Influence of cumulus cells and sperm concentration on cleavage rate and subsequent embryonic development of buffalo (Bubalus bubalis) oocytes matured and fertilized in vitro

Sperm selection by the oviduct: perspectives for male fertility and assisted reproductive technologies†

The contribution of sperm to embryogenesis is gaining attention with up to 50% of infertility cases being attributed to a paternal factor. The traditional methods used in assisted reproductive technologies for selecting and assessing sperm quality are mainly based on motility and viability parameters. However, other sperm characteristics, including deoxyribonucleic acid integrity, have major consequences for successful live birth. In natural reproduction, sperm navigate the male and female reproductive tract to reach and fertilize the egg. During transport, sperm encounter many obstacles that dramatically reduce the number arriving at the fertilization site. In humans, the number of sperm is reduced from tens of millions in the ejaculate to hundreds in the Fallopian tube (oviduct). Whether this sperm population has higher fertilization potential is not fully understood, but several studies in animals indicate that many defective sperm do not advance to the site of fertilization. Moreover, the oviduct plays a key role in fertility by modulating sperm transport, viability, and maturation, providing sperm that are ready to fertilize at the appropriate time. Here we present evidence of sperm selection by the oviduct with emphasis on the mechanisms of selection and the sperm characteristics selected. Considering the sperm parameters that are essential for healthy embryonic development, we discuss the use of novel in vitro sperm selection methods that mimic physiological conditions. We propose that insight gained from understanding how the oviduct selects sperm can be translated to assisted reproductive technologies to yield high fertilization, embryonic development, and pregnancy rates.

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.

A standardized extract of Asparagus officinalis stem improves HSP70-mediated redox balance and cell functions in bovine cumulus-granulosa cells

Heat shock (HS) protein 70 (HSP70), a well-known HS-induced protein, acts as an intracellular chaperone to protect cells against stress conditions. Although HS induces HSP70 expression to confer stress resistance to cells, HS causes cell toxicity by increasing reactive oxygen species (ROS) levels. Recently, a standardized extract of Asparagus officinalis stem (EAS), produced from the byproduct of asparagus, has been shown to induce HSP70 expression without HS and regulate cellular redox balance in pheochromocytoma cells. However, the effects of EAS on reproductive cell function remain unknown. Here, we investigated the effect of EAS on HSP70 induction and oxidative redox balance in cultured bovine cumulus-granulosa (CG) cells. EAS significantly increased HSP70 expression; however, no effect was observed on HSP27 and HSP90 under non-HS conditions. EAS decreased ROS generation and DNA damage and increased glutathione (GSH) synthesis under both non-HS and HS conditions. Moreover, EAS synergistically increased HSP70 and HSF1 expression and increased progesterone levels in CG cells. Treatment with an HSP70 inhibitor significantly decreased GSH level, increased ROS level, and decreased HSF1, Nrf2, and Keap1 expression in the presence of EAS. Furthermore, EAS significantly increased progesterone synthesis. Thus, EAS improves HSP70-mediated redox balance and cell function in bovine CG cells.

Multi potent aromatic nano colloid: synthesis, characterization and applications

In this study the aromatic nanocolloids (CANCs) are synthesized using the noble metal silver by using Citronella extract and confirmed through physio chemical analysis. The synthesised CANCs were evaluated for its antimicrobial activity and antibiofilm activity against pathogenic biofilm forming E. coli. In addition, synthesized CANCs were evaluated for the expression of virulent genes encoding AmpC and CTX-M-15. The results confirmed that CANCs showed effective antimicrobial activity through its bacteriostatic, bactericidal and quorum quencher activity and downregulated CTX-M-15 gene. CANCs were validated as alternate to the commercial fungicides to control plant pathogenic fungi such as A. niger MTCC (281), Fusarium graminearum MTCC (2089) and F. udum MTCC (2204). Furthermore, analysis of CANCs on breast cancer (MCF-7) cells under in vitro condition showed that the cytotoxicity of CANCs is dose dependent. Thus, the multifunctional CANCs can be utilized as potential antimicrobial, antifungal and anticancer agent.

A Brief Incubation of Cumulus-Enclosed Mouse Eggs in a Calcium-Free Medium Containing a High Concentration of Calcium-Chelator Markedly Improves Preimplantation Development

The presence of cumulus cells (CCs) surrounding ovulated eggs is beneficial to in vitro fertilization and preimplantation development outcomes in several mammalian species. In the mouse, this contribution has a negligible effect on the fertilization rate; however, it is not yet clear whether it has positive effects on preimplantation development. Here, we compared the rates of in vitro fertilization and preimplantation development of ovulated B6C3F1 CC-enclosed vs. CC-free eggs, the latter obtained either after a 5 min treatment in M2 medium containing hyaluronidase or after 5-25 min in M2 medium supplemented with 34.2 mM EDTA (M2-EDTA). We found that, although the maintenance of CCs around ovulated eggs does not increment their developmental rate to blastocyst, the quality of the latter is significantly enhanced. Most importantly, for the first time, we describe a further quantitative and qualitative improvement, on preimplantation development, when CC-enclosed eggs are isolated from the oviducts in M2-EDTA and left in this medium for a total of 5 min prior to sperm insemination. Altogether, our results establish an important advancement in mouse IVF procedures that would be now interesting to test on other mammalian species.

Ovum pick-up interval in buffalo (Bubalus bubalis) managed under wetland conditions in Argentina: Effect on follicular population, oocyte recovery, and in vitro embryo development

The excellent adaptation of water buffalo (Bubalis bubalis) to swampy environments means that animals are frequently managed in areas with restricted access for reproductive procedures. The objective of this study was to evaluate the effect of the ovum pick-up (OPU) interval on follicular population, oocyte recovery, oocyte quality and in vitro embryo production. Twelve Murrah buffaloes were subjected to two consecutive dominant follicle reductions, and randomly assigned to either 7-day (n=6) or 14-day (n=6) OPU interval groups. Although there was no significant difference in the average number of small (<3mm) and large (>8mm) diameter follicles available per OPU, a higher proportion of medium-sized follicles (3-8mm) were observed in the 14-day interval group (5.129 vs 3.267; p<0.05). The number of recovered oocytes per donor was also significantly higher (4.51 vs. 2.8; p<0.05) in the 14-day interval group, although this was attributed to an increase in the proportion of lower quality oocytes (grades III and IV). After in vitro fertilization, embryo developmental competence from grade I and II oocytes was superior to that from grade III and IV oocytes, irrespective of OPU interval group. There was no significant difference in the proportion of grade I and II oocytes cleaved after sperm co-incubation; however, there was a higher proportion of blastocysts produced in 14-day interval group (28 vs. 6%, p<0.05). No blastocysts were produced from grade III and IV oocytes. This study indicates it is possible to use a 14-day interval for oocyte collection in water buffalo; this approach could be considered as an alternative when access to animals is restricted.

Differential expression dynamics of Growth differentiation factor9 (GDF9) and Bone morphogenetic factor15 (BMP15) mRNA transcripts during in vitro maturation of buffalo (Bubalus bubalis) cumulus-oocyte complexes

The present study has evaluated the association of growth differentiation factor9 (GDF9) and bone morphogenetic protein15 (BMP15) mRNA expression in cumulus-oocyte complexes (COCs) of buffalo ovary during in vitro maturation (IVM). GDF9 and BMP15 are expressed specifically in mammalian oocytes and also participate in cumulus-oocyte crosstalk. Quantitative real-time polymerase chain reaction (qRT-PCR) technique was applied to investigate the relative abundance (RA) of GDF9 and BMP15 mRNA transcripts throughout the IVM process. Relative mRNA expression pattern of these specific genes were assessed in oocytes and cumulus cells at 0, 6, 12 and 24 h of in vitro culture. Our results revealed that RA of GDF9 during different hours of IVM showed significant reduction between 0 h and 24 h of maturation in oocytes and BMP15 transcript increased significantly (P<0.05) between 6 h and 12 h and decreased again between 12 h and 24. In cumulus cells, GDF9 remained stable during IVM upto 12 h of maturation and decreased significantly between 12 h and 24 h of maturation. Conversely, significant reduction of BMP15 was observed between 0 h and 6 h, stayed stable upto 12 h and became undetectable at 24 h of maturation. In conclusion, these two genes were differentially expressed during the period of oocyte maturation process and notably, BMP15 expression pattern is associated specifically with the period of cumulus cell expansion.

Chlorpyrifos and endosulfan affect buffalo oocyte maturation, fertilization, and embryo development in vitro directly and through cumulus cells

This study was undertaken to examine the effect of 10 different levels (0, 0.005, 0.01, 0.02, 0.05, 0.1, 0.5, 1.0, 2.0, and 4.0 μg/mL) of two pesticides (chlorpyrifos and endosulfan) on buffalo oocyte viability, maturation, fertilization, and developmental competences in vitro. Studies were conducted to test the development of oocytes cultured with pesticides during maturation, fertilization, and during different embryo development stages. We also conducted experiments to test the hypotheses that the effects of these pesticides are hormones and somatic cells mediated. We observed a dose dependent decline in viability and developmental competence rates of oocytes. Chlorpyrifos and endosulfan had a negative impact on oocytes at 0.02 and 0.1 μg/mL levels, respectively. These pesticides reduced the oocyte nuclear maturation by a direct effect on oocytes, cumulus cell-mediated action, and by blocking the action of hormones. Chlorpyrifos was found to be more ovotoxic and embryotoxic than endosulfan. This study will provide information on dose-response relationship and risk assessment in domestic buffaloes.

Chronological Reorganization of Microtubules, Actin Microfilaments, and Chromatin during the First Cell Cycle in Swamp Buffalo (Bubalus bubalis) Embryos

This paper aimed to study the dynamics of early embryonic development, in terms of redistribution of cytoskeleton (microtubules, actin microfilaments) and chromatin configurations during the first cell cycle in swamp buffalo embryos. Oocytes were matured and fertilized in vitro, and they were fixed at various time points after IVF. At 6 h after IVF, 44.4% matured oocytes were penetrated by spermatozoa. Partial ZP digestion, however, did not improve fertilization rate compared to control (P > .05). At 12 h after IVF, the fertilized oocytes progressed to the second meiotic division and formed the female pronucleus simultaneously with the paternal chromatin continued to decondense. A sperm aster was observed radiating from the base of the decondensing sperm head. At 18 h after IVF, most presumptive zygotes had reached the pronuclear stage. The sperm aster was concurrently enlarged to assist the migration and apposition of pronuclei. Cell cleavage was facilitated by microfilaments and firstly observed by 30 h after IVF. In conclusion, the cytoskeleton actively involves with the process of fertilization and cleavage in swamp buffalo oocytes. The centrosomal material is paternally inherited. Fertilization failure is predominantly caused by poor sperm penetration. However, partial digestion of ZP did not improve fertilization rate.

Effects of exposure to heavy metals on viability, maturation, fertilization, and embryonic development of buffalo (Bubalus bubalis) oocytes in vitro

The aim of the present study was to examine the effect of heavy metals, cadmium and lead, on buffalo oocyte viability and in vitro development. Oocytes were aspirated from ovaries of slaughtered buffaloes. Only viable and metabolically active oocytes with more than three layers of cumulus cell layers and homogeneous ooplasm were selected. Effects of nine concentrations (0, 0.005, 0.05, 0.5, 1.0, 1.5, 2.5, 5, and 10 microg/mL) of cadmium or lead on buffalo oocyte viability, morphological abnormities, maturation, and embryonic development in vitro were studied. Oocytes were cultured for 24 h and then checked for viability (0.05% trypan blue staining for 2 min), morphological abnormalities, and reduction assay by MTT test in experiment 1. The doses of cadmium and lead causing 100% oocyte death (1-day culture) were determined (experiment 2). In experiment 3, viable oocytes were matured in vitro in media containing different levels of cadmium or lead and then inseminated in vitro with frozen-thawed spermatozoa, and the resultant cleaved embryos were cultured in a control embryo culture medium for 8 days. In experiment 4, oocytes were cultured in control oocyte maturation medium, then fertilized, and the resultant embryos were cultured in media containing different levels of cadmium or lead for 8 days. The number of cells in the trophectoderm and inner cell mass (ICM) and the total cell counts (TCN) of blastocysts derived by in vitro culture of two- to four-cell-stage embryos (produced in control medium) in media containing 0, 0.005, 0.05, 0.5, and 1.0 microg/mL of cadmium or lead were analyzed by differential staining technique (experiment 5). Cadmium and lead were found to have a dose-dependent effect on viability, morphological abnormities, maturation, cleavage and morula/blastocyst yield, and blastocyst hatching. A significant decline in viability of oocytes was observed at 1.0 mg/mL cadmium or lead compared to the control group. The doses of cadmium and lead causing 100% oocyte death (1-day culture) were 18 and 32 microg/mL, respectively. Cadmium and lead at 1.0 and 2.5 microg/mL, respectively, caused a significant reduction of maturation of oocytes compared to the lower concentrations. No cleavage or morulae/blastocysts were produced when the oocytes/embryos were cultured in media containing 2.5 and 5.0 mg/mL of either cadmium or lead, respectively. Similarly, no morulae/blastocysts were produced from cleaved embryos cultured in media containing 2.5 and 5.0 microg/mL cadmium and lead, respectively. The developmental block, degeneration, and asynchronous divisions were higher in embryos exposed to cadmium than in those exposed to lead. TCN and number of cells in ICM were significantly lower in blastocysts derived from two- to four-cell-stage embryos cultured in media containing heavy metals. In conclusion, cadmium and lead lowered the viability and development of buffalo oocytes but at a concentration higher than that estimated in the body fluids and environment. Cadmium was found to be more ovotoxic than lead.

Factors affecting laboratory production of buffalo embryos: a meta-analysis

In vitro fertilization (IVF) provides an excellent and inexpensive source of embryos for carrying out basic research on developmental physiology, farm animal breeding, and for commercial applications. Meta-analysis of the results from different publications rather than a narrative review may provide a current status of this technology in buffalo (Bubalus bubalis). In order to gain an idea of the factors affecting the IVF in buffalo, a review of the various studies conducted on buffalo IVF and a meta-analysis of their findings was undertaken. More than 100 articles published from 1991 to 2008 were searched, and results were subjected to meta-analysis to determine the treatment variations without any bias. Thirty factors affecting in vitro embryo production in buffalo were considered. Initially, both fixed- and random-effect models were used. We did not observe any heterogeneity between the studies. Thereafter, all the studies were pooled using the fixed-effect model for analysis. Our analysis suggested that good buffalo oocytes with more than three to five cumulus layers recovered from large-sized follicles in cold seasons when cultured in TCM-199 supplemented with serum, follicle-stimulating hormone, and cysteamine resulted in maximum maturation rate and subsequent embryonic development after insemination. The values obtained in the current study may be considered for a simulation model in establishing a cost-effective suitable method for buffalo IVF in further planned research.

Some studies on the morphological aspects of buffalo oocytes in relation to the ovarian morphology and culture condition

The present study was conducted to establish 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 hormones production. A total of 52 ovarian pairs were grouped into three types: type I (with functional corpus luteum), type II (with regressed corpus luteum), and type III (without corpus luteum). The number of follicles and oocytes/ovary were documented. The follicles were classified into three groups (<2, 2-6, and >6 mm Ø). Oocytes were classified according to their morphology into four grades (grades A, B, C, and D), or according to their cumulus compactness into four groups (more than three layers, one to three layers of cumulus cells, partial remnants of cumulus cells, and no cumulus cells). A PGCs was used to investigate their steroidogenic potential on the in vitro maturation. The highest number of follicles and oocytes was found in type III than types II and I. Grades A and B oocytes were significantly higher (P < 0.01) in number in type III ovaries. Oocytes with more than three layers of cumulus cells showed higher maturation rate than oocytes with partial remnants or no cumulus cells but with small difference from oocytes having one to three layers of cumulus cells. Beside the higher maturation rate in compact than denuded oocytes, a significantly higher (P < 0.01) rates obtained in compact or denuded oocytes when cultured in vitro with PGCs than the corresponding oocytes with no PGCs. These maturation rates coincided with higher level (P < 0.05) of estradiol-17ss when compact oocytes cultured with or without PGCs than denuded oocytes and higher level (P < 0.05) of progesterone after culture with PGCs for both compact and denuded oocytes than the corresponding oocytes with no PGCs. In summary, buffalo ovaries with no corpus luteum may be suggested for obtaining high number of follicles and good oocytes than the others. Oocytes with intact cumulus showed better maturation than those with partial or denuded cumulus, although the denuded oocytes improved their meiotic competence to a less or greater extent when cultured in vitro with PGCs.

Motility, acrosome integrity, membrane integrity and oocyte cleavage rate of sperm separated by swim-up or Percoll gradient method from frozen-thawed buffalo semen

Frozen-thawed semen of five buffalo bulls was used to compare efficacy of swim-up and Percoll gradient methods for separating viable spermatozoa. Sperm separated by the two methods were also tested to differentiate buffalo bulls on the basis of in vitro fertilization (IVF) rates. Recovery of motile sperm (%), increase in membrane integrity (%) and acrosome integrity (%) were compared after two sperm separation methods in experiment I, and in vitro fertilization rate (cleavage rate and cleavage index) was compared in experiment II. Swim-up separated sperm showed a higher motility (P<0.05), while percent recovery of motile sperm was higher with Percoll separation (P<0.05). Membrane integrity (%) of sperm separated with swim-up was significantly higher (P<0.05) as compared to sperm separated with Percoll gradient. Swim-up separated sperm gave a higher cleavage rate and cleavage index (P<0.001). Sperm separated by swim-up showed significant difference among the bulls in cleavage rate and cleavage index (P<0.05), while the Percoll gradient method did not. It has been concluded that separation of sperm from frozen-thawed buffalo semen by swim-up method can be more expedient for IVF in buffalo.

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.

The oxidative stress adaptor p66Shc is required for permanent embryo arrest in vitro

BACKGROUND

Excessive developmental failure occurs during the first week of in vitro embryo development due to elevated levels of cell death and arrest. We hypothesize that permanently arrested embryos enter a stress-induced "senescence-like" state that is dependent on the oxidative stress-adaptor and lifespan determinant protein p66Shc. The aim of this study was to selectively diminish p66Shc gene expression in bovine oocytes and embryos using post-transcriptional gene silencing by RNA-mediated interference to study the effects of p66Shc knockdown on in vitro fertilized bovine embryos.

RESULTS

Approximately 12,000-24,000 short hairpin (sh)RNAi molecules specific for p66Shc were microinjected into bovine germinal vesicle stage oocytes or zygotes. Experiments were comprised of a control group undergoing IVF alone and two groups microinjected with and without p66Shc shRNAi molecules prior to IVF. The amount of p66Shc mRNA quantified by Real Time PCR was significantly (P < 0.001) lowered upon p66Shc shRNAi microinjection. This reduction was selective for p66Shc mRNA, as both histone H2a and p53 mRNA levels were not altered. The relative signal strength of p66Shc immuno-fluorescence revealed a significant reduction in the number of pixels for p66Shc shRNAi microinjected groups compared to controls (P < 0.05). A significant decrease (P < 0.001) in the incidence of arrested embryos upon p66Shc shRNAi microinjection was detected compared to IVF and microinjected controls along with significant reductions (P < 0.001) in both cleavage divisions and blastocyst development. No significant differences in p66Shc mRNA levels (P = 0.314) were observed among the three groups at the blastocyst stage.

CONCLUSION

These results show that p66Shc is involved in the regulation of embryo development specifically in mediating early cleavage arrest and facilitating development to the blastocyst stage for in vitro produced bovine embryos.

Nuclear morphology, diameter and meiotic competence of buffalo oocytes relative to follicle size

The nuclear morphology, diameter and in vitro meiotic competence of buffalo oocytes was compared relative to follicle size. Cumulus-oocyte complexes (COCs) were collected from 1-<2, 2-<3, 3-<4, 4-<6 and 6-<8 mm follicles from abattoir ovaries. Cumulus cells were removed using 3 mg mL(-1) hyaluronidase in saline and repeated pipetting. Denuded oocytes were measured, fixed in 3% glutaraldehyde, stained with 4,6-diamidoino-2-phenylindole and evaluated for nuclear morphology, namely the stage of germinal vesicle (GV) development before in vitro maturation (IVM). The COCs from >2-mm follicles were matured in vitro in their respective size groups for 24 h in Medium 199 supplemented with 10 microg mL(-1) follicle-stimulating hormone, 10 microg mL(-1) luteinizing hormone, 1.5 microg mL(-1) oestradiol, 75 microg mL(-1) streptomycin, 100 IU mL(-1) penicillin, 10 mM HEPES and 10% fetal bovine serum. Matured oocytes were fixed, stained and evaluated for GV status and meiotic development. The number of oocytes collected from follicles 1-<8 mm in diameter averaged 1.82 per ovary. Oocytes from follicles 1-<2 mm (107.7 +/- 1.6 microm), 2-<3 mm (108 +/- 1.1 microm) and 3-<4 mm (114.6 +/- 1.3 microm) in diameter were smaller in diameter (P < 0.05) than oocytes from follicles 4-<6 mm (124.4 +/- 1.3 microm) and 6-<8 mm (131.9 +/- 1.4 microm) in diameter. A majority of oocytes (P< 0.05) from <4-mm follicles was at the initial stages of GV development (GV-I, II and III), whereas oocytes from 4-<6- and 6-<8-mm follicles were at the final stages of GV-IV (35.0 and 21.6% respectively) and GV-V (49.1 and 67.5% respectively). Poor IVM rates of 32.0% and 32.7% to metaphase (M)-II were observed for oocytes isolated from 2-<3- and 3-<4-mm follicles, respectively, whereas significantly (P< 0.05) more oocytes from 4-<6- and 6-<8-mm follicles reached M-II (67.1% and 79.1% respectively). In conclusion, buffalo oocytes displayed a size-dependent ability to undergo meiotic maturation and we suggest that oocytes from >4-mm follicles should be considered in buffalo in vitro fertilization systems for better results.

Reproduction in the Water Buffalo

In this paper, an account of various aspects related to buffalo reproduction are given. Fundamental concepts of the reproductive physiology as well as manipulation of the reproductive function will be presented. This will include an overview of the most recent developments of the oestrous cycle and the ovulation control, new strategies of reproductive management for the improvement of genetic gain and the application of newly developed reproductive technologies, such as in vitro embryo production, embryo and sperm sexing and cloning.

Cryopreservation of in vitro matured buffalo (Bubalus bubalis) oocytes by minimum volumes vitrification methods

The aim of this study was to evaluate the efficiency of the solid surface vitrification (SSV) and the cryoloop vitrification (CLV) methods to cryopreserve in vitro matured buffalo oocytes. Another objective of the work was to investigate whether the presence of cumulus cells affects the efficiency of oocyte vitrification in this species. In the SSV method, oocytes were vitrified in a solution of 35% ethylene glycol, 5% polyvinyl-pyrrolidone and 0.4% trehalose and they were warmed in a 0.3M trehalose solution. In the CLV method, oocytes were vitrified in 16.5% ethylene glycol and 16.5% dimethyl sulfoxide and warmed in decreasing concentrations of sucrose. The oocytes that survived vitrification were fertilized and cultured in vitro up to the blastocyst stage. Although high survival rates were recorded in all groups, when the oocytes were vitrified by the CLV method in the absence of cumulus cells, the survival rate was significantly (P<0.05) lower. However, the CLV gave a significantly higher cleavage rate compared to the SSV with the denuded oocytes (45% versus 26%, respectively; P<0.05), whereas no differences were found between methods with the cumulus-enclosed oocytes (14% versus 15%, respectively). Blastocysts were produced for the first time from in vitro matured oocytes that were vitrified-warmed in buffalo. Nevertheless, vitrification significantly decreased blastocyst yield, regardless of both the method employed and the presence or absence of cumulus cells.

A comparative study of parthenogenic activation and in vitro fertilization of bubaline oocytes

The effect of chemical activation protocols on in vitro-matured oocytes were compared to results with IVF (natural activation). Buffalo ovaries were collected in normal saline and transported to the laboratory within 2 h of slaughter. Good quality oocytes, collected by aspiration from 3 to 10 mm follicles, were matured for 22-24 h. Matured oocytes were subjected to either IVF (control) or chemical activation (treatment). For IVF, in vitro-matured oocytes were co-incubated with in vitro-capacitated approximately 1x10(6) frozen/thawed sperm of a Murrah bull and fertilized in modified synthetic oviductal fluid (mSOF) medium. Chemicals for oocytes activation comprised (a) 7% ethanol (ET) for 7 min+2.5 mM 6-dimethyl amino purine (6-DMAP) for 4h, (b) 7% ET for 7 min+10 microg/ml cycloheximide (CHX) for 6h and (c) 7% ET for 7 min+2.5 mM 6-DMAP+10 microg/ml CHX for 6 h. To study embryo development, fertilized and chemically activated oocytes were cultured in mSOF medium for up to 8 days. In this study, a mean of 1.9+/-0.02 maturable oocytes/ovary were recovered and 90.4% matured. Cleavage rate was significantly higher following ET+DMAP, ET+CHX and ET+CHX+DMAP activation (52.5%, 52.5% and 44.4%, respectively) compared to IVF (36.5%, 23.4% and 26.8%, respectively). Blastocyst development (30.9% versus 15.2%) was also significantly higher following ET+CHX+DMAP activation than IVF. The results of parthenogenesis reveal that buffalo oocytes had better inherent developmental competence and that the poor cleavage and embryo development following IVF may be due partly to the poor quality of frozen/thawed sperm, improper sperm capacitation and/or fertilization.

Experimental Evidence for the Influence of Cumulus-Oocyte-Complexes on Sperm Release from the Porcine Oviductal Sperm Reservoir

In the pig, a temporal relationship is suggested between sperm release from the sperm reservoir (SR) and ovulation, but the mechanism(s) is still under discussion. In two experiments, the influence of transferred ova on the release of SR-spermatozoa at ovulation and the effect of supplementation with non-sulfated glycosaminoglycan hyaluronan (HA) on embryo development and the number of accessory spermatozoa, respectively, were examined. PMSG/hCG primed ovectomized gilts that had previously received endoscopic low-dose insemination into the cranial uterine horn were used as an experimental model. After salpingectomy, tubal segments (ampulla, cranial, and caudal isthmus) were flushed and sperm numbers or respective accessory spermatozoa were counted. In Experiment 1, the distribution of the sperm population was altered in the presence of cumulus-oocyte-complexes (COCs). A higher proportion of spermatozoa was found after transfer of COCs into one oviduct in the ampulla and cranial isthmus segments compared with the controls (17.5 vs. 4.9%, p<0.05). In Experiment 2, the quality of the transferred ova and treatment influenced the presence of accessory spermatozoa. Transfer of COCs together with HA increased (p<0.05) the number of accessory spermatozoa compared with the other treatment groups and was similar to those in the "undisturbed" controls. No modifications were obtained regarding mean blastomere numbers (2.6 +/- 0.2 to 3.1 +/- 0.2). In summary, this study was demonstrated that cumulus-oocyte-complexes may be involved in triggering sperm release from the pig oviductal SR and that HA might be related to sperm release.

Exogenous luteinizing hormone activity may influence the treatment outcome in in vitro fertilization but not in intracytoplasmic sperm injection cycles

Additional analysis of a multinational, open-label, randomized study comparing highly purified hMG and recombinant FSH in a long protocol revealed that LH activity might favorably influence pregnancy outcome in IVF cycles.

In vitro maturation and fertilization of buffalo oocytes: effects of storage of ovaries, IVM temperatures, storage of processed sperm and fertilization media

Studies were conducted to examine the possibility of preserving slaughterhouse-derived buffalo ovaries at 4 degrees C for 0 (control), 12 and 24 h to maintain the developmental competence of the oocytes (experiment 1), to assess the effect of incubation temperature during oocyte maturation on rates of in vitro maturation (IVM) and in vitro fertilization (IVF) of buffalo oocytes and embryo development (experiment 2), and to examine the effect of storage at 25 degrees C for 0 (control), 4 and 8 h of frozen-thawed buffalo sperm and BO and H-TALP as sperm processing and fertilization media on cleavage and embryo development in vitro of buffalo oocytes (experiment 3) in order to optimize the IVF technology in buffalo. Results suggested that storage of ovaries at 4 degrees C for 12 or 24 h significantly (p < 0.05) reduced the developmental potential of oocytes. Incubation temperatures during the IVM influenced the fertilization rate but had no significant effect on maturation and subsequent embryo development. The incubation temperature of 38.5 degrees C during IVM was found to be optimum for embryo production in vitro. Storage of frozen-thawed sperm at 25 degrees C for 8 h significantly (p < 0.05) decreased its ability to cleave the oocytes. Sperm processed in BO medium had significantly (p < 0.05) higher ability to cleave the oocytes than the H-TALP medium.

Effect of insulin, transferrin and selenium and epidermal growth factor on development of buffalo oocytes to the blastocyst stage in vitro in serum-free, semidefined media

The in vitro development of buffalo oocytes up to the blastocyst stage was studied in serum-free, semidefined media containing bovine serum albumin, follicle-stimulating hormone (FSH), insulin, transferrin and selenium (ITS) and epidermal growth factor (EGF). In experiment 1, oocytes aspirated from abattoir-derived ovaries were cultured in eight serum-free, semidefined culture media containing different combinations of these four factors. In experiment 2, the maturation of buffalo oocytes and the development of the embryos were compared in a complex co-culture system and in the serum-free, semidefined media. Supplementation with FSH and EGF significantly (P < 0.05) increased the maturation rates of buffalo oocytes, and the yield of blastocysts was higher (P < 0.05) in media containing EGF and ITS. The yield of blastocysts was lower in the serum-free semidefined media (P < 0.05) than in the complex co-culture system.

Production of buffalo (Bubalus bubalis) embryos in vitro: premises and promises

Techniques for in vitro production (IVP) of buffalo embryos adopting the procedures developed in cattle have received increasing interest in the recent times. A high oocyte maturation, fertilization and cleavage rate and a low rate of blastocyst yield and calving following transfer of in vitro produced buffalo embryos have been obtained. The efficiency of IVP in buffalo is much lower than that in cattle. Several problems need to be resolved before IVP technology can be used regularly in buffalo breeding. This review attempts to present an overview of the different techniques used in buffalo to produce transferable embryos in vitro, namely in vitro maturation and fertilization of immature oocytes and in vitro development of the resulting cleaved embryos to the blastocyst stage before transfer. The problems associated with IVP, the possible solutions and the new biotechniques linked to IVP are discussed.

Effect of cumulus cell removal of in vitro matured bovine oocytes prior to in vitro fertilization on subsequent cleavage rate

The aim of this study is to identify the effect of cumulus cells removal prior to the in vitro fertilization of matured bovine oocytes on cleavage rate. Denuded, matured oocytes were fertilized in presence or absence of loose cumulus cells, cumulus cell conditioned IVF medium (CCCM), charcoal-treated CCCM and charcoal-treated CCCM supplemented with progesterone at a final concentration of 150 ng/ml. After 18 h of incubation with sperm, the presumptive embryos were cultured on a BRL monolayer and the percentage of cleaved embryos was evaluated on Day 4. Removal of cumulus cells prior to IVF significantly reduced the cleavage rate (25% for denuded oocytes versus 56% for cumulus-oocyte complexes (COCs)). The addition of loose cumulus cells partially restored the effect of denudation (cleavage rate: 37% for denuded oocytes supplemented with loose cumulus cells versus 27% for denuded oocytes and 58% for COCs). CCCM also had a positive effect on the cleavage rate of oocytes denuded prior to IVF (36% for denuded oocytes fertilized in CCCM versus 14% for denuded oocytes). Treating the CCCM with charcoal resulted in complete loss of its effect on cleavage rate (18% for denuded oocytes fertilized in charcoal-treated CCCM versus 34% for denuded oocytes fertilized in CCCM). The addition of progesterone to charcoal-treated CCCM partially restored the reduction of the cleavage rate caused by charcoal treatment (27% for denuded oocytes fertilized in charcoal-treated CCCM supplemented with progesterone versus 14% for denuded oocytes fertilized in charcoal-treated CCCM and 36% for denuded oocytes fertilized in CCCM). In conclusion, removal of cumulus cells prior to IVF adversely affects the cleavage rate through loss of a factor secreted by these cells. This factor probably is progesterone.

Timing of sequential changes in cumulus cells and first polar body extrusion during in vitro maturation of buffalo oocytes

Studies were conducted to investigate the degree of the cumulus cell expansion and expulsion of the first polar body in relation to time of incubation in three different culture media during in vitro maturation of buffalo oocytes and to suggest a suitable practical method for assessment of in vitro maturation rate of buffalo oocytes. Buffalo oocytes were aspirated from ovaries collected from a local slaughterhouse. Only oocytes with more than two layers of cumulus cells and homogenous ooplasm were cultured into 50 microl droplets of three different culture systems: (1) TCM-199 + steer serum (10%): (2) TCM-199 + steer serum (10%) + PMSG (40 IU/ml); and (3) TCM-199 + steer serum (10%) + PMSG (40 IU/ml) + estradiol 17beta (1 microg/ml) in a 35 mm Petri dish. The droplets were covered with warm (39 degrees C) mineral oil and incubated in a CO2 incubator (39 degrees C, 5% CO2 in air, 90-95% relative humidity) for 16-18, 20, 22, and 24 h. The maturation rate was assessed by evaluation of degree of cumulus cells expansion and identifying first polar body extrusion into the perivitelline space under stereo zoom microscope. Matured oocytes were inseminated in vitro with 9-10 million sperm/ml of Brackett and Oliphant (BO) medium. Cleaved embryos were cultured in TCM-199 supplemented with steer serum (10%) for 8 days. Cumulus expansion and extrusion of first polar body commenced at 16 and 17 h, respectively, of buffalo oocyte culture. These events mainly exhibited during 22-24 h of culture. Oocytes with Degrees 1 and 2 cumulus cells expansion and extruded first polar body in degree 0 oocytes may be considered as matured and can be used in IVF studies.

The effects of oocyte storage and cumulus cell presence on canine zona penetration by domestic dog spermatozoa

Zona penetration assays (ZPAs) have been developed in numerous species to evaluate sperm fertilizing potential. Preservation methods to stockpile oocytes would be beneficial because of the difficulty in obtaining sufficient numbers of fresh oocytes. Using a canine ZPA, the objectives of this study were to evaluate: (1) two methods of storing canine oocytes (salt storage and intrafollicular cooling) and (2) the effects of cumulus cells on oocyte penetration. In experiment 1. oocytes from fresh ovaries were assigned at random to 3 categories: fresh control (FRE), salt storage in solution 1 (1.5 M MgCl2.6H2O; SS1) and salt storage in solution 2 (0.5 M (NH4)2SO4, 0.75 M MgCl2.6H2O, 0.2 mM ZnCl2; SS2). Each category was subdivided into two treatments: cumulus cells intact (intact) and cumulus cells removed (denuded), resulting in a total of six treatments with n > 15 oocytes per treatment for each ejaculate. Fresh (FRE) intact oocytes demonstrated greater sperm-oocyte interaction than other treatments, including FRE denuded oocytes (11.7 +/- 0.6 versus <4.1 +/- 0.5 sperm-oocyte and 94.9 versus <55.6% penetration; P < 0.01). Poor sperm-oocyte interaction was demonstrated with all salt-stored oocytes (< or = 1.6 +/- 0.2 sperm-oocyte and < 51% penetration), but was further attenuated in the absence of cumulus cells. In experiment 2, oocytes obtained from fresh (FRESH) or cooled (24 h COOL, 48 h COOL) ovaries were used with cumulus cells intact for a total of three treatments with n > 15 oocytes per treatment for each ejaculate. No significant difference was observed in sperm interaction between oocytes from fresh, 24 and 48 h COOL ovaries ( 12.3 +/- 0.5 to 13.1 +/- 0.4 sperm-oocyte and 92.2-97.7% penetration; P > 0.01). These results indicate that salt storage may cause damage to canine oocytes, subsequently impairing sperm penetration, whereas short-term intrafollicular cooling does not affect the oocyte's penetrability. Furthermore, greater sperm interaction in oocytes with an intact cumulus suggests a possible role for cumulus cells in canine gamete interaction.

In vitro embryo production in buffalo species: state of the art

In the last several years, there has been an increasing interest in in vitro embryo production (IVEP) technologies for faster propagation of superior germplasm in buffalo because of the low efficiency of superovulation (SO) and embryo transfer (ET) programs in this species. Although the IVEP efficiency has improved, embryo yield and development to term are still very low. This paper reviews the progress made in optimizing the IVM, IVF, and IVC systems. It also highlights the importance of embryo cryopreservation, which might critically contribute to the diffusion of ET procedures in the field. The acquisition of more information on embryo physiology, metabolism, and culture requirements in this species is critical to optimize the efficiency of advanced reproductive strategies. Further studies are also needed to improve the cryopreservation of IVEP embryos. The second part of the work underlines the potential impact of ovum pick-up (OPU) technique combined with IVEP on genetic improvement of buffalos. The OPU technique is a non-invasive and repeatable procedure for recovering large numbers of meiotically competent oocytes from antral follicles of live animals. Our experience, in buffalo, has demonstrated that OPU is superior to SO because it can yield more transferable embryos (TE) per donor on a monthly basis (2 TE vs 0.6, respectively). Therefore this technology has great potential to improve the genetic progress of buffalo through the maternal lineage.

Influence of oocyte quality, culture media and gonadotropins on cleavage rate and development of in vitro fertilized buffalo embryos

The present study was designed to examine the influence of oocyte quality, culture media and gonadotropins on cleavage rate and development of in vitro fertilized buffalo embryos. Three experiments were conducted. In experiment 1, oocytes were classified by number of cumulus cell layers and morphology of the ooplasm as good, fair or poor. Oocytes were cultured for IVM, IVF and IVC in CR1aa medium. In experiment 2, good quality oocytes were cultured for maturation in: (1) CR1aa; (2) CR2aa; (3) TCM-199; (4) MEM or (5) RPMI-1640, and then fertilized using frozen thawed buffalo spermatozoa in CR1aa. The oocytes were cultured in the same medium used for maturation after fertilization. In experiment 3, oocytes were classified into three groups: group (1) was without gonadotropin and serve as a control; group (2) in which IVM medium was supplemented with 10microg/ml FSH and group (3) in which IVM medium was supplemented with 10IUml(-1) eCG. In all experiments, oocytes were kept at 38.5 degrees C under 5% CO(2) for IVM, IVF, IVC and examined for cleavage and embryo development rates on days 3 and 8, respectively. Good and fair quality oocytes produced a higher cleavage rate (P<0.01) than poor quality oocytes. Morula production rate was also higher (P<0.01) for good as compared with fair quality oocytes. Embryo development with poor quality oocytes was arrested at the two to sixteen cell stage. In experiment 2, the cleavage rate was higher (P<0.05) in CR1aa than CR2aa, and higher (P<0.01) than TCM-199, MEM and RPMI-1640. The numbers of morulae and blastocysts were higher (P<0.01) for oocytes cultured in CR1aa and CR2aa media than TCM-199 or MEM. In experiment 3, the addition of FSH or eCG to the maturation medium increased (P<0.01) cleavage and developmental rates of buffalo embryo compared with control medium. In conclusion, the IVM of good quality buffalo oocytes in CR1aa or CR2aa medium and the addition of FSH or eCG in maturation medium produced higher cleavage and developmental rates of IVF buffalo embryos.