Embryo production by intracytoplasmic injection of sperm retrieved from Meishan neonatal testicular tissue cryopreserved and grafted into nude mice.

Testicular xenografting, combined with cryopreservation can assist conservation of the genetic diversity of indigenous pigs by salvaging germ cells from their neonatal testes. Using Meishan male piglets as an example, we examined whether testicular tissue would acquire the ability to produce sperm after cryopreservation and grafting into nude mice (MS group). For comparison, testicular tissue from neonatal Western crossbreed male piglets was used (WC group). Sixty days after xenografting (day 0 = grafting), MS grafts had already developed seminiferous tubules containing sperm, whereas in the WC grafts, sperm first appeared on day 120. The proportion of tubules containing spermatids and sperm was higher in the MS group than in the WC group between days 90 and 120. Moreover, in vitro-matured porcine oocytes injected with a single sperm obtained from the MS group on day 180 developed to the blastocyst stage. The blastocyst formation rate after injection of the xenogeneic sperm was 14.6%, whereas the ratio in the absence of such injection (attributable to parthenogenesis) was 6.7%. Thus, cryopreserved Meishan testicular tissue acquired spermatogenic activity in host mice 60 days earlier than Western crossbreed tissue. Such xenogeneic sperm are likely capable of generating blastocysts in vitro.