Sperm Membrane Behaviour during Cooling and Cryopreservation

Abstract

Contents Native sperm is only marginally stable after collection. Cryopreservation of semen facilitates transport and storage for later use in artificial reproduction technologies, but cryopreservation processing may result in cellular damage compromising sperm function. Membranes are thought to be the primary site of cryopreservation injury. Therefore, insights into the effects of cooling, ice formation and protective agents on sperm membranes may help to rationally design cryopreservation protocols. In this review, we describe membrane phase behaviour of sperm at supra‐ and subzero temperatures. In addition, factors affecting membrane phase transitions and stability, sperm osmotic tolerance limits and mode of action of cryoprotective agents are discussed. It is shown how cooling only results in minor thermotropic non‐cooperative phase transitions, whereas freezing causes sharp lyotropic fluid‐to‐gel phase transitions. Membrane cholesterol content affects suprazero membrane phase behaviour and osmotic tolerance. The rate and extent of cellular dehydration coinciding with freezing‐induced membrane phase transitions are affected by the cooling rate and ice nucleation temperature and can be modulated by cryoprotective agents. Permeating agents such as glycerol can move across cellular membranes, whereas non‐permeating agents such as sucrose cannot. Both, permeating and non‐permeating protectants preserve biomolecular and cellular structures by forming a protective glassy state during freezing.

Characteristics of the post-thawed Balinese bull semen extended in three different extenders and equilibration times

“…Sperm membrane is the main site of damage from freezing process because of the freezing deteriorating effect on the sperm phospholipids and the loss of cholesterol. (Sieme et al, 2015). In the present study, hypo-osmotic swelling (HOS) test was used as a predictor of the functional integrity of sperm plasma membrane in sperm tail area.…”

Cryopreservation of human spermatozoa with minimal non-permeable cryoprotectant

“…It has also been shown that trehalose can enter red blood cells [14], and blood platelets [11,27] in significant concentrations when the temperature is lowered through Tm. The cell membrane of mammalian spermatozoa also undergoes a phase transition, associated with leakiness, as the temperature is lowered through T m [9,24]. Although we have no direct evidence, trehalose might have entered our spermatozoa at a critical Tm when they were cooling in the LN2 vapor where it would protect the cell membranes and later participate in the formation of a favorable glass in the specimen [12,19], possibly protecting cells from subsequent chilling and warming injuries.…”

Membrane stability and mitochondrial activity of bovine sperm frozen with low‐density lipoproteins and trehalose

“…Throughout the freezing and thawing process, spermatozoa are subjected to thermal, osmotic and oxidative stresses that result in alterations in the plasma membrane, reducing their functionality and compromising the results of fertilization (Beran et al, ; Sieme, Oldenhof, & Wolkers, ). During bovine sperm cryopreservation, the plasma membrane is the most affected structure because it may suffer from severe swelling or complete loss (Khalil, El‐Harairy, Zeidan, Hassan, & Mohey‐Elsaeed, ).…”