Functions of epidymosomes in sperm maturation

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In the mammalian male reproductive tract, the spermatozoa have to transit along the epididymis. The epididymis is a long, single convoluted tubule located between the testis (vas efferens) and the ejaculation duct (vas deferens). The length of the unravelled epididymis varies from one species to the other. It is estimated to be 5-7 meters in men and as long as 40 and 80 meters in bull and stallion respectively. The epididymal transit time for spermatozoa is of three to twelve days depending on the species. The epididymal epithelium secretes proteins within the intraluminal compartment that interact with the transiting spermatozoa. The pattern of proteins secreted in the intraluminal compartment varies along the epididymis, modifying the maturing male gamete in a sequential manner. The epididymis plays different functions which are essential for male fertility. It is involved in sperm transport, concentration, maturation, and storage. The proximal part of the epididymis is responsible for sperm maturation i.e. the acquisition of fertilizing ability whereas the distal portion of the epididymidis is involved in sperm storage ensuring that male gametes are available in sufficient number at ejaculation. Since many years my laboratory investigates the function of the epididymis to understand how spermatozoa acquire their fertilizing ability during its transit along this organ. The objective of this research program is to understand how proteins are transferred to spermatozoa and how the addition of these new molecules modulates sperm functions. This research program may leads to in vitro strategies to increase fertility of spermatozoa of high genetic values bulls presenting with low fertility.