24 EFFECT OF DONOR CELL TYPE ON IN VITRO AND IN VIVO DEVELOPMENTAL COMPETENCE OF CLONED BUFFALO (BUBALUS BUBALIS) EMBRYOS

Abstract

Selection of the donor cell type for somatic cell NT is very important based on its capability to be reprogrammed by the oocyte cytoplasm. A very wide variety of donor cells of different origin have been used for somatic cell NT, having differences in the overall efficiency. The aim of this study was to compare the cloning efficiency of donor cells derived from the ventral side of origin of tail skin and seminal plasma of a buffalo bull (age: 3 years old). Somatic cells from skin and seminal plasma were isolated and cultured as described by Selokar et al. (2014 PLOS ONE 9(3), e90755). Cultured seminal plasma cells had classic epithelial morphology, grew in clusters, were hexagonal in outline shape, and were positive for immunocytochemical detection of keratin marker, indicating that they were of epithelial origin, whereas tail-derived cells were spindle in shape and found positive for vimentin expression, indicating the fibroblast origin. To determine their reprogramming potential, these cells between passages 5 to 8 were used for the production of buffalo cloned embryos by handmade cloning as per the method described by Selokar et al. (2012 Theriogenology 78, 930–936). In brief, oocytes were isolated from slaughter-house ovaries and matured in vitro. After 21 h of maturation, cumulus cell mass and zona pellucida were removed by enzymatic treatment, hyaluronidase and pronase, respectively. Zona-free buffalo oocytes were enucleated on the basis of protrusion cone. A single somatic cell was attached to an enucleated oocyte with addition of phytohemagglutinin, followed by sandwich type of electrofusion between the somatic cell-bearing oocyte and enucleated oocyte using BTX electrofusion machine. Fused oocytes were activated by 4 μM calcium ionophore for 5 min and incubated in 2 mM 6-DMAP for 4 h and were cultured in K-RVCL-50^® medium for 7 days on a flat surface in a 4-well dish in an incubator (5% CO₂ and 38.5°C temperature). The total numbers of embryos reconstructed from tail-derived cells and semen-derived cells were 132 and 158, respectively. Cleavage and blastocyst rate were calculated from total embryos cultured, and data were analysed by Student’s t-test. We found no significant effect on both cleavage (89.30 ± 2.1 v. 94.1 ± 0.6) and blastocyst rate (40.7 ± 4.0 v. 43.1 ± 9.6) for the embryos produced from cells derived from tail and seminal plasma. To study the in vivo developmental competence of embryos derived from the 2 donor cell types, one embryo of each cell type was transferred into 6 recipient animals. Pregnancies were confirmed by ultrasonography at 30 to 35 days after transfer and monitored regularly at 15-day intervals up to 90 days. Three pregnancies were found for tail-derived cells, whereas no pregnancy was obtained for semen-derived cells. Out of 3 pregnancies obtained, 1 embryonic death was observed before 45 days, and 2 are continuing at advance stage. In conclusion, tail-derived cells are the better donor cell choice for buffalo somatic cell NT research. Currently, our focus is on epigenetic reprogramming behaviour of these 2 different cell types to elucidate the possible reprogramming mechanism.