Abstract
Cell-secreted vesicles, such as exosomes, have recently been recognized as mediators of cell communication. A recent study in cattle showed the involvement of exosome-like vesicles in the control of cumulus expansion, a prerequisite process for normal ovulation; however, whether this is the case in other mammalian species is not known. Therefore, this study aimed to examine the presence of exosome-like vesicles in ovarian follicles and their effects on cumulus expansion in vitro in pigs. The presence of exosome-like vesicles in porcine follicular fluid (pFF) was confirmed by transmission electron microscopic observation, the detection of marker proteins, and RNA profiles specific to exosomes. Fluorescently labeled exosome-like vesicles isolated from pFF were incorporated into both cumulus and mural granulosa cells in vitro. Exosome-like vesicles were not capable of inducing cumulus expansion to a degree comparable to that induced by follicle-stimulating hormone (FSH). Moreover, exosome-like vesicles had no significant effects on the expression levels of transcripts required for the normal expansion process (HAS2, TNFAIP6, and PTGS2). Interestingly, FSH-induced expression of HAS2 and TNFAIP6 mRNA, but not of PTGS2 mRNA, was significantly increased by the presence of exosome-like vesicles; however, the degree of FSH-induced expansion was not affected. In addition, porcine exosome-like vesicles had no significant effects on the expansion of mouse cumulus-oocyte complexes. Collectively, the present results suggest that exosome-like vesicles are present in pFF, but they are not efficient in inducing cumulus expansion in pigs.