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

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.

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.

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.