Relevance of Aquaporins for Gamete Function and Cryopreservation

Abstract

The interaction between cells and the extracellular medium is of great importance, and drastic changes in extracellular solute concentrations drive water movement across the plasma membrane. Aquaporins (AQPs) are a family of transmembrane channels that allow the transport of water and small solutes across cell membranes. Different members of this family have been identified in gametes. In sperm, they are relevant to osmoadaptation after entering the female reproductive tract, which is crucial for sperm motility activation and capacitation and, thus, for their fertilizing ability. In addition, they are relevant during the cryopreservation process, since some members of this family are also permeable to glycerol, one of the most frequently used cryoprotective agents in livestock. Regarding oocytes, AQPs are very important in their maturation but also during cryopreservation. Further research to define the exact sets of AQPs that are present in oocytes from different species is needed, since the available literature envisages certain AQPs and their roles but does not provide complete information on the whole set of AQPs. This is of considerable importance because, in sperm, specific AQPs are known to compensate the role of non-functional members.

Glycerol-Free Equilibration with the Addition of Glycerol Shortly before the Freezing Procedure: A Perspective Strategy for Cryopreservation of Wallachian Ram Sperm

“…Furthermore, we were not able to demonstrate any significant toxic effect of glycerol in the non-frozen state upon ram spermatozoa by means of flow cytometry (on the contrary, we found a higher viability and higher mitochondrial membrane potential of equilibrated sperm in the GA method over the GFA method). Our results are in line with a previously published study reporting that glycerol can be used by a sperm cell as a source of energy after transporting through sperm aquaporins [ 36 ]. We hypothesized that ram sperm cells equilibrated in the presence of glycerol might better preserve their cellular fitness, as opposed to sperm cells equilibrated without glycerol.…”

Oviducal gland transcriptomics of Octopus maya through physiological stages and the negative effects of temperature on fertilization

“…It is well known that aquaporins are essential for male fertility since they are responsible for the regulation of sperm volume, which is crucial for fertilization. They are also important for the osmotic adaptation of the spermatozoa to different microenvironments until reaching the egg, and for maintaining the osmotic homeostasis for both male and female gametes during fertilization ( Delgado-Bermúdez, Ribas-Maynou & Yeste, 2022 ; Yeung et al, 2009 ; Ribeiro et al, 2021 ). The high expression of sperm genes during the fertilization stage is evidence of the synchronized reactivation of the sperm that was stored in the spermathecae.…”

Aquaporins in the male reproductive system: A chance for paternity or a road to nowhere?

“…According to Delgado‐Bermúdez et al. after entering the female tract, sperm cells swell, as a result of rapid water influx, and their volume increases, resulting in the destabilization of the cell membrane 6 . The proper sperm volume is restored relatively quickly, but it is the destabilization of the membranes caused by excessive water uptake that triggers the entrance of calcium and bicarbonate, which activates sperm capacitation through the protein kinase A signaling pathway that drives hyperactive motility and prepares the spermatozoa to the acrosome reaction.…”

“…After ejaculation, the spermatozoa have to travel a long way before reaching their destination in the female reproductive tract in a hypoosmotic medium.The hypoosmotic environment triggers a series of changes in spermatozoa, in which AQPs appear to play essential roles. According to Delgado-Bermúdez et al after entering the female tract, sperm cells swell, as a result of rapid water influx, and their volume increases, resulting in the destabilization of the cell membrane 6. The proper sperm volume is restored relatively quickly, but it is the destabilization…”