A new test based on the hypotonic resistance and functional competence to evaluate the sperm quality, cryotolerance and in vitro fertilizing ability in pigs

NPC2, a seminal plasma protein with membrane cholesterol-binding ability, influences the cryotolerance and functionality of spermatozoa from Chino Santandereano bulls

Despite Latin America's rich biodiversity, active genetic material conservation programs are scarce. This study investigates potential freezability markers in both sperm and seminal plasma (SP) in Chino Santandereano, a Colombian Creole breed. Thirty ejaculates from ten Chino Santandereano bulls were cryopreserved and subsequently classified as of good (GFE) or poor (PFE) freezability according to their post-thaw total sperm motility (TMOT) and plasma membrane integrity (PMI). Sperm cholesterol and NPC2 protein levels in SP were measured prior to cryopreservation using colorimetric detection, densitometric quantification, and Western blot. Sperm functional competence (SFC), a functional test, was evaluated before and after cryopreservation. Correlation and t-student tests, a binomial regression model and two multiple linear regression models were utilized to evaluate the predictive power of NPC2 protein and sperm related variables. Two bands (14 kDa and 15 kDa) for NPC2 protein were identificated. NPC2 14 kDa is associated with a significant decrease in freezability (P < 0.01). The TMOT in fresh semen highly significant (P < 0.01) for sperm freezability and the interaction between NPC2 14 kDa and cholesterol content in sperm was significant (P < 0.01). Correlation between SFC and TMOT and PMI post-thaw (P < 0.01), along with the significantly different values between PFE and GFE (P < 0.05) were observed. We can conclude that NPC2 protein as a marker for sperm freezability of Chino Santandereano bull, and this depends on sperm content of cholesterol. In addition, our findings support the utility SFC combined tests in providing a precise assessment of sperm freezability.

Clustering of spermatozoa examined through flow cytometry provides more information than the conventional assessment: a resilience to osmotic stress example

Context Conventional sperm quality tests may not be sufficient to predict the fertilising ability of a given ejaculate; thus, rapid, reliable and sensitive tests are necessary to measure sperm function. Aims This study sought to address whether a cluster analysis approach based on flow cytometry variables could provide more information about sperm function. Methods Spermatozoa were exposed to either isotonic (300mOsm/kg) or hypotonic (180mOsm/kg) media for 5 and 20min, and were then stained with SYBR14 and propidium iodide (PI). Based on flow cytometry dot plots, spermatozoa were classified as either viable (SYBR14+ /PI- ) or with different degrees of plasma membrane alteration (SYBR14+ /PI+ and SYBR14- /PI+ ). Moreover, individual values of electronic volume (EV), side scattering (SS), green (FL1) and red (FL3) fluorescence were recorded and used to classify sperm cells through cluster analysis. Two strategies of this approach were run. The first one was based on EV and the FL3/FL1 quotient, and the second was based on EV, SS and the FL3/FL1 quotient. Key results The two strategies led to the identification of more than three sperm populations. In the first strategy, EV did not differ between membrane-intact and membrane-damaged sperm, but it was significantly (P P P Conclusions Cluster analysis based on flow cytometry variables provides more information about sperm function than conventional assessment does. Implications Combining flow cytometry with cluster analysis is a more robust approach for sperm evaluation.

Predicting the cryotolerance of boar sperm through antioxidant stress

High sperm cryotolerance is crucial to the successful cryopreservation of boar sperm. Evaluating the cryotolerance of boar sperm by using a rapid and convenient technique can enhance the commercial viability of these sperm. This study investigated the correlation between sperm parameters for three sample subsets-fresh sperm, sperm with H2O2-induced oxidative damage (hereinafter referred to as H2O2-induced sperm), and frozen-thawed sperm-to identify the potential of these correlations to predict cryotolerance. A total of 64 sperm samples were obtained from 64 Duroc boars. The sperm parameters of the three subsets, where the frozen-thawed sperm were analysed at 30 or 180 min after thawing, were determined, and the coefficients of correlation between these parameters were calculated. The results indicated that H2O2-induced oxidative stress resulted in decreases in various sperm parameters-including total motility (TM), viability (VIA), mitochondrial membrane potential (MMP), and live sperm with MMP (LMP)-but increased their coefficients of variation. Receiver operating characteristic (ROC) curve analysis revealed that the kinematic parameters of the H2O2-induced sperm effectively predicted those of the frozen-thawed boar sperm at 30 min after thawing; the corresponding area under the ROC curve (AUC) was 0.8667 for TM and 0.8733 for progressive motility in the H2O2-induced sperm. For measurement at 180 min after thawing, the sperm membrane and mitochondrial parameters of the H2O2-induced sperm effectively predicted the LMP of the frozen-thawed boar sperm; the corresponding AUC was 0.8489 for VIA, 0.8289 for MMP, and 0.8444 for LMP. To our knowledge, this is the first study to directly establish a strong correlation between post-thaw boar sperm quality and H2O2-induced oxidative stress before freezing. Our proposed technique can serve as a valuable reference for the development of practical applications aimed at enhancing techniques for cryopreserving boar sperm.

Dietary alpha-lipoic acid supplementation improves spermatogenesis and semen quality via antioxidant and anti-apoptotic effects in aged breeder roosters

The purpose of the present study was to investigate the effects of dietary alpha-lipoic acid (ALA) supplementation on the reproductive performance of aged breeder roosters. Sixteen 50-wk-old ROSS 308 breeder roosters were randomly allocated to two groups: roosters received a basal diet (CON), or a basal diet supplemented with 300 mg/kg of ALA (ALA). The results indicated that dietary ALA supplementation significantly increased sperm concentration, motility, viability, and membrane functional integrity. ALA also dramatically increased seminiferous tubule epithelial height (SEH) and testis scores. The ALA group had a higher serum concentration of testosterone than the CON group. ALA supplementation remarkably increased total antioxidant capacity (T-AOC), the enzyme activities of glutathione peroxidase (GPx), and catalase (CAT) in the testes; following a decrease in malondialdehyde (MDA) levels. In addition, we noted significant upregulation of Nrf2 mRNA and protein expression of and mRNA expression of its Downstream Genes (GPx1, NQO1, and GCLC), as well as significant downregulation of Keap1 mRNA expression in testicular tissue of aged roosters with ALA supplementation. The protein expression of Caspase 3 was downregulated and the protein expression of proliferating cell nuclear antigen (PCNA) was upregulated by ALA supplementation. The mRNA expression of spermatogenesis-related genes (ER1, AKT1, and Cav1) were markedly augmented in the ALA group compared with the CON group. In conclusion, dietary ALA supplementation enhanced the testicular antioxidant capacity through the Nrf2-signaling pathway, exerted anti-apoptotic effects, and improved the reproductive performance of aged roosters.