Effect of varying glucose concentrations during in vitro maturation and embryo culture on efficiency of in vitro embryo production in buffalo

The occurrence of follicular cyst affects the embryonic developmental competences of buffalo oocytes under in vitro culture conditions

Cystic ovarian disease (COD) is a major cause of infertility in dairy cows. This study aimed to investigate the impact of follicular cysts on the invitro blastocyst developmental competence of oocytes and the relative gene expression of blastocysts developed from the subordinate follicles of ipsilateral (ovary with cyst), contralateral (ovary opposite to cyst), and normal ovaries of buffaloes. A total of 2059 ovaries were collected from slaughterhouse and classified into three categories based on the presence of follicular cysts: a) ipsilateral, b) contralateral, and c) control (absence of cysts). Oocytes of grades A, B, and C were used for invitro maturation, invitro fertilization, and invitro culture. The cleavage rates of the ipsilateral (91.54 %) and contralateral (95.71 %) categories were higher (P < 0.01) than those of the control (76.82 %). Conversely, the blastocyst development rate was higher (P < 0.01) in control (32.67 %) than in ipsilateral (8.46 %) and contralateral (7.14 %) groups. The mRNA expression levels of maturation (BMP15), steroidogenesis (STAR, CYP19), antioxidant (SOD2, HSPB1) and anti-apoptotic (BCL2) genes were decreased in arrested embryos derived from both cystic (ipsilateral and contralateral) and control category follicles when compared to blastocysts derived from their respective category follicles. Conversely, BAX expression increased in arrested embryos. Expression of SOD2 and BAX was downregulated in blastocysts from both ipsilateral and contralateral categories compared to controls. The presence of one or more follicular cysts in either ovary affected the developmental competence of oocytes derived from subordinate follicles. Therefore, the buffaloes with cysts in either ovary should be avoided when aspirating follicles for IVF.

Cleavage and in vitro cultivation rates monitoring in culture media supplemented with energy sources, non-essential amino acids, and antioxidants in the buffalo embryos

The study was designed to monitor the cleavage rate (CR) and in-vitro cultivation rate (IVC) after addition of energy sources, non-essential amino acids, and antioxidants to the Synthetic oviductal fluid (SOF) and FertiCult. After in-vitro maturation and in-vitro fertilization, presumptive zygotes were cultured in one of two culture media: FertiCult media and SOF medium, supplemented with pyruvate, glucose, and sodium lactate as energy sources, as well as 10, 20, 250, 500, and 750 mg non-essential amino acids, and antioxidants. All stages of cleavage rate (CR), and in-vitro cultivation rate (IVC) of embryonic development including morula stage (MOR) and blastocyst (BLAS) have been assessed. The findings revealed that there were no significant differences in the CR between the control and other treated groups with sources of energy when added to SOF media (P > 0.05), while there were significant differences (P < 0.05) in the IVC of embryonic development between groups (The percentages of MOR stage in the control, pyruvate, glucose and mixture of source of energy (MIX) were at 50%, 62.5%, 60%, and 63.6%, respectively). The highest percentage of the BLAS was recorded after SOF supplementation with glucose (40%). Similarly, there were no significant differences (P > 0.05) in the CR between control and FertiCult supplemented with sources of energy, while the IVC stages increased significantly (P < 0.05) in the FertiCult media supplemented with glucose, pyruvate, sodium lactate, and MIX. The percentages of the MOR stage in the control, pyruvate, glucose and mix media were at 50%, 55.6%, 55.6%, 54.5%, 57.1% respectively. The lowest percentage of the BLAS was recorded after FertiCult supplementation with pyruvate (11.1%). Replenishing the SOF maturation media with 20 mg of non-essential amino acids significantly (P < 0.05) enhanced the MOR stage (100%). There was also an improvement in the development of BLAS stage, where it reached 31.2% and 47.4% in the SOF maturation media supplemented with 10, and 750 mg non-essential amino acids, respectively. There were no significant differences (P > 0.05) in neither CR nor IVC between control and FertiCult supplemented with antioxidants. There were significant differences (P < 0.05) in the MOR stages (control, 42.9% & treated, 57.9%) and BLAS stages (control, 21.4% & treated, 42.1%) in antioxidant supplemented SOF maturation media compared to control. In conclusion, supplementation of SOF cultivation medium with energy sources, 20 mg of non-essential amino acids and antioxidant addition may improve the cleavage rate (CR) and in vitro cultivation rate (IVC) of buffalos' embryonic development.

RNA sequencing and gene co-expression network of in vitro matured oocytes and blastocysts of buffalo

In reproductive technologies, uncovering the molecular aspects of oocyte and embryo competence under different conditions is crucial for refining protocols and enhancing efficiency. RNA-seq generates high-throughput data and provides transcriptomes that can undergo additional computational analyses. This study presented the transcriptomic profiles of in vitro matured oocytes and blastocysts produced in vitro from buffalo crossbred (Bubalus bubalis), coupled with gene co-expression and module preservation analysis. Cumulus Oophorus Complexes, obtained from slaughterhouse-derived ovaries, were subjected to in vitro maturation to yield metaphase II oocytes (616) or followed in vitro fertilization and culture to yield blastocysts for sequencing (526). Oocyte maturation (72%, ±3.34 sd) and embryo development (21.3%, ±4.18 sd) rates were obtained from three in vitro embryo production routines following standard protocols. Sequencing of 410 metaphase II oocytes and 70 hatched blastocysts (grade 1 and 2) identified a total of 13,976 genes, with 62% being ubiquitously expressed (8,649). Among them, the differentially expressed genes (4,153) and the strongly variable genes with the higher expression (fold-change above 11) were highlighted in oocytes (BMP15, UCHL1, WEE1, NLRPs, KPNA7, ZP2, and ZP4) and blastocysts (APOA1, KRT18, ANXA2, S100A14, SLC34A2, PRSS8 and ANXA2) as representative indicators of molecular quality. Additionally, genes exclusively found in oocytes (224) and blastocysts (2,200) with specific biological functions were identified. Gene co-expression network and module preservation analysis revealed strong preservation of functional modules related to exosome components, steroid metabolism, cell proliferation, and morphogenesis. However, cell cycle and amino acid transport modules exhibited weak preservation, which may reflect differences in embryo development kinetics and the activation of cell signaling pathways between buffalo and bovine. This comprehensive transcriptomic profile serves as a valuable resource for assessing the molecular quality of buffalo oocytes and embryos in future in vitro embryo production assays.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

MeDIP-sequencing for profiling global DNA methylation in buffalo embryos produced by in vitro fertilization

Assisted reproductive technique like in vitro fertilization has contributed immensely in producing genetically improved livestock. Production of embryos under in vitro conditions can affect global DNA methylation pattern during the course of embryonic development. The present study is aimed at the generation and comparison of global DNA methylome of embryos at 2-cell, 8-cell and blastocyst stage of buffalo embryos produced by in vitro fertilization using MeDIP-Sequencing. It is observed that there is a profound difference in the global DNA methylation profile of IVF embryos at different developmental stages. These differences are manifested throughout the course of embryonic development. Pathways like Wnt signaling pathway, gonadotropin-releasing hormone receptor pathway and integrin signaling were found to be majorly affected by hypermethylation of DNA in IVF embryos throughout the development.

Semen parameters and fertility potency of a cloned water buffalo (Bubalus bubalis) bull produced from a semen-derived epithelial cell

Semen contains epithelial cells that can be cultured in vitro. For somatic cell nuclear transfer applications, it is essential to know whether clone(s) produced from semen-derived epithelial cells (SedECs) are healthy and reproductively competent. In this study, the semen and fertility profile of a cloned bull (C1) that was produced from a SedEC were compared with its donor (D1) and with two cloned bulls (C2, C3) that were produced from commonly used skin-derived fibroblast cells (SkdFCs). We observed variations in some fresh semen parameters (ejaculated volume and mass motility), frozen-thawed sperm parameters (plasma membrane integrity, and computer-assisted semen analysis (CASA) indices), but values are within the normal expected range. There was no difference in sperm concentration of ejaculated semen and frozen-thawed semen parameters which include sperm motility, percentage of live and normal morphology sperm, and distance traveled through oestrus mucus. Following in vitro fertilization (IVF) experiments, zygotes from C1 had higher (P < 0.05) cleavage rates (81%) than C2, C3, and D1 (71%, 67%, and 75%, respectively); however, blastocyst development per cleaved embryo and quality of produced blastocysts did not differ. The conception rate of C1 was 46% (7/15) and C2 was 50% (8/15) following artificial insemination with frozen-thawed semen. Established pregnancies resulted in births of 7 and 6 progenies sired by C1 and C2, respectively, and all calves show no signs of phenotypical abnormalities. These results showed that semen from a cloned bull derived from SedECs is equivalent to semen from its donor bull and bulls cloned from SkdFCs.

Contributions of RNA-seq to improve in vitro embryo production (IVP)

In Vitro Embryo Production (IVP) is widely used to improve the reproductive efficiency of livestock animals, however increasing the embryo development rates and pregnancy outcomes is still a challenge for some species. Thus, the lack of biological knowledge hinders developing specie-specific IVP protocols. Therefore, the contributions of RNA-seq to generate relevant biological knowledge and improve the efficiency of IVP in livestock animals are reviewed herein.

In vitro embryo production in buffaloes: from the laboratory to the farm

Transvaginal follicular aspiration technique together with in vitro embryo production are the biotechnological alternatives currently available to support genetic improvement breeding programs in buffalo species. However, aspects related to animal management, lack of knowledge of the metabolic needs and biochemical peculiarities of gametes and embryos, as well as the reproductive physiology characteristics have hampered progress in the results. Despite the low availability of good quality oocytes collected after OPU in donors as a physiological characteristic of buffalo species, high rates of oocyte maturation, modest embryo cleavage, blastocyst production and pregnancy rates after transvaginal embryo transfer in recipients could be obtained in buffalo in vitro embryo production programs. The results of implementing an in vitro embryo production program in buffaloes in the northern region of Pará state, Brazil, and results published by other groups demonstrate the feasibility of implementing this biotechnology in the routine of breeding programs. Nevertheless, in order to achieve better and consistent results, it is necessary to deepen the knowledge on the peculiarities of reproductive biology in this specie. Selection of donor animals based on ovarian size and ovarian follicular reserve and on the rate of blastocyst production is presented as an effective alternative to increase the efficiency of the in vitro embryo production technique applied to the buffalo species.

Suppressed expression of macrophage migration inhibitory factor in the oviducts of lean and obese cows

Oviducts synthesise macrophage migration inhibitory factor (MIF) to promote sperm capacitation and embryogenesis. This study aimed to test a hypothesis that the oviducts of obese cows may express MIF at a lower level than those of normal and lean cows. Ampullar and isthmic oviduct sections were collected from lean (n=5; body condition score (BCS) on a 5-point scale, 2.5), normal (n=6; BCS, 3.0) and obese (n=5; BCS, 4.0) Japanese Black cows. MIF mRNA and protein were extracted from ampullae and isthmuses and their levels measured by real-time polymerase chain reaction or western blot. Immunohistochemistry was performed on frozen sections of ampullae and isthmuses by using antibodies to MIF. MIF mRNA and protein expression were lower in the obese and lean groups than in the normal group (P<0.05). Immunohistochemistry revealed that the primary site of MIF expression in the ampulla and isthmus is the tunica mucosa. In conclusion, obese cows have suppressed MIF expression in the ampullae and isthmuses of their oviducts, as hypothesised, but, unexpectedly, MIF expression was also lower in lean cows.

Follicle-stimulating hormone-induced rescue of cumulus cell apoptosis and enhanced development ability of buffalo oocytes

The effect of follicle-stimulating hormone (FSH) on apoptotic status of cumulus cells, expression of proapoptotic and antiapoptotic genes, and development rate of in vitro fertilization-produced buffalo embryos were investigated. FSH supplementation in in vitro maturation-medium resulted in a dose-dependent reduction in the expression of proapoptotic genes namely, BCL2-associated X protein (BAX), cytochrome c, and caspase-3 and increase in the expression of antiapoptotic genes such as B-cell lymphoma 2 (BCL2) and X-linked inhibitor of apoptosis protein (XIAP) in cumulus cells of mature oocyte. Cumulus expansion, oocyte maturation, cleavage, and blastocyst development rates were significantly higher (P < 0.05) in 5 and 10-μg/mL FSH-supplemented groups as compared with control. Significant increase in the expression of FSH receptor messenger RNA was also found with 5 and 10-μg/mL FSH (P < 0.05). Terminal deoxynucleotidyl transferase dUTP nick end labeling assay confirmed that the population of apoptotic cumulus cells of matured oocytes was reduced in the FSH-treated groups as compared with control (P < 0.05). In conclusion, our data suggest that FSH may attenuate apoptosis in cumulus cells via mitochondria-dependent apoptotic pathway by increasing XIAP expression, resulting in a more favorable ratio of BCL2/BAX expression and decreasing the cytochrome c and caspase-3 expression, eventually contributing to developmental competence of oocytes. The information generated will help in improving the in vitro embryo production program in buffalo.

Expression pattern of glucose metabolism genes correlate with development rate of buffalo oocytes and embryos in vitro under low oxygen condition

PURPOSE

This study evaluates the effect of low oxygen conditions (5 Vs 20%) on buffalo embryo development. Expression patterns of key glucose metabolism genes (HK, PFK, LDH, PDH, G6PDH and Glut1) were assessed in buffalo oocytes and embryos cultured at 5 and 20% oxygen and correlated with development rate.

METHODS

Maturation rate was observed by determining MII stages by Aceto-orcein method and blastocyst formation was observed at 7 day post insemination (dpi). Expression levels of genes were determined by real time PCR in oocytes / embryos at 5 and 20% O2.

RESULTS

Oocyte maturation and blastocyst formation rates were significantly higher at 5% O2 as compared to 20% O2 (P < 0.05). The expression pattern of glycolytic genes (HK, PFK and G6PDH) indicated that oocytes and embryos under 5% O2 tend to follow anaerobic glycolysis and pentose phosphate pathways to support optimum embryo development. Under 20% O2, oocytes and embryos had high expression of PDH indicating higher oxidative phosphorylation. Further, less G6PDH expression at 20% O2 was indicative of lower pentose phosphate activity. Higher expression of LDH was observed in oocytes and embryos under 20% O2 indicating sub-optimal culture conditions. High Glut1 activity was observed in the oocytes / embryos at 5% O2, indicative of high glucose uptake correlating with high expression of glycolytic genes.

CONCLUSION

The expression patterns of glucose metabolism genes could be a valuable indicator of the development potential of oocytes and embryos. The study indicates the importance of reduced oxygen conditions for production of good quality embryos.