aim of this study is to evaluate the effect of sheep follicular fluid (SFF) supplementation of the in vitro maturation (IVM) media of sheep oocytes on the resumption of meiosis, glutathione (GSH) level, and expression of apoptosis (Bax, Bcl-2) as well as heat shock protein beta-1 (HSPB1) genes. Sheep ovaries were collected from the central slaughterhouse of Riyadh city, KSA. Oocytes were aspirated from 3 to 8 mm follicles. Sheep oocytes were cultured in maturation medium with different concentrations of sheep follicular fluid: 0% (control), 10%, 20% and 40% for 24 h. The results indicated that the maturation rate of oocytes was significantly (p ≤ .05) decreased in 40% SFF (36.87%) versus the control (61.3%), 10% SFF (63.95%) and 20% SFF (64.08%). The supplementation of the IVM medium with 10% SFF induced an intra-oocyte GSH concentration that was significantly higher than in sheep oocytes cultured with 20% and 40% SFF and similar to the GSH content in oocytes cultured without SFF. Real-time polymerase chain reaction analysis of gene expression revealed no significant differences in the Bax and HSPB1 genes between the control and 10% SFF, whereas they were significantly higher in 40% FF (p ≤ .05) compared to the control. The expression of Bax:Bcl-2 was significantly higher in 20% and 40% SFF compared to the control group. In conclusion, the addition of SFF to the IVM culture of sheep oocytes is recommended to support nuclear maturation and increase oocyte competence.

The influence of the corpus luteum on metabolites composition of follicular fluid from different sized follicles and their relationship to serum concentrations in dairy cows

The presence of corpus luteum may have a local effect on metabolite composition of follicular fluid (FF) and could indirectly influence follicular development and oocyte quality. The purpose of this study was to examine the influence of the corpus luteum on metabolite composition of follicular fluid (FF), harvested from different-sized follicles and the relationship between metabolite composition of FF to blood serum in dairy cows. Ovaries and blood samples were collected from 30 female adult Holstein Friesian cows, 4-7 years old, with clinically normal reproductive tracts. The animals were in the diestrus stage and selected post mortem. The ovaries collected were classified based on the presence and absence of corpus luteum (CL(+/-)). Visible follicles on the surface of the ovaries were classified into (i) small (3-5mm), (ii) medium (6-9 mm) and (iii) large (10-20mm) based on their diameter. Follicular fluid was aspirated from follicles with different sizes in CL(+) and CL(-) ovaries. Blood and FF samples were analyzed for various biochemical constituents including glucose, cholesterol, triglyceride, total protein, albumin and globulin. The results showed that serum concentration of glucose, cholesterol and triglyceride was significantly different (p≤0.05) in FF from follicles of different size categories. Differences between various follicle size categories in CL(-) ovaries were only significant for concentrations of glucose, cholesterol and triglyceride. FF concentration of glucose and cholesterol in the same follicle size categories in CL(+) ovaries was significantly lower than that of CL(-) ovaries. These results indicate that levels of the biochemical metabolites in serum and FF differ significantly. In addition, FF concentrations of biochemical metabolites were related to follicular size and to the presence or absence of corpus luteum.

Effect of a partially purified 30.1 kDa ovine follicular fluid protein on ovine follicle and ovarian somatic cell growth, and oocyte maturation in vitro

AIM

Regulation of folliculogenesis and oocyte-somatic cell interactions in the ovarian follicles is under the control of gonadotrophins and various local factors. In the present study, an attempt was made to isolate and examine the biological activities of ovarian follicular fluid protein(s) in sheep in vitro.

METHODS

Follicular fluids aspirated from ovarian follicles of slaughterhouse-derived ovaries were made cell free by centrifugation (5000 g for 30 min) and steroid free by charcoal treatment. The follicular fluid was then subjected to ammonium sulphate precipitation and gel filtration chromatography using G-75 Sephadex. Protein detection was performed using a UV spectrophotometer at 280 nm. The 35-50% fraction yielded a detectable peak and a protein of 30.1 kDa as examined by SDS-PAGE. The effect of increasing doses of the 30.1 kDa ovine follicular fluid protein (oFFP) was tested at different doses on pre-antral and antral follicle growth; cumulus cell expansion; oocyte maturation; changes in protein, calcium and phosphorus levels of oocytes after culture in media containing different levels of isolated protein; mural granulosa cell, polar granulosa cell (cumulus cell), oviductal epithelial cell monolayer formation and granulosa cell proliferation in vitro.

RESULTS

The oFFP significantly inhibited antral follicle growth, cumulus expansion, oocyte maturation and somatic cell growth in vitro in a dose-dependent manner. The oFFP did not have a significant effect on the pre-antral follicle growth in vitro. The protein, calcium and phosphorus contents of oocytes were found to decrease in oocytes cultured in maturation medium containing the oFFP.

CONCLUSION

The present study demonstrates a follicular fluid factor regulating folliculogenesis and oocyte maturation in sheep.