a b s t r a c t
Xenografting of immature testicular tissue combined with cryopreservation can preserve
and use genetic information of prepubertal animals. For establishment of this new
approach, it is essential to clarify whether offspring derived from sperm grown in host
mice harboring cryopreserved xenografts show normal reproductive development. This
study examined serum profiles of gonadal hormones during sexual maturation in pigs
generated by intracytoplasmic sperm injection using sperm derived from cryopreserved
xenografts (CryoXeno pigs; three males and three females). We also assessed the reproductive
abilities of the male CryoXeno pigs by mating them with conventionally produced
(conventional) pigs, and by examining the in vitro fertilizing ability of their sperm. For
female CryoXeno pigs, reproductive ability was evaluated by artificial insemination with
semen from a conventional boar. During the growth of male CryoXeno pigs, the serum
concentrations of inhibin and testosterone showed similar changes (P > 0.17) to those in
conventional pigs (n ¼ 4). Histologic analyses of the testes revealed no differences (P > 0.2)
in the growth and differentiation of seminiferous tubules between CryoXeno and conventional
pigs. Three conventional sows delivered 13.0 1.0 (mean standard error of the
mean) live piglets after being mated with the three CryoXeno males. Sperm obtained from
all CryoXeno pigs had the ability to penetrate oocytes, and these fertilized oocytes reached
the blastocyst stage in vitro. During the growth of female CryoXeno pigs, the serum inhibin
profile was similar (P > 0.17) to that observed in conventional pigs (n ¼ 5). The first rise in
serum progesterone concentration to more than 2 ng/mL was noted at 32.0 2.3 weeks of
age in the CryoXeno pigs and at 32.0 3.3 weeks in the conventional pigs, suggesting that
both pigs reached puberty at a similar age. After puberty, female CryoXeno pigs farrowed
8.3 1.7 (mean standard error of the mean; n ¼ 3) live piglets after artificial insemination
with semen from a conventional boar. In conclusion, these findings demonstrate
that both male and female CryoXeno pigs have normal reproductive abilities.