Role of microvesicles in sperm functions

点击翻译按钮获取中文摘要

Spermatozoa are produced in the testis. They have to transit both the male and female reproductive tracts before reaching the vicinity of the egg. The male reproductive tract shows great variability when comparing the anatomy of vertebrate species. One particularity of species practicing internal fertilization is the epididymis. Formed from the Greek epi meaning «on» and didymos «testis», this organ is a long convoluted tubule linking the testis to the vas deferens followed by the ejaculatory duct. In farm animals, the unravelled epididymis can reach 90 m long and sperm transit can take as long as 15 days. The differentiated male gamete is incapable of fertilization upon leaving the testis and it is during epididymal transit that it will acquire its fertilizing ability and its forward motility properties. These modifications are collectively called sperm maturation. During this process, spermatozoa interact with the epididymal intraluminal compartment, which is characterized by an unusual biochemical composition that varies along the epididymis. The epididymal fluid interacts sequentially with the male gamete to modify its biochemical composition and properties: these modifications are necessary for sperm maturation. ***For many years, my studies have focussed on the biochemical modifications involved in sperm maturation. One of our major contributions to the understanding of this critical step in vertebrate male reproductive physiology is the characterization of epididymosomes. These microvesicles are secreted into the lumen of the epididymis and play major roles in sperm modifications. We have shown that the biochemical properties and composition of epididymosomes vary along the epididymis and that they selectively transfer some of their protein constituents to maturing spermatozoa. Our ongoing work is to understand the heterogeneity, the protein composition and the origin of epididymosomes. We also want to understand the molecular mechanisms governing interactions of these vesicles with the maturing spermatozoa. We will also investigate the role of epididymosomes in sperm physiological parameters. Altogether, our research program will bring new understanding to the complex process of sperm processing along the male reproductive tract in vertebrate species. This work will have application to the artificial insemination industry, to reproductive technologies concerned with breeding species and to endangered species preservation. *****