Ectopic porcine spermatogenesis in murine subcutis: tissue grafting versus cell-injection methods.

Fragments of testis tissue from immature animals grow and develop spermatogenesis when grafted onto subcutaneous areas of immunodeficient mice. The same results are obtained when dissociated cells from immature testes of rodents are injected into the subcutis of nude mice. Those cells reconstitute seminiferous tubules and facilitate spermatogenesis. We compared these two methods, tissue grafting and cell-injection methods, in terms of the efficiency of spermatogenesis in the backs of three strains of immunodeficient mice, using neonatal porcine testicular tissues and cells as donor material. Nude, severe combined immunodeficient (SCID) and NOD/Shi-SCID, IL-2Rgammacnull (NOG) mice were used as recipients. At 10 months after surgery, the transplants were examined histologically. Both grafting and cell-injection methods resulted in porcine spermatogenesis on the backs of recipient mice; the percentage of spermatids present in the transplants was 67% and 22%, respectively. Using the grafting method, all three strains of mice supported the same extent of spermatogenesis. As for the cell-injection method, although SCID mice were the best host for supporting reconstitution and spermatogenesis, any difference from the other strains was not significant. As NOG mice did not show any better results, the severity of immunodeficiency seemed to be irrelevant for supporting xeno-ectopic spermatogenesis. Our results confirmed that tubular reconstitution is applicable to porcine testicular cells. This method as well as the grafting method would be useful for studying spermatogenesis in different kinds of animals.