Pretreatment of Asian elephant (Elephas maximus) spermatozoa with cholesterol-loaded cyclodextrins and glycerol addition at 4°C improves cryosurvival

Abstract

Asian elephant spermatozoa are sensitive to chilling and do not respond well to cryopreservation. The objectives of the present study were to: (1) determine whether cholesterol content can be modified by preincubation of Asian elephant spermatozoa with cholesterol-loaded cyclodextrin (CLC); and (2) assess the effects of CLC concentration(s), temperature at time of glycerol addition (22°C vs 4°C) and dilution medium on post-thaw sperm survival. Spermatozoa incubated with ≥1.5 mg CLC exhibited increased (P < 0.05) cholesterol concentrations. Pretreatment of spermatozoa with 1.5 mg CLC resulted in improvements (P < 0.05) in all post-thaw parameters. Glycerol addition at 4°C also improved all post-thaw parameters compared with 22°C. Dilution of thawed spermatozoa in an egg yolk-based medium improved (P < 0.05) motility compared with Ham's F-10 culture medium. In summary, our findings indicate that modifying cholesterol content within the plasma membrane improves the cryosurvival of Asian elephant spermatozoa. The development of an improved cryopreservation method that includes modification of membrane cholesterol and the addition of glycerol at 4°C, as reported in the present study, is an important step towards utilisation of cryopreserved spermatozoa in captive management of this species.

Protective effect of cholesterol-loaded cyclodextrin pretreatment against hydrogen peroxide induced oxidative damage in ram sperm

“…A significant protection was observed against in vitro induced oxidative stress in CLC treated sperm. It is well known that CLC treatment of sperm protects them against harsh influence of freezing and thawing procedure in different animal species [9,[13][14][15]24,26,28,30,33,35,46]. The low concentrations of ROS (Superoxide anion; O 2À and H 2 O 2 ) in semen initiate the sperm capacitation [6], whereas high concentrations of ROS reduce the acrosin activity [48], motility [40], acrosome reaction, fertilizing ability [16] and increase the DNA fragmentation [17].…”

“…The enrichment of CLC in sperm membrane increased the membrane fluidity during cooling and cryopreservation and, decreased upon thawing which enhance the cryosurvival rate [34]. Through this method, the sperm cryosurvival rate of large variety of species including bull [33], ram [24], buck [15], buffalo [35], bison [13], mouse [26], elephant [14], rabbit [28], donkey [30], fish [46] and camel [9] has dramatically been increased. However, some species' sperm like swine [45], equine [27], rooster [44] and feline [32] did not show any improvement in motility, viability and acrosome integrity except membrane integrity.…”

Lactotransferrin in Asian Elephant (Elephas maximus) Seminal Plasma Correlates with Semen Quality

“…This high incidence of variability in ejaculate quality is not only observed among bulls (including bulls of known fertility), but also among ejaculates from the same bull, even if collected on the same day. This lack of consistency and availability of good quality ejaculates has reduced the utility of AI, and also has been a major impediment towards optimizing sperm cryopreservation and establishing a GRB for Asian elephants [4]. Therefore, there is an urgent need to better understand the physiological basis for good versus poor ejaculate quality in elephants.…”

Cholesterol efflux from sperm: approaches and applications

“…Inducing cholesterol in sperm plasma membrane with cyclodextrin molecules (CLCs) (44) enhanced the cryotolerance in rams (45), bulls (46)(47)(48), bucks (49), elephants (50), and stallions (51). This might be due to the fact that increased cholesterol in the sperm cell membrane enhanced the osmotic tolerance and inhibited the acrosome reaction (52).…”