Extracellular vesicles in the male reproductive tract of the softshell turtle.

Extracellular vesicles (EVs) are a heterogeneous group of cell-derived membranous structures comprising exosomes and microvesicles that originate from the endosomal system or are shed from the plasma membrane respectively. As mediators of cell communication, EVs are present in biological fluids and are involved in many physiological and pathological processes. The role of EVs has been extensively investigated in the mammalian male reproductive tract, but the characteristics and identification of EVs in reptiles are still largely unknown. In this review we focus our attention on EVs and their distribution in the male reproductive tract of the Chinese softshell turtle Pelodiscus sinensis , mainly discussing the potential roles of EVs in intercellular communication during different phases of the reproductive process. In softshell turtles, Sertoli-germ cell communication via multivesicular bodies can serve as a source of EVs during spermatogenesis, and these EVs interact with epithelia of the ductuli efferentes and the principal cells of the epididymal epithelium. These EVs are involved in sperm maturation, transport and storage. EVs are also shed by telocytes, which contact and exchange information with other, as well as distant interstitial cells. Overall, EVs play an indispensable role in the normal reproductive function of P. sinensis and can be used as an excellent biomarker for understanding male fertility.