Homologous testis transplantation in dogs.
There is growing interest in the possible use of homologous testis transplantation for the treatment of anorchia and male infertility. In order to test the surgical and immunological feasibility of this therapy, three series of experimental studies of homologous testis transplantation were carried out in dogs. In the first pilot study, four beagles from the same litter were transplanted using microsurgical techniques for end-to-end anastomosis of the testicular vessels and the vas deferens. These dogs received cyclosporin A (CyA) for 3 months after transplantation. The longest functional graft survival in this series was 163 days, strongly suggesting that long-term survival of a homologously transplanted testis graft is possible. A second series of operations was performed on ten mongrel dogs. The same surgical technique was employed and the series was divided into three groups. Group 1 received CyA monotherapy, group 2 a combination of CyA and prednisolone, and group 3 received no immunosuppression. The average graft survival time in this series was 28 days, significantly less than the 71 days in the first series. The dogs in group 2, however, had graft survival times that were three times longer than those in the other two groups, suggesting that CyA in combination with prednisolone yields the best graft survival. In the third series, five littermates received a testis graft after castration. Immunosuppression was achieved by administration of CyA and prednisolone for 3 months. In three out of five animals, the graft survived until the immunosuppressive therapy was suspended. Histological biopsies of the graft 3 months after transplantation showed the same maturation of sperm cells as in the control testis of the same dog. The results of the last series suggest that long-term survival of homologously transplanted testis grafts in dogs is, indeed, possible with the aid of CyA and prednisolone.