Postnatal germ cell development during mini-puberty in the mouse does not require androgen receptor: implications for managing cryptorchidism.

PURPOSE

Undescended testis leads to infertility and malignancy resulting from aberrant germ cell development. Androgens are proposed to control early germ cell development during the transient postnatal surge of gonadotropins and androgen, known as mini-puberty. We assessed the effect of androgen receptor on perinatal germ cell development in mice.

MATERIALS AND METHODS

Testes from androgen receptor knockout mice and wild-type littermates (3 to 4 per group) were collected at embryonic day 17 and postnatal days 0 (birth), 2, 4, 6, 8 and 10 for immunohistochemical analysis. Antibodies against mouse VASA homologue (germ cell marker), antimüllerian hormone (Sertoli cell marker), Ki67 (proliferating cell marker) and DAPI (nuclei) were used and visualized by confocal microscopy. Number of germ cells per tubule, germ cells on the tubular basement membrane and Sertoli cells per tubule, and percentage of proliferating germ cells (Ki67(+)) per tubule and germ cells (Ki67(+)) on the basement membrane on confocal images were counted using Image J, version 1.44 (http://imagej.nih.gov/ij/). Data were analyzed using nonparametric one-way ANOVA with GraphPad Prism® 5.02 software.

RESULTS

In wild-type and androgen receptor knockout testes germ cells per tubule decreased from embryonic day 17 to postnatal day 2, then increased normally. Number of mouse VASA homologue positive germ cells per tubule and germ cells on the basement membrane were similar in androgen receptor knockout and wild-type testes (p > 0.05) at each age, and percentages of proliferating germ cells (Ki67(+)) per tubule and proliferating germ cells on the basement membrane were similar at each age (p > 0.05).

CONCLUSIONS

Androgen receptors are not required for gonocyte migration from the center of the testicular tubules to the basement membrane and transformation into spermatogonia stem cells up to day 10 in androgen receptor knockout mice. Identifying nonandrogenic factors might improve the fertility potential of boys with undescended testis who are undergoing orchiopexy.