Seasonal variations in developmental competence and relative abundance of gene transcripts in buffalo (Bubalus bubalis) oocytes

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.

Oocyte competence and gene expression in parthenogenetic produced embryos from repeat breeder and normally fertile buffaloes (Bubalus bubalis) raised in sub-humid tropical climate

The reproductive management of the buffalo species still faces several unresolved problems, which directly affect the productivity of the herd, one of them being the presence of repeat breeder females. Given this scenario, this study aimed to verify the developmental competence of oocytes obtained from repeat breeder females and submitted to parthenogenetic activation. In addition, embryo gene expression was compared to normally fertile females. Murrah buffaloes were divided into two groups: repeat breeder (RB, n = 8) and normally fertile or control (CR, n = 7). Cumulus-oocyte complexes (COCs) were aspirated by transvaginal ovum pick-up from estrus synchronized females. The COCs were submitted to IVM for 24 h, and subsequently, the oocytes were activated using ionomycin, followed by 6-DMAP. Afterwards, the presumptive parthenotes were cultured for six or seven days in a microenvironment of 5 % CO2, 5 % O2, and 90 % N2 at 38.5 °C. The expression of OCT4, GLUT1, BCL2 and TFAM genes from blastocysts was evaluated. The overall COCs recovery rate was 70.9 % (190/268). The maturation (57.8 vs 71.1), cleavage (45.2 vs 62.2) and blastocyst (30.1 vs 45.9) rates did not differ (P > 0.05) between RB and CR females, respectively. Similarly, no significant difference (P > 0.05) was observed for the expression of studied genes in both RB and CR females. In conclusion, oocytes obtained from RB were as developmentally competent as those collected from CR females, with similar energy metabolism and in vitro development capacity. Thus, the low fertility rate of repeat breeder buffaloes, when compared to normal cyclic females, must be due to subsequent events to the blastocyst stage.

Improved the in vitro blastocyst development in oocytes recovered from cyclic buffaloes

This study examined the impact of cyclicity (with or without cycle corpus luteum; CL) on oocyte quality and embryonic development in buffaloes. We collected oocytes from the ovaries of slaughtered buffaloes (N = 158 cyclic; n = 316 ovaries and N = 177 acyclic; n = 353 ovaries). Blood progesterone concentration and number of oocytes per ovary were higher in cyclic buffaloes. Cyclic buffalo ovaries produce higher oocytes with I + II and fewer III + IV grades. Oocytes from cyclic buffaloes had a higher maturation rate based on cumulus expansion, cleavage rate and embryo development to the 8-cell, morula and blastocyst stages than acyclic buffaloes. In conclusion, oocytes recovered from the ovaries of the cyclic buffaloes showed improved oocyte competence and subsequent in vitro blastocyst development.

Seasonal Alterations in Testicular Hemodynamics and Echotexture in Relation to Semen Quality in Buffalo Bulls

The present study is aimed at investigating the usefulness of the pulsed-wave Doppler ultrasonography for the characterization of testicular blood flow in buffaloes during the nonbreeding and breeding seasons. Ten Egyptian buffalo bulls were evaluated for changes in the blood flow (Doppler’s indices: resistive index (RI) and pulsatility index (PI)) at the levels of supratesticular (STA) during the breeding (winter) and nonbreeding season (summer). The alterations in testicular parenchyma echotexture (pixel intensity (PIX) and echotexture heterogeneity (EH)) were assessed by computer analysis software. Circulating testosterone and nitric oxide (NO) concentrations and total antioxidant capacity (TAC) were measured colorimetrically. Sperm parameters including total and progressive motility %, viability %, morphology %, and concentrations were assessed. Results revealed lower values ( $p<0.05$ ) of RI ( $0.55\pm 0.02$ ) and PI ( $0.82\pm 0.03$ ) within the STA in the breeding period compared to the nonbreeding period (RI: $0.67\pm 0.03$ ; PI: $0.99\pm 0.01$ ). Higher ( $p<0.05$ ) PIX and EH were found in the nonbreeding season (PIX: $72.09\pm 1.81$ ; EH: $14.99\pm 1.37$ ) compared to the breeding season (PIX: $60.95\pm 1.51$ ; EH: $11.75\pm 0.63$ ). Concentrations of testosterone and TAC were not significantly changed. However, the concentrations of NO were greater ( $p<0.05$ ) during the breeding season ( $78.21\pm 0.87$ ) compared to those of the nonbreeding one ( $59.74\pm 2.97$ ). Total motility %, progressive motility %, viability %, and sperm concentrations were higher during the breeding season compared to that during the nonbreeding season ( $p<0.05$ ). In conclusion, seasonality alters testicular hemodynamics and echotexture, NO concentrations, and sperm quality in buffaloes without alterations in the testosterone and TAC levels.

Variations of follicular fluid extracellular vesicles miRNAs content in relation to development stage and season in buffalo

In buffalo (Bubalus bubalis) reproductive seasonality, causing cycles of milk production, is one of the major factors affecting farming profitability. Follicular fluid (FF) contains extracellular vesicles (EVs) playing an important role in modulating oocyte developmental competence and carrying microRNAs (miRNAs) essential for in vitro fertilization outcomes. The aim of this work was to characterize the FF-EVs-miRNA cargo of antral (An) and preovulatory (pO) follicles collected in the breeding (BS) and non-breeding (NBS) seasons, to unravel the molecular causes of the reduced oocyte competence recorded in buffalo during the NBS. In total, 1335 miRNAs (538 known Bos taurus miRNAs, 324 homologous to known miRNAs from other species and 473 new candidate miRNAs) were found. We identified 413 differentially expressed miRNAs (DE-miRNAs) (FDR < 0.05) between An and pO groups. A subset of the most significant DE-miRNAs between An and pO groups targets genes which function is related to the lipid and steroid metabolism, response to glucocorticoid and oestradiol stimulus. Comparison between BS and NBS showed 14 and 12 DE-miRNAs in An-FF-EVs and pO-FF-EVs, which regulate IL6 release and cellular adhesion, respectively. In conclusion, these results demonstrated that the miRNA cargo of buffalo FF-EVs varies in relation to both follicular development and season.

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.

Reproductive seasonality influences oocyte retrieval and embryonic competence but not uterine receptivity in buffaloes

Since buffaloes are a seasonal, polyestrous species, optimizing reproduction during the non-breeding season is a key factor in increasing the reproductive and productive efficiency of herds. Ovum pick-up associated with in vitro embryo production and embryo cryopreservation is an alternative to reduce seasonal impacts. We studied the effects of seasonality in buffalo oocyte donors and embryo recipients during the favorable and non-favorable breeding seasons. Donors were evaluated for oocyte recovery and blastocyst production rate as dFBS (donors in favorable breeding season) or dNBS (donors in non-favorable breeding season). Embryos produced from dFBS or dNBS were cryopreserved by vitrification or the slow-freeze method for direct transfer and transferred to recipients in the favorable (rFBS) or non-favorable breeding season (rNBS). The heifers or cows were subjected to a fixed-time embryo transfer protocol and conception rates were determined on day 30 and on day 60. The oocyte recovery was lower in dFBS than in dNBS (7.6 vs. 10.0 oocyte/OPU, p = 0.0262); while no difference was found comparing blastocyst production rate (23.7% vs. 30.9% of blastocysts, respectively). Embryos from dFBS resulted in greater (p = 0.0013) conception rates on day 30 compared to dNBS (46.5% vs. 22.4%, respectively), despite the breeding season. The rFBS and rNBS treatments had similar (p = 0.6714) conception rates on day 30 (38.0% vs. 33.0%, respectively), indicating similar uterine receptivity. However, heifers on FBS had higher (p = 0.0003) conception rates on day 30 than cows (73.9% vs. 13.3%, respectively) when receiving embryos from dFBS. Vitrification and direct transfer had similar (p = 0.1698) conception rates on day 30 (30.4% vs. 41.4%, respectively). In conclusion, in vitro-produced embryos derived from dFBS were more competent in establishing pregnancy than dNBS counterparts, independent of recipients' reproductive seasonality. Heifers achieved better conception rates than cows during the favorable breeding season when the embryo came from dFBS. Cryopreserved in vitro produced embryos represent a reliable alternative to reduce seasonal variations in buffalo reproduction. The data elucidate the seasonal effects on embryo competence and on recipients' uterine receptivity, affording new strategies to implement ovum pick-up associated with in vitro embryo production programs in buffalo herds.

Reproductive Seasonality Affects In Vitro Embryo Production Outcomes in Adult Goats

Reproductive seasonality may have a considerable influence on the efficiency of assisted reproductive technologies in seasonal species. This study evaluated the effect of season on cleavage, blastocyst rates and quality of in vitro produced (IVP) goat embryos. In total, 2348 cumulus-oocyte complexes (COCs) were recovered from slaughterhouse ovaries and subjected to the same IVP system throughout 1.5 years (49 replicates). The odds ratio (OR) among seasons was calculated from values of cleavage and blastocyst rates in each season. Cleavage rate was lower (p < 0.05) in spring (anestrus), in comparison with either autumn (peak of breeding season) or summer, while the winter had intermediate values. Furthermore, lower OR of cleavage was observed in spring. Blastocyst formation rate (from initial number of COCs) was higher (p < 0.05) in autumn (52 ± 2.5%) when compared with the other seasons (combined rates: 40 ± 1.9%). Moreover, its OR was higher (p < 0.05) in autumn compared to all other seasons and impaired in the spring compared to winter (OR: 0.54) and summer (OR: 0.48). Embryo hatchability and blastocyst cell number were similar (p > 0.05) among seasons. In conclusion, the breeding season leads to improved oocyte developmental competence, resulting in higher cleavage and blastocyst yield, whereas embryo quality remained similar throughout the years.

Effect of oxygen tension and antioxidants on the developmental competence of buffalo oocytes cultured in vitro

Aim:

Oxidative stress (OS) is one of the major disruptors of oocyte developmental competence, which appears due to the imbalance between the production and neutralization of reactive oxygen species (ROS).

Materials and Methods:

In Experiment 1, buffalo oocytes were in vitro matured, fertilized, and cultured at 38.5°C under 5% CO₂ + 20% O₂ in standard CO₂ incubator (OS) or under 5% O₂ + 5% CO₂ + 90% N₂ (Multi-gas incubator, low O₂). In Experiment 2, buffalo cumulus oocytes complexes (COCs) were matured in Basic maturation medium (BMM) composed of TCM199+ 10% FCS+ 10 µg/ml FSH+ 50 µg/ml gentamicin (control group) or in BMM supplemented with 50 μM ascorbic acid (ascorbic acid group) or 3.0 mM glutathione (glutathione group) or 10^-5 M melatonin (melatonin group) and cultured at 38.5°C under 20% O₂ for 24 h. Matured buffalo oocytes in control, ascorbic acid, or melatonin groups were fertilized and zygotes were cultured for 8 days under the same conditions.

Results:

In both experiments, maturation, cleavage, and blastocyst rates were recorded. Results showed that culture of buffalo oocytes under low O₂ (5% O₂) significantly increased maturation, cleavage, and blastocyst rates (p<0.05). Meanwhile, under 20% O₂, addition of 10^-5 M melatonin or 50 μM ascorbic acid to in vitro maturation (IVM) medium significantly improved cumulus cell expansion, nuclear maturation rates of buffalo oocytes (p<0.05), and increased cleavage and blastocyst rates (p<0.05).

Conclusion:

About 5% O₂ is the optimum condition for in vitro production of buffalo embryos, and addition of 10^-5 M melatonin to IVM medium for oocytes cultured under 20% O₂ could alleviate the adverse effect of high oxygen tension and increased embryo yield.

Seasonal effects on miRNA and transcriptomic profile of oocytes and follicular cells in buffalo (Bubalus bubalis)

Season clearly influences oocyte competence in buffalo (Bubalus bubalis); however, changes in the oocyte molecular status in relation to season are poorly understood. This study characterizes the microRNA (miRNA) and transcriptomic profiles of oocytes (OOs) and corresponding follicular cells (FCs) from buffalo ovaries collected in the breeding (BS) and non-breeding (NBS) seasons. In the BS, cleavage and blastocyst rates are significantly higher compared to NBS. Thirteen miRNAs and two mRNAs showed differential expression (DE) in FCs between BS and NBS. DE-miRNAs target gene analysis uncovered pathways associated with transforming growth factor β (TGFβ) and circadian clock photoperiod. Oocytes cluster in function of season for their miRNA content, showing 13 DE-miRNAs between BS and NBS. Between the two seasons, 22 differentially expressed genes were also observed. Gene Ontology (GO) analysis of miRNA target genes and differentially expressed genes (DEGs) in OOs highlights pathways related to triglyceride and sterol biosynthesis and storage. Co-expression analysis of miRNAs and mRNAs revealed a positive correlation between miR-296-3p and genes related to metabolism and hormone regulation. In conclusion, season significantly affects female fertility in buffalo and impacts on oocyte transcriptomic of genes related to folliculogenesis and acquisition of oocyte competence.

Seasonality and photoperiod influence in vitro production of buffalo embryos

Buffalo is considered short-day breeder in tropical and subtropical part of the world and seasonality and photoperiodism impart major influence on its fertility. However, its impact on in vitro embryo production (IVEP) remains elusive. Therefore, this study investigated the effect of seasonal variations and photoperiodism on morphological and molecular parameters of IVEP in buffalo. For this purpose, we conducted two different experiments on the oocytes obtained by aspirating follicles from abattoir derived ovaries. In Exp. I, retrospective analysis was performed for oocyte recovery, blastocyst and hatching rate, during four consecutive seasonal periods (i.e. January-March, April-June, July-September and October-December). In Exp. II, oocytes from peak breeding and non-breeding seasons were subjected to 24 hr in vitro maturation and evaluated for polar body extrusion to assess maturation rate. Results showed that embryo development was markedly low during second quarter (April-June) and maximum during fourth quarter (October-December) of the year; referred as non-breeding and breeding seasons, respectively. Comparative data analysis demonstrated that poor oocyte quality is major reason for lesser efficiency of embryo production during non-breeding season than peak breeding season as suggested by poor oocyte recovery (2.31 ± 0.10 vs. 3.65 ± 0.27) and maturation rate (33.32 ± 2.1 vs. 63.15 ± 7.31). Subsequently, comparative gene expression analysis of blastocysts during peak breeding season significantly upregulated pluripotency gene (OCT-4) and downregulated heat shock protein 90, as compared to non-breeding season. Therefore, it could be divulged from the present study that seasonal variations and photoperiodism have profound effect on oocyte quality and subsequent embryo development. It is recommended to find suitable additives for in vitro maturation that could mitigate seasonal effects.

Effect of season on the in-vitro maturation and developmental competence of buffalo oocytes after somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is a valuable technology tool with various uses in transgenic animals, regenerative medicine, and stem cell research. However, the efficiency of SCNT embryos appears to have poor developmental competency. Environmental issues may adversely affect SCNT embryos in buffalo. Thereafter, the present study aimed to explore the effect of season on the maturation of buffalo oocytes and subsequent developmental capability after parthenogenetic activation and SCNT in buffalo. Buffalo oocytes (n = 6353) were collected from local slaughterhouse at various seasons; spring (March-April), summer (May-August), autumn (September-November), and winter (December-January). A significant increase (p < 0.05) was recorded in the maturation rate (57.07%) at autumn compared with spring, summer, and winter (50.46, 50.93, and 50.66%, respectively). No significant differences were recorded in the fusion and the cleavage rates among all seasons. Blastocyst development rate was higher (p < 0.05) in autumn and winter (16.52 ± 8.45% and 15.98 ± 7.17%, respectively) than in spring and summer (9.47 ± 6.71% and 10.84 ± 6.58%, respectively) seasons. It could be concluded that the season had a significant effect on oocyte development competence which can be used for SCNT in buffalo.

Exogenous and endogenous factors in seasonality of reproduction in buffalo: A review

Seasonal breeding in buffalo is influenced by exogenous (photoperiod, climate, nutrition, management) and endogenous (hormones, genotype) factors. Buffalo are negatively photoperiodic and show a natural increase in fertility during decreasing day length. The hormone melatonin is produced by the pineal gland and has a fundamental role in photoperiodic time measurement within the brain. This drives annual cycles of gonadotropin secretion and gonadal function in buffaloes. Some melatonin is released into the systemic circulation and, together with peripherally produced melatonin, acts at somatic tissues. In the ovaries and testes of buffalo, melatonin acts as an antioxidant and scavenges oxygen free radicals to reduce both oxidative stress and apoptosis. This has beneficial effects on gametogenesis and steroidogenesis. Female buffalo treated with melatonin show an improved response to estrus synchronization protocols in out-of-season breeding. Melatonin acts through melatonin receptors MT₁ and MT₂ and the gene for MT₁ (MTNR1A) is polymorphic in buffaloes. Single nucleotide polymorphisms (SNPs) in gene MTNR1A have been associated with fertility in female buffalo. The knowledge and tools are available to lift the reproductive performance of buffalo. This is highly important as the global demand for nutritious buffalo food products has undergone a sharp rise, and continues to grow. Buffalo can make an important contribution to affordable, nutritious animal protein. This will help address global nutritional security.

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.

Low developmental competence and high tolerance to thermal stress of ovine oocytes in the warm compared with the cold season

Heat stress can potentially affect most aspects of reproduction in mammals. To our knowledge, no studies have ever been conducted for evaluating the influences of hot season on the developmental competence of ewe oocytes. In the present study, for the first time, we evaluated the effects of season (winter or summer), in vitro thermal stress, and their interaction on the ewe oocytes harvested from slaughterhouse ovaries. Cumulus-oocyte complexes (COCs) were either incubated at 39 °C for the entire length of IVM period or first incubated at 41 °C for 12 h and then at 39 °C. Evaluated endpoints included the ratios of total aspirated COCs/ovary and good-quality COCs/ovary, the apoptosis (Annexin V staining) and nuclear maturation of oocytes after 24-h IVM, and the developmental competence of oocytes after IVF. Our results showed that the number of aspirated oocytes per ovary was similar in both seasons, but the winter ovaries yielded significantly more oocytes with acceptable morphology in winter than in summer (2.1 ± 0.14 vs. 1.5 ± 0.09, P < 0.05). There was a significant interaction between season and thermal stress on the apoptosis, some nuclear maturation parameters, and blastocyst development of oocytes (P < 0.05). Although the winter oocytes were more developmentally competent than the summer oocytes, the winter oocytes were more sensitive to the thermal stress than summer oocytes. In conclusion, the developmental competence of ovine oocytes was lower in summer than in winter. However, it seemed that summer oocytes were more resistant to the in vitro thermal stress during IVM period compared with winter oocytes.

Effects of reproductive season on embryo development in the buffalo

Interest in buffalo farming is increasing worldwide due to the critical role played by buffaloes as sources of animal protein in tropical and subtropical environments. However, reproductive seasonality negatively affects the profitability of buffalo farming. Buffaloes tend to be short-day breeders, with seasonality patterns increasing with greater distances from the Equator. Although ovarian cyclic activity may occur throughout the year, seasonal anoestrus and cycles in calving and milk production are recorded. When buffaloes are forced to mate during the unfavourable season, to meet market demand, they may undergo a higher incidence of embryo mortality. This review addresses the effects of the reproductive season on embryo development in the buffalo, analysing the different factors involved in determining embryo mortality during the unfavourable season, such as impaired luteal function, oocyte competence and sperm quality. The review then focuses on strategies to control the photoperiod-dependent annual fluctuations in conception and embryo mortality in the female buffalo.

Developmental and molecular responses of buffalo (Bubalus bubalis) cumulus–oocyte complex maturedin vitrounder heat shock conditions

To investigate the effects of physiologically relevant heat shock during oocyte maturation, buffalo cumulus–oocyte complexes (COCs) were cultured at 38.5°C (control) or were exposed to 39.5°C (T1) or 40.5°C (T2) for the first 6 h ofin vitromaturation (IVM), followed by 38.5°C through the next 18 h/IVM and early embryonic development up to the blastocyst stage. Gene expression analysis was performed on selected target genes (HSF-1,HSF-2,HSP-70,HSP-90,BAX,p53,SOD1,COX1,MAPK14) in denuded oocytes and their isolated cumulus cells resulting from control COCs as well as from COCs exposed to a temperature of 39.5°C (T1). The results indicated that heat shock significantly (P< 0.01) decreased the maturation rate in T1 and T2 cells compared with the control. Afterin vitrofertilization (IVF), cleavage rate was lower (P< 0.01) for oocytes exposed to heat stress, and the percentage of oocytes arrested at the 2- or 4-cell stage was higher (P< 0.01) than that of the control. The percentage of oocytes that developed to the 8-cell, 16-cell or blastocyst stage was lower (P< 0.01) in both T1 and T2 groups compared with the control group. mRNA expression levels for the studied genes were decreased (P< 0.05) in treated oocytes (T1) except forHSP-90andHSF-1, which were increased. In cumulus cells isolated from COCs (T1), the expression for the target genes was upregulated except forBAX, which was downregulated. The results of this study demonstrated that exposure of buffalo oocytes to elevated temperatures for 6 h severely compromised their developmental competence and gene expression.

Folliculogenic factors in photoregressed ovaries: Differences in mRNA expression in early compared to late follicle development

The early stages of ovarian folliculogenesis generally progress independent of gonadotropins, whereas later stages require signaling initiated by FSH. In Siberian hamsters, cycles of folliculogenesis are mediated by changes in photoperiod which depress the hypothalamic pituitary gonadal axis. Reduced gonadotropins lead to decreases in mature follicle development and ovulation; however, early stages of folliculogenesis have not been explored in regressed ovaries. We hypothesized that intraovarian factors that contribute predominantly to later stages of folliculogenesis would react to changes in photoperiod, whereas factors contributing to earlier stages would not change. To probe if the early stages of folliculogenesis continue in the photoinhibited ovary while late stages decline, we measured the mRNA abundance of factors that interact with FSH signaling (Fshr, Igf1, Cox2) and factors that can function independently of FSH (c-Kit, Kitl, Foxo3, Figla, Nobox, Sohlh1, Lhx8). While plasma FSH, antral follicles, and corpora lutea numbers declined with exposure to inhibitory photoperiod, the numbers of primordial, primary, and secondary follicles did not change. Expression of factors that interact with FSH signaling changed with changes in photoperiod; however, expression of factors that do not interact with FSH were not significantly altered. These results suggest that the photoinhibited ovary is not completely quiescent, as factors important for follicle selection and early follicle growth are still expressed in regressed ovaries. Instead, the lack of gonadotropin support that characterizes the non-breeding season appears to inhibit only final stages of folliculogenesis in Siberian hamsters.

Developmental competence and expression profile of genes in buffalo (Bubalus bubalis) oocytes and embryos collected under different environmental stress

The study examined the effects of different environmental stress on developmental competence and the relative abundance (RA) of various gene transcripts in oocytes and embryos of buffalo. Oocytes collected during cold period (CP) and hot period (HP) were matured, fertilized and cultured in vitro to blastocyst hatching stage. The mRNA expression patterns of genes implicated in developmental competence (OCT-4, IGF-2R and GDF-9), heat shock (HSP-70.1), oxidative stress (MnSOD), metabolism (GLUT-1), pro-apoptosis (BAX) and anti-apoptosis (BCL-2) were evaluated in immature and matured oocytes as well as in pre-implantation stage embryos. Oocytes reaching MII stage, cleavage rates, blastocyst yield and hatching rates increased (P < 0.05) during the CP. In MII oocytes and 2-cell embryos, the RA of OCT-4, IGF-2R, GDF-9, MnSOD and GLUT-1 decreased (P < 0.05) during the HP. In 4-cell embryos, the RA of OCT-4, IGF-2R and BCL-2 decreased (P < 0.05) in the HP, whereas GDF-9 increased (P < 0.05). In 8-to 16-cell embryos, the RA of OCT-4 and BCL-2 decreased (P < 0. 05) in the HP, whereas HSP-70.1 and BAX expression increased (P < 0.05). In morula and blastocyst, the RA of OCT-4, IGF-2R and MnSOD decreased (P < 0.05) during the HP, whereas HSP-70.1 was increased (P < 0.05). In conclusion, deleterious seasonal effects induced at the GV-stage carry-over to subsequent embryonic developmental stages and compromise oocyte developmental competence and quality of developed blastocysts.

Exposure of Lactating Dairy Cows to Acute Pre-Ovulatory Heat Stress Affects Granulosa Cell-Specific Gene Expression Profiles in Dominant Follicles

High environmental temperatures induce detrimental effects on various reproductive processes in cattle. According to the predicted global warming the number of days with unfavorable ambient temperatures will further increase. The objective of this study was to investigate effects of acute heat stress during the late pre-ovulatory phase on morphological, physiological and molecular parameters of dominant follicles in cycling cows during lactation. Eight German Holstein cows in established lactation were exposed to heat stress (28°C) or thermoneutral conditions (15°C) with pair-feeding for four days. After hormonal heat induction growth of the respective dominant follicles was monitored by ultrasonography for two days, then an ovulatory GnRH dose was given and follicular steroid hormones and granulosa cell-specific gene expression profiles were determined 23 hrs thereafter. The data showed that the pre-ovulatory growth of dominant follicles and the estradiol, but not the progesterone concentrations tended to be slightly affected. mRNA microarray and hierarchical cluster analysis revealed distinct expression profiles in granulosa cells derived from heat stressed compared to pair-fed animals. Among the 255 affected genes heatstress-, stress- or apoptosis associated genes were not present. But instead, we found up-regulation of genes essentially involved in G-protein coupled signaling pathways, extracellular matrix composition, and several members of the solute carrier family as well as up-regulation of FST encoding follistatin. In summary, the data of the present study show that acute pre-ovulatory heat stress can specifically alter gene expression profiles in granulosa cells, however without inducing stress related genes and pathways and suggestively can impair follicular growth due to affecting the activin-inhibin-follistatin system.

Seasonal variations of the ovarian activity and pregnancy rate in the Egyptian buffalo cows (Bubalus bubalis)

The objective of this study was to investigate the effect of season on the follicular and luteal dynamics and pregnancy rate in Egyptian buffaloes. A total of 327 genital tracts and 596 animals were used. The genital tracts were examined in winter (n = 58), spring (n = 179), summer (n = 49), and autumn (n = 41) for follicular population, incidence of presence of developed or mature corpus luteum (CL), and diameters of the preovulatory follicle (OF) and the mature CL. Buffaloes were mated in winter (n = 297) and summer (n = 299) and examined for pregnancy rate. Results showed that the mean number of the large follicles was higher in winter (1.21 ± 0.08 mm) and spring (1.04 ± 0.05 mm) than in summer (0.64 ± 0.1 mm) and autumn (0.78 ± 0.1 mm) (P = 0.0001). Likewise, the mean diameter of the OF was greater in winter (14.71 ± 0.7 mm) and spring (14.36 ± 0.5 mm) than in summer (12.4 ± 0.8 mm) and autumn (12 ± 0.8 mm) (P = 0.02). In addition, the mean diameter of the mature CL was higher in winter (15.8 ± 0.4 mm) and spring (15.5 ± 1.1 mm) than in summer (14.2 ± 1 mm) and autumn (13.2 ± 0.7 mm) (P = 0.003). The incidence of presence of developed or mature CL was lower in summer (69.4 %) than in winter (74.1 %), spring (87.2 %), or autumn (85.4 %) (P = 0.01). Double CLs (0.9 %) were observed only in spring. Ovarian cysts (2.5 %) were detected in winter and spring. The pregnancy rate was higher in buffaloes mated in winter (75.4 %) than in those mated in summer (61.9 %) (P = 0.0004). In conclusion, season affects the ovarian activity and reproductive efficiency of buffaloes, where winter and spring are the optimum seasons for breeding.