Isolation, culture and characterisation of somatic cells derived from semen and milk of endangered sheep and eland antelope

The ART of bringing extinction to a freeze - History and future of species conservation, exemplified by rhinos

The ongoing mass extinction of animal species at an unprecedented rate is largely caused by human activities. Progressive habitat destruction and fragmentation is resulting in accelerated loss of biodiversity on a global scale. Over decades, captive breeding programs of non-domestic species were characterized by efforts to optimize species-specific husbandry, to increase studbook-based animal exchange, and to improve enclosure designs. To counter the ongoing dramatic loss of biodiversity, new approaches are warranted. Recently, new ideas, particularly the application of assisted reproduction technologies (ART), have been incorporated into classical zoo breeding programs. These technologies include semen and oocyte collection, artificial insemination, and in-vitro embryo generation. More futuristic ideas of advanced ART (aART) implement recent advances in biotechnology and stem-cell related approaches such as cloning, inner cell mass transfer (ICM), and the stem-cell-associated techniques (SCAT) for the generation of gametes and ultimately embryos of highly endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni) of which only two female individuals are left. Both, ART and aART greatly depend on and benefit from the rapidly evolving cryopreservation techniques and biobanking not only of genetic, but also of viable cellular materials suitable for the generation of induced pluripotent stem cells (iPSC). The availability of cryopreserved materials bridges gaps in time and space, thereby optimizing the available genetic variability and enhancing the chance to restore viable populations.

Isolation and culture of epithelial cells from stored buffalo semen and their use for the production of cloned embryos

The aim of the present study was to isolate somatic cells from semen, a non-invasive source of donor somatic cells, for somatic cell nuclear transfer (SCNT) experiments. The study had two parts: (1) isolation and culture of somatic cells from semen, which was stored at 4°C; and (2) investigating the SCNT competence of semen-derived somatic cells. We successfully cultured somatic cells from freshly ejaculated semen, which was stored for different times (0, 4, 12, 24, 72 and 144h after semen collection) at 4°C, using a Percoll gradient method. Up to 24h storage, 100% cell attachment rates were observed; cell attachment rates of 66% were observed for the 72 and 144h storage groups. The attached cells observed in all groups examined were proliferated (100%). Cultured cells exhibited epithelial cell morphology and culture characteristics, which was further confirmed by positive expression of cytokeratin 18, an epithelial cell-type marker. We compared the SCNT competence of semen-derived epithelial cells and skin-derived fibroblasts. The cleavage rate, blastocyst production rate, total number of cells in blastocysts and the apoptotic index of blastocysts were similar for embryos produced from semen-derived epithelial cells and skin-derived fibroblasts, indicating that semen-derived epithelial cells can serve as donors for SCNT experiments. In conclusion, we demonstrate a method to culture epithelial cells from stored semen, which can be used to produce cloned embryos of breeding bulls, including remote bulls.

Successful cloning of a superior buffalo bull

Somatic cell nuclear transfer (SCNT) technology provides an opportunity to multiply superior animals that could speed up dissemination of favorable genes into the population. In the present study, we attempted to reproduce a superior breeding bull of Murrah buffalo, the best dairy breed of buffalo, using donor cells that were established from tail-skin biopsy and seminal plasma. We studied several parameters such as cell cycle stages, histone modifications (H3K9ac and H3K27me3) and expression of developmental genes in donor cells to determine their SCNT reprogramming potentials. We successfully produced the cloned bull from an embryo that was produced from the skin-derived cell. Growth, blood hematology, plasma biochemistries, and reproductive organs of the produced cloned bull were found normal. Subsequently, the bull was employed for semen production. Semen parameters such as CASA (Computer Assisted Semen Analysis) variables and in vitro fertilizing ability of sperms of the cloned bull were found similar to non-cloned bulls, including the donor bull. At present, we have 12 live healthy progenies that were produced using artificial insemination of frozen semen of the cloned bull, which indicate that the cloned bull is fertile and can be utilized in the buffalo breeding schemes. Taken together, we demonstrate that SCNT can be used to reproduce superior buffalo bulls.

Handmade Cloned Buffalo (Bubalus bubalis) Embryos Produced from Somatic Cells Isolated from Milk and Ear Skin Differ in Their Developmental Competence, Epigenetic Status, and Gene Expression

We compared the cloning efficiency of buffalo embryos produced by handmade cloning (HMC) using ear skin- and milk-derived donor cells. The blastocyst rate was lower (p < 0.05) for milk-derived than that for skin-derived embryos, whereas the total cell number and apoptotic index were similar. The global level of H3K9ac was higher (p < 0.05) in skin- than in milk-derived cells, whereas the level of H3K27me3 was similar in the two groups. The global level of H3K9ac was similar between milk-derived and in vitro-fertilized (IVF) blastocysts, which was higher (p < 0.05) than that in skin-derived blastocysts. The level of H3K27me3 was similar among the three groups. The expression level of IGF-1R and G6PD was higher (p < 0.05) in skin- than in milk-derived cells, whereas DNMT1, DNMT3a, and HDAC1 expression level was similar. In the blastocysts, the expression level of DNMT1, HDAC1, OCT4, and CDX2 was higher (p < 0.05) in skin-derived than that in IVF blastocysts. The expression level of DNMT3a and IGF-1R, was in the order (p < 0.05) skin-derived and IVF > milk-derived blastocysts and that of NANOG was (p < 0.05) IVF-> milk-derived > skin-derived blastocysts. The expression level of all these genes, except NANOG, was lower (p < 0.05) in milk- than in skin-derived or IVF blastocysts. In conclusion, milk-derived cells can be used for producing HMC embryos of quality similar to that of skin-derived embryos, although with a lower blastocyst rate.

A Road Map for 21st Century Genetic Restoration: Gene Pool Enrichment of the Black-Footed Ferret

Interspecies somatic cell nuclear transfer (iSCNT) could benefit recovery programs of critically endangered species but must be weighed with the risks of failure. To weigh the risks and benefits, a decision-making process that evaluates progress is needed. Experiments that evaluate the efficiency and efficacy of blastocyst, fetal, and post-parturition development are necessary to determine the success or failure or species-specific iSCNT programs. Here, we use the black-footed ferret (Mustela nigripes) as a case study for evaluating this emerging biomedical technology as a tool for genetic restoration. The black-footed ferret has depleted genetic variation yet genome resource banks contain genetic material of individuals not currently represented in the extant lineage. Thus, genetic restoration of the species is in theory possible and could help reduce the persistent erosion of genetic diversity from drift. Extensive genetic, genomic, and reproductive science tools have previously been developed in black-footed ferrets and would aid in the process of developing an iSCNT protocol for this species. Nonetheless, developing reproductive cloning will require years of experiments and a coordinated effort among recovery partners. The information gained from a well-planned research effort with the goal of genetic restoration via reproductive cloning could establish a 21st century model for evaluating and implementing conservation breeding that would be applicable to other genetically impoverished species.

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.

Somatic cells, stem cells, and induced pluripotent stem cells: how do they now contribute to conservation?

More than a decade has now passed since the birth of the first endangered species produced from an adult somatic cell reprogrammed by somatic cell nuclear transfer. At that time, advances made in domestic and laboratory animal species provided the necessary foundation for attempting cutting-edge technologies on threatened and endangered species. In addition to nuclear transfer, spermatogonial stem cell transplantation and induction of pluripotent stem cells have also been explored. Although many basic scientific questions have been answered and more than 30 wild species have been investigated, very few successes have been reported. The majority of studies document numerous obstacles that still need to be overcome to produce viable gametes or embryos for healthy offspring production. This chapter provides an overview of somatic cell and stem cell technologies in different taxa (mammals, fishes, birds, reptiles and amphibians) and evaluates the potential and impact of these approaches for animal species conservation.

Identification and functional characterization of a novel monotreme- specific antibacterial protein expressed during lactation

Monotremes are the only oviparous mammals and exhibit a fascinating combination of reptilian and mammalian characters. They represent a component of synapsidal reproduction by laying shelled eggs which are incubated outside the mother’s body. This is accompanied by a prototherian lactation process, marking them as representatives of early mammals. The only extant monotremes are the platypus, and the short- and long- beaked echidnas, and their distributions are limited to Australia and New Guinea. Apart for a short weaning period, milk is the sole source of nutrition and protection for the hatchlings which are altricial and immunologically naive. The duration of lactation in these mammals is prolonged relative to the gestational length and period of incubation of eggs. Much of the development of monotreme young occurs in the non-sterile ex-utero environment. Therefore the role of milk in the growth, development and disease protection of the young is of significant interest. By sequencing the cDNA of cells harvested from monotreme milk, we have identified a novel monotreme- specific transcript, and the corresponding gene was designated as the EchAMP. The expression profile of this gene in various tissues revealed that it is highly expressed in milk cells. The peptides corresponding to the EchAMP protein have been identified in a sample of echidna milk In silico analysis indicated putative antimicrobial potential for the cognate protein of EchAMP. This was further confirmed by in vitro assays using a host of bacteria. Interestingly, EchAMP did not display any activity against a commensal gut floral species. These results support the hypothesis of enhancement of survival of the young by antimicrobial bioactives of mammary gland origin and thus emphasize the protective, non- nutritional role of milk in mammals.

Embryo production and possible species preservation by nuclear transfer of somatic cells isolated from bovine semen

Somatic cells in semen are a potential source of nuclei for nuclear transfer to produce genetically identical animals; this is especially important when an animal has died and the only viable genetic material available is frozen semen. Usefulness of somatic cells obtained from fresh (cultured) and frozen (isolated, not cultured) bovine semen for nuclear transfer was evaluated. Twelve ejaculates were collected from nine bulls representing three breeds: Charolais, Brahman, and crossbred Rodeo bull. All samples were processed immediately and cell growth was obtained from seven of the twelve ejaculates (58.3%). Cells from three bulls (with the best growth rates) were evaluated by optical microscopy and used in cloning experiments. In culture, these cells exhibited classic epithelial morphology and expressed cytokeratin and vimentin, indicating they were of epithelial origin. When cells from the three bulls were used as donor cells, 15.9% (18/113), 34.5% (29/84), and 14.4% (13/90) of the fused embryos developed into blastocysts, respectively. Of the blastocyst stage embryos, 38.9% (7/18), 72.4% (21/29), and 61.5% (8/13) hatched, respectively. Somatic cells isolated (not cultured) from frozen bovine semen were also used in the cloning experiments. Although cleavage occurred, no compact morulae or blastocysts were obtained. In conclusion, epithelial cell growth was obtained from fresh bovine ejaculates with relatively high efficiency. Somatic cells from semen can be used as nucleus donors to produce cloned blastocyst-stage embryos.

Evaluation of culture systems for attachment and proliferation of epithelial cells cultured from ovine semen

Different culture systems were evaluated for their ability to support attachment and proliferation of the somatic cells obtained from ovine semen. Ejaculates (n=14) were collected from eight rams representing three breeds, Dorper, Suffolk and Hampshire. All samples were processed immediately and somatic cells were obtained from 11 of the 14 ejaculates. These cells had classic epithelial morphology and expressed cytokeratin, indicating they were of epithelial origin. Cells from four rams with the greatest growth rates were used for subsequent studies. Cells were cultured in four different media for 5 days and total numbers of attached cells vs. total numbers of seeded cells were counted and compared each day. Four media were evaluated: (1) a supplemented medium composed of DMEM/F12, 10% fetal bovine serum (FBS), 10 ng/ml epidermal growth factor, 30 microg/ml bovine pituitary extract, 5 microg/ml insulin, 10 ng/ml cholera toxin, and 50 microg/ml gentamycin; (2) sheep fetal fibroblast (SFF)-conditioned medium; (3) swiss 3T3 fibroblast-conditioned medium; and (4) basic medium composed of DMEM/F12, 10% FBS, and 50 microg/ml gentamycin. Cell proliferation was greater in the supplemented medium, SFF-conditioned medium, and 3T3 fibroblast-conditioned medium compared to the basic medium by day 2 of culture (p<0.05, n=24), and greater in supplemented medium compared to the SFF-conditioned medium and 3T3 fibroblast-conditioned medium by day 4 of culture (p<0.05, n=24). Three different surfaces: (1) Matrigel basement membrane matrix-coated plastic; (2) collagen I-coated plastic; and (3) uncoated plastic were evaluated for their ability to support proliferation and attachment of the cells obtained from semen. Cell proliferation was greater when cells were cultured on the Matrigel-coated compared to the collagen I-coated and uncoated plastic by day 2 of culture (p<0.05, n=16). Cell attachment was greater when cells were plated on the Matrigel-coated and collagen I-coated plastic compared to the uncoated plastic (p<0.05, n=16). These studies describe an effective system for the culture and proliferation of epithelial cells obtained from ovine semen samples. The system may increase the likelihood of obtaining cells from frozen semen, which could be used for cloning to recover animals of genetic value in which semen is the only material that is available.

Cloned embryos from semen. Part 1: in vitro proliferation of epithelial cells on embryonic fibroblasts after isolation from semen by gradient centrifugation

Although epithelial-like somatic cells have been previously isolated from semen, cell proliferation rates were low. Culture of whole semen samples resulted in loss of potentially valuable spermatozoa. The aims of the present study were to: (1) isolate somatic cells from semen, while preserving sperm viability, and (2) optimize in vitro culture conditions for semen-derived epithelial cells. Density gradient centrifugation of washed ejaculates of two rams (Ovis aries) (n = 24) and one eland bull (Taurotragus oryx) (n = 4) was performed using a three-layer discontinuous Percoll column consisting of 90% (P-90), 50% (P-50), and 20% (P-20) Percoll. In vitro culture and Trypan Blue staining indicated that live somatic cells settled in the P-20 layer. Nonmotile spermatozoa were recovered at the P-50 and P-90 interfaces, whereas motile spermatozoa were collected in the pellet from the P-90 layer. Subsequently, somatic cells isolated from the P-20 layer were plated either on inactivated 3T3 mouse embryonic fibroblast feeder layers, collagen-coated plates with 3T3 feeder cell inserts, or on collagen-coated plates. Initial somatic cell plating was similar among treatments, but proliferation significantly increased when cocultured with 3T3 cells (feeder or insert). Furthermore, two different types of epithelial cells were obtained. The exact origin of the cells in the male reproduction system is uncertain and probably variable. The present method of cell isolation and in vitro culture may be of value for preserving endangered species. Specifically, cells isolated and cultured from cryopreserved semen of nonliving males could be used for producing embryos by somatic cell nuclear transfer.