Reduced sperm number of murrah (Bubalus bubalis) bull semen in french mini-straw affects kinetic and functional competence after cryopreservation.

BACKGROUND: Extensive dilution of cattle semen with tris-based extender compromises certain sperm kinetic and functional traits following cryopreservation. OBJECTIVE: To study sperm functions of buffalo bulls under high dilution rates. MATERIALS AND METHODS: Twenty-four ejaculates were harvested twice a week from four buffalo bulls, and diluted to sperm concentrations of 80, 60, 40 and 20 million/mL. Diluted samples were filled in straws, equilibrated at refrigeration temperature for 4 h, and frozen in liquid nitrogen. Frozen sperm samples were thawed for evaluation of kinetic and functional attributes. RESULTS: Compared to 20 million/mL (million/mL) sperm sample, the total motility, progressive motility and rapid motility were reduced (P < 0.05) in 5 million/mL sample. The proportion of live sperm were significantly (P < 0.05) higher in 10, 15 and 20 million/mL samples than in 5 million/mL sample. The percentage of moribund sperm, dead sperm, and sperm with lipid per oxidation increased significantly (P < 0.05) in 5 million/mL sample. CONCLUSION: The reduction of sperm concentrations to < 10 million/mL affects post-thaw Buffalo sperm kinetic and functional attributes.. https://doi.org/10.54680/fr24110110712.

Time and dose-dependent effect of preconditioning with sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1) on post-thaw semen quality of Karan-Fries (KF) bulls.

A novel strategy, focused on the induction of sub-lethal oxidative stress to optimize sperm cryosurvival, has been used before cryopreservation. The present study compared the effect of preconditioning with various concentrations of nitric oxide-donor (sodium nitroprusside, SNP) and peroxynitrite-generator (3-morpholinosydnonimine, SIN-1) on in vitro sperm functions and lipid peroxidation status (LPO) of cryopreserved Karan-Fries (KF) crossbred bull semen. To optimize the concentration of additives, spermatozoa obtained from 36 ejaculates were supplemented with different concentrations of SNP (0.01, 0.05, 0.1 µM) and SIN-1 (80, 160, 200 µM) versus control in the extender. The post-freezing sperm motility and viability were greater (p < 0.05) in 0.1 µM SNP and 80 µM SIN-1 in comparison to other concentrations used. Furthermore, the spermatozoa obtained from 48 ejaculates were supplemented with 0.1 µM SNP and 80 µM SIN-1 in the extender. A significant increase (p < 0.05) was observed in progressive motility, viability and membrane integrity in SNP and SIN-1 treated extender at 24 h, 15 days, and 2-month post-cryopreservation (PC) periods. There was no significant difference in sperm abnormality in the extended groups and the control group. The seminal plasma of SNP-treated extender had less (p < 0.05) lipid peroxidation as compared to SIN-1 treated and control groups. In post-thaw semen, both SNP and SIN-1 showed a higher (p < 0.05) proportion of acrosome intact (FITC-PNA) sperm with a greater decrease (p < 0.05) in membrane scrambling and lipid peroxidation. SNP and SIN-1 improved (p < 0.05) the proportion of sperm with higher mitochondrial membrane potential (Δψm) as compared to the control. In conclusion, it seems that the preconditioning of SNP and SIN-1 at lower doses may have beneficial effects on post-thawed crossbred bull sperm quality.

Targeted antioxidant delivery modulates mitochondrial functions, ameliorates oxidative stress and preserve sperm quality during cryopreservation.

Mitochondria are vital organelles with a multifaceted role in cellular bioenergetics, biosynthesis, signaling and calcium homeostasis. During oxidative phosphorylation, sperm mitochondria generate reactive oxygen species (ROS) at physiological levels mediating signaling pathways essential for sperm fertilizing competence. Moreover, sperm subpopulation with active mitochondria is positively associated with sperm motility, chromatin and plasma membrane integrity, and normal morphology. However, the osmotic and thermal stress, and intracellular ice crystal formation generate excess ROS to cause mitochondrial dysfunction, potentiating cryoprotectant-induced calcium overload in the mitochondrial matrix. It further stimulates the opening of mitochondrial permeability transition pores (mPTP) to release pro-apoptotic factors from mitochondria and initiate apoptotic cascade, with a decrease in Mitochondrial Membrane Potential (MMP) and altered sperm functions. To improve the male reproductive potential, it is essential to address challenges in semen cryopreservation, precisely the deleterious effects of oxidative stress on sperm quality. During semen cryopreservation, the supplementation of extended semen with conventional antioxidants is extensively reported. However, the outcomes of supplementation to improve semen quality are inconclusive across different species, which is chiefly attributed to the unknown bioavailability of antioxidants at the primary site of ROS generation, i.e., mitochondria. Increasing evidence suggests that the targeted delivery of antioxidants to sperm mitochondria is superior in mitigating oxidative stress and improving semen freezability than conventional antioxidants. Therefore, the present review comprehensively describes mitochondrial-targeted antioxidants, their mechanism of action and effects of supplementation on improving semen cryopreservation efficiency in different species. Moreover, it also discusses the significance of active mitochondria in determining sperm fertilizing competence, cryopreservation-induced oxidative stress and mitochondrial dysfunction, and its implications on sperm fertility. The potential of mitochondrial-targeted antioxidants to modulate mitochondrial functions and improve semen quality has been reviewed extensively.

Comparative evidence support better antioxidant efficacy of mitochondrial-targeted (Mitoquinone) than cytosolic (Resveratrol) antioxidant in improving in-vitro sperm functions of cryopreserved buffalo (Bubalus bubalis) semen.

The present study compared the effect of mitochondria-targeted (Mitoquinone, MitoQ) and untargeted cytosolic antioxidant (Resveratrol, RESV) supplementation on lipid peroxidation (LPO) and in-vitro sperm functions of cryopreserved buffalo bull semen. To optimize additive's concentration, sperm pellet obtained from twenty-four ejaculates was supplemented with different concentrations of MitoQ (20 nM, 100 nM, 200 nM); and RESV (10 µM, 25 µM, 50 µM) against control in the extender. The post-thaw sperm motility, livability, and membrane integrity were higher (P < 0.05) in 200 nM MitoQ and 50 µM RESV than other concentrations used. In another experiment, sperm pellet from thirty-two ejaculates was supplemented with 200 nM MitoQ and 50 µM RESV in the extender. Pre-freeze and post-thaw progressive motility and livability were higher (P < 0.05) in MitoQ (200 nM) than RESV (50 µM) treatment. MitoQ supplementation improved post-thaw membrane integrity (CFDA-PI) higher (P < 0.05) than RESV, however, hypo-osmotic swelling response observed no improvement with RESV treatment. Post-thaw LPO rate was lower (P < 0.05) and Bovine cervical mucus penetration was higher (P < 0.05) in MitoQ than RESV treatment. In post-thaw semen, MitoQ showed higher (P < 0.05) proportion of acrosome intact (FITC-PNA), live non-apoptotic (P < 0.01) sperm with a higher reduction (P < 0.05) in membrane scrambling. MitoQ improved (P < 0.01) proportion of sperm with high Mitochondrial Membrane Potential and low LPO (P < 0.01) than RESV treatment. In conclusion, improvement in post-thaw in-vitro sperm functions and cryo-tolerance was more evident in MitoQ than RESV supplemented buffalo bull semen. Our study provides a better strategy to mitigate oxidative stress by enhancing mitochondrial antioxidant system with targeted antioxidants than cytosolic antioxidant supplementation.