Naresh L. Selokar

Hope for restoration of dead valuable bulls through cloning using donor somatic cells isolated from cryopreserved semen.

Somatic cells were isolated from cryopreserved semen of 4 buffalo bulls, 3 of which had died over 10 years earlier, and were established in culture. The cells expressed cytokeratin-18, keratin and vimentin indicating that they were of epithelial origin. The cells were used as nuclear donors for hand-made cloning for producing buffalo embryos. The blastocyst rate and quality, as indicated by apoptotic index, were comparable among embryos produced using cells obtained from fresh or frozen-thawed semen or those obtained from conventional cell sources such as skin. Examination of the epigenetic status revealed that the global level of H3K27me3 but not that of H3K9/14ac and H4K5ac differed significantly (P<0.05) among cloned embryos from different bulls. The relative mRNA abundance of HDAC1, DNMT1, P53 and CASPASE 3 but not that of DNMT3a differed in cells and in cloned embryos. Following transfer of 24 cloned embryos produced from fresh semen-derived cells to 12 recipients, one calf weighing 55 kg, which is now 6 months of age and is normal, was born through normal parturition. Following transfer of 20 embryos produced from frozen-thawed semen-derived cells to 10 recipients, 2 became pregnant, one of which aborted in the first trimester; the calf born was severely underweight (17 kg), and died 12 h after birth. The ability of cells derived from fresh and frozen-thawed semen to produce live offspring confirms the ability of these cells to be reprogrammed. Our findings pave the way for restoration of highly precious progeny-tested bulls, which has immense economic importance, and can also be used for restoration of endangered species.

Effect of post-fusion holding time, orientation and position of somatic cell-cytoplasts during electrofusion on the development of handmade cloned embryos in buffalo (Bubalus bubalis).

The present study was conducted primarily to optimize electrofusion conditions for efficient production of zona-free nuclear transfer embryos in buffalos (Bubalus bubalis). We found that 4V AC current for proper triplet alignment and single step fusion method, using a single DC pulse of 3.36 kV/cm for 4-μs duration, produced the most convincing results for efficient reconstitution of zona-free cloned embryos. Lysis rate was very high (84.28 ± 2.59%) when triplets were in physical contact with negative electrode after applying DC current, however, cleavage rate and blastocyst rate were found to be similar when the triplets were not in physical contact with either positive or negative electrodes or when they were in physical contact with the positive electrode. Significant improvement in blastocyst production was observed when the somatic cell faced the positive electrode than when it faced the negative electrode (39.17 ± 2.74% vs. 25.91 ± 2.00%, respectively) during electrofusion. Similarly, the blastocyst rate (52.0 ± 3.4%) was found to be significantly higher when reconstructed embryos were activated 6 h post electrofusion as compared to 0, 2, 4 and 8 h (16.04 ± 6.3%; 18.36 ± 1.4%; 22.44 ± 3.7% and 30.02 ± 4.6%, respectively). This study establishes the application of zona-free nuclear transfer procedures for the production of handmade cloned buffalo embryos through optimization of electrofusion parameters and post fusion holding time for enhancing their preimplantation development.

Roscovitine Treatment Improves Synchronization of Donor Cell Cycle in G0/G1 Stage and In Vitro Development of Handmade Cloned Buffalo (Bubalus bubalis) Embryos

This study investigated the effects of serum-starvation, total confluence, and roscovitine treatment on cell-cycle synchronization of buffalo ear skin fibroblasts to the G0/G1 stage and on the developmental competence of cloned embryos. Serum starvation of total confluence cultures for 24 h had a higher (p<0.05) proportion of cells at G0/G1 stage (94.4%) compared with serum starved cyclic and nonstarved confluent cultures (76.8 and 86.0%, respectively), whereas differences between cyclic cells with or without serum starvation were not significant. The proportion of cells at G0/G1 was higher (p<0.05) with 20 and 30 μM roscovitine treatment than that with 10 μM (94.4, 96.4, and 86.6%, respectively), which was similar to that for total confluence (86.0%). MTT assay showed that cell viability decreased as dose of roscovitine increased. The blastocyst rate was significantly higher (p<0.05) when nuclear transfer embryos were reconstructed using donors cells from total confluence, confluence serum starved, and roscovitine-treated (20 and 30 μM) groups (48.8, 48.9, 57.9, and 62.9%, respectively) compared to nontreated cyclic cells (20.2%). However, the cleavage rate and total cell number of cloned embryos were similar for all the groups. The number of ICM cells was improved by 30 μM roscovitine treatment (45.25 ± 2.34). The cryosurvival rate of blastocysts derived from cells synchronized with 20 or 30 μM roscovitine was higher compared to that for total confluence group (33.6, 37.8 vs. 23.8%). In conclusion, treatment with 30 μM roscovitine is optimal for harvesting G0/G1 stage cells for producing high quality cloned buffalo embryos, and that it is better than serum-starvation or total confluence for cell synchronization.

Effect of histone deacetylase inhibitor valproic acid treatment on donor cell growth characteristics, cell cycle arrest, apoptosis, and handmade cloned bovine embryo production efficiency.

In this study, we tested the effects of valproic acid (VPA), a known histone deacetylase inhibitor (HDACi), on the growth characteristics, apoptosis, and cell cycle stages distribution of donor cells, as well as cloning efficiency, embryo development, and histone methylation. Our results showed that treatment of donor cells with VPA (2.5 mM, 5.0 mM, 7.5 mM, or 10 mM) for 24 h resulted in altered cell proliferation, extent of apoptosis and necrosis, and cell cycle stage distribution, whereas no changes in cell viability and chromosomal complements were observed. Measurement of relative gene expression using real-time PCR of a few developmentally important genes in treated donor cells showed decreased expression of HDAC1 and increased expression of BAX (p<0.05). No change in relative expression of HDAC2 and Bcl2 was noticed. Treatment of donor cells with VPA for 24 h before electrofusion significantly (p<0.05) increased the blastocyst formation rate of somatic cell nuclear transfer (SCNT) embryos compared to the control embryos. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive nuclei in SCNT blastocysts derived from VPA-treated donor cells were significantly decreased compared to the control blastocysts (p<0.05). Immunolocalization studies revealed that the levels of histone H3 at lysine 9 (H3K9me3) were lower in VPA-treated donor cells derived cloned blastocysts than nontreated cloned embryos, and was at the level of in vitro fertilization (IVF) counterparts, although no effects of treatments were found in donor cells. Our study demonstrates that the use of VPA in SCNT has been beneficial for efficient reprogramming of donor cells. Its effect on histone methylation in cloned embryos correlates with their developmental potential and may be a useful epigenetic marker to predict the efficiency of SCNT.

Effect of donor cell type on developmental competence, quality, gene expression, and epigenetic status of interspecies cloned embryos produced using cells from wild buffalo and oocytes from domestic buffalo

This study compared the cloning efficiency of donor cells of fibroblast and epithelial origin isolated from ear skin of a wild buffalo (Bubalus arnee) and used with cytoplasts from domestic buffalo (Bubalus bubalis) in interspecies SCNT by hand-made cloning. The cleavage (93.0 ± 2.8% vs. 85.6 ± 2.4%) and blastocyst rates (50.6 ± 4.0% vs. 20.5 ± 2.6%) were higher (P < 0.05) for fibroblasts than those for epithelial cells, whereas the total cell number (490 ± 42 and 492 ± 95, respectively) and apoptotic index (2.3 ± 0.3 and 2.5 ± 0.6, respectively) of blastocysts were similar. The global level of H3K18ac and H3K27me3 was lower (P < 0.05) in fibroblasts than that in epithelial cells. The global level of H3K18ac was higher (P < 0.05) in fibroblast than that in epithelial cell-derived blastocysts, whereas that of H3K27me3 was similar between the two groups. The expression level of HDAC1, DNMT1, DNMT3a, and P53 was higher (P < 0.05) in fibroblasts than that in epithelial cells; that of CASPASE3 showed an opposite pattern (P < 0.001), whereas CASPASE7 expression level was similar in the two groups. In the embryos, the expression level of HDAC1, DNMT3a, and CDX2 was lower (P < 0.05) in fibroblast than that in epithelial cell-derived blastocysts; that of NANOG showed an opposite pattern (P < 0.05), whereas that of OCT4 was similar between the two groups. In conclusion, donor cells of fibroblast origin are easier to reprogram than those of epithelial origin in interspecies SCNT, and cloning efficiency, epigenetic status, and gene expression pattern vary among cells having different origin although they may be from the same tissue.

EQUIVALENCY OF BUFFALO (BUBALUS BUBALIS) EMBRYONIC STEM CELLS DERIVED FROM FERTILIZED, PARTHENOGENETIC AND HAND-MADE CLONED EMBRYOS

This study was aimed at establishing buffalo embryonic stem cells (ESCs) from in vitro fertilized (IVF), parthenogenetic, and hand-made cloned (HMC) embryos and to check their equivalency in terms of stem cell marker expression, longevity, proliferation, and differentiation pattern. ESCs derived from all three sources were found by immunofluorescence to express the pluripotency markers SSEA-4, TRA-1-60, TRA-1-81, OCT4, and SOX2 and were able to form embryoid bodies containing cells expressing genes specific to endoderm (AFP, HNF4, and GATA4), mesoderm (MSX1, BMP4, and ASA), and ectoderm (cytokeratin 8 and NF68). Reverse transcriptase PCR (RT-PCR) showed cells from all sources to be positive for pluripotency markers OCT4, SOX2, NANOG, STAT3, REX1, FOXD3, NUCLEOSTEMIN, and TELOMERASE. Pluripotency markers OCT4, SOX2, NANOG, and c-MYC were also analyzed by real-time PCR. No significant differences were observed among ESCs from all three sources for all these genes except NANOG, whose expression was higher (p<0.05) in HMC-derived ESCs (6.897±2.3) compared to that in parthenogenesis- and IVF-derived cells (1.603±0.315 and 1±0, respectively). Pluripotent, stable buffalo ESC lines derived from IVF, parthenogenesis, and HMC embryos may be genetically manipulated to provide a powerful tool for studies involving embryonic development, genomic imprinting, gene targeting, cloning, chimera formation, and transgenic animal production.

Production of interspecies handmade cloned embryos by nuclear transfer of cattle, goat and rat fibroblasts to buffalo (Bubalus bubalis) oocytes.

The possibility of producing interspecies handmade cloned (iHMC) embryos by nuclear transfer from donor cells of cattle, goat and rat using buffalo oocytes as recipient cytoplasts was explored. Zona-free buffalo oocytes were enucleated by protrusion cone-guided bisection with a microblade. After electrofusion with somatic cells, reconstructed oocytes were activated by calcimycin A23187, treated with 6-dimethylaminopurine and were cultured in K-RVCL-50® medium for 8 days. Although the cleavage rate was not significantly different when buffalo, cattle, goat or rat cells were used as donor nuclei (74.6 ± 3.8, 82.8 ± 5.3, 86.0 ± 4.9 and 82.3 ± 3.6%, respectively), the blastocyst rate was significantly higher (P<0.01) for buffalo (51.4 ± 2.6) than for cattle (3.5 ± 1.0) or the goat (2.2 ± 0.9), whereas none of the embryos crossed the 32-cell stage when rat cells were used. However, the total cell number was similar for buffalo-buffalo (175.0 ± 5.07) and cattle-buffalo embryos (178.0 ± 11.84). Following transfer of 3 buffalo-buffalo embryos each to 6 recipients, 3 were found to be pregnant, though the pregnancies were not carried to full term. These results suggest that interspecies blastocyst stage embryos can be produced by iHMC using buffalo cytoplasts and differentiated somatic cells from cattle and goat and that the source of donor nucleus affects the developmental competence of interspecies embryos.

Production of wild buffalo (Bubalus arnee) embryos by interspecies somatic cell nuclear transfer using domestic buffalo (Bubalus bubalis) oocytes.

The objective of this study was to explore the possibility of producing wild buffalo embryos by interspecies somatic cell nuclear transfer (iSCNT) through handmade cloning using wild buffalo somatic cells and domestic buffalo (Bubalus bubalis) oocytes. Somatic cells derived from the ear skin of wild buffalo were found to express vimentin but not keratin and cytokeratin-18, indicating that they were of fibroblast origin. The population doubling time of skin fibroblasts from wild buffalo was significantly (p < 0.05) higher, and the cell proliferation rate was significantly (p < 0.05) lower compared with that of skin fibroblasts from domestic buffalo. Neither the cleavage (92.6 ± 2.0% vs 92.8 ± 2.0%) nor the blastocyst rate (42.4 ± 2.4% vs 38.7 ± 2.8%) was significantly different between the intraspecies cloned embryos produced using skin fibroblasts from domestic buffalo and interspecies cloned embryos produced using skin fibroblasts from wild buffalo. However, the total cell number (TCN) was significantly (p < 0.05) lower (192.0 ± 25.6 vs 345.7 ± 42.2), and the apoptotic index was significantly (p < 0.05) higher (15.1 ± 3.1 vs 8.0 ± 1.4) for interspecies than that for intraspecies cloned embryos. Following vitrification in open-pulled straws (OPS) and warming, although the cryosurvival rate of both types of cloned embryos, as indicated by their re-expansion rate, was not significantly different (34.8 ± 1.5% vs 47.8 ± 7.8), the apoptotic index was significantly (p < 0.05) higher for vitrified-warmed interspecies than that for corresponding intraspecies cloned embryos (48.9 ± 7.2 vs 23.9 ± 2.8). The global level of H3K18ac was significantly (p < 0.05) lower in interspecies cloned embryos than that in intraspecies cloned embryos. The expression level of HDAC1, DNMT3a and CASPASE3 was significantly (p < 0.05) higher, that of P53 was significantly (p < 0.05) lower in interspecies than in intraspecies embryos, whereas that of DNMT1 was similar between the two types of embryos. In conclusion, these results demonstrate that wild buffalo embryos can be produced by iSCNT.

Production of Nuclear Transfer Embryos by Using Somatic Cells Isolated From Milk in Buffalo (Bubalus bubalis)

Somatic cells in milk are a potential source of nuclei for nuclear transfer to produce genetically identical animals; this is especially important in animals that are susceptible to risks of bacterial infection on biopsy collection. In this study, a minimum of 10 milk samples were collected from each of the three buffaloes representing Murrah breed. All the samples were processed immediately and cell colonies were obtained. Cell colonies from one buffalo (MU-442) survived beyond 10 passages and were evaluated by fluorescence microscopy and used in nuclear transfer experiments. In culture, these cells expressed vimentin, indicating they were of fibroblast origin similar to ear cells. We compared the effectiveness of cloning using those milk-derived fibroblast (MDF) cells and fibroblast cells derived from the ear derived fibroblast (EDF). Fusion and cleavage rates of MDF-NT and EDF-NT embryos were found to be similar (92.43 ± 1.28% vs 94.98 ± 1.24%, and 80.27 ± 1.75% vs 84.56 ± 3.73%, respectively; p > 0.01); however, development to blastocyst stage and total cell number was higher for EDF-NT embryos (50.24 ± 2.54%, 227.14 ± 13.04, respectively, p < 0.01), than for MDF-NT embryos (16.44 ± 0.75%, 170.57 ± 4.50 respectively). We conclude that somatic cells from milk can be cultured effectively and used as nucleus donor to produce cloned blastocyst-stage embryos.

Buffalo (Bubalus bubalis) SCNT embryos produced from somatic cells isolated from frozen-thawed semen: effect of trichostatin A on the in vitro and in vivo developmental potential, quality and epigenetic status.

This study examined the effects of trichostatin A (TSA) treatment of reconstructed buffalo embryos, produced by hand-made cloning using somatic cells isolated from over a decade old frozen-thawed semen, on their in vitro and in vivo developmental competence, quality and epigenetic status. Following treatment of reconstructed embryos with TSA (0, 50 or 75 nM) for 10 h prior to culture, the cleavage (100.0 ± 0, 94.5 ± 2.3 and 96.1 ± 1.2%, respectively) and blastocyst rate (50.6 ± 2.3, 48.4 ± 2.7 and 48.1 ± 2.6%, respectively), total cell number (275 ± 17.4, 289 ± 30.1 and 317 ± 24.2, respectively) and apoptotic index (5.6 ± 0.7, 3.4 ± 0.9 and 4.5 ± 1.4, respectively) were not significantly different among the three groups. However, TSA treatment increased (P < 0.05) the global level of H4K5ac and decreased (P < 0.05) that of H3K27me3 in blastocysts whereas the global level of H3K18ac was not affected significantly. Transfer of embryos treated with 75 nM TSA (n = 10) to recipients resulted in two pregnancies (20%), one out of which was aborted in the second and the other in the third trimester whereas transfer of control embryos (n = 20) or those treated with 50 nM TSA (n = 12) did not result in any pregnancy. In conclusion, these results suggest that TSA treatment of cloned buffalo embryos produced using somatic cells isolated from frozen-thawed semen improved their epigenetic status but not the in vitro developmental potential and offspring rate.