Changes in lipids and membrane anisotropy in human spermatozoa during epididymal maturation

Abstract

Previously it was demonstrated that immature and immotile human spermatozoa from the caput epididymides developed a good progressive motility after in-vitro stimulation with phosphatidylcholine (PC). In order to define the role of PC and membrane anisotropy in epididymal maturation and to determine the exact lipid composition of human spermatozoa during epididymal maturation, spermatozoa from seven epididymides from patients who underwent orchiectomy because of prostatic cancer were investigated. Lipids were determined by high-performance thin-layer chromatography and gas chromatography. Membrane anisotropy was measured by fluorescence polarization. The ratio between PC and phosphatidylserine (PS) plus phosphatidyl ethanolamine (PE) plus sphingomyelin (SM) was significantly higher in spermatozoa from the cauda compared to those from the caput and corpus. This was due to an increase of PC and a decrease of the concentration of PS plus PE plus SM. With regard to fatty acids, those with saturated chains predominated in caput spermatozoa while the highest concentration of unsaturated long-chain fatty acids was in cauda spermatozoa. A lower membrane anisotropy of cauda spermatozoa compared with caput or corpus spermatozoa was found. In conclusion, during epididymal maturation human spermatozoa integrate lipids, particularly PC, which is strongly associated with the induction of progressive motility. A change in the pattern of fatty acids and a decrease in the cholesterol/phospholipid molar ratio cause a decrease in membrane anisotropy in cauda spermatozoa.

Sterols in spermatogenesis and sperm maturation

“…The cholesterol content of sperm membranes is decreased during epididymal transit in several species, resulting in the decreased ratio of cholesterol (CH) to phospholipids (PL) ( 48 ). The loss of cholesterol results in an increase in sperm membrane fl uidity and sperm motility ( 71 ). The content of cholesterol in the sperm membrane is further decreased in the female reproductive tract, mostly by the process of capacitation.…”

“…In some species, cholesterol content increased during sperm maturation ( 69 ) or remained unchanged ( 70 ). The loss of cholesterol is known to increase the fl uidity of sperm membranes, as demonstrated in human spermatozoa ( 71 ), which might be necessary for the fi nal steps of sperm maturation in the female reproductive tract. The importance of the stage-specifi c sterol content of sperm membranes is additionally demonstrated by the presence of vesicular formations produced and secreted by the prostate, known as prostatic secretory granules or prostasomes.…”

Nuclear oxysterol receptors, LXRs, are involved in the maintenance of mouse caput epididymidis structure and functions

“…Cholesterol is also important when it comes to post-testicular maturation of spermatozoa. A well-documented feature of epididymal maturation of spermatozoa is either their progressive loss of cholesterol while they transit through the organ or a decrease in the cholesterol/phospholipid molar ratio via the uptake of phospholipids into the sperm plasma membrane (Haidl & Opper 1997). This results in changes in the sperm plasma membrane ability to fuse with the oocyte.…”

Mountant-induced loss of Shorr-stained blue sperm tails

“…(2010) plasma or liposomes was correlated with more red tails [5,6] and corpus spermatozoa showed parallel increases in motility and red-staining after pentoxyfylline and phospholipid treatment [6]. As the sperm cholesterol/ phospholipid ratio decreases upon epididymal maturation [7], lipid components may be eliminated from immature spermatozoa affecting flagellar motility and red staining; indeed, impaired epididymal sperm maturation reflected in asthenozoospermia results in blue sperm-tail staining [8]. These interesting observations, generated by one laboratory, need confirmation.…”

“…As the sperm cholesterol/ phospholipid ratio decreases upon epididymal maturation [7], lipid components may be eliminated from immature spermatozoa affecting flagellar motility and red staining; indeed, impaired epididymal sperm maturation reflected in asthenozoospermia results in blue sperm-tail staining [8]. These interesting observations, generated by one laboratory, need confirmation.…”