Successful transplantation of bovine testicular cells to heterologous recipients.

While heterologous germ cell transplantation was successful in pigs and goats, autologous transplantation alone has been reported to result in donor-derived spermatogenesis in cattle. The objective of this study was to investigate whether the transplantation of heterologous germ cells could result in colonization of recipient testes in cattle of different breeds. Testicular cells were isolated from 8 Bos taurus donor bull calves and then transferred into 15 Bos indicus-cross bull calves. All animals were prepubertal, donors were aged 5-7 months and recipients 5-11 months, and scrotal circumferences ranged from 15 to 22 cm. Single cell suspensions of donor testicular cells, prepared by enzymatic digestion, were labelled with fluorescent dyes PKH26 or CFDA-SE, before transfer into the rete testis of recipients under ultrasonographic guidance. To assess the longevity of colonization by donor cells, recipients were castrated 2-30 weeks after cell transfer. Donor cells were observed in 15/25 (60%) of the testes that received PKH26-labelled cells, whereas no CFDA-SE-positive cell was identified in any recipients. The maturity of the donors or recipients (measured by scrotal circumference) did not affect colonization potential. In freshly isolated tubules, clumps of PKH26-positive cells were observed, which indicated either cell division or extensive local colonization of specific areas of the tubules. In frozen sections, PKH26-positive cells were identified on the seminiferous tubule basement membrane, which indicated that these cells had successfully migrated from the tubule lumen and were likely to be spermatogonia. We conclude that PKH26 was more suitable for labelling donor testis cells and donor cells can be identified up to 6 months following transfer. These results indicate that allogeneic transplantation of testicular cells can occur between Bos taurus and Bos indicus cattle. Further studies will investigate functionality of transferred testicular cells.