Lipid Remodeling of Murine Epididymosomes and Spermatozoa During Epididymal Maturation1

Abstract

We have isolated vesicular structures from mouse epididymal fluid, referred to as epididymosomes. Epididymosomes have a roughly spherical aspect and a bilayer membrane, and they are heterogeneous in size and content. They originate from the epididymal epithelium, notably from the caput region, and are emitted in the epididymal lumen by way of apocrine secretion. We characterized their membranous lipid profiles in caput and cauda epididymidal fluid samples and found that epididymosomes were particularly rich in sphingomyelin (SM) and arachidonic acid. The proportion of SM increased markedly during epididymal transit and represented half the total phospholipids in cauda epididymidal epididymosomes. The cholesterol:phospholipid ratio increased from 0.26 in the caput to 0.48 in the cauda epididymidis. Measures of epididymosomal membrane anisotropy revealed that epididymosomes became more rigid during epididymal transit, in agreement with their lipid composition. In addition, we have characterized the membrane lipid pattern of murine epididymal spermatozoa during their maturation. Here, we have shown that mouse epididymal spermatozoa were distinguished by high percentages of SM and polyunsaturated membranous fatty acids (PUFAs), principally represented by arachidonic, docosapentanoic, and docosahexanoic acids. Both SM and PUFA increased throughout the epididymal tract. In particular, we observed a threefold rise in the ratio of docosapentanoic acid. Epididymal spermatozoa had a constant cholesterol:phospholipid ratio (average, 0.30) during epididymal transit. These data suggest that in contrast with epididymosomes, spermatozoal membranes seem to become more fluid during epididymal maturation.

Cystatin-related epididymal spermatogenic subgroup members are part of an amyloid matrix and associated with extracellular vesicles in the mouse epididymal lumen

“…In other cell systems, exosomes are usually formed in the endosomal compartments that contain multivesicular bodies which then fuse with the plasma membrane to release the vesicles (Yanez-Mo et al, 2015). Larger vesicles up to 1000 nm have also previously been described in the rodent epididymal lumen, as were multivesicular bodies, suggesting there may be several populations of extracellular vesicles in the epididymal lumen that are released from distinct cell types by different mechanisms and that this may vary between species (Rejraji et al, 2006;Caballero et al, 2013). Our studies showing that the apical bleb in narrow/apical cells contained the tetraspanin CD9, a marker for exosomes and that CD9 positive vesicles were observed distal to the intermediate zone suggests that narrow/apical cells may also release exosomes but possibly by the more conventional mechanism involving endosomes and multivesicular bodies and that these vesicles in the epididymis may be larger in size.…”

Methyl-parathion decreases sperm function and fertilization capacity after targeting spermatocytes and maturing spermatozoa

“…During epididymal transit (7 dpt) sperm plasma membrane undergoes substantial remodeling (Dacheux et al, 2005) and mouse epididymal spermatozoa are characterized by high percentages of sphingomyelin and PUFA, mainly arachidonic, docosapentanoic and docosahexanoic acids that confer fluidity to sperm membranes (Rejraji et al, 2006). In addition, considering that most of sperm functions required for fertilization are developed in the epididymis, such as motility, zona binding and membrane fusion abilities (Cooper, 2007), it is not far fetched to hypothesize that a disturbed maturation of epididymal spermatozoa by Me-Pa exposure could impact their fertilizing capacity.…”

Efficiency of selenium in attenuating epididymal histopathological changes in hypercholesterolaemic adult rat

“…These changes were also associated with a reduction in motility percentage and appearance of abnormal sperm morphology. In an attempt to explain the mechanism by which hypercholesterolaemia produced deleterious effects on male fertility, Rejraji et al [21] reported that lipid homeostasis is of particular importance in germ cells. These cells undergo different modifications in lipid concentrations, especially cholesterol, desmosterol and phospholipids during their differentiation.…”