Role of exosomes in the reproductive tract Oviductosomes mediate interactions of oviductal secretion with gametes/early embryo

The oviductal epithelial membrane releases into the luminal environment extracellular vesicles (EVs) which are pleomorphic in nature and fall into two categories: exosomes and microvesicles. Both of these membrane vesicles are referred to as Oviductosomes (OVS), and to date have been identified in the murine and bovine species. Bovine EVs derived in vivo and from in vitro culture show differences in their protein cargo which includes CD9 and HSC70 biochemical markers and fertility-modulating proteins such as oviduct-specific glycoprotein (OVGP) and Plasma Membrane Ca2+ ATPase 4 (PMCA4). PMCA4, an essential multifunctional sperm protein, is hormonally-regulated with elevated levels seen in proestrus/estrus. OVS deliver PMCA4 to sperm via a fusogenic mechanism involving the interaction between CD9 and integrins which are present on their surfaces. Studies of OVS are needed to determine the components of their cargoes and their interaction with oocytes and the very early embryo. Based on our present knowledge of their interaction with sperm, they are expected to play pivotal roles in regulating fertility and promise to inform the current IVF practice.