Control of ovulation with a GnRH agonist after superstimulation of follicular growth in buffalo: fertilization and embryo recovery

Embryo transfer in buffalo (Bubalus bubalis)

The use of assisted reproductive technologies, such as superovulation and in vivo embryo production and in vitro embryo production (IVEP), has increased rapidly in recent years and is now applied worldwide for genetic improvement in beef and dairy buffaloes. Although in vivo embryo production has been shown to be feasible in buffalo, low efficiency and limited commercial application has been documented. These results could be associated with low antral follicle populations, high levels of follicular atresia and/or failures of the oocyte to enter the oviduct after superovulation. Additionally, IVEP technology has been shown to be an important tool for multiplying genetic material from donors of superior merit, and promising results have been achieved with the use of ovum pick-up (OPU) along with IVEP in buffalo. However, several factors appear to be critical for successful OPU/IVEP, including circulating levels of anti-Müllerian hormone, antral follicle populations, sizes of the follicles available for the OPU, reproductive seasonality, semen (sire) used for IVEP, donor category and farm. Furthermore, technologies applied to control follicular wave emergence and ovulation at predetermined times, without the need for estrus detection in recipients, has facilitated management and improved the efficiency of embryo transfer programs in buffalo herds. Conclusively, with the considerable evidence of poor results with in vivo embryo production in buffaloes, the association of OPU with IVEP represents a new alternative for the exploitation of buffalo genetics.

Composing the Early Embryonic Microenvironment: Physiology and Regulation of Oviductal Secretions

The oviductal fluid is the first environment experienced by mammalian embryos at the very beginning of life. However, it has long been believed that the oviductal environment was not essential for proper embryonic development. Successful establishment of in vitro embryo production techniques (which completely bypass the oviduct) have reinforced this idea. Yet, it became evident that in vitro produced embryos differ markedly from their in vivo counterparts, and these differences are associated with lower pregnancy outcomes and more health issues after birth. Nowadays, researchers consider the oviduct as the most suitable microenvironment for early embryonic development and a substantial effort is made to understand its dynamic, species-specific functions. In this review, we touch on the origin and molecular components of the oviductal fluid in mammals, where recent progress has been made thanks to the wider use of mass spectrometry techniques. Some of the factors and processes known to regulate oviductal secretions, including the embryo itself, as well as ovulation, insemination, endogenous and exogenous hormones, and metabolic and heat stress, are summarized. Special emphasis is laid on farm animals because, owing to the availability of sample material and the economic importance of fertility in livestock husbandry, a large part of the work on this topic has been carried out in domestic animals used for dairy and/or meat production.

Effect of season and superstimulatory treatment on in vivo and in vitro embryo production in wood bison (Bison bison athabascae)

Two experiments were done using a two-by-two design to determine the effects of season and superstimulatory protocol on embryo production in wood bison. In Experiment 1 (in vivo-derived embryos), ovarian superstimulation was induced in female bison during the ovulatory and anovulatory seasons with either two or three doses of FSH given every-other-day (FSH × 2 vs. FSH × 3, respectively). Bison were given hCG to induce ovulation, inseminated 12 and 24 hr after hCG, and embryos were collected 8 days after hCG (n = 10 bison/group). In Experiment 2 (in vitro embryo production), ovarian superstimulation was induced in female bison during the ovulatory and anovulatory seasons with two doses of FSH, and in vivo maturation of the cumulus-oocyte complexes (COC) was induced with hCG at either 48 or 72 hr after the last dose of FSH. COC were collected 34 hr after hCG, and expanded COC were used for in vitro fertilization and culture. In Experiment 1, the number of follicles ≥9 mm, the proportion of follicles that ovulated, the number of CL, and the total number of ova/embryos collected did not differ between seasons or treatment groups, but the number of transferable embryos was greater (p < .05) in the ovulatory season. In Experiment 2, no differences were detected between seasons or treatment groups for any end point. The number of transferable embryos produced per bison was greatest (p < .05) using in vitro fertilization and was unaffected by season (1.5 ± 0.2 and 1.1 ± 0.3 during anovulatory and ovulatory seasons, respectively), in contrast to in vivo embryo production which was affected by season (0.1 ± 0.01 and 0.7 ± 0.2 during anovulatory and ovulatory seasons, respectively). Results demonstrate that transferable embryos can be produced throughout the year in wood bison by both in vivo and in vitro techniques, but the efficiency of embryo production of in vivo-derived embryos is significantly lower during the anovulatory season.

Administration of PGF2α during the periovulatory period increased fertilization rate in superovulated buffaloes

The aim of the present study was to determine the recovery of embryonic structures (ova/embryos) and fertilization rate in superovulated buffaloes treated with PGF_2α during the periovulatory period. On day 0 (D0), buffaloes at random stages of the estrous cycle were treated with an intravaginal progesterone device (P4; 1.0 g) and estradiol benzoate (EB, 2.0 mg i.m.). From D4 to D7, all buffaloes received i.m. FSH (200 mg total) twice-daily over 4 days in decreasing doses. On D6 and D7, the animals were given PGF_2α analogue (0.53 mg i.m. sodium cloprostenol) and the P4 device was removed on D7. On D8, all buffaloes received GnRH (20 μg i.m. buserelin acetate). Buffaloes were then randomly allocated to one of three groups: control (Group C, n = 18), no further treatment; PGF_2α analogue injection (Group IM-PGF; n = 18), four injections (0.53 mg i.m. sodium cloprostenol) 12 h apart, from D8 to D10; PGF_2α analogue osmotic pump (Group OP-PGF; n = 18), s.c. osmotic mini-pump (2.12 mg sodium cloprostenol) from D8 to D10. The study had a crossover design (three treatments x three replicates). All animals underwent timed AI, 12 and 24 h after treatment with GnRH. Embryonic structures were recovered on D14. Ovarian ultrasonography was used on D8 and D14 to record follicular superstimulation and superovulatory responses. Blood samples were obtained on Days 7, 8, 9 and 10 to measure circulating concentrations of P4, E2 and PGFM. Data were analyzed by GLIMMIX procedure of SAS®. There was no effect (P = 0.58) of treatment on the total number of embryonic structures (Group C, 2.1 ± 0.8; Group IM-PGF, 2.1 ± 0.6; Group OP-PGF, 1.4 ± 0.4). There was also no effect (P = 0.93) of treatment on the recovery rate of embryonic structures (oocytes and embryos D14/CL D14). The fertilization rate was higher (P = 0.04) in Groups IM-PGF (84.6%) and OP-PGF (88.0%), which did not differ, than Group C (63.2%). The viable embryos rate was greater (P < 0.01) for Groups IM-PGF (82.0%) and OP-PGF (88.0%) than Group C (52.6%). There was no interaction between treatment and time and treatment effects for P4, E2 and PGFM concentrations. The findings showed that treatment with PGF_2α during the periovulatory period has potential to increase fertilization rate and embryo production in superovulated buffaloes.

Evaluation of factors involved in the failure of ovum capture in superovulated buffaloes

The aim of this work was to evaluate factors affecting ovum capture in superovulated buffaloes, by comparing the morphological features of pre-ovulatory follicles and oocytes, the intrafollicular and plasmatic steroid profile, as well as the expression of genes involved in cumulus expansion and steroid cascade in granulosa cells (GCs) and that of genes involved in contraction-relaxation of the oviduct between superovulated and synchronized buffaloes. Italian Mediterranean Buffalo cows were either synchronized by Ovsynch (n = 25) and superovulated (n = 10) with conventional FSH protocol and sacrificed 18 h after last GnRH. Antral follicular count, recovery rate and oocyte quality were recorded, and plasma and follicular fluid were collected for steroid profile determination. In addition, in 10 animals (5/group), GCs were collected to analyse the mRNA expression of gonadotropin receptors (LHR and FSHR) and genes involved in steroid synthesis, as the cytochrome P450 family 19 (CYP19A1) and the steroidogenic acute regulatory protein (STAR). Moreover, oviducts were collected to evaluate the mRNA expression of estrogen receptor 1 (ER1) and the progesterone receptor (PGR), the vascular endothelial growth factor (VEGF) and the VEGF receptors, i.e. the kinase insert domain receptor (FLK1) and the fms related tyrosine kinase 1 (FLT1). No differences were recorded in steroids plasma concentration between synchronized and superovulated animals whereas intrafollicular E₂ and P₄ concentrations decreased in superovulated group (63.2 ± 10.6 vs 30.3 ± 5.9 ng/mL of E₂ and 130.1 ± 19.8 vs 71.6 ± 8.5 ng/mL of P₄, respectively in synchronized and superovulated animals; P < 0.05). Interestingly, both the recovery rate (85.7% vs 56.6%, respectively in synchronized and in superovulated animals; P < 0.05) and the percentage of oocytes exhibiting proper cumulus expansion (75% vs 28.1%, respectively in synchronized and in superovulated animals; P < 0.01) decreased in superovulated animals. In addition, the expression of FSHR and CYP19A1 increased while the expression of STAR in GCs decreased (P < 0.05). Finally, in superovulated buffaloes a decreased expression of PGR, ER1, VEGF and its receptor FLK1 in the oviduct was observed. The results suggest that the exogenous FSH treatment impairs steroidogenesis, affecting both the oviduct and the ovarian function, accounting for the failure of ovum capture in superovulated buffaloes.

The relationship between circulating concentration of AMH and LH content in the follicle stimulating hormone (FSH) preparations on follicular growth and ovulatory response to superovulation in water buffaloes

The relationship between circulating concentration of anti-mullerian hormone (AMH) and the LH content of follicle stimulating hormone (FSH) preparation on follicular growth and ovulatory response in water buffaloes was evaluated. A single blood sample was taken from cows (N=31; age: 9.06±0.98years) to determine systemic AMH. Animals with concentrations higher or lower than 194±30pg/ml were placed into LOW and HIGH AMH groups and were assigned randomly to be superovulated FSH containing either a high (FSHp, HLH) or low (FolltropinV, LLH) LH content. Follicular growth and ovulation were monitored using transrectal ultrasonography. In animals with HIGH systemic AMH, treatment with FSH with a high LH content was associated with more small follicles (AMH X FSH; P=0.02). AMH had no effect on small follicles in animals treated with LLH. Females with a HIGH AMH had greater numbers of small follicles (P=0.01) and total follicles (P=0.005) than LOW AMH cows. Animals treated with HLH had more small follicles (P=0.001) but fewer large (P<0.001) and total follicles (P=0.0005) than those treated with LLH. Among animals with HIGH AMH, those treated with LLH, ovulated more follicles than those treated with HLH. (AMH X FSH; P=0.03). In conclusion, selecting animals with high AMH concentration and the use of FSH preparations with a lower LH content may improve the superovulatory response in water buffaloes.

Comparison of follicular dynamics, superovulatory response, and embryo recovery between estradiol based and conventional superstimulation protocol in buffaloes (Bubalus bubalis)

Aim:

To evaluate the follicular dynamics, superovulatory response, and embryo recovery following superstimulatory treatment initiated at estradiol-17β induced follicular wave emergence and its comparison with conventional superstimulatory protocol in buffaloes.

Materials and Methods:

Six normal cycling pluriparous buffaloes, lactating, 90-180 days post-partum, and weighing between 500 and 660 kg were superstimulated twice with a withdrawal period of 35 days in between two treatments. In superstimulation protocol-1 (estradiol group) buffaloes were administered estradiol-17β (2 mg, i.m.) and eazibreed controlled internal drug release (CIDR) was inserted intravaginally (day=0) at the random stage of the estrous cycle. On the day 4, buffaloes were superstimulated using follicle stimulating hormone (FSH) 400 mg, divided into 10 tapering doses given at 12 hourly intervals. Prostaglandin F2α analogs (PGF2α) was administered at day 7.5 and day 8, and CIDR was removed with the second PGF2α injection. In superstimulation protocol - 2 (conventional group) buffaloes were superstimulated on the 10^th day of the estrous cycle with same FSH dose regimen and similar timings for PGF2α injections. In both groups, half of the buffaloes were treated with luteinizing hormone (LH) 25 mg and other half with 100 ug buserelin; gonadotrophin releasing hormone (GnRH) analog at 12 h after the end of FSH treatment. All buffaloes in both protocols were inseminated twice at 12 and 24 h of LH/GnRH treatment. Daily ultrasonography was performed to record the size and number of follicles and superovulatory response.

Results:

Significantly higher number of small follicles (<8 mm) was present at the time of initiation of superstimulatory treatment in the estradiol group compared to the conventional group (12.5±0.80 vs. 7.3±1.21, respectively, p=0.019), however, the number of ovulatory size follicles (≥8 mm) did not differ significantly between the respective groups (15.5±1.24 vs. 12.2±1.30; p=0.054). Total embryos and transferable embryos recovered were non-significantly higher in the estradiol group compared to the conventional group (5.83±0.86 vs. 4.67±1.16, p=0.328, and 3.67±0.93 vs. 2.67±0.68, p=0.437, respectively). The significant higher proportion of transferable embryos were recovered in buffaloes treated with LH compared to GnRH (73.3% vs. 48.5%; p=0.044).

Conclusion:

The average number of ovulatory size follicles (>8 mm), corpora lutea, and transferable embryos was higher in buffaloes superstimulated at estradiol-induced follicular wave compared to the conventional protocol: Further the percentage of transferable embryos was significantly higher in buffaloes administered with LH compared to GnRH.

Anti-Mullerian hormone (AMH) concentration in follicular fluid and mRNA expression of AMH receptor type II and LH receptor in granulosa cells as predictive markers of good buffalo (Bubalus bubalis) donors

High individual variability in follicular recruitment and hence in the number of embryos produced is a major factor limiting the application of reproductive technologies in buffalo. Therefore, the identification of reliable markers to select embryo donors is critical to enroll buffaloes in embryo production programs. Better understanding of factors involved in follicular growth is also necessary to improve the response to superovulation in this species. The aim of this work was thus to determine the anti-Mullerian hormone (AMH) concentration in follicular fluid (FF) recovered from different size follicles and evaluate the mRNA expression profiles of development-related (AMHR2, CYP19A1, FSHR, and LHR) and apoptosis-related genes (TP53INP1 and CASP3) in the corresponding granulosa cells (GCs) in buffalo. Another objective was to evaluate whether the AMH concentration in FF and gene expression of GCs is associated with the antral follicular count. Ovaries were collected at the slaughterhouse, and all follicles were counted and classified as small (3-5 mm), medium (5-8 mm), and large (>8 mm). Follicular fluid was recovered for AMH determination, and the mRNA expression of AMHR2, FSHR, LHR, CYP19A1, TP53INP1, and CASP3 was analyzed in GCs. The AMH concentration in FF decreased (P < 0.01) at increasing follicular diameter. The mRNA expression of AMHR2 and FSHR was higher (P < 0.05) in small follicles, whereas that of LHR and CYP19A1 was higher (P < 0.05) in large follicles. The intrafollicular AMH concentration was positively correlated with the antral follicular count (r = 0.31; P < 0.05). Interestingly, good donors (≥12 follicles) had a higher (P < 0.05) concentration of AMH and AMHR2 levels in small follicles and higher (P < 0.05) LHR levels in large follicles than bad donors (<12 follicles). These results suggest a potential use of AMH to select buffalo donors to enroll in embryo production programs, laying the basis for further investigations.

Ovarian follicular growth suppression by long-term treatment with a GnRH agonist and impact on small follicle number, oocyte yield, and in vitro embryo production in Zebu beef cows

The aim of the present study was to evaluate small follicle number, oocyte yield, and in vitro embryo production (IVEP) in Zebu beef cows treated long term with a GnRH agonist to suppress ovarian follicular growth. Nelore (Bos indicus) cows (n = 20) showing regular estrous cycles were randomly assigned to one of two groups: control (n = 10, placebo ear implant without a GnRH agonist); GnRH agonist (n = 10, GnRH agonist ear implant containing 9.4-mg deslorelin). All cows underwent an ovum pick-up (OPU) session 14 days (Day 14) before the start of treatments (Day 0) followed by seven OPU-IVEP procedures at 30-day intervals (Days 0, 30, 60, 90, 120, 150, and 180). Semen from a single batch of a previously tested bull was used for all the IVEP. Cows treated with agonist reported a decrease over time in the proportion of animals with a (CL; P ≤ 0.05) and large follicles (>10 mm, P ≤ 0.05). These cows had a lesser number of medium + large follicles (>5 mm; 1.74 ± 0.5 vs. 4.13 ± 0.5; P ≤ 0.05), greater number of small follicles (2-5 mm; 44.3 ± 2.8 vs. 30.8 ± 1.8; P ≤ 0.05), greater yield of cumulus-oocyte complexes (COCs; 21.0 ± 2.3 vs. 15.6 ± 1.9; P ≤ 0.05), greater proportion of COCs cultured (79.2 vs. 73.9%; P ≤ 0.05), COCs cleaved (10.6 ± 1.5 vs. 6.8 ± 1.1, P ≤ 0.05), and cleaved rate (52.8 vs. 44.3%; P ≤ 0.05) compared with control cows. The number (3.4 ± 0.7 vs. 3.0 ± 0.6; P > 0.05) and proportion (16.5 vs. 19.1%; P > 0.05) of blastocysts produced were similar between agonist and control cows, respectively. The study has shown that Zebu beef cows treated long term with a GnRH agonist had follicular growth restricted to small follicles. This did not compromise the ability of oocytes to undergo IVF and embryonic development.

Paradoxical effects of bovine somatotropin treatment on the ovarian follicular population and in vitro embryo production of lactating buffalo donors submitted to ovum pick-up

The aim of the present study was to evaluate the effect of bovine somatotropin (bST; 500mg) administration on lactating buffalo donors submitted to two different ovum pick-up (OPU) and in vitro embryo production schemes with a 7 or 14d intersession OPU interval. A total of 16 lactating buffalo cows were randomly assigned into one of four experimental groups according to the bST treatment (bST or No-bST) and the OPU intersession interval (7 or 14d) in a 2×2 factorial design (16 weeks of OPU sessions). The females submitted to OPU every 14d had a larger (P<0.001) number of ovarian follicles suitable for puncture (15.6±0.7 vs. 12.8±0.4) and an increased (P=0.004) number of cumulus-oocyte complexes (COCs) recovered (10.0±0.5 vs. 8.5±0.3) compared to the 7d interval group. However, a 7 or 14d interval between OPU sessions had no effect (P=0.34) on the number of blastocysts produced per OPU (1.0±0.1 vs. 1.3±0.2, respectively). In addition, bST treatment increased (P<0.001) the number of ovarian follicles suitable for puncture (15.3±0.5 vs. 12.1±0.4) but reduced the percentage (18.9% vs. 10.9%; P=0.009) and the number (1.4±0.2 vs. 0.8±0.1; P=0.003) of blastocysts produced per OPU session compared with the non-bST-treated buffaloes. In conclusion, the 14d interval between OPU sessions and bST treatment efficiently increased the number of ovarian follicles suitable for puncture. However, the OPU session interval had no effect on embryo production, and bST treatment reduced the in vitro blastocyst outcomes in lactating buffalo donors.

The interval between the emergence of pharmacologically synchronized ovarian follicular waves and ovum pickup does not significantly affect in vitro embryo production in Bos indicus, Bos taurus, and Bubalus bubalis

The aim of the present study was to determine the optimal phase of the follicular wave to perform ovum pickup (OPU) for in vitro embryo production (IVEP) in various genetic groups. For this purpose, 27 heifers-nine Bos taurus (Holstein), nine Bos indicus (Nelore), and nine Bubalus bubalis (Mediterranean)-were maintained under the same nutritional, management, and environmental conditions. Heifers within each genetic group were submitted to six consecutive OPU trials with 14-day intersession intervals, at three different phases of the pharmacologically synchronized follicular wave (Day 1, 3, or 5 after follicular wave emergence), in a 3 × 3 crossover design. When OPU was performed at different phases of the pharmacologically synchronized follicular wave (Day 1, 3, or 5), no differences were found in the percent of oocytes recovered (70.5 ± 3.1%, 75.0 ± 3.1%, 76.0 ± 3.2%, respectively; P = 0.41) or blastocyst production rates (19.4 ± 2.9%, 16.6 ± 2.9%, 15.9 ± 2.6%, respectively; P = 0.36). Comparing genetic groups, B indicus showed a higher blastocyst rate (28.3(a) ± 2.8%; P < 0.01) than B taurus and B bubalis (14.1(b) ± 2.9% and 10.2(b) ± 2.0%, respectively). However, only B indicus heifers showed a variation in the number of visualized follicles and the total and viable oocytes along consecutive OPU sessions. In conclusion, different phases of the pharmacologically synchronized ovarian follicular wave did not affect OPU-IVEP in B indicus, B taurus, and B bubalis heifers. Additionally, B indicus heifers showed greater OPU-IVEP efficiency than did the other genetic groups, under the same management conditions.

Ovum pick up, intracytoplasmic sperm injection and somatic cell nuclear transfer in cattle, buffalo and horses: from the research laboratory to clinical practice

Assisted reproductive techniques developed for cattle in the last 25 years, like ovum pick up (OPU), intracytoplasmic sperm injection (ICSI), and somatic cell nuclear transfer, have been transferred and adapted to buffalo and horses. The successful clinical applications of these techniques require both the clinical skills specific to each animal species and an experienced laboratory team to support the in vitro phase of the work. In cattle, OPU can be considered a consolidated technology that is rapidly outpacing conventional superovulation for embryo transfer. In buffalo, OPU represents the only possibility for embryo production to advance the implementation of embryo-based biotechnologies in that industry, although it is still mainly in the developmental phase. In the horse, OPU is now an established procedure for breeding from infertile and sporting mares throughout the year. It requires ICSI that in the horse, contrary to what happens in cattle and buffalo, is very efficient and the only option because conventional IVF does not work. Somatic cell nuclear transfer is destined to fill a very small niche for generating animals of extremely high commercial value. The efficiency is low, but because normal animals can be generated it is likely that advancing our knowledge in that field might improve the technology and reduce its cost.

Influence of oocyte donor on in vitro embryo production in buffalo

The aim of this research was to estimate the variability between buffalo as oocyte donors. In Experiment 1, reproductive variables were retrospectively analyzed in buffalo (n=40) that underwent repeated ovum pick up (OPU), over 16 puncture sessions (PS). The follicular recruitment among individuals and the relationship between follicular population and oocyte production were evaluated. In Experiment 2, eight buffalo underwent OPU for 28 PS and the oocytes were processed separately to correlate follicular and oocyte population at the first PS to blastocyst (BL) production. In Experiment 1, the average number of total follicles (TFL), small follicles (SFL), cumulus-oocyte complexes (COC) and Grade A+B COC recorded in each 4-PS period had great repeatability (r=0.52, 0.54, 0.60 and 0.57, respectively). The average number of Grade A+B COC recovered during the subsequent 15 PS was positively correlated with the first PS number of TFL (r=0.60; P<0.001), SFL (r=0.68; P<0.001), COC (r=0.48; P<0.01) and Grade A+B COC (r=0.40; P<0.05). In Experiment 2, a large variability among animals was observed in blastocyst yields. When animals were grouped according to the BL yield, the greatest BL yield group had a greater (P<0.05) number of TFL (8.3 ± 0.9 compared with 5.6 ± 0.7) and SFL (7.3 ± 0.3 compared with 3.8 ± 0.7) at the first PS than the lesser BL yield group. The average number of BL produced over the subsequent sessions was correlated with the number of TFL (r=0.80; P<0.05) and COC (r=0.76; P<0.05) observed at the first PS. These results demonstrated a donor influence on the oocyte and BL production, suggesting a preliminary screening to select the donors with greater potential.

FSH up-regulates angiogenic factors in luteal cells of buffaloes

Follicle-stimulating hormone has been widely used to induce superovulation in buffaloes and cows and usually triggers functional and morphologic alterations in the corpus luteum (CL). Several studies have shown that FSH is involved in regulating vascular development and that adequate angiogenesis is essential for normal luteal development. Angiogenesis is regulated by many growth factors, of which vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) have an established central role. Therefore, we have used a combination of in vitro and in vivo studies to assess the effects of FSH on the expression of VEGF and FGF2 and their receptors in buffalo luteal cells. The in vivo model consisted of 12 buffalo cows, divided into control (n = 6) and superovulated (n = 6) groups, and CL samples were collected on day 6 after ovulation. In this model, we analyzed the gene and protein expression of FGF2 and its receptors and the protein expression of VEGFA systems with the use of real-time PCR, Western blot analysis, and immunohistochemistry. In the in vitro model, granulosa cells were collected from small follicles (diameter, 4-6 mm) of buffaloes and cultured for 4 d in serum-free medium with or without FSH (10 ng/mL). To induce in vitro luteinization, LH (250 ng/mL) and fetal bovine serum (10%) were added to the medium, and granulosa cells were maintained in culture for 4 d more. The progesterone concentration in the medium was measured at days 4, 5, and 8 after the beginning of cell culture. Cells were collected at day 8 and subjected to real-time PCR, Western blot analysis, and immunofluorescence for assessment of the expression of FGF2, VEGF, and their receptors. To address the percentage of steroidogenic and growth factor-expressing cells in the culture, flow cytometry was performed. We observed that in superovulated buffalo CL, the FGF2 system mRNA expression was decreased even as protein expression was increased and that the VEGF protein was increased (P < 0.05). In vitro experiments with granulosa cells showed an increase in the mRNA expression of VEGF and FGF2 and its receptors 1 and 2 and protein expression of VEGF, kinase insert domain receptor, FGF receptor 2, and FGF receptor 3 in cells treated with FSH (P < 0.05), in contrast to the in vivo experiments. Moreover, the progesterone production by FSH-treated cells was elevated compared with untreated cells (P < 0.05). Our findings indicate that VEGF, FGF2, and their receptors were differentially regulated by FSH in vitro and in vivo in buffalo luteal cells, which points toward a role of CL environment in modulating cellular answers to gonadotropins.

Effect of recombinant bovine somatotropin (bST) on follicular population and on in vitro buffalo embryo production

The objective of this study was to evaluate the effect of bovine somatotropin (bST) on ovarian follicular population in buffalo heifers and its influence on oocyte quality, recovery rates and in vitro embryo production. We tested the hypothesis that bST treatment in buffalo females submitted to an ovum pick-up (OPU) program would improve the number of follicles recruited, oocyte quality and in vitro embryo production. A total of 10 heifers were assigned into two treatment groups: group bST (n=5; receiving 500 mg of bST in regular intervals) and control group (n=5; without additional treatment). Both groups were subjected to OPU sessions twice a week (every 3 or 4 days), for a total of 10 sessions per female, although due to procedural problems, only the first five OPU sessions produced embryos. The number of follicles and the diameters were recorded at all OPU sessions. The harvested oocytes were counted and classified according to their quality as either A, B, C, D or E, with A and B considered good quality. Cleavage and blastocyst production rates were evaluated 2 and 7 days after in vitro fertilization, respectively. The bST treatment increased the total number of antral follicles (>3mm in diameter; 12.2 compared with 8.7; p<0.05) and of small antral follicles (<5mm; 9.1 compared with 6.5; p<0.05) per OPU session. The bST also tended to increase the number of oocytes recovered per session (5.2 compared with 4.1; p=0.07), and enhanced the percentage of good quality oocytes (48.8% compared with 40.6%; p=0.07). bST showed no effect on cleavage and blastocyst production rates (p>0.05). The significant effects of performing repeated OPU sessions were decreasing the follicular population (p<0.001) as well as the number of follicles aspirated (p<0.001), and oocytes recovered (p<0.02). In conclusion, bST treatment improves the follicular population, demonstrating its possible application in buffalo donors submitted to OPU programs.

VEGF system expression in different stages of estrous cycle in the corpus luteum of non-treated and superovulated water buffalo

Water buffaloes are easily adaptable animals, whose raising and economical exploitation have been growing in the last three decades all over the world. Hyperstimulation of ovarian function in this species is a common technique aiming to improve reproductive performance. Superovulatory treatment affects corpus luteum (CL) function, which is highly correlated to angiogenic process. The aim of this study was therefore to assess the temporal protein and mRNA expression of VEGF and its receptors in the CL of non-treated and superovulated buffaloes. For that purpose blood samples and CL from 36 healthy (30 untreated, groups 1-5, and 6 superovulated, group 6) non-pregnant buffaloes were collected and the samples were divided into 6 groups according to the age of CL. Plasma samples were submitted to RIA to measure progesterone concentration and CL were subjected to immunohistochemistry and real time PCR for VEGF (vascular endothelial growth factor), Flt-1 (fms-like tyrosine kinase receptor 1) and KDR (kinase insert domain containing region). The VEGF system protein and mRNA expression during CL life span of untreated animals showed a specific time-dependent profile, although protein did not always reflect mRNA concentrations. VEGF expression in luteal cells was high correlated to plasma progesterone levels. Superovulated CL showed a significant increase of the VEGF-system protein and a significant decrease of mRNA expression compared to untreated animals in the same stage of the oestrous cycle. We conclude that VEGF, Flt-1 and KDR protein and mRNA expression in buffalo CL is dependent of estrous cycle stage and superovulatory treatment is able to increase the translation rate of this system.