Signalling pathways regulating the blood-testis barrier.

Throughout mammalian spermatogenesis, preleptotene/leptotene spermatocytes traverse the blood-testis barrier during stages VIII-XI of the seminiferous epithelial cycle while trapped within a dynamic intermediate compartment that is sealed at north and south poles by tight junctions, basal ectoplasmic specializations, desmosomes and gap junctions. In order for spermatocytes to gain entry into the adluminal compartment of the seminiferous epithelium for continued development, 'old' junctions present above migrating spermatocytes disassemble, while 'new' junctions assemble simultaneously below these germ cells. In this way, the integrity of the blood-testis barrier and the homeostasis of the seminiferous epithelium can remain intact during spermatogenesis. Previous studies have shown an array of cellular events, including protein internalization and cytoskeletal remodeling, to underline blood-testis barrier restructuring, whereas other studies have reported BTB dysfunction to associate with activation of the p38 mitogen-activated protein kinase pathway. Herein, we discuss the signaling pathways and mechanisms involved in blood-testis barrier restructuring in the mammalian testis.