The role of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) in comparison with whole egg yolk for sperm cryopreservation in rhesus monkeys

Abstract

Low-density lipoprotein (LDL) extracted from hen egg yolk has recently been considered to be superior to whole egg yolk in sperm cryopreservation of various animal species. Meanwhile, there was a notion that high-density lipoprotein (HDL) in egg yolk may have a negative effect on post-thaw survival. The role of LDL and HDL in sperm cryopreservation of rhesus monkeys has not been explored. The present study evaluates their effect in comparison with egg yolk with or without the addition of permeable cryoprotectant (glycerol) on sperm cryopreservation of rhesus macaques. In addition, various additives intended to change the lipid composition of LDL-sperm membrane complex have also been tested for their effectiveness in preserving post-thaw viability. Our findings indicated that LDL is the main component in egg yolk that is responsible for its protective role for sperm cryopreservation in rhesus monkeys. Regardless of the presence or absence of glycerol, the protective role of LDL is similar to that of egg yolk and we did not observe any superiority in post-thaw survival with LDL when compared to egg yolk. Modifying the lipid composition of LDL-sperm membrane complex with the addition of cholesterol, cholesterol loaded cyclodextrin and phosphatidylcholine also did not yield any improvements in post-thaw survival; while addition of methyl-b-cyclodextrin reduced post-thaw motility. HDL plays a neutral role in sperm cryopreservation of rhesus monkeys. The present study suggests that egg yolk may still hold advantages when compared with LDL as effective components in extenders for sperm cryopreservation in rhesus monkeys.

Use of phosphatidylcholine in Tris-based extender with or without egg yolk to freeze Bapedi ram semen

“…In the present study, frozen-thawed semen extended with egg yolk and without PC liposome resulted in higher sperm motility rates such as TM, PM, RM, VCL, VSL, and VAP compared with extender without egg yolk. The extenders containing egg yolk, with or without PC liposome were able to maintain the VCL, VSL and VAP of the spermatozoa, characteristics that have been linked to fertility (Del Olmo et al, 2013).The biochemical composition of egg yolk, which includes phospholipids, cholesterol and low-density lipoproteins, makes it an excellent cryoprotective ingredient of the extender used in freezing semen (Kulaksiz et al, 2010;Dong et al, 2011;Toker et al, 2016). But because the composition of egg yolk is variable and may carry pathogens, an alternative cryoprotective agent for use in freezing semen would be desirable.…”

“…Egg yolk is a reliable cryoprotective component of the extender that is used when freezing semen owing to its ability to protect the spermatozoa against cold shock (Amirat et al, 2004;Kulaksiz et al, 2010;Dong et al, 2011;Toker et al, 2016). However, its use has been disputed because of the risk of introducing disease (Chelucci et al, 2015) and owing to inconsistency in its biochemical composition (Kulaksiz et al, 2010;Emamverdi et al, 2013).…”

Coconut water-based extender for seminal preservation in small ruminants: A meta-analysis study

“…Since the discovery of the protective effect exerted by egg yolk on sperm preservation, this cryoprotectant has been widely used with considerable efficiency in seminal dilution, protecting sperm from heat stress and preserving their functions after storage (Phillips, 1939;Barak et al, 1992;Bergeron et al, 2004;Dong et al, 2011).…”

Cryopreservation in mammalian conservation biology: current applications and potential utility

“…4,[55][56][57] Glycerol (4%-6%) in the CPA allows the recovery of thawed spermatozoa in a diverse range of species including felids, 55,58 marine mammals, 59,60 Asian elephants (Elephas maximus), 61,62 rhinos (Ceratotherium simum, C.s. cottoni), 63 leopards (Neofelis nebulosa), 64 bears (Ursus arctos), 65 monkeys (rhesus monkeys), 66 collared peccaries (Pecari tajacu), 57 and many other species. Although glycerol is used for sperm cryopreservation of a wide range of species, some studies point out that there are some restrictions in its use due to its cytotoxic effects.…”