The effects of oestrogen receptors α and β on testicular cell number and steroidogenesis in mice

Oestrogen plays an important role in testicular function. This study used mice null for oestrogen receptor α (ERα) or β (ERβ) to investigate which receptor mediates the effects of oestrogen within the testis. Groups of ERα knockout mice (αERKO) and ERβ knockout mice (βERKO) and wild-type littermates (n=5–8) were killed at 11 weeks post partum. One testis was fixed in Bouin’s fluid for stereology and the other frozen for testosterone measurement. Trunk blood was collected for testosterone RIA. The optical disector combined with the fractionator methodology was used to estimate Leydig, Sertoli and germ cell numbers. At all times, the knockout animals were compared with their wild-type littermates. The physical disector quantified cells stained immunohistochemically for the apoptotic marker active caspase-3 and Hoechst staining was used to identify nuclear fragmentation. The mean Leydig cell volume was measured using the point sampled intercept method. The Leydig cell number per testis was significantly increased in βERKO mice but not in αERKO mice. Plasma and testicular testosterone concentrations were increased in αERKO mice but no changes were observed in βERKO mice. Hypertrophic Leydig cell changes were observed in αERKO mice, and a decreased mean cell volume was seen in βERKO mice. No difference in Sertoli cell number per testis was observed in any of the groups. The spermatogonial cell number per testis was increased in βERKO mice. Immunohistochemistry identified increased numbers of active caspase-3-labelled germ cells per testis in αERKO mice but not βERKO mice. Hoechst staining supported these findings. There was significant germ cell loss in αERKO mice. This study suggests that ERβ may be involved in regulation of Leydig cell proliferation and testosterone production in the adult mouse testis.