Effects of 2‐hydroxypropyl‐β‐cyclodextrin and cholesterol on porcine sperm viability and capacitation status following cold shock or incubation

Abstract

Porcine sperm are extremely sensitive to the damaging effects of cold shock. It has been shown that cholesterol-binding molecules, such as 2-hydroxypropyl-beta-cyclodextrin (HBCD), improve post-cooling porcine sperm viability when added to an egg yolk-based extender, but also enhance sperm capacitation in other species. The objective of this study was to determine the effects of HBCD and cholesterol 3-sulfate (ChS) on porcine sperm viability and capacitation following cold shock or incubation under conditions that support capacitation using a defined medium. We report here that porcine sperm incubated in medium containing both HBCD and ChS have significantly improved viability following cold shock (10 min at 10 degrees C) when compared to sperm incubated without HBCD or ChS, or with either component alone. Treatment with HBCD plus ChS also completely inhibited the increase in protein tyrosine phosphorylation induced by the cold shock treatment or by incubation for 3 hr under conditions that support capacitation. Two assays of sperm capacitation, the rate of calcium ionophore-induced acrosome reactions and chlortetracycline (CTC) staining, were not significantly altered by HBCD and ChS following cold shock. However, 3-hr incubation with HBCD plus ChS or with 1 mM ChS alone decreased the percentage of sperm undergoing the induced acrosome reaction without significantly affecting viability when compared to the control. These results indicate that the manipulation of sperm plasma membrane cholesterol content affects porcine sperm viability and capacitation status and could therefore be useful to protect sperm from cold shock during cryopreservation by improving viability without promoting premature capacitation.

Substitution of egg yolk by a cyclodextrin-cholesterol complex allows a reduction of the glycerol concentration into the freezing medium of equine sperm

“…Similar results were also reported with equine sperm treated with a small amount of cyclodextrin-cholesterol complex [7]. A 2-hydroxypropyl-beta-cyclodextrin cholesterol (HPbCD-C) complex showed good results for the preservation of pig semen but has never been tested in horses [11].…”

Signal transduction mechanisms involved in in vitro ram sperm capacitation

“…However, it was recently demonstrated in boar sperm (using calcium ionophore-induced AR and protein tyrosine phosphorylation) that although cholesterol efflux does not appear to be necessary for boar sperm capacitation, it could be completely inhibited by incubation with hydroxyl-b-cyclodextrin plus cholesterol sulphate. The cyclodextrin delivers the cholesterol sulphate to the plasma membrane and increases the C:P ratio blocking capacitation (Galantino-Homer et al 2006). Further investigations to prove this effect in ram sperm have to be done, as the concentration of cholesterol sulphate that inhibited boar sperm capacitation was much higher than that used in our study.…”

Current Concepts of Molecular Events During Bovine and Porcine Spermatozoa Capacitation

“…In contrast to the tight correlations between protein tyrosine phosphorylation and conditions supporting sperm capacitation in other species, p32 tyrosine phosphorylation can be dissociated from porcine sperm capacitation and is not dependent upon the presence of albumin or bicarbonate [Tardif et al 2003]. Tyrosine phosphorylation of p32 in porcine sperm is also induced by cold shock, correlating with cell death, suggesting that it may relate to a cytotoxicity pathway in this species or that it is regulated differently during cold shock and capacitation [Galantino-Homer et al, 2006;Vadnais and Roberts 2006].…”

“…Similarly, porcine spermatozoa capacitation is dependent upon calcium and bicarbonate, but does not appear to require albumin, possibly due to the remarkably low cholesterol: phospholipid ratio of porcine spermatozoa [Althouse 1992;Tardif et al 2003]. However, porcine spermatozoa capacitation can be inhibited by an increase in membrane cholesterol mediated by cyclodextrin (Galantino-Homer et al 2006).…”