Maturation Of Buffalo Oocytes Research Articles

The Effect of Different Ovarian Storage Times and Oocyte Collection Methods on the Quantity, Quality, and Maturation of Buffalo Oocytes In Vitro

The Effect of Different Ovarian Storage Times and Oocyte Collection Methods on the Quantity, Quality, and Maturation of Buffalo Oocytes In Vitro

Effects of MEK1/2 inhibitor U0126 on FGF10-enhanced buffalo oocyte maturation in vitro

Fibroblast growth factor 10 (FGF10) plays critical roles in oocyte maturation and embryonic development; however, the specific pathway by which FGF10 promotes in vitro maturation of buffalo oocytes remains elusive. The present study was aimed at investigating the mechanism underlying effects of the FGF10-mediated extracellular regulated protein kinases (ERK) pathway on oocyte maturation and embryonic development in vitro. MEK1/2 (mitogen-activated protein kinase kinase) inhibitor U0126, alone or in combination with FGF10, was added to the maturation culture medium during maturation of the cumulus oocyte complex. Morphological observations, orcein staining, apoptosis detection, and quantitative real-time PCR were performed to evaluate oocyte maturation, embryonic development, and gene expression. U0126 affected oocyte maturation and embryonic development in vitro by substantially reducing the nuclear maturation of oocytes and expansion of the cumulus while increasing the apoptosis of cumulus cells. However, it did not have a considerable effect on glucose metabolism. These findings suggest that blocking the MEK/ERK pathway is detrimental to the maturation and embryonic development potential of buffalo oocytes. Overall, FGF10 may regulate the nuclear maturation of oocytes and cumulus cell expansion and apoptosis but not glucose metabolism through the MEK/ERK pathway. Our findings indicate that FGF10 regulates resumption of meiosis and expansion and survival of cumulus cells via MEK/ERK signaling during in vitro maturation of buffalo cumulus oocyte complexes. Elucidation of the mechanism of action of FGF10 and insights into oocyte maturation should advance buffalo breeding. Further studies should examine whether enhancement of MEK/ERK signaling improves embryonic development in buffalo.

Mito-Q supplementation of in vitro maturation or in vitro culture medium improves maturation of buffalo oocytes and developmental competence of cloned embryos by reducing ROS production

Mito-Q is a well-known mitochondria-specific superoxide scavenger. To our knowledge, the effect of Mito-Q on buffalo oocyte maturation and developmental competency of cloned embryos has not been examined. To investigate the effects of Mito-Q on the in vitro maturation (IVM) of buffalo oocytes and the developmental competence of cloned embryos, different concentration of Mito-Q were supplemented with IVM (0, 0.1, 0.5, 1, 2 μM) and in vitro culture (IVC) medium (0, 0.1 μM). Supplementation of IVM medium with 0.1 μM Mito-Q significantly (P ≤ 0.05) increased the cumulus expansion, nuclear maturation, mitochondrial membrane potential (MMP) and antioxidants genes (GPX1 and SOD2) expression and effectively reduced ROS production leading to a significant improvement in the maturation rate of buffalo oocytes. Further, the supplementation of 0.1 μM Mito-Q in IVC medium promotes the cleavage and blastocyst rate significantly over the control. Mito-Q supplementation improves (P ≤ 0.05) MMP, antioxidant gene (GPX1) expression and reduced the ROS level and apoptosis related genes (caspase 9) expression in cloned blastocysts. In conclusion, the present study demonstrated that the supplementation of 0.1 μM Mito-Q in IVM and IVC media exerts a protective role against oxidative stress by reducing ROS production and improving MMP, fostering improved maturation of buffalo oocytes and enhanced developmental competence of cloned embryos. These findings contribute valuable insights into the optimization of assisted reproductive technologies protocols for buffalo breeding and potentially offer novel strategies to enhance reproductive outcomes in livestock species.

Follistatin (FST) is expressed in buffalo (Bubalus bubalis) ovarian follicles and promotes oocyte maturation and early embryonic development.

Follistatin (FST), a member of the transforming growth factor-β (TGF-β) superfamily, has been identified as an inhibitor of follicle-stimulating hormone. Previous studies showed that it plays an important role in animal reproduction. Therefore, this study aims to investigate its effect on the maturation of buffalo oocytes invitro, and the underlying mechanism of FST affecting oocyte maturation was also explored in buffalo cumulus cells. Results showed that FST was enriched in the ovary and expressed at different stages of buffalo ovarian follicles as well as during oocyte maturation and early embryo development. The FST expression level was up-regulated in MII buffalo oocytes compared with the GV stage (p < .05). To study the effects of FST on buffalo oocytes' maturation and early embryonic development, we added the pcD3.1 skeleton vector and PCD3.1-EGFP-FST vector into the maturation fluid of buffalo oocytes, respectively. It was demonstrated that FST promoted the invitro maturation rate of buffalo oocytes and the blastocyst rate of embryos cultured invitro (p < .05). By interfering with FST expression, we discovered that FST in cumulus cells plays a crucial role in oocyte maturation. Interference with the FST expression during the buffalo oocyte maturation did not affect the first polar body rate of buffalo oocyte (p > .05). In contrast, the location of mitochondria in oocytes was abnormal, and the cumulus expansion area was reduced (p < .05). After parthenogenetic activation, the cleavage and blastocyst rates of the FST-interfered group were reduced (p < .05). Furthermore, RT-qPCR was performed to investigate further the underlying mechanism by which FST enhances oocyte maturation. We found that overexpression of FST could up-regulate the expression level of apoptosis suppressor gene Bcl-2 and TGF-β/SMAD pathway-related genes TGF-β, SMAD2, and SMAD3 (p < .05). In contrast, the expression levels of SMAD4 and pro-apoptotic gene BAX were significantly decreased (p < .05). The FST gene could affect buffalo oocyte maturation by regulating the oocyte mitochondria integrity, the cumulus expansion, cumulus cell apoptosis, and the expression levels of TGF-β/SMAD pathway-related genes.

Efficiency Evaluation of Two Media for In Vitro Maturation of Buffalo Oocytes

This study was conducted to evaluate morphometry of ovarian functional structures and effect of two different commercially available in vitro maturation (IVM) media on cytoplasmic and nuclear maturation of slaughter origin buffalo oocytes. The buffalo ovaries were collected from Ahmedabad Municipal slaughter-house, Ahmedabad and were transported at the laboratory within 2-3 h of slaughter at 33 to 35°C warm normal saline. The ovaries were washed and processed under laminar floor and evaluated for functional structures like mature corpus luteum (CL) and follicles i) &lt;3 mm (small), ii) 3 to 6 mm (medium) and iii) 6 mm (large). The cumulus oocytes complexes (COCs) were aspirated with 18 G needle in 5 mL sterile disposable needle. The COCs were graded in to four categories (I to IV) and first three categories of COCs were used for IVM. For IVM 90 µL drops of BO IVM (IB; Bioscience) and IVM (VB; Vitrogen, Brazil) media were prepared and kept in benchtop incubator at 5 % O2, 5% CO2 and rest N2 at 38.5 °C. The selected COCs were randomly allocated to two media treatments and incubated for 22 h. The cytoplasmic and nuclear maturation were observed using morphology and nuclear staining method (Hoechst 334452). The weight of ovaries with CL (6.63 ± 0.18 g) was significantly higher as compared to without CL (4.33 ± 0.14 g). Total 546 visible follicles with average 2.15 per ovary observed were aspirated from 254 buffalo ovaries and 440 COCs were collected. Overall oocyte recovery per ovary (OR/O), follicle recovery per ovary (FR/O) and oocyte retrieval per follicle (OR/F) were 1.73, 2.15 and 0.81, respectively. The small, medium and large follicles were 43.04, 41.94 and 15.01 %, respectively. The mean ± SE (n) count of oocytes with Grade I, Grade II, Grade III and Grade IV were 6.90 ± 0.61 (138), 6.50 ± 0.48 (130), 4.35 ± 0.40 (87) and 4.25 ± 0.54 (85) with recovery rate of 31.36, 29.54, 19.77 and 19.31 %, respectively. Total 133 and 137 COCs were randomly allocated to IB and VB media treatment. Total cytoplasmic maturation in IB and VB was 79.69 and 73.71 %. Similarly, the nuclear maturation was 78.19 and 71.53 % in IB and VB media. No significant differences in cytoplasmic or nuclear maturation between two media were observed. The study concludes that CL influences ovarian weight and both commercial medias can be used for successful in vitro maturation of COCs of buffaloes.

Beneficial effects of fibroblast growth factor 10 supplementation during in vitro maturation of buffalo cumulus-oocyte complexes

Fibroblast growth factor 10 (FGF10) is an important regulator of the mammalian cumulus-oocyte complex that plays a crucial role in oocyte maturation. In this study, we investigated the effects of FGF10 supplementation on the in vitro maturation (IVM) of buffalo oocytes and its related mechanisms. During IVM, the maturation medium was supplemented with a range of concentrations of FGF10 (0, 0.5, 5, and 50 ng/mL) and the resulting effects were corroborated using aceto-orcein staining, TUNEL apoptosis assay, detection of Cdc2/Cdk1 kinase in oocytes, and real-time quantitative PCR. In matured oocytes, the 5 ng/mL-FGF10 treatment resulted in a significantly increased nuclear maturation rate, which increased the activity of maturation-promoting factor (MPF) and enhanced buffalo oocyte maturation. Furthermore, it treatment significantly inhibited the apoptosis of cumulus cells, while simultaneously promoting its proliferation and expansion. This treatment also increased the absorption of glucose in cumulus cells. Thus, our results indicate that adding an appropriate concentration of FGF10 to a maturation medium during IVM can be beneficial to the maturation of buffalo oocytes and improve the potential of embryo development.

L-Carnitine Supports the In Vitro Growth of Buffalo Oocytes.

Simple SummaryThe objective of this study was to examine the effect of L-carnitine on the growth and subsequent nuclear maturation of buffalo growing oocytes in vitro. Oocyte-granulosa cell complexes (OGCs) were collected from early antral follicles of slaughtered buffaloes and cultured in in vitro growth (IVG) medium with the supplementation of different concentrations (0, 1.25, 1.875 or 2.5 mM) of L-carnitine for 6 days. The results showed that L-carnitine increased the diameter of buffalo oocytes in vitro. L-carnitine also enhanced the antrum-like structure formation and prevented the degeneration of buffalo oocytes in culture. Furthermore, L-carnitine-treated oocytes showed a higher rate of nuclear maturation up to the metaphase II (MII) stage and a lower rate of degeneration. In conclusion, L-carnitine enhances the growth, prevents degeneration, promotes the formation of antrum-like structures and supports nuclear maturation of buffalo oocytes in vitro.This study aimed to determine the effect of L-carnitine on the growth and subsequent nuclear maturation of buffalo small growing oocytes (92–108 µm in diameter) in vitro. Oocyte-granulosa cell complexes (OGCs) were dissected from early antral follicles of slaughtered buffaloes and cultured in in vitro growth (IVG) medium with the supplementation of different concentrations (0, 1.25, 1.875 or 2.5 mM) of L-carnitine for 6 days. The results revealed that L-carnitine increased the diameter of buffalo oocytes in vitro. The degeneration rate was significantly (p < 0.05) lower in 2.5 mM of L-carnitine-treated oocytes (10%) than others (55%, 45% and 32.5% in 0, 1.25 and 1.875 mM of L-carnitine-supplemented groups, respectively). The OGCs showed antrum-like structures significantly (p < 0.05) higher in the 2.5 mM of L-carnitine group (74.0%) than the 0- and 1.25-mM groups (34.6% and 38.1%, respectively). Furthermore, in vitro grown oocytes were placed in in vitro maturation (IVM) medium for 24 h to examine meiotic competence of in vitro grown oocytes with L-carnitine. The L-carnitine (1.875 and 2.5 mM) treated oocytes showed a higher rate of nuclear maturation up to the metaphase II (MII) stage and a lower rate of degeneration. In conclusion, L-carnitine enhances the growth, prevents degeneration, promotes the formation of antrum-like structures and supports nuclear maturation of buffalo oocytes in vitro.

Effect of Culture Media, Gonadotropins, Proteins, Growth Factors and Hyaluronic Acid on In-Vitro Maturation of Buffalo Oocytes

Effect of Culture Media, Gonadotropins, Proteins, Growth Factors and Hyaluronic Acid on In-Vitro Maturation of Buffalo Oocytes

Effect of milrinone on the meiosis resumption and cytoplasm maturation of buffalo oocytes.

Buffalo has many excellent economic traits and it is one of the greatest potential livestock. Compared with cattle, buffalo has poorer reproductivity, it is of great significance to improve the development potential of oocytes. Buffalo oocyte in vitro maturation (IVM) has been widely used in production, but the poor development ability of bovine oocytes IVM limits the development of buffalo reproductivity. Milrinone as a phosphodiesterase inhibitor could affect the maturation of oocytes in goat and mice, but there have been few reported studies in water buffalo. To optimize buffalo oocyte in vitro maturation systems, the effects of phosphodiesterase inhibitor (milrinone) on pre-maturation culture of buffalo oocytes were investigated in this study. Buffalo cumulus-oocyte complexes (COCs) were cultured in medium with different concentrations (0, 12, 25, 50 and 100 mol/l) of milrinone for different times (0, 4, 8, 12, 16, 22 and 24 h). The results showed that the buffalo COCs nuclear maturation process could be inhibited by milrinone (25-100 mol/l) in a dose-dependent manner. The inhibitory effect of milrinone on in vitro maturation of buffalo oocytes did not decrease with the extension of time. This indicated that milrinone can be used as a nuclear maturation inhibitor during the maturation process in buffalo oocytes. In addition, milrinone can inhibit the effect of follicle stimulating hormone (FSH)-induced IVM of buffalo oocytes, but with time FSH partially eliminated the inhibition. Therefore, inhibition of milrinone on the nuclear maturation of buffalo oocytes was reversible, and buffalo oocytes can mature normally after the inhibition is lessened.

In vitro Maturation of Buffalo Oocytes and Expression of Selected Biomarker Candidate Genes

Background: Number of genes expressed during in vitro maturation (IVM) of which selected genes can be used as the potential biomarkers of oocyte competence. Hence, this study was planned to evaluate selected gene expression of GDF9, HAS2, SPRY, ARHGAP22, COL18A1 and GPC4 in IVM and immature cumulus oocyte complexes (COCs). Methods: The COCs were recovered from slaughter origin ovaries of buffaloes. Of which first three grade COCs were randomly allotted in immature (IMT; n=217) and IVM group (n=272). IVM of COCs was performed under drops of BO-maturation media in CO2 incubator at 39.0°C for 24 hours. The expression of genes was evaluated using qPCR and the relative expression of each gene was calculated using the ΔΔCt method with efficiency correction. The logarithmic transformation of fold change of each candidate genes in the IVM group was computed against the IMT group using the Ct values. Result: The expression obtained for IVM group of earlier reported up-regulated genes (GDF9, HAS2, SPRY1) was higher (upto 10xfold) compared to the IMT group. Relatively lower expression was observed for the rest of the three candidate genes (ARHGAP22, COL18A1, GPC4) in the bovine transcripts of oocyte which were earlier also reported as down regulated.

Cellular and molecular alterations of buffalo oocytes cultured under two different levels of oxygen tension during in vitro maturation.

This study was conducted to monitor the cellular and molecular changes of buffalo cumulus-oocytes complexes (COCs) cultured under high or low oxygen levels. Morphologically good quality COCs (n = 1627) were screened using brilliant cresyl blue (BCB) staining and placed into three groups (BCB+, BCB- and control). All groups of COCs were cultured under low (5%) or high (20%) oxygen tensions. Intracellular and molecular changes including oocyte ultrastructure, lipid contents, mitochondrial activity and transcript abundance of genes regulating different pathways were analyzed in the matured oocyte groups. The results revealed that oxygen tension did not affect cumulus expansion rates, however the BCB+ group had a higher (P ≤ 0.05) expansion rate compared with the BCB- group. BCB- oocytes recorded the lowest meiotic progression rate (P ≤ 0.05) under high oxygen levels that was linked with an increased level of reactive oxygen species (ROS) compared with the BCB+ oocytes. Ultrastructure examination indicated that BCB+ oocytes had a higher rate of cortical granules migration compared with BCB- under low oxygen tension. In parallel, our results indicated the upregulation of NFE2L2 in groups of oocytes cultured under high oxygen tension that was coupled with reduced mitochondrial activity. In contrast, the expression levels of MAPK14 and CPT2 genes were increased (P ≤ 0.05) in groups of oocytes cultured under low compared with high oxygen tension that was subsequently associated with increased mitochondrial activity. In conclusion, data from the present investigation indicated that low oxygen tension is a favourable condition for maintaining the mitochondrial activity required for nuclear maturation of buffalo oocytes. However, low-quality oocytes (BCB-) responded negatively to high oxygen tension by reducing the expression of gene-regulating metabolic activity (CPT2). This action was an attempt by BCB- oocytes to reduce the increased levels of endogenously produced ROS that was coupled with decreased expression of the gene controlling meiotic progression (MAPK14) in addition to nuclear maturation rate.

Effect of Kisspeptin on in vitro Maturation of Buffalo Oocytes

To explore the effect of kisspeptin on in vitro maturation of buffalo oocytes under different hormonal combinations. For the present study, Kp@10 µg/ml was selected as optimum by assessing the proportion of Cumulus Cell Expansion (CCE) and extrusion of 1st polar body (PB) from the earlier study conducted. Media containing TCM 199 (supplemented with Gentamicin) and oocytes were used as control. Overall, oocytes were allowed to mature in 12 different maturation media viz., Control (T1), Kp at 10 µg/ml (T2), FSH alone (T3), FSH +Kp (T4), LH (T5), LH +Kp (T6), E2 (T7), E2+Kp (T8), FSH+LH+E2 (T9), FSH+LH+E2+Kp (T10), FSH+LH+E2+FCS+BSA (T11) and FSH+LH+E2+FCS+BSA+Kp (T12), incubated at 38.5°C and 5% CO2 under humidified atmosphere for 22 hours. The results showed significantly (P £ 0.5) higher percentages of CCE and PB in groups supplemented with Kp (T4, T6, T8, T10 and T12,) compared to control (T1) and other treatment groups supplemented with individual hormones either alone (T3, T5 and T7) or combination of hormones (T9) and IVM alone (T11). Therefore, it has been clearly demonstrated that addition of Kp (10 µg/ml) to FSH, LH, E2 supplemented media, in various combinations enhances buffalo oocyte maturation rates in vitro.

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.

A new three-dimensional glass scaffold increases the in vitro maturation efficiency of buffalo (Bubalus bubalis) oocyte via remodelling the extracellular matrix and cell connection of cumulus cells.

At present, many three-dimensional (3D) culture systems have been reported, improving the oocyte quality of in vitro maturation (IVM), yet the mechanism still needs to be further explored. Here we examined the effects of a new self-made 3D glass scaffold on buffalo oocyte maturation; meanwhile, the underlying mechanism on buffalo oocyte maturation was also detected. Compared to the two-dimensional (2D) glass dish culture, results revealed that the 3D culture can improve the first polar body rate of oocytes, subsequent cleavage and blastocysts rate of parthenogenetic activation embryos (p<.05). The extracellular matrix-related proteins COL1A1, COL2A1, COL3A1, FN and cell connection-related proteins N-cadherin, E-cadherin, GJA1 were found higher in cumulus cells of 3D culture. Moreover, in cumulus cells, proteins of the PI3K/AKT pathway reported being regulated by FN and E-cadherin including PI3K P85 and p-AKT were also higher in 3D culture. Furthermore, proapoptosis proteins P53, BAX, caspase-3 were lower in both cumulus cells and oocytes in 3D culture, while proteins PCNA and BCL2 showed the opposite result. Results also showed that the apoptosis was inhibited, and the proliferation was enhanced in cumulus cells of 3D culture. Finally, the cumulus expansion-related genes HAS2, CD44, HMMR, PTX3, PTGS2 were found higher in cumulus cells of 3D culture. Taken together, the 3D culture could promote oocyte maturation by regulating proteins correlated with the ECM, cell connection and PI3K/AKT pathway, inhibiting the apoptosis of cumulus cells and oocytes, enhancing the proliferation of cumulus cells and the cumulus expansion.

Effects of stem cell factor on in vitro growth of buffalo oocytes

Stem cell factor (SCF) plays important roles in primordial follicle activation, oocyte growth and survival, granulosa cell proliferation, theca cell recruitment, and ovarian steroidogenesis. The aim of this study was to investigate the effect of SCF on in vitro growth of buffalo oocytes. Oocyte-granulosa cell complexes (OGCs) were dissected from early antral follicles of slaughtered buffalo ovaries and cultured for 6 days in media supplemented with 0, 50 or 100 ng/mL SCF. In vitro grown oocytes were further cultured for in vitro maturation for 24 h. The results showed that SCF significantly (P < 0.05) increased oocyte diameter in vitro. The percentages of surviving oocytes were 60, 81 and 92 in 0, 50 and 100 ng/mL SCF supplemented group, respectively. SCF promoted formation of antrum-like structures in culture. The results also showed that SCF enhanced the maturation of in vitro grown buffalo oocytes. Here, 14% in vitro grown oocytes reached metaphase II (MII) stage in 50 ng/mL SCF supplemented group, whereas the percentage was increased to 26% in 100 ng/mL SCF treated group. These results show that SCF supports the growth, viability and nuclear maturation of buffalo oocytes in vitro.

Effect of Season and Ovarian Morphology of Egyptian Buffalo on Oocyte Quality and In Vitro Maturation Rate

The aim of the current study was to investigate the effect of season, follicle size and corpus luteum (CL) on yield, quality and in vitro maturation of Egyptian buffalo oocytes. Ovaries were collected from abattoirs allover the year and cumulus oocytes complexes (COCs) were aspirated from visible small (≤3 mm), medium (3-6 mm) and large (>6 mm) follicles of normal ovaries. Ovaries were classified according to bearing CL into with and without CL. Oocytes quality were classified into good, fair, poor and denuded. Only good and fair quality oocytes were used for in vitro maturion in TCM-199 medium supplemented with 10% FCS, 10 µg/ml ovine FSH, 10 IU/ml hCG, 1 µg/ml Estradiol and 1% antibiotic antimycotic mix. Results revealed that a significant difference between the four seasons with significant increase of oocyte yield, quality and maturation for winter and spring than autumn and summer seasons. Oocytes aspirated from medium sized follicles (3-6 mm) were of higher in quality and maturation rate than large (>0.6) and small size follicles (≤ 3 mm). Recovery rate, quality and maturation rate of oocytes were higher for ovaries without CL than ovaries with CL. In conclusion, the winter season, medium sized follicles and ovaries without CL showed positive effects on recovery rate, quality and in vitro maturation of buffalo oocytes.

Brain-derived neurotrophic factor (BDNF) is expressed in buffalo (Bubalus bubalis) ovarian follicles and promotes oocyte maturation and early embryonic development

Brain-derived neurotrophic factor (BDNF) has been discovered and characterized for several decades, yet its expression pattern in non-neuronal tissues like ovary and potential mechanism during oocyte maturation are still poorly understood. Thus the present study was devised to determine the expression pattern and mechanism of BDNF during buffalo oocyte maturation. The results revealed that BDNF was presented at different stages of buffalo ovarian follicles as well as during oocyte maturation and early embryo development. BDNF’s receptor p75 was detected in granulosa cells, cumulus cells, oocytes, and early embryos, while another receptor neurotrophic tyrosine kinase receptor, type2 (NTRK2) was only identified in granulosa cells and cumulus cells. To determine the effect of BDNF on oocyte maturation and early embryo development, different concentrations (0, 1, 10, 100 ng/mL) of BDNF were added into the in vitro maturation media, respectively. It was divulged that 10 ng/mL BDNF promoted the in vitro maturation rate of buffalo oocytes and the blastocysts rate of embryos cultured in vitro (P < 0.05). Then through using NTRK2 inhibitor K-252a, we found BDNF and its receptor NTRK2 in cumulus cells played an essential role during oocyte maturation. Moreover, to further investigate the underlying mechanism by which BDNF enhances oocyte maturation, RT-qPCR was performed. 10 ng/mL BDNF treatment could decrease the expression level of apoptosis-related genes CCASP9, FAS, up-regulate the expression level of receptor gene NTRK2, cell proliferation-related genes CCNB1, PCNA, gap junction-related genes GJA4, GJA1 as well as cumulus cells expansion-related genes HAS2, PTX3 and TNFAIP6 (P < 0.05). Altogether, our results showed for the first time that BDNF was expressed throughout buffalo ovarian follicle development, oocyte maturation and early embryogenesis. Furthermore, BDNF treatment could improve the efficiency of buffalo oocyte maturation through regulating genes expression in cumulus cells and then promote early embryo development.

117 Kit ligand enhances growth and nuclear maturation of buffalo oocytes in vitro

This study aimed to investigate the effect of Kit ligand (KL), a growth factor that regulates folliculogenesis in mammalian ovaries, on growth of buffalo oocytes in early antral follicles in vitro. Cumulus-oocyte complexes were dissected from early antral follicles (1mm) of slaughtered buffaloes and cultured in Dulbecco’s minimum essential medium supplemented with fetal bovine serum, sodium pyruvate, gentamycin, hypoxanthine, dexamethasone, cysteine, polyvinylpyrolidione, l-ascorbic acid, oestradiol-17β, and androstenedione in a 96-well culture plate at 38.5°C under an atmosphere of 5% CO2 in air for 6 days. The culture medium was supplemented with 0, 50, and 100 ng/mL KL (recombinant human SCF, Cat. No. H8416, R&amp;amp;D Systems, Minneapolis, MN, USA). Sixty oocytes were cultured in each group with 6 replications. In vitro-grown oocytes were cultured for maturation in tissue culture medium-199 supplemented with 5% fetal bovine serum, sodium pyruvate, gentamycin, and 100 ng/mL FSH at 38.5°C for 24h under an atmosphere of 5% CO2 in air. The oocytes were then stained with aceto-orcein and examined under a differential interference contrast microscope. Data were analysed using SAS/STAT version 9.1.3 for Windows (SAS Institute Inc., Cary, NC, USA) by one-way ANOVA and means compared with Tukey’s HSD test. The mean diameter of oocytes measured at the time of seeding on the culture substrate was 100.6±0.4μm (n=180). After 6 days of culture, the diameters of oocytes increased to 110.8±0.5, 114.0±0.5, and 115.0±0.6µm in 0, 50, and 100 ng/mL KL-treated groups, respectively. The survival rates were 60.0±6, 81.2±1.2, and 92.0±4.9% in 0, 50, and 100 ng/mL KL-supplemented oocytes at Day 6. Moreover, KL pretreatment enhanced maturation of buffalo oocytes dose dependently. A small proportion of oocytes (8.4%) treated with 50 ng/mL KL reached the MII stage. This number increased to 25% when oocytes were treated with 100 ng/mL KL. These results show that KL enhances growth, viability, and meiotic progression of buffalo oocytes in vitro.

Maturation of buffalo oocytes in vitro with acetyl-L-carnitine improves cryotolerance due to changes in mitochondrial function and the membrane lipid profile.

The effects of acetyl-l-carnitine (ALC) supplementation during IVM on subsequently vitrified buffalo oocytes were evaluated, followed by determination of the mitochondrial DNA copy number, measurement of mitochondrial membrane potential (MMP) and identification of the lipid profile of oocyte membranes as markers of oocyte quality after vitrification. Supplementation with ALC during IVM significantly improved the rates of oocyte cleavage and morula and blastocyst formation, and increased MMP after vitrification compared with unsupplemented vitrified oocytes (P<0.05). Using a bidirectional orthogonal projection to latent structures discriminant analysis based on positive ion matrix-assisted laser desorption ionisation time-of-flight mass spectrometry data, five phospholipid ions (m/z 728.7 (phosphatidylcholine (PC) 32:3), 746.9 (PC 32:5), 760.6 (PC 34:1), 768.8 (PC P-36:3) and 782.6 (PC 36:4); P<0.05) were identified as significantly more abundant in fresh oocytes than in unsupplemented vitrified oocytes. Meanwhile, three phospholipid ions (m/z 734.6 (PC 32:0), 760.6 (PC 34:1), and 782.6 (PC 36:4); P<0.05) were more abundant in ALC-supplemented vitrified oocytes than in unsupplemented vitrified oocytes. Therefore, supplementation with ALC during IVM may improve buffalo oocyte quality after vitrification by enhancing mitochondrial function and altering the phospholipid composition of vitrified oocyte membranes.

Treatment with acetyl-l-carnitine during in vitro maturation of buffalo oocytes improves oocyte quality and subsequent embryonic development

Oocyte quality is one of the important factors in female fertility, in vitro maturation (IVM), and subsequent embryonic development. In the present study, we assessed whether acetyl-l-carnitine (ALC) supplementation during in vitro maturation of buffalo oocytes could improve oocyte quality and subsequent embryonic development. To determine the optimal level of ALC supplementation, we matured cumulus-oocyte complexes in maturation medium supplemented with 0, 2.5, and 5 mM ALC. The oocytes with a polar body were selected for parthenogenetic activation (PA) and in vitro fertilization (IVF). We found that oocytes matured in 2.5 mM ALC had significantly higher PA blastocyst rate (P < 0.05) and blastocyst cell number than those of unsupplemented oocytes (P < 0.05) and a significantly higher IVF blastocyst rate than that of oocytes matured in 5 mM ALC (P < 0.05). In all further experiments, we supplemented the maturation medium with 2.5 mM ALC. We then tested whether ALC supplementation could improve various markers of oocytes and cumulus cells. We compared cell proliferation; concentrations of reactive oxygen species (ROS), intracellular ATP, estradiol, and progesterone; mitochondrial distribution; mitochondrial DNA copy number (mtDNA); and expression levels of four genes encoding oocyte-derived factors (GDF9, BMP15) and steroid hormones (StAR, P450scc) between the supplemented and unsupplemented oocytes and cumulus cells. Cumulus cells matured with ALC supplementation were more prolific than those matured without ALC supplementation (P < 0.05). Oocytes treated with ALC had lower concentrations of intracellular ROS (P < 0.05) and a higher rate of diffuse mitochondrial distributions (P < 0.05) than those of untreated oocytes. Additionally, the mtDNA was higher in the ALC-treated oocytes (P < 0.05) and cumulus cells (P < 0.05) than that in the untreated cells. The ALC-treated maturation medium had a higher postmaturation concentration of estradiol than that of the untreated medium (P < 0.05). Finally, the gene expression levels of P450scc and GDF9 were greater in ALC-treated oocytes and cumulus cells than those in untreated cells (P < 0.05). Therefore, in buffalo, our results suggest that ALC affects mitochondrial function, regulates oocyte-derived paracrine factors, and increases the production of steroid hormones, leading to increased quality of matured oocytes and improved embryonic development in vitro.