Temporal leakage of Cu,Zn superoxide dismutase and loss of two low-molecular-weight forms of glutathione peroxidase-1 from buffalo (Bubalus bubalis) sperm after freezing and thawing

Differential proteome between ejaculate and epididymal sperm represents a key factor for sperm freezability in wild small ruminants

Epididymal sperm shows higher cryoresistance than ejaculated sperm. Although the sperm proteome seems to affect cell cryoresistance, studies aiming at identifying proteins involved in sperm freezing-tolerance are scarce. The aims of this study were to investigate differences of sperm freezability and proteome between epididymal and ejaculated sperm in three mountain ungulates: Iberian ibex, Mouflon and Chamois. Sperm samples were cryopreserved in straws by slow freezing. Tandem mass tag-labeled peptides from sperm samples were analyzed by high performance liquid chromatography coupled to a mass spectrometer in three technical replicates. The statistical analysis was done using the moderated t-test of the R package limma. Differences of freezability between both types of sperm were associated with differences of the proteome. Overall, epididymal sperm showed higher freezability than ejaculated sperm. Between 1490 and 1883 proteins were quantified in each species and type of sperm sample. Cross species comparisons revealed a total of 76 proteins that were more abundant in epididymal than in ejaculated sperm in the three species of study whereas 3 proteins were more abundant in ejaculated than epididymal sperm in the three species of study (adjusted P < 0.05; |log₂| fold-change > 0.5). Many of the proteins that were associated with higher cryoresistance are involved in stress response and redox homeostasis. In conclusion, marked changes of sperm proteome were detected between epididymal and ejaculated sperm. This work contributes to update the sperm proteome of small ruminants and to identify candidate markers of sperm freezability.

Reduced cytochrome oxidase activity and increased protein tyrosine phosphorylation of mitochondria-rich fractions of buffalo (Bubalus bubalis) spermatozoa after a cycle of freezing and thawing

The motility and fertility of mammalian spermatozoa are compromised when they are cryopreserved. Sperm mitochondrial proteins play a vital role in conferring motility. However, the effects of cryopreservation on mitochondria-specific proteins remain primarily unexplored in domestic animals, including buffaloes, so the present study aimed to evaluate this issue. Mitochondria were isolated from both non-cryopreserved and cryopreserved buffalo spermatozoa by sonication followed by sucrose density gradient ultracentrifugation. The purity of the mitochondrial preparation was assessed by cytochrome oxidase assay and electron microscopy. Mitochondria separated from cryopreserved buffalo spermatozoa were associated with significantly lower (P ≤ 0.05) cytochrome oxidase activity as compared with non-cryopreserved spermatozoa. The intensities of two low-molecular-mass mitochondrial proteins (30.1 kDa and 26.1 kDa) were significantly reduced as compared with the non-cryopreserved group. In addition, in cryopreserved buffalo sperm mitochondria, the intensities of three tyrosine phosphorylated proteins (126.6, 106.7 and 26 kDa) increased significantly compared with the non-cryopreserved group. Of these, tyrosine phosphorylation of the 26-kDa mitochondrial protein of cryopreserved sperm was very intense and unique because it could not be detected in the mitochondria of non-cryopreserved sperm. Thus, the study confirmed that both cytochrome oxidase activity and the proteins of buffalo sperm mitochondria undergo significant cryogenic changes in terms of quantity and quality after a cycle of freezing and thawing and this may be one of the important causes of reduced post-thaw motility and fertility of cryopreserved buffalo spermatozoa.

Dynamics of HSPA1A and redox status in the spermatozoa and fluid from different segments of goat epididymis

The present study was attempted to investigate the dynamics of HSPA1A and redox status in the spermatozoa and fluid of different segments of buck epididymis. Testes were collected from sexually mature and healthy bucks aged between 2 and 3 years. The fluid and spermatozoa from different segments (caput, corpus and cauda) were harvested for further processing and analysis. The concentration of HSPA1A in spermatozoa lysate and epididymal fluid and its relative mRNA expression in spermatozoa from different segments of epididymis were studied. The HSPA1A concentration in epididymal fluid was significantly (P < 0.01) higher in the corpus as compared with caput and cauda, whereas, its concentration and relative mRNA expression decreased significantly (P < 0.01) in the spermatozoa from caput to cauda. The activities of SOD, GR, GST, and concentrations of manoldialdehyde and ROS decreased significantly (P < 0.01) in the spermatozoa from caput to cauda. The glutathione concentration and GPx activity decreased significantly (P < 0.01) in the spermatozoa of cauda as compared with the corpus. The SOD activity and ROS concentration were significantly (P < 0.01) higher in corpus, and GR and GST activity were significantly (P < 0.01) higher in caput fluid as compared with corpus and cauda. It may be concluded that HSPA1A concentration and its relative mRNA expression in spermatozoa decreased progressively, and redox status was altered during transit from caput to cauda.

Sperm antioxidant defences decrease during epididymal transit from caput to cauda in parallel with increases in epididymal fluid in the goat (Capra hircus)

The status of antioxidant defences of both spermatozoa and their associated fluids during epididymal transit from the caput to cauda have not been studied so far in any species. Herein we report for the first time that sperm antioxidant defences, namely Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and catalase activity, decrease significantly (P<0.05) from the caput to cauda during epididymal transit in parallel with increases in Cu,Zn-SOD, total SOD and total glutathione peroxidase (GPx) activity in the luminal fluid of the respective segments. However, levels of GPX1 and GPX3 in epididymal fluid did not change significantly from the caput to cauda. Catalase was detected for the first time in goat spermatozoa. A significantly higher total antioxidant capacity of caudal fluid than of the caput suggests a requirement for a rich antioxidant environment for the storage of spermatozoa. The retention of cytoplasmic droplets in most of the caudal spermatozoa confirmed that these droplets do not contribute to the increased antioxidant defences of cauda epididymidal fluid. Thus, the antioxidant defences of the spermatozoa and their associated epididymal fluid are modulated from the caput to cauda in a region-specific manner. This may be one of the compensatory mechanisms of epididymal fluid to scavenge any excess reactive oxygen species produced in the microenvironment of spermatozoa.

Study on correlation of sperm quality parameters with antioxidant and oxidant status of buffalo bull semen during various stages of cryopreservation

This investigation was carried out to study the correlation of sperm quality parameters with antioxidant and oxidant status of buffalo bull semen during various stages of cryopreservation. Semen samples were evaluated for sperm parameters (mass motility [MM], concentration [CON], progressive motility [PM], viability [VIB], acrosomal integrity [AI] and hypo-osmotic swelling [HOS] response), antioxidants (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx] and total antioxidant capacity [TAC]) and oxidants (Lipid peroxidation [LPO] and reactive oxygen species [ROS]) at fresh, pre-freeze and post-thaw stages. Sperm parameters (PM, VIB, AI and HOS response) and antioxidants (SOD, CAT and TAC) were significantly (p < .05) reduced at fresh stage, and oxidants (LPO and ROS) were significantly (p < .05) increased at pre-freeze and post-thaw stages. At fresh stage, MM was negatively correlated with LPO (p < .05), and CON was positively correlated with SOD, TAC and CAT, negatively correlated with LPO and CAT was positively (p < .01) correlated with VIB and HOS response. At pre-freeze stage, CAT was positively correlated with PM and AI (p < .05), and AI was negatively (p < .05) correlated with ROS. At post-thaw stage, CAT was positively correlated with PM, VIB, HOS response and AI,, and LPO was negatively correlated with HOS, AI and VIB. The study of correlations of these parameters at different preservation stages with bull fertility may play an important role in developing models for predicting future fertility of bulls in the absence of conception rate data.

Identification of protein changes in human spermatozoa throughout the cryopreservation process

Cryoinjury is a consequence of cryopreservation and may have a negative impact on sperm quality regarding motility, morphology, and viability. This study was designed to identify potential proteomic changes in human sperm cells throughout the cryopreservation process. Comparisons made within this study included the detection of the sperm proteomic changes induced by incubation of the sperm cells with a protein-free cryoprotectant (with and without CryoSperm), and the proteomic changes induced by freezing, thawing, and subsequent after-thawing incubation at two different temperatures (0 °C vs. 23 °C). Tandem Mass Tag (TMT) peptide labeling coupled with LC-MS/MS was used for protein quantification. LC-MS/MS resulted in the identification of 769 quantifiable proteins. The abundance of 105 proteins was altered upon CryoSperm incubation. Freezing and thawing also induced substantial protein changes. However, fewer changes were observed when semen was thawed and then maintained after-thawing at approximately 0 °C than when it was maintained after-thawing at 23 °C, with 60 and 99 differential proteins detected, respectively, as compared to unfrozen semen incubated in CryoSperm. Collectively, these differences indicate that substantial changes occur in the sperm proteome at every stage of the cryopreservation process which may ultimately impair the sperm fertilizing capability. This is the first study to compare protein levels in fresh and cryopreserved semen using the TMT technology coupled to LC-MS/MS.