Production of cloned and transgenic embryos using buffalo (Bubalus bubalis) embryonic stem cell-like cells isolated from in vitro fertilized and cloned blastocysts

Production of MSTN Gene-Edited Embryos of Buffalo Using the CRISPR/Cas9 System and SCNT

The clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system and somatic cell nuclear transfer (SCNT) have been used to produce genome-edited farm animal species for improved production and health traits; however, these tools are rarely used in the buffalo and can play a pivotal role in milk and meat production in tropical and subtropical countries. In this study, we aimed to produce myostatin (MSTN) gene-edited embryos of the Murrah buffalo using the CRISPR/Cas9 system and SCNT. For this, fibroblast cells were electroporated with sgRNAs carrying all-in-one CRISPR/Cas9 plasmids targeting the first exon of the MSTN gene. Following puromycin selection, single-cell clonal populations were established and screened using the TA cloning and Sanger sequencing methods. Of eight single-cell clonal populations, one with a monoallelic and another with a biallelic heterozygous gene editing event were identified. These two gene-edited clonal cell populations were successfully used to produce blastocyst-stage embryos using the handmade cloning method. This work establishes the technical foundation for generation of genome-edited cloned embryos in the buffalo.

Production of Water Buffalo SCNT Embryos by Handmade Cloning

Cloning by somatic cell nuclear transfer (SCNT) involves the transfer of a somatic nucleus into an enucleated oocyte followed by chemical activation and embryo culture. Further, handmade cloning (HMC) is a simple and efficient SCNT method for large-scale embryo production. HMC does not require micromanipulators for oocyte enucleation and reconstruction since these steps are carried out using a sharp blade controlled by hand under a stereomicroscope. In this chapter, we review the status of HMC in the water buffalo (Bubalus bubalis) and further describe a protocol for the production of buffalo-cloned embryos by HMC and assays to estimate their quality.

Stem Cells as Nuclear Donors for Mammalian Cloning

Mammals are routinely cloned by introducing somatic nuclei into enucleated oocytes. Cloning contributes to propagating desired animals, to germplasm conservation efforts, among other applications. A challenge to more broader use of this technology is the relatively low cloning efficiency, which inversely correlates with donor cell differentiation status. Emerging evidence suggests that adult multipotent stem cells improve cloning efficiency, while the greater potential of embryonic stem cells for cloning remains restricted to the mouse. The derivation of pluripotent or totipotent stem cells from livestock and wild species and their association with modulators of epigenetic marks in donor cells should increase cloning efficiency.

Strategies to Improve the Efficiency of Somatic Cell Nuclear Transfer

Mammalian oocytes can reprogram differentiated somatic cells into a totipotent state through somatic cell nuclear transfer (SCNT), which is known as cloning. Although many mammalian species have been successfully cloned, the majority of cloned embryos failed to develop to term, resulting in the overall cloning efficiency being still low. There are many factors contributing to the cloning success. Aberrant epigenetic reprogramming is a major cause for the developmental failure of cloned embryos and abnormalities in the cloned offspring. Numerous research groups attempted multiple strategies to technically improve each step of the SCNT procedure and rescue abnormal epigenetic reprogramming by modulating DNA methylation and histone modifications, overexpression or repression of embryonic-related genes, etc. Here, we review the recent approaches for technical SCNT improvement and ameliorating epigenetic modifications in donor cells, oocytes, and cloned embryos in order to enhance cloning efficiency.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

Production of Transgenic Handmade Cloned Goat (Capra hircus) Embryos by Targeted Integration into Rosa 26 Locus Using Transcription Activator-like Effector Nucleases

Transgenic goats are ideal bioreactors for the production of therapeutic proteins in their mammary glands. However, random integration of the transgene within-host genome often culminates in unstable expression and unpredictable phenotypes. Targeting desired genes to a safe locus in the goat genome using advanced targeted genome-editing tools, such as transcription activator-like effector nucleases (TALENs) might assist in overcoming these hurdles. We identified Rosa 26 locus, a safe harbor for transgene integration, on chromosome 22 in the goat genome for the first time. We further demonstrate that TALEN-mediated targeting of GFP gene cassette at Rosa 26 locus exhibited stable and ubiquitous expression of GFP gene in goat fetal fibroblasts (GFFs) and after that, transgenic cloned embryos generated by handmade cloning (HMC). The transfection of GFFs by the TALEN pair resulted in 13.30% indel frequency at the target site. Upon cotransfection with TALEN and donor vectors, four correctly targeted cell colonies were obtained and all of them showed monoallelic gene insertions. The blastocyst rate for transgenic cloned embryos (3.92% ± 1.12%) was significantly (p < 0.05) lower than cloned embryos (7.84% ± 0.68%) used as control. Concomitantly, 2 out of 15 embryos of morulae and blastocyst stage (13.30%) exhibited site-specific integration. In conclusion, the present study demonstrates TALEN-mediated transgene integration at Rosa 26 locus in caprine fetal fibroblasts and the generation of transgenic cloned embryos using HMC.

Perspectives of pluripotent stem cells in livestock

The recent progress in derivation of pluripotent stem cells (PSCs) from farm animals opens new approaches not only for reproduction, genetic engineering, treatment and conservation of these species, but also for screening novel drugs for their efficacy and toxicity, and modelling of human diseases. Initial attempts to derive PSCs from the inner cell mass of blastocyst stages in farm animals were largely unsuccessful as either the cells survived for only a few passages, or lost their cellular potency; indicating that the protocols which allowed the derivation of murine or human embryonic stem (ES) cells were not sufficient to support the maintenance of ES cells from farm animals. This scenario changed by the innovation of induced pluripotency and by the development of the 3 inhibitor culture conditions to support naïve pluripotency in ES cells from livestock species. However, the long-term culture of livestock PSCs while maintaining the full pluripotency is still challenging, and requires further refinements. Here, we review the current achievements in the derivation of PSCs from farm animals, and discuss the potential application areas.

Effects of ovary storage temperature and embryo vitrification on somatic cell nuclear transfer outcomes in goats

Improving the genetic potential of farm animals is one of the primary aims in the field of assisted reproduction. In this regard, somatic cell nuclear transfer (SCNT) can be used to produce a large number of embryos from genetically elite animals. The aims of the present study were to assess the effects of: (1) ovary storage conditions on preimplantation development of recovered oocytes and the freezability of the derived blastocysts; and (2) vitrification of goat SCNT-derived blastocysts on postimplantation development. Goat oocytes were recovered from ovaries and stored under warm (25°C-27°C) or cold (11°C-12°C) conditions before being used to produce SCNT embryos. There were no differences in oocytes recovered from ovaries kept under cold versus warm storage conditions in terms of cleavage (mean (±s.d.) 95.68±1.67% vs 95.91±2.93% respectively) and blastocyst formation (10.69±1.17% vs 10.94±0.9% respectively) rates. The re-expansion rate of vitrified blastocysts was significantly lower for cold- than warm-stored ovaries (66.3±8.7% vs 90±11% respectively). To assess the effects of vitrification on postimplantation development, blastocysts from cold-stored ovaries only were transferred from fresh and vitrified-warmed groups. The pregnancy rate was comparable between the fresh and vitrified-warmed groups (41.65% and 45.45% respectively). In addition, established pregnancy in Day 28-38 and full-term pregnancy rates were similar between the two groups. In conclusion, this study shows similar invitro preimplantation developmental potential of warm- and cold-stored ovaries. This study introduces the vitrification technique as an appropriate approach to preserve embryos produced by SCNT for transfer to recipient goats at a suitable time.

An update: Reproductive handmade cloning of water buffalo (Bubalus bubalis)

The first birth of a cloned animal produced through the Handmade cloning (HMC) technique was reported more than 15 years ago in cattle. This method of somatic cell nuclear transfer (SCNT) has subsequently been evolving as a much simpler alternative to the classical micromanipulator-based SCNT. Several farm animal species such as cattle, buffalo, pigs, sheep, and goats have been successfully cloned using HMC. In buffalo, HMC technique is now well established, and several births of cloned calves have been reported by us. Several factors such as source of somatic cells, quality of recipient oocytes, cell cycle stage prior to SCNT, electrofusion and culture conditions, and epigenetic status of somatic cells, have been optimized leading to the production of good quality cloned embryos. The preservation through cloning of proven breeding bulls that have died by producing live offspring using somatic cells isolated from frozen semen as donor cells and birth of a cloned calf from urine-derived cells are impressive examples of the success of HMC in buffalo. In conclusion, HMC is a valued reproductive technique in buffalo that offers the opportunity to make multiple copies of highly valuable animals, particularly proven breeding bulls. In this review, there is a discussion of the advancement of the HMC technique in buffalo and factors responsible for the efficient production of cloned embryos.

Cytoplasmic volume of recipient oocytes affects the nucleus reprogramming and the developmental competence of HMC buffalo (Bubalus bubalis) embryos

The present study was undertaken to examine the effects of cytoplasmic volume on nucleus reprogramming and developmental competence of buffalo handmade cloning (HMC) embryos. We found that both HMC embryos derived from ~150% cytoplasm or ~225% cytoplasm resulted in a higher blastocyst rate and total cell number of blastocyst in comparison with those from ~75% cytoplasm (25.4 ± 2.0, 27.9 ± 1.6% vs. 17.9 ± 3.1%; 150 ± 10, 169 ± 12 vs. 85 ± 6, P<0.05). Meanwhile, the proportions of nuclear envelope breakdown (NEBD) and premature chromosome condensation (PCC) were also increased in the embryos derived from ~150 or ~225% enucleated cytoplasm compared to those from ~75% cytoplasm. Moreover, HMC embryos derived from ~225% cytoplasm showed a decrease of global DNA methylation from the 2-cell to the 4-cell stage in comparison with those of ~75% cytoplasm (P<0.05). Furthermore, the expression of embryonic genome activation (EGA) relative genes (eIF1A and U2AF) in HMC embryos derived from ~225% cytoplasm at the 8-cell stages was also found to be enhanced compared with that of the ~75% cytoplasm. Two of seven recipients were confirmed to be pregnant following transfer of blastocysts derived from ~225% cytoplasm, and one healthy cloned calf was delivered at the end of the gestation period, whereas no recipients were pregnant after the transfer of blastocysts derived from ~75% cytoplasm. These results indicate that the cytoplasmic volume of recipient oocytes affects donor nucleus reprogramming, and then further accounted for the developmental ability of the reconstructed embryos.

Advances in reproductive biotechnologies

In recent times, reproductive biotechnologies have emerged and started to replace the conventional techniques. It is noteworthy that for sustained livestock productivity, it is imperative to start using these techniques for facing the increasing challenges for productivity, reproduction and health with impending environment conditions. These recent biotechniques, both in male and female, have revolutionized and opened avenues for studying and manipulating the reproductive process both in vitro and in vivo in various livestock species for improving tis efficiency. This review attempts to highlight pros and cons, on the recent developments in reproductive biotechnologies, both in male and female in livestock species.

Production of a Cloned Buffalo (Bubalus bubalis) Calf from Somatic Cells Isolated from Urine

This study was aimed at isolation of cells from urine and skin on the ventral part of the tails of healthy adult female buffaloes (Bubalus bubalis), an area rarely exposed to solar radiation, establishment of the cells in culture, and their use as donor cells for production of buffalo embryos by handmade cloning (HMC). The blastocyst rate and total cell number of urine- and tail skin-derived embryos were similar to those of control embryos derived from ear skin cells; however, their apoptotic index was lower (p<0.05) than that of control blastocysts. The global level of histone H3 acetylated at lysine 9 (H3K9ac) was similar in the three types of donor cells and in urine- and tail skin-derived HMC blastocysts and in vitro-fertilized (IVF) blastocysts (controls). The global level of histone H3 trimethylated at lysine 27 (H3K27me3) in the cells was in the order (p<0.05) urine≥tail skin>ear skin-derived cells, whereas in blastocysts, it was higher (p<0.05) in urine- and tail skin-derived HMC blastocysts than that in IVF blastocysts. The expression level of CASPASE3, CASPASE9, P53, DNMT1, DNMT3a, OCT4, and NANOG, which was similar in HMC blastocysts of three the groups, was lower (p<0.05) than that in IVF blastocysts, whereas that of HDAC1 was similar among the four groups. Following transfer of urine-derived embryos (n=10) to five recipients (two embryos/recipient), one of the recipients delivered a normal calf that is now 5 weeks old.

Treatment of buffalo (Bubalus bubalis) donor cells with trichostatin A and 5-aza-2’-deoxycytidine alters their growth characteristics, gene expression and epigenetic status and improves the in vitro developmental competence, quality and epigenetic status of cloned embryos

We examined the effects of treating buffalo skin fibroblast donor cells with trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, and 5-aza-2′-deoxycytidine (5azadC), a DNA methyltransferase (DNMT) inhibitor, on the cells and embryos produced by hand-made cloning. Treatment of donor cells with TSA or 5azadC resulted in altered expression levels of the HDAC1, DNMT1, DNMT3a, P53, CASPASE3 and CASPASE9 genes and global levels of acetylation of lysine at position 9 or 14 in histone 3 (H3K9/14ac), acetylation of lysine at position 5 in histone 4 (H4K5ac), acetylation of lysine at position 18 in histone 3 (H3K18ac) and tri-methylation of lysine at position 27 in histone 3 (H3K27me3). Moreover, global levels of DNA methylation and activity of DNMT1 and HDAC1 were decreased, while global acetylation of H3 and H3K9 was significantly increased in comparison to untreated cells. Simultaneous treatment of donor cells with TSA (50 nM) and 5azadC (7.5 nM) resulted in higher in vitro development to the blastocyst stage, reduction of the apoptotic index and the global level of H3K27 me3 and altered expression levels of HDAC1, P53, CASPASE3, CASPASE9 and DNMT3a in cloned blastocysts. Transfer of cloned embryos produced with donor cells treated with TSA led to the birth of a calf that survived for 21 days. These results show that treatment of buffalo donor cells with TSA and 5azadC improved developmental competence and quality of cloned embryos and altered their epigenetic status and gene expression, and that these beneficial effects were mediated by a reduction in DNA and histone methylation and an increase in histone acetylation in donor cells.

Differential developmental competence and gene expression patterns in buffalo (Bubalus bubalis) nuclear transfer embryos reconstructed with fetal fibroblasts and amnion mesenchymal stem cells

The developmental ability and gene expression pattern at 8- to 16-cell and blastocyst stages of buffalo (Bubalus bubalis) nuclear transfer (NT) embryos from fetal fibroblasts (FFs), amnion mesenchymal stem cells (AMSCs) and in vitro fertilized (IVF) embryos were compared in the present studies. The in vitro expanded buffalo FFs showed a typical "S" shape growth curve with a doubling time of 41.4 h and stained positive for vimentin. The in vitro cultured undifferentiated AMSCs showed a doubling time of 39.5 h and stained positive for alkaline phosphatase, and these cells also showed expression of pluripotency markers (OCT 4, SOX 2, NANOG), and mesenchymal stem cell markers (CD29, CD44) and were negative for haematopoietic marker (CD34) genes at different passages. Further, when AMSCs were exposed to corresponding induction conditions, these cells differentiated into adipogenic, chondrogenic and osteogenic lineages which were confirmed through oil red O, alcian blue and alizarin staining, respectively. Donor cells at 3-4 passage were employed for NT. The cleavage rate was significantly (P < 0.05) higher in IVF than in FF-NT and AMSC-NT embryos (82.6 ± 8.2 vs. 64.6 ± 1.3 and 72.3 ± 2.2 %, respectively). However, blastocyst rates in IVF and AMSC-NT embryos (30.6 ± 2.7 and 28.9 ± 3.1 %) did not differ and were significantly (P < 0.05) higher than FF-NT (19.5 ± 1.8 %). Total cell number did not show significant (P > 0.05) differences between IVF and AMSC-NT embryos (186.7 ± 4.2, 171.2 ± 3.8, respectively) but were significantly (P < 0.05) higher than that from FF-NT (151.3 ± 4.1). Alterations in the expression pattern of genes implicated in transcription and pluripotency (OCT4, STAT3, NANOG), DNA methylation (DNMT1, DNMT3A), histone deacetylation (HDAC2), growth factor signaling and imprinting (IGF2, IGF2R), apoptosis (BAX, BCL2), metabolism (GLUT1) and oxidative stress (MnSOD) regulation were observed in cloned embryos. The transcripts or expression patterns in AMSC-NT embryos more closely followed that of the in vitro derived embryos compared with FF-NT embryos. The results demonstrate that multipotent amnion MSCs have a greater potential as donor cells than FFs in achieving enhanced production of cloned buffalo embryos.

Handmade cloning: recent advances, potential and pitfalls

Handmade cloning (HMC) is the most awaited, simple and micromanipulator-free version of somatic cell nuclear transfer (SCNT). The requirement of expensive micromanipulators and skilled expertise is eliminated in this technique, proving it as a major revolution in the field of embryology. During the past years, many modifications have been incorporated in this technique to boost its efficiency. This alternative approach to micromanipulator based traditional cloning (TC) works wonder in generating comparable or even higher birth rates in addition to declining costs drastically and enabling cryopreservation. This technique is not only applicable to intraspecies nuclear transfer but also to interspecies nuclear transfer (iSCNT) thus permitting conservation of endangered species. It also offers unique possibilities for automation of SCNT which aims at production of transgenic animals that can cure certain human diseases by producing therapeutics hence, providing a healthier future for the wellbeing of humans. The present review aims at highlighting certain aspects of HMC including recent advancements in procedure and factors involved in elevating its efficiency besides covering the potentials and pitfalls of this technique.

A comparative study on expression profile of developmentally important genes during pre-implantation stages in buffalo hand-made cloned embryos derived from adult fibroblasts and amniotic fluid derived stem cells

Abnormal gene expression in somatic cell nuclear transfer embryos due to aberrant epigenetic modifications of the donor nucleus may account for much of the observed diminished viability and developmental abnormalities. The present study compared the developmentally important gene expression pattern at 4-cell, 8- to 16-cell, morula, and blastocyst stages of buffalo nuclear transfer (NT) embryos from adult fibroblasts (AFs) and amniotic fluid stem cells (AFSCs). In vitro fertilized embryos were used as control embryos. Alterations in the expression pattern of genes implicated in transcription and pluripotency (OCT4, STAT3, NANOG), DNA methylation (DNMT1, DNMT3A), histone deacetylation (HDAC2), growth factor signaling, and imprinting (IGF2, IGF2R), apoptosis (BAX, BCL2), oxidative stress (MnSOD), metabolism (GLUT1) regulation were observed in cloned embryos. The expression of transcripts in AFSC-NT embryos more closely followed that of the in vitro fertilized embryos compared with AF-NT embryos. It is concluded that AFSCs with a relatively undifferentiated genome may serve as suitable donors which could be reprogrammed more efficiently to reactivate expression of early embryonic genes in buffalo NT.

Establishment of Trophectoderm Cell Lines from Buffalo (Bubalus bubalis) Embryos of Different Sources and Examination of In Vitro Developmental Competence, Quality, Epigenetic Status and Gene Expression in Cloned Embryos Derived from Them

Despite being successfully used to produce live offspring in many species, somatic cell nuclear transfer (NT) has had a limited applicability due to very low (>1%) live birth rate because of a high incidence of pregnancy failure, which is mainly due to placental dysfunction. Since this may be due to abnormalities in the trophectoderm (TE) cell lineage, TE cells can be a model to understand the placental growth disorders seen after NT. We isolated and characterized buffalo TE cells from blastocysts produced by in vitro fertilization (TE-IVF) and Hand-made cloning (TE-HMC), and compared their growth characteristics and gene expression, and developed a feeder-free culture system for their long-term culture. The TE-IVF cells were then used as donor cells to produce HMC embryos following which their developmental competence, quality, epigenetic status and gene expression were compared with those of HMC embryos produced using fetal or adult fibroblasts as donor cells. We found that although TE-HMC and TE-IVF cells have a similar capability to grow in culture, significant differences exist in gene expression levels between them and between IVF and HMC embryos from which they are derived, which may have a role in the placental abnormalities associated with NT pregnancies. Although TE cells can be used as donor cells for producing HMC blastocysts, their developmental competence and quality is lower than that of blastocysts produced from fetal or adult fibroblasts. The epigenetic status and expression level of many important genes is different in HMC blastocysts produced using TE cells or fetal or adult fibroblasts or those produced by IVF.

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.

Birth of cloned calves from vitrified-warmed zona-free buffalo (Bubalus bubalis) embryos produced by hand-made cloning

The availability of techniques for the vitrification of cloned blastocysts can improve their effective use. The present study compared the developmental competence of buffalo cloned embryos derived from adult (BAF), newborn (BNF) and fetal fibroblast (BFF) before and after vitrification. Despite similar cleavage rates among the three groups, the blastocyst rate was lower for BAF- than BNF- and BFF-derived embryos (30.2±2.2% vs 41.7±1.7% and 39.1±2.1%, respectively; P<0.01). The total cell number of BNF-derived blastocysts was significantly higher (P<0.01) than that of BFF-derived blastocysts, which, in turn, was higher (P<0.01) than that of BAF-derived blastocysts. Following transfer of vitrified-warmed blastocysts to recipients, no pregnancy was obtained with fresh (n=8) or vitrified-warmed (n=18) BAF-derived blastocysts, whereas transfer of fresh BNF- (n=53) and BFF-derived (n=32) blastocysts resulted in four and three pregnancies, respectively, which aborted within 90 days of gestation. The transfer of vitrified-warmed BNF-derived blastocysts (n=39) resulted in the live birth of a calf weighing 41kg, which is now 23 months old and has no apparent abnormality, whereas the transfer of vitrified-warmed BFF-derived blastocysts (n=18) resulted in one live birth of a calf that died within 6h. These results demonstrate that cloned buffalo embryos cryopreserved by vitrification can be used to obtain live offspring.

Pluripotent cells in farm animals: state of the art and future perspectives

Pluripotent cells, such as embryonic stem (ES) cells, embryonic germ cells and embryonic carcinoma cells are a unique type of cell because they remain undifferentiated indefinitely in in vitro culture, show self-renewal and possess the ability to differentiate into derivatives of the three germ layers. These capabilities make them a unique in vitro model for studying development, differentiation and for targeted modification of the genome. True pluripotent ESCs have only been described in the laboratory mouse and rat. However, rodent physiology and anatomy differ substantially from that of humans, detracting from the value of the rodent model for studies of human diseases and the development of cellular therapies in regenerative medicine. Recently, progress in the isolation of pluripotent cells in farm animals has been made and new technologies for reprogramming of somatic cells into a pluripotent state have been developed. Prior to clinical application of therapeutic cells differentiated from pluripotent stem cells in human patients, their survival and the absence of tumourigenic potential must be assessed in suitable preclinical large animal models. The establishment of pluripotent cell lines in farm animals may provide new opportunities for the production of transgenic animals, would facilitate development and validation of large animal models for evaluating ESC-based therapies and would thus contribute to the improvement of human and animal health. This review summarises the recent progress in the derivation of pluripotent and reprogrammed cells from farm animals. We refer to our recent review on this area, to which this article is complementary.

Expression pattern of pluripotent markers in different embryonic developmental stages of buffalo (Bubalus bubalis) embryos and putative embryonic stem cells generated by parthenogenetic activation

In this study, we describe the production of buffalo parthenogenetic blastocysts and subsequent isolation of parthenogenetic embryonic stem cell (PGESC)-like cells. PGESC colonies exhibited dome-shaped morphology and were clearly distinguishable from the feeder layer cells. Different stages of development of parthenogenetic embryos and derived embryonic stem cell (ESC)-like cells expressed key ESC-specific markers, including OCT-4, NANOG, SOX-2, FOXD3, REX-1, STAT-3, TELOMERASE, NUCLEOSTEMIN, and cMYC. Immunofluorescence-based studies revealed that the PGESCs were positive for surface-based pluripotent markers, viz., SSEA-3, SSEA-4, TRA 1-80, TRA 1-60, CD-9, and CD-90 and exhibited high alkaline phosphatase (ALP) activity. PGEC cell-like cells formed embryoid body (EB)-like structures in hanging drop cultures and when cultured for extended period of time spontaneously differentiated into derivatives of three embryonic germ layers as confirmed by RT-PCR for ectodermal (CYTOKERATIN8, NF-68), mesodermal (MSX1, BMP-4, ASA), and endodermal markers (AFP, HNF-4, GATA-4). Differentiation of PGESCs toward the neuronal lineage was successfully directed by supplementation of serum-containing media with retinoic acid. Our results indicate that the isolated ESC-like cells from parthenogenetic blastocyst hold properties of ESCs and express markers of pluripotency. The pluripotency markers were also expressed by early cleavage-stage of buffalo embryos.

Effect of TGF-β1 superfamily members on survival of buffalo (Bubalus bubalis) embryonic stem-like cells

This study examined the effects of supplementation of ES-like cell culture medium with bone morphogenetic protein (BMP)-4 (0, 10, 20 or 100 ng/ml) or Noggin (250, 500 or 750 ng/ml) or TGF-β1 (0, 0.1, 1 or 10 ng/ml) or SB431542 (0, 10, 25 or 50 μm), an inhibitor of TGF-β1 signalling, on survival, colony area and expression level of pluripotency genes in buffalo ES-like cells at passage 40-80, under different culture conditions. BMP-4 supplementation significantly reduced (p < 0.05) colony survival rate, percentage increase in colony area and relative mRNA abundance of OCT4, whereas that of NANOG and SOX-2 was increased significantly (p < 0.05). Noggin supplementation did not affect the colony survival rate and percentage increase in colony area in the presence of FGF-2 and LIF. In the presence of FGF-2 alone, it significantly reduced (p < 0.05) the relative mRNA abundance of OCT4 and SOX-2 and increased (p < 0.05) that of NANOG. Supplementation with TGF-β1 at 1.0 ng/ml but not at other concentrations increased colony survival rate but had no effect on percentage increase in colony area at any concentration. Supplementation with SB-431542 decreased (p < 0.05) colony survival rate at 50 μm but not at other concentrations. The percentage increase in colony area was lower (p < 0.05) with 10 μm SB-431542 than that in the controls, whereas at higher concentrations of 25 or 50 μm, SB-431542 decreased (p < 0.05) the colony size instead of increasing it. In conclusion, these results suggest that BMP-4 induces differentiation in buffalo ES-like cells, whereas TGF-β/activin/nodal pathway may not be playing a crucial role in maintaining pluripotency in these cells.

ROCK inhibitor Y-27632 enhances the survivability of dissociated buffalo (Bubalus bubalis) embryonic stem cell-like cells

This study investigated the effects of supplementation of culture medium with 10 μM Y-27632, a specific inhibitor of Rho kinase activity, for 6 days on self-renewal of buffalo embryonic stem (ES) cell-like cells at Passage 50–80. Y-27632 increased mean colony area (P < 0.05) although it did not improve their survival. It decreased OCT4 expression (P < 0.05), increased NANOG expression (P < 0.05), but had no effect on SOX2 expression. It also increased expression of anti-apoptotic gene BCL-2 (P < 0.05) and decreased that of pro-apoptotic genes BAX and BID (P < 0.05). It increased plating efficiency of single-cell suspensions of ES cells (P < 0.05). Following vitrification, the presence of Y-27632 in the vitrification solution or thawing medium or both did not improve ES cell colony survival. However, following seeding of clumps of ES cells transfected with pAcGFP1N1 carrying green fluorescent protein (GFP), Y-27632 increased colony formation rate (P < 0.01). ES cell colonies that formed in all Y-27632-supplemented groups were confirmed for expression of pluripotency markers alkaline phosphatase, SSEA-4 and TRA-1–60, and for their ability to generate embryoid bodies containing cells that expressed markers of ectoderm, mesoderm and endoderm. In conclusion, Y-27632 improves survival of buffalo ES cells under unfavourable conditions such as enzymatic dissociation to single cells or antibiotic-assisted selection after transfection, without compromising their pluripotency.

Effects of glial cell line-derived neurotrophic factor, fibroblast growth factor 2 and epidermal growth factor on proliferation and the expression of some genes in buffalo (Bubalus bubalis) spermatogonial cells

The present study evaluated the effects of glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor (FGF) 2 and epidermal growth factor (EGF) on proliferation and the expression of some genes in spermatogonial cells. Spermatogonial cells were isolated from prepubertal buffalo testes and enriched by double enzyme treatment, filtration through 80- and 60-μm nylon mesh filters, differential plating on lectin-coated dishes and Percoll density gradient centrifugation. Cells were then cultured on a buffalo Sertoli cell feeder layer and formed colonies within 15–18 days. The colonies were found to predominantly contain undifferentiated Type A spermatogonia because they bound Dolichos biflorus agglutinin and did not express c-kit. The colonies expressed alkaline phosphatase, NANOG, octamer-binding transcription factor (OCT)-4 and tumour rejection antigen (TRA)-1–60. Cells were subcultured for 15 days, with or without growth factor supplementation. After 15 days, colony area and the relative mRNA abundance of PLZF were higher (P < 0.05) following supplementation with 40 ng mL–1 GDNF + 10 ng mL–1 EGF + 10 ng mL–1 FGF2 than with the same concentrations of GDNF alone or GDNF plus either EGF or FGF2. Expression of TAF4B was higher (P < 0.05) in the presence of FGF2, whereas the expression of THY1 was not affected by growth factor supplementation. In the Sertoli cell feeder layer, EGF and FGF2 decreased (P < 0.05), whereas GDNF increased (P < 0.05), the relative mRNA abundance of ETV5 compared with control. In conclusion, an in vitro culture system that incorporates various growth factors was developed for the short-term culture of buffalo spermatogonia.

Kinetics of GDF9 expression in buffalo oocytes during in vitro maturation and their associated development ability

The capacity of fully grown oocytes to regulate their own microenvironment by secreted paracrine factors contribute to their developmental competence. In spite of growing evidence about the vital role of Growth Differentiation Factor 9 (GDF9) in determination of oocyte developmental competence, there is insufficient information about time dependent behavior of its expression during in vitro maturation (IVM) to have definite understanding about at what time point during IVM it plays most crucial role. The study reports the kinetics of GDF9 expression under four different IVM supplement conditions in buffalo oocytes and their concomitant development rate up to blastocyst. Oocytes matured under an ideal media condition with all supplements and those cultured with only FSH resulted in significantly higher cumulus expansion, nuclear maturation, cleavage and blastocyst rates. GDF9 expression at both mRNA and protein levels at different time points of IVM revealed that magnitude of mRNA abundance at 8h of IVM was most important towards imparting development competence to buffalo oocytes. Appearance of GDF9 protein in maturing oocytes was found asynchronous with mRNA appearance in the time course of IVM suggesting possible posttranscriptional regulation of this gene under dynamic oocyte cumulus cell communication process. Abundance of mature GDF9 protein at 16 h was most consistently related with all oocyte development parameters.

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.

Generation of induced pluripotent stem cells from buffalo (Bubalus bubalis) fetal fibroblasts with buffalo defined factors

Ectopically, expression of defined factors could reprogram mammalian somatic cells into induced pluripotent stem cells (iPSCs), which initiates a new strategy to obtain pluripotent stem cell lines. Attempts have been made to generate buffalo pluripotent stem cells by culturing primary germ cells or inner cell mass, but the efficiency is extremely low. Here, we report a successful method to reprogram buffalo fetal fibroblasts (BFFs) into pluripotent stem cells [buffalo induced pluripotent stem cell (biPSCs)] by transduction of buffalo defined factors (Oct4, Sox2, Klf4, and c-Myc) using retroviral vectors. The established biPSCs displayed typical morphological characteristics of pluripotent stem cells, normal karyotype, positive staining of alkaline phosphatase, and expressed pluripotent markers including Oct4, Sox2, Nanog, Lin28, E-Cadherin, SSEA-1, SSEA-4, TRA-1-81, STAT3, and FOXD3. They could form embryoid bodies (EBs) in vitro and teratomas after injecting into the nude BALB/C mice, and 3 germ layers were identified in the EBs and teratomas. Methylation assay revealed that the promoters of Oct4 and Nanog were hypomethylated in biPSCs compared with BFFs and pre-biPSCs, while the promoters of Sox2 and E-Cadherin were hypomethylated in both BFFs and biPSCs. Further, inhibiting p53 expression by coexpression of SV40 large T antigen and buffalo defined factors in BFFs or treating BFFs with p53 inhibitor pifithrin-a (PFT) could increase the efficiency of biPSCs generation up to 3-fold, and nuclear transfer embryos reconstructed with biPSCs could develop to blastocysts. These results indicate that BFFs can be reprogrammed into biPSCs by buffalo defined factors, and the generation efficiency of biPSCs can be increased by inhibition of p53 expression. These efforts will provide a feasible approach for investigating buffalo stem cell signal pathways, establishing buffalo stem cell lines, and producing genetic modification buffaloes in the future.

Cloning and characterization of buffalo NANOG gene: alternative transcription start sites, splicing, and polyadenylation in embryonic stem cell-like cells

NANOG is a critical homeodomain transcription factor responsible for maintaining embryonic stem cell (ESC) self-renewal and pluripotency. In the present study, we isolated, sequenced, and characterized the NANOG gene in buffalo ESC-like cells. Here, we demonstrated that NANOG mRNA is expressed as multiple isoforms and uses four alternative transcriptional start sites (TSSs) and five different polyadenylation sites. The TSSs identified by 5'-RNA ligase-mediated rapid amplification of cDNA ends (RLM-5'-RACE) were positioned at 182, 95, 35, and 17 nucleotides upstream relative to the translation initiation codon. 3'-RACE experiment revealed the presence of tandem polyadenylation signals, which leads to the expression of at least five different 3'-untranslated regions (269, 314, 560, 566, and 829 nucleotides). Expression analysis showed that these alternatively polyadenylated transcripts expressed differentially. Sequence analysis showed that the open reading frame of buffalo NANOG codes for a 300-amino-acid-long protein. Further, results showed that alternative splicing leads to the expression of two types of transcript variants encoded by four and five exons. In silico analysis of cloned 5'-flanking region (3366 nucleotides upstream of translation start codon) identified several putative transcription factors binding sites in addition to a TATA box and CAAT box at -30 and -139 bp (upstream to the distal most TSS), respectively, in the buffalo NANOG promoter.

Optimization of culture conditions to support long-term self-renewal of buffalo (Bubalus bubalis) embryonic stem cell-like cells

A culture system capable of sustaining self-renewal of buffalo embryonic stem (ES) cell-like cells in an undifferentiated state over a long period of time was developed. Inner cell masses were seeded on KO-DMEM+15% KO-serum replacer on buffalo fetal fibroblast feeder layer. Supplementation of culture medium with 5 ng/mL FGF-2 and 1000 IU/mL mLIF gave the highest (p<0.05) rate of primary colony formation. The ES cell-like cells' colony survival rate and increase in colony size were highest (p<0.05) following supplementation with FGF-2 and LIF compared to other groups examined. FGF-2 supplementation affected the quantitative expression of NANOG, SOX-2, ACTIVIN A, BMP 4, and TGFβ1, but not OCT4 and GREMLIN. Supplementation with SU5402, an FGFR inhibitor (≥20 μM) increased (p<0.05) the percentage of colonies that differentiated. FGFR1-3 and ERK1, K-RAS, E-RAS, and SHP-2, key signaling intermediates of FGF signaling, were detected in ES cell-like cells. Under culture conditions described, three ES cell lines were derived that, to date, have been maintained for 135, 95, and 85 passages for over 27, 19, and 17 months, respectively, whereas under other conditions examined, ES cell-like cells did not survive beyond passage 10. The ES cell-like cells were regularly monitored for expression of pluripotency markers and their potency to form embryoid bodies.

Characterization of POU5F1 (OCT4) gene and its promoter in buffalo ESC-like cells identifies multiple transcription start sites and expression of four pseudogenes

In the present study, we cloned and characterized the buffalo (Bubalus bubalis) OCT4 ortholog expressed in embryonic stem cell (ESC) like cells and its promoter region. The 5'- and 3'-RACE experiments were conducted to analyze the transcription initiation site and regulatory regions. The comparative analysis of buffalo OCT4 promoter with other mammalian orthologs revealed high conservation. Among the regulatory regions highest similarity was observed between buffalo, bovine and sheep. Interestingly, buffalo OCT4 promoter exhibited a 78 bp deletion between two proximal enhancers (PE-1A and PE-1B) when compared to other mammalian orthologs. 5'-RACE revealed four different transcription start sites for OCT4 gene. As far as we know there is no previous report regarding multiple transcription initiation sites for OCT4 gene in any species. In addition, we identified expression of four pseudogenes in buffalo ESC-like cells. Among the multiple transcripts characterized, we found four cDNA clones (1083 bp) derived from ESC-like cells sharing 96.9-99.3% sequence homology with the parent gene and having the capacity of encoding 139, 206, 206 and 324 amino acid long truncated proteins. Multiple pseudogenes have been proposed for OCT4 which might contribute to the false detection of this gene during expression studies. However, only few of them were reported to be transcribed and none were reported to be translated in stem cells. Western blot analysis of OCT4 protein using ESC-like cells revealed multiple bands, indicating that some of the hypothetical pseudogenes are being translated. These novel pseudogenes or their protein products may have some important regulatory functions.