Alterations of basal lamina of the seminiferous epithelium during the seasonal suppression of spermatogenesis in the Japanese monkey (Macaca fuscata)

Primate spermatogenesis is characterized by yet unidentified mechanisms to regulate its rate-limiting process, spermatogonial proliferation. In the previous study using a seasonal breeder, Japanese monkey (Macaca fuscata), we demonstrated that the spermatogonial proliferation is suppressed through cytoplasmic liberation of PGP 9.5 when the spermatogenetic activity declines in the nonbreeding season. By comparing the morphology of the seminiferous tubules between the breeding and nonbreeding seasons, the present study demonstrates that in the nonbreeding season a basal lamina of seminiferous epithelium, with which spermatogonia directly keep contact, enlarges its extent at levels of lamina densa and lamina fibroreticularis. and is frequently invaginated. The invagination is composed of only the three laminae, not of cell components. The invaginations expand contact area between the spermatogonia and the basal lamina. which would interrupt spermatogonial proliferation. An ultrastructural distribution of laminin suggests that the invagination during the nonbreeding season is due to rearrangement of laminin molecules inside the basal lamina. The present results indicate that the alteration of the basal lamina of the seminiferous epithelium would mediate effects of the hormonal regulators and enable the fully restorable, transient suppression of spermatogenesis in primate.