Cholesterol and desmosterol incorporation into ram sperm membrane before cryopreservation: Effects on membrane biophysical properties and sperm quality

Evaluation of Cryopreserved Ram Sperm with Nano-Ozone Solution and Post-Thaw Life Span by Flow Cytometric Analysis

Ozone has been used as a therapy tool in medical science for conditions such as ulcers, peritonitis, wounds, and mostly joint problems. Ozone therapy strengthens the resistance to infections by kick-starting antioxidant, anti-inflammatory, and immune modulation systems. Ozone creates a defensive response against oxidative stress in membranes and protects metabolism against reactive oxygen species (ROS). Sperm membranes are one of ROS's main targets; therefore, the cells' cryopreservation process requires more defensive elements for better results. This study aimed to investigate the protective effect of nano-ozone solution (NOS) on ram sperm cryopreservation and the influence of the process on various sperm parameters for post-thaw (0 hour) and postincubation (6 hours) time points. Samples were collected from six Merino rams in the breeding season by electroejaculation five times at 3-day intervals. The study was conducted by cryopreservation of the samples using a tris citric acid-egg yolk-based extender. The samples were subjected to freezing in control and NOS (0.5, 1, and 2 μg/mL nano-ozone supplemented). Post-thaw motility, hypo-osmotic swelling test, acrosome (fluorescein isothiocyanate-conjugated Pisum sativum agglutinin [PSA-FITC]), and DNA integrities (terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL]) were evaluated with a phase-contrast microscope. Mitochondrial membrane potential (MMP) assessments were conducted by JC1-PI dual staining with a flow cytometer. Malondialdehyde and glutathione (GSH) levels were measured by a spectrophotometer. Sperm kinematics were investigated by a computer-assisted sperm analyzer (CASA) at the post-thaw time point. Compared with the control, relatively low doses of NOS (0.5 and 1 μg/mL) yielded better results in many parameters (motility, membrane and acrosomal integrities, MMP, various sperm kinematics, and GSH levels) (p < 0.05). The addition of low ozone doses to cryopreservation extenders improved the results compared with the control group at post-thaw and postincubation time points. Despite the valuable potential of nano-ozone supplementation in ram sperm cryopreservation, this subject requires further investigations with fertility trials soon.

Reduction of cryopreservation-induced structural, functional and molecular damages in ram sperm by hydrated C60 fullerene

This study aimed to investigate the morphological, functional and molecular changes in frozen-thawed ram sperm using an extender containing different concentrations of hydrated carbon 60 fullerene (C60 HyFn), a nanotechnological product. Semen taken from each of the seven Akkaraman rams were pooled. Semen collection was done twice a week and it continued for 3 weeks. Each pooled semen sample was divided into six equal groups and diluted with tris + egg yolk extender including 0 (control), 200, 400, 800 nM, 1 and 5 μM concentrations of C60 HyFn at 37°C. They were then frozen in liquid nitrogen vapour at -140°C, stored in liquid nitrogen container (-196°C) and thawed at 37°C for 25 s before analysis. In comparison with control, C60 HyFn addition prior to freezing procedure provided significant increases in total and progressive motility rates, glutathione peroxidase, catalase activities and percentage of highly active mitochondria, and significant decreases in dead and abnormal sperm rates, lipid peroxidation, caspase-3 and DNA fragmentation levels in frozen-thawed ram semen. When compared to control, C60 HyFn supplementation significantly down-regulated the expression levels of miR-200a and KCNJ11, and significantly up-regulated the expression levels of miR-3958-3p (at the concentrations of 200, 400, 800 nM and 1 μM), CatSper1 (at the concentrations of 200, 400 nM and 5 μM), CatSper2 (at the concentrations of 1 and 5 μM), CatSper3 (at the concentrations of 200, 400 nM, 1 and 5 μM), CatSper4 (at all concentrations), ANO1 (at the concentrations of 800 nM, 1 and 5 μM) and TRPV5 (at the concentrations of 200, 400 and 800 nM). The addition of C60 HyFn had no effect on global DNA methylation rates. As a result, C60 HyFn supplementation to ram semen extenders may be beneficial in reducing some of the functional, structural and molecular damages in sperm induced by the freeze-thawing procedure.

Problems of human spermatozoa cryopreservation: research methods, solutions

Cryopreservation of male gametes is one of the most important methods of assisted reproductive technologies, which allows preserving gametes for research or further use. However, the fertilizing ability of spermatozoa after cryopreservation decreases by 30-70%, which makes it urgent to search for new substances with cryoprotective properties. The review considers the main causes of cell damage during cryopreservation. The relevance of methods for assessing the formation of crystals and the physicochemical properties of cryoprotective media depending on various compositions is discussed. The problem of stabilization of the spermatozoa membrane during cryopreservation is considered. A possible solution to the problem of membrane integrity may consist in modification of the basic cryoprotective media with yolk emulsion or development of methods for saturation of the membrane phospholipid layer with cholesterol.

Improvement of Fertilization Capacity and Developmental Ability of Vitrified Bovine Oocytes by JUNO mRNA Microinjection and Cholesterol-Loaded Methyl-β-Cyclodextrin Treatment

Vitrification of oocytes is crucial for embryo biotechnologies, germplasm cryopreservation of endangered and excellent female animals, and the fertility of humans. However, vitrification significantly impairs the fertilization ability of oocytes, which significantly limits its widely used application. JUNO protein, a receptor for Izumo1, is involved in sperm-oocyte fusion and is an indispensable protein for mammalian fertilization, and its abundance is susceptible to vitrification. However, it is still unclear how vitrification reduces the fertilization capacity of bovine oocytes by affecting JUNO protein. This study was designed to investigate the effect of vitrification on the abundance and post-translational modifications of JUNO protein in bovine oocytes. Our results showed that vitrification did not alter the amino acid sequence of JUNO protein in bovine oocytes. Furthermore, the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis results showed that vitrification significantly reduced the number and changed the location of disulfide bonds, and increased the number of both phosphorylation and glycosylation sites of JUNO protein in bovine oocytes. Finally, the fertilization capacity and development ability of vitrified oocytes treated with 200 pg JUNO mRNA microinjection and cholesterol-loaded methyl-β-cyclodextrin (CLC/MβCD) were similar to those of fresh oocytes. In conclusion, our results showed that vitrification of bovine oocytes did not alter the protein sequence of JUNO, but induced post-translational modifications and changed protein abundance. Moreover, the fertilization and development ability of vitrified bovine oocytes were improved by the combination treatment of JUNO mRNA microinjection and CLC/MβCD.

The Cryopreserved Sperm Traits of Various Ram Breeds: Towards Biodiversity Conservation

The aim of our research was to compare three Slovak sheep breeds in the quality parameters of cryopreserved sperm. The ejaculates of Slovak Dairy (SD), Native Wallachian (NW), and Improved Wallachian (IW) sheep rams (n = 12) were collected by electro-ejaculation. Heterospermic samples were created from suitable ejaculates, separately for each breed (at least 90% of total and 80% of progressive motility). Samples were equilibrated in a Triladyl® diluent and frozen by automated freezing. Sperm samples were subjected to the motility, morphology, (CASA), viability and apoptosis (DRAQ7/Yo-Pro-1), fertilizing capability (penetration/fertilization test (P/F) in vitro) and acrosomal status (transmission electron microscopy) assays before freezing and after thawing. It was found that there were no significant differences (p < 0.05) between the evaluated breeds in motility, viability, apoptosis, morphological properties, and fertilizing ability of cryopreserved sperm. Significant differences occurred in acrosomal status. Our results demonstrate that the use of the selected cryopreservation protocol is suitable for at least three different sheep breeds, which can greatly benefit the biodiversity protection and simplifies the creation of an animal genetic resources gene bank.

Desmosterol Incorporation Into Ram Sperm Membrane Before Cryopreservation Improves in vitro and in vivo Fertility

Pregnancy rates in ewes are markedly low after cervical insemination with frozen-thawed sperm. Sensitivity of ram sperm to freeze-thawing is related to the lipid composition of the membrane, particularly to its low sterol content. Recently, we proved that sterol content of ram sperm can be increased by treatment with methyl-β-cyclodextrin-sterol complexes and we provided mechanistic based evidence on the differential behavior of cholesterol and desmosterol in the ram sperm membrane. In the present study, we evaluated the role of increasing cholesterol and desmosterol content of ram sperm before cryopreservation, on the extent and distribution of sterols, cryocapacitation status, acrosome integrity, DNA damage associated with apoptosis and fertility competence in vitro and in vivo of post-thawed sperm. After freeze-thawing, similar levels of sterol content were evidenced in control sperm cells and in those pre-incubated with either cholesterol or desmosterol. Still, moderately higher levels of sterols were registered in treated sperm compared to the control, indicating no physiological excess of sterols after thawing or sterol losses that exceed the control. Live cell imaging of fluorescent cholesterol evidenced the presence of sperm sub-populations differentially affected by freeze-thawing. Similar unimodal frequency profiles were observed between sterol-enriched groups, while the control exhibited a sub-population of sperm compatible with low sterol content. Tyrosine phosphorylation was significantly lower when ram sperm incorporated cholesterol compared to the control. No difference in this capacitation parameter was found between the latter and desmosterol-enriched sperm. The percentage of sperm with damaged acrosomes post-thawing, assessed by a fluorescent lectin, was reduced in sperm that incorporated sterols before freezing, irrespective of the sterol class. These results suggest that sterols exert a stabilizing effect on the acrosome. No differences were found in levels of apoptotic DNA fragmentation among experimental groups. As to fertility trials, desmosterol-enriched sperm gave rise to higher rates of in vitro activated oocytes by heterologous fertilization and to significantly lower pregnancy loss in vivo. Our research provides new insights on sterol incorporation into ram sperm prior to cryopreservation, in particular on the additional benefit of incorporating desmosterol as a strategy to improve fertility outcome.