Development of in vitro produced buffalo (Bubalus bubalis) embryos in relation to time

Global DNA methylation profiles of buffalo (Bubalus bubalis) preimplantation embryos produced by handmade cloning and in vitro fertilization

Somatic cell nuclear transfer technique (SCNT) has proved to be an outstanding method of multiplication of elite animals but accompanied with low efficiency and live birth rate of cloned animals. Epigenetic alterations of DNA has been one of the culprits behind this issue. Cloned embryos are found to deviate slightly from regular pattern of demethylation and re-methylation at the time of nuclear reprogramming and embryonic development when compared with embryos produced by in vitro fertilization (IVF). Thus, the present study was aimed at evaluating global DNA methylation profiles of cloned embryos at 2-cell, 8-cell and blastocyst stages and compare it with corresponding stages of embryos produced by IVF by using MeDIP-Sequencing on Illumina-based platform. We found out that cloned embryos exhibited significantly different DNA methylation pattern as compared to IVF embryos with respect to distribution of differentially methylated regions in different components of genome, CpG islands distribution and methylation status, gene ontological profiles and pathways affected throughout the developmental stages. The data generated from MeDIP-Seq was validated at blastocyst stage cloned and IVF embryos by bisulfite-sequencing PCR on five randomly selected gene regions.

A comparative study on efficiency of adult fibroblasts and amniotic fluid-derived stem cells as donor cells for production of hand-made cloned buffalo (Bubalus bubalis) embryos

The efficiency of two cell types, namely adult fibroblasts, and amniotic fluid stem (AFS) cells as nuclear donor cells for somatic cell nuclear transfer by hand-made cloning in buffalo (Bubalus bubalis) was compared. The in vitro expanded buffalo adult fibroblast cells showed a typical "S" shape growth curve with a doubling time of 40.8 h and stained positive for vimentin. The in vitro cultured undifferentiated AFS cells showed a doubling time of 33.2 h and stained positive for alkaline phosphatase, these cells were also found positive for undifferentiated embryonic stem cell markers like OCT-4, NANOG and SOX-2, which accentuate their pluripotent property. Further, when AFS cells were exposed to corresponding induction conditions, these cells differentiated into osteogenic, adipogenic and chondrogenic lineages which was confirmed through alizaran, oil red O and alcian blue staining, respectively. Cultured adult fibroblasts and AFS cells of passages 10-15 and 8-12, respectively, were used as nuclear donors. A total of 94 embryos were reconstructed using adult fibroblast as donor cells with cleavage and blastocyst production rate of 62.8 ± 1.8 and 19.1 ± 1.5, respectively. An overall cleavage and blastocyst formation rate of 71.1 ± 1.2 and 29.9 ± 2.2 was obtained when 97 embryos were reconstructed using AFS cells as donor cells. There were no significant differences (P > 0.05) in reconstructed efficiency between the cloned embryos derived from two donor cells, whereas the results showed that there were significant differences (P < 0.05) in cleavage and blastocyst rates between the cloned embryos derived from two donor cell groups. Average total cell numbers for blastocyst generated using AFS cells (172.4 ± 5.8) was significantly (P < 0.05) higher than from adult fibroblasts (148.2 ± 6.1). This study suggests that the in vitro developmental potential of the cloned embryos derived from AFS cells were higher than that of the cloned embryos derived from adult fibroblasts in buffalo hand-made cloning.

Expression profile of developmentally important genes between hand-made cloned buffalo embryos produced from reprogramming of donor cell with oocytes extract and selection of recipient cytoplast through brilliant cresyl blue staining and in vitro fertilized embryos

PURPOSE

To compare the expression profile of developmentally important genes between hand-made cloned buffalo embryos produced from reprogramming of donor cell with oocyte extracts and selection of recipient cytoplast through brilliant cresyl blue staining and in vitro fertilized (IVF) embryos.

METHODS

Hand-made cloned embryos were produced using oocyte extracts treated donor cells and brilliant cresyl blue (BCB) stained recipient cytoplasts. IVF embryos were produced by culturing 15-20 COCs in BO capacitated sperms from frozen thawed buffalo semen and the mRNA expression patterns of genes implicated in metabolism (GLUT1), pluripotency (OCT4), DNA methylation (DNMT1), pro- apoptosis (BAX) and anti-apoptosis (BCL2) were evaluated at 8- to16- cell stage embryos.

RESULTS

A significantly (P < 0.05) higher number of 8- to16- cell and blastocyst stages (73.9 %, 32.8 %, respectively) were reported in hand-made cloning (HMC) as compared to in vitro fertilization (49.2 %, 24.2 %, respectively). The amount of RNA recovered from 8- to 16- cell embryos of HMC and in vitro fertilization did not appear to be influenced by the method of embryo generation (3.76 ± 0.61 and 3.82 ± 0.62 ng/μl for HMC and in vitro fertilization embryos, respectively). There were no differences in the expression of the mRNA transcripts of genes (GLUT1, OCT4, DNMT1, BAX and BCL2) were analysed by real-time PCR between hand-made cloned and IVF embryos.

CONCLUSIONS

Pre-treatment of donor cells with oocyte extracts and selection of developmentally competent oocytes through BCB staining for recipient cytoplast preparations may enhance expression of developmentally important genes GLUT1, OCT4, DNMT1, BAX, and BCL2 in hand-made cloned embryos at levels similar to IVF counterparts. These results also support the notion that if developmental differences observed in HMC and in vitro fertilization produced foetuses and neonates are the results of aberrant gene expression during the pre-implantation stage, those differences in expression are subtle or appear after the maternal to zygotic transition stage of development.

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.

Selection of developmentally competent buffalo oocytes by brilliant cresyl blue staining before IVM

The brilliant cresyl blue (BCB) test determines the activity of glucose-6-phosphate dehydrogenase (G6PDH); the activity of this enzyme is greatest in growing oocytes, but it declines as oocytes mature. The objective was to develop and evaluate this test for assessing development of buffalo oocytes (to select developmentally competent oocytes for increased in vitro embryo production). Oocytes were exposed to BCB stain diluted in mDPBS (DPBS with 0.4% BSA) for 90 min at 38.5 degrees C in a humidified air atmosphere; those with or without blue coloration of the cytoplasm were designated as BCB+ and BCB-, respectively. In Experiment 1, oocytes were exposed to 13, 26, or 39 microM BCB. There were fewer BCB+ oocytes after exposure to 13 microM BCB (10%) than after exposure to 26 or 39 microM BCB (57.2 and 61.8%; P<0.05), but there was no significant difference among treatments for blastocyst production rate. In Experiment 2, the diameter of BCB+ oocytes (144.4+/-4.2 microm; mean+/-S.E.M.) was higher (P<0.05) than that of BCB- oocytes (136.8+/-4.6 microm). In Experiment 3, oocytes were allocated into three groups: control (immediately cultured); holding-control (kept in mDPBS for 90 min before cultured); and treatment-incubation (incubated with 26 microM BCB). After IVM, oocytes were fertilized in vitro and cultured on an oviductal monolayer. The nuclear maturation rate was higher (P<0.05) in BCB+ (86.2%), control (83.4%) and holding-control (82.6%) oocytes than BCB- (59.2%) oocytes. The BCB+ oocytes yielded more blastocysts than control or holding-control oocytes (33.4, 20.2, and 21.0%, P<0.05); blastocyst development was lowest in BCB- oocytes (5.2%). In conclusion, staining of buffalo oocytes with BCB before IVM may be used to select developmentally competent oocytes for increased in vitro embryo production.

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.

In vitro developmental competence of buffalo oocytes collected at various stages of the estrous cycle

The objective was to determine the in vitro developmental competence of buffalo oocytes collected from abattoir-derived ovaries at various stages of the estrous cycle and follicular status. In Experiment 1, ovaries (n=476 pairs) were collected and divided into the following five groups: (a) ovaries with a corpus hemorragicum and no dominant follicle (CH-NO-DF); (b) ovaries with a mature functional corpus luteum (CL) and a dominant follicle (CL-DF); (c) ovaries with a mature functional CL and no dominant follicle (CL-NO-DF); (d) ovaries with a regressing CL and a dominant follicle (RCL-DF); and (e) ovaries without any luteal structures and only small follicles (ANEST). In Experiment 2, 144 pairs of ovaries with a CL (or regressing CL) and a dominant follicle were collected and follicles were classified as dominant, largest subordinate, and subordinate. In both experiments, the dominant follicle was defined as any follicle >10mm in diameter that exceeded the diameter of all other (subordinate) follicles. Although oocytes were collected from each group of ovaries, only Grades A or B oocytes were used for in vitro embryo production. Cleavage rates were higher (P<0.05) from oocytes collected from ovaries in the CH-NO-DF (59.6%) and CL-NO-DF (59.2%) groups than those collected from CL-DF (52.2%) and ANEST (43.6%) groups. The yield of transferable embryos was higher (P<0.05) from oocytes collected from CH-NO-DF (27.4%) and CL-NO-DF (24.0%) ovaries than from CL-DF (16.2%), RCL-DF (15.4%), and lowest (P<0.05) from ANEST (8.8%). In Experiment 2, oocytes from the dominant follicle had a higher (P<0.05) cleavage rate (65.2 %) and transferable embryo yield (30.2%) than those collected from the largest subordinate and subordinate follicles. In conclusion, oocyte competence depended on the morphofunctional state of ovaries. Oocyte development was maximal in pairs of ovaries with a corpus hemorragicum or CL and no dominant follicle; in paired ovaries with a CL and a dominant follicle, development was maximal in oocytes derived from the dominant follicle.

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.

Effects of beta-mercaptoethanol on formation of pronuclei and developmental competence of swamp buffalo oocytes

This study was conducted to determine the effect of supplementing maturation medium with beta-mercaptoethanol (betaME) on pronuclei formation and developmental competence of swamp buffalo oocytes. Buffalo oocytes were matured in TCM199 medium either with 10mM betaME or without betaME supplementation for 24h. In Experiment 1, oocytes were fixed and stained for cytological evaluation after in vitro fertilization (IVF). In Experiment 2, presumptive zygotes were cultured and their developmental competency was assessed. It was found that betaME significantly improved the proportion of oocytes that exhibited synchronous pronuclei formation (31.8+/-5.1% versus 17.9+/-3.3%, P<0.05). There were no significant differences between oocytes matured with or without betaME in their capability of developing into blastocyst-stage embryos (3.0+/-1.3% versus 1.8+/-0.9%). However, blastocysts produced from oocytes matured in the presence of betaME appeared to develop faster than those from oocytes matured in the absence of betaME (P<0.05). Cavitation of embryos from oocytes matured in the presence of betaME occurred at 156 hpi, whereas those matured in the absence of betaME occurred at 180 hpi. Although in vitro production of blastocysts did not increase by addition of betaME to maturation medium, quality of blastocysts produced from oocytes matured in the presence of betaME was improved. This study provides information for further investigations on optimizing a system for in vitro production of swamp buffalo embryos.

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.