The participation of extracellular vesicles in many cellular processes, including reproduction, is unquestionable. Although currently, the tetraspanin proteins found in extracellular vesicles are mostly applied as markers, increasing evidence points to their role in extracellular vesicle biogenesis, cargo selection, cell targeting, and cell uptake under both physiological and pathological conditions. In this review, we bring other insight into the involvement of tetraspanin proteins in extracellular vesicle physiology in mammalian reproduction. We provide knowledge regarding the involvement of extracellular vesicle tetraspanins in these processes in somatic cells. Furthermore, we discuss the future direction towards an understanding of their functions in the tissues and fluids of the mammalian reproductive system in gamete maturation, fertilization, and embryo development; their involvement in mutual cell contact and communication in their complexity.

Mammalian spermatozoa, produced by the testes, must undergo maturation in the epididymis to gain the ability to fertilize an ovum. This process includes structural modifications, such as changes in the lipid and protein composition of the plasma membrane. The CD81 and CD9 proteins, which are members of tetraspanin superfamily, have been found to be involved in the fertilization process. Our study examined the presence of CD81 in the bull testis and epididymis, and then compared CD81’s distribution profile with that of the molecule CD9. We detected CD81 in the basement membrane along the whole epididymis. In comparison, an abundant expression of CD9 molecule was found in the testis as well as in all three segments of the epididymis. Both molecules are part of the tetraspanin web, and are considered key elements in the sperm-egg interaction.