Abstract
BackgroundCryopreservation is currently the most efficient method for long-term preservation of mammalian gametes and is extensively used in swine artificial insemination (AI) centres. However, it is well-known that cryopreservation procedures induce changes in the water phase in both intra and extracellular compartments, which alter the content and localisation of several proteins and ends up curtailing the structural integrity of functional sperm (i.e., cryoinjuries). Alterations and deficiencies of sperm-oocyte binding proteins during gamete recognition are one of the causes of reproductive failure both in vitro and in vivo. In this sense, characterisation of cryopreservation effects upon oocyte-binding proteins of sperm, such as IZUMO1 and GSTM3, is essential when assessing the impact of this technique in swine reproduction.ResultsCryopreservation was found to induce changes in the localisation of IZUMO1 and GSTM3 in boar sperm. However, the relative content of both proteins was not altered after thawing. Furthermore, whereas IZUMO1 content was found not to be related to the cryotolerance of boar sperm, GSTM3 content was observed to be higher in poor (PFE) than in good (GFE) freezability ejaculates in both pre-frozen (1.00 INT·mm2 ± 0.14 INT·mm2 vs. 0.72 INT·mm2 ± 0.15 INT·mm2; P < 0.05) and post-thawed (0.96 INT·mm2 ± 0.20 INT·mm2 vs. 70 INT·mm2 ± 0.19 INT·mm2; P < 0.05) samples. Moreover, GSTM3 levels were found to be higher in those spermatozoa that exhibited low mitochondrial activity, high reactive oxygen species (ROS) production, and high membrane lipid disorder post-thaw (P < 0.05).ConclusionsThe difference in GSTM3 content between GFE and PFE, together with this protein having been found to be related to poor sperm quality post-thaw, suggests that it could be used as a cryotolerance marker of boar spermatozoa. Furthermore, both IZUMO1 and GSTM3 relocate during cryopreservation, which could contribute to the reduced fertilising capacity of frozen-thawed boar sperm.
Highlights
Sperm cryopreservation is currently the most efficient method for long-term storage of mammalian gametes for artificial insemination (AI)
Classification of boar ejaculates in good freezability ejaculates (GFE) and poor freezability ejaculates (PFE) groups Sperm viability assessed at 30 min post-thaw was used to classify ejaculates as GFE and PFE
No differences were found between groups in pre-frozen samples (P > 0.05), sperm total and progressive motility, and viability were higher (P < 0.05) in GFE than in PFE at both 30 and 240 min post-thaw (Table 1)
Summary
Sperm cryopreservation is currently the most efficient method for long-term storage of mammalian gametes for artificial insemination (AI). Llavanera et al Journal of Animal Science and Biotechnology (2019) 10:61 lower than or equal to 5 °C lead to the destabilisation of sperm plasma membrane [2] This leads to protein translocation and/or loss of function, thereby being a potential cause of subfertility in frozen-thawed sperm [2]. Cryopreservation is currently the most efficient method for long-term preservation of mammalian gametes and is extensively used in swine artificial insemination (AI) centres. It is well-known that cryopreservation procedures induce changes in the water phase in both intra and extracellular compartments, which alter the content and localisation of several proteins and ends up curtailing the structural integrity of functional sperm (i.e., cryoinjuries). Characterisation of cryopreservation effects upon oocyte-binding proteins of sperm, such as IZUMO1 and GSTM3, is essential when assessing the impact of this technique in swine reproduction
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