Insulin-like growth factor (IGF) performance in ovarian function and applications in reproductive biotechnologies.

The role of the insulin-like growth factor (IGF) system has attracted close attention. The activity of IGF binding proteins (IGFBPs) within the ovary has not been fully elucidated to date. These proteins bind to IGF with an equal, or greater, affinity than to the IGF1 receptor, thus being in the main position to regulate IGF signalling, in addition to extending the half-life of IGFs within the bloodstream and promoting IGF storage in specific tissue niches. IGF1 has an important part in cell proliferation, differentiation and apoptosis. Considering the importance of IGFs in oocyte maturation, this review sought to elucidate aspects including: IGF production mechanisms; constituent members of their family and their respective functions; the role that these factors play during folliculogenesis, together with their functions during oocyte maturation and apoptosis, and their performance during luteal development. This review also explores the role of IGFs in biotechnological applications, focusing specifically on animal genetic gain.

In vitro maturation in synthetic oviductal fluid increases gene expression associated with quality and lipid metabolism in bovine oocytes.

Traditionally, in vitro oocyte and embryo culture progresses through a series of varying culture medium. To investigate simplifying the in vitro production of bovine cumulus-oocyte complexes (COCs), this study used synthetic oviductal fluid (SOF) supplemented with conjugated linoleic acid (CLA). Special interest was placed on gene expression linked to lipid metabolism and oocyte maturation. COCs were matured in different media: Medium 199 (M199 group), M199 with 100 µM CLA (M199 + CLA group), SOF (SOF group), and SOF with 100 µM CLA (SOF + CLA group). COCs matured with SOF showed a higher relative abundance of mRNA of quality indicators gremlin 1 (GREM1) and prostaglandin-endoperoxide synthase 2 (PTGS2) in oocytes, and GREM1 in cumulus cells compared with in the M199 group. SOF medium COCs had a higher relative abundance of fatty acid desaturase 2 (FADS2) compared with the M199 group, which is essential for lipid metabolism in oocytes. Furthermore, the abundance of stearoyl-coenzyme A desaturase 1 (SCD1) in oocytes matured with SOF was not influenced by the addition of CLA, whereas the relative abundance of SCD1 was reduced in M199 medium with CLA. We concluded that maturation in SOF medium results in a greater abundance of genes linked to quality and lipidic metabolism in oocytes, regardless of the addition of CLA.

IMD/ADM2 operates as a secretory factor that controls cumulus-oocyte complexes (COCs) conformation for oocytes in vitro maturation.

During in vitro maturation (IVM), the compact structure of cumulus-oocyte complexes (COCs) is vital for oocyte competence acquisition. Intermedin/Adrenomedullin-2 (IMD/ADM2) binds to the receptor RAMP (1, 2, or 3):CLR. Recently, it was demonstrated that IMD/ADM2 stimulates oocyte competence and improves bovine embryo quality. Therefore, this study aimed to examine the IMD/ADM2 as a secretory factor controlling COCs conformation for oocyte maturation. The results showed that traditional M-CDM medium induced in COCs the Imd/Adm2 gene expression during IVM and produced IMD/ADM2 peptide secretion. Furthermore, after IVM, in the oocytes, the expression of ramps (1, 2, or 3) and clr was demolished, and RAMPs and CLR proteins were decreased, with a negative Pearson correlation. These results suggest that RAMPs and CLR are synthesized and stored during oocyte maturation. Supplementing the M-CDM with α-RAMP1 or α-IMD/ADM2 antibodies elicits a negative effect (P < 0.05) in COCs compaction. Blocking the IMD/ADM2 signaling pathway with any α-RAMPs or α-CLR antibodies produces a similar lower yield of oocytes in metaphase II (P > 0.05) but was lower than control culture medium (P < 0.05). In conclusion, when COCs are cultured with M-CDM, the IMD/ADM2 becomes expressed and secreted. In turn, it acts as a ligand preferentially to RAMP1:CLR or RAMP3:CLR, present in cumulus cells and oocytes. Sequentially, COCs compact structure is conformed to promote an adequate bidirectional communication that conduces the oocytes' maturation.

IMD/ADM21-47, a factor that improves embryo quality.

Starting in vitro fertilization process with competent oocytes that may endure first cellular divisions is a critical step for obtaining an embryo. To obtain in vitro competent oocytes, culture conditions should emulate the in vivo microenvironment as close as possible. With the aim of improving the in vitro culture medium, the present study evaluated the IMD/ADM21-47 peptide as a factor that promotes oocyte competence and improves embryo quality in bovine systems. The culture supplemented with 153 µg/mL of IMD/ADM21-47 was correlated with the production of healthy oocytes in metaphase II (MII) stage in compacted cumulus-oocyte complexes (COC) with a decrease of BAX/BCL-2 to mRNA ratio and a reduction of late apoptosis by TUNEL in MII oocytes. In addition to this, treatment with IMD/ADM21-47 caused cAMPi level to be constant over time, and the cAMPi level kept increasing until 6 h. COC supplementation with 153 µg/mL of IMD/ADM21-47 increased the blastocyst production rate two-fold in comparison with control conditions. Only embryos from COC treatment with this peptide were capable of developing blastocysts in stage-6 grade I; compared with the control culture, it was the treatment with the greater number of blastocysts stage-5; these are characteristics of good quality blastocysts.

Influence of eCG and breed on the number of oocytes collected and the production of in vitro embryos of young goats during the reproductive season.

The objective of this study was to determine the effect of breed and equine chorionic gonadotropin (eCG) on ovarian response and in vitro embryo production from young goats. Thirty-one (12 Alpine, 10 Nubian, and 9 Saanen) were randomly assigned into three treatments of eCG (T1, 0 IU; T2, 500 IU; and T3, 1000 IU). Alpine goats showed the highest amount and largest size of follicles (P = 0.003). The effect of eCG dose 24 h post application was significant (P < 0.05), and was superior in goats undergoing T2. The aspiration rate of cumulus-oocyte complexes (COC) was 34% (P > 0.05), except for percentage of denuded oocytes, which obtained the highest number (P = 0.003) in the Saanen goats. The same difference was found (P = 0.02) in oocytes grade III in T2 and T3, with 42.5 and 37.9% respectively. In vitro embryo production was 80.0% of IVF/cleavage in the Alpine goats (P = 0.003). Embryo production was the greatest for T2 (69.2%; P = 0.004). T3 goats had higher percentage of morula stage (66.6%; P = 0.030). It is concluded that the application of eCG has a significant effect on the ovarian status, and quality and quantity of embryos with a differential response depending on the breed.

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: 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 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.

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.(AU)