Cryoprotection effectiveness of low concentrations of natural and lyophilized LDL (low density lipoproteins) on canine spermatozoa

Post-thaw quality of ram sperm frozen with different concentrations of low-density lipoproteins associated with non-enzymatic antioxidants

The cryopreservation reduces ram sperm quality, decreasing the pregnancy rate of ewes inseminated with thawed sperm. Hence, we aimed to improve the post-thaw quality of ram sperm replacing egg yolk on Tris-Glucose extender with different concentrations of LDL (2 or 8%), associated with the addition of 10 mM non-enzymatic antioxidants (ascorbic acid, hydroxytoluene butylate, ascorbyl palmitate, and trehalose). Semen samples were collected from six rams, split into different treatments, and frozen. After thawing, kinematic (CASA), structural (propidium iodide and carboxyfluorescein diacetate) and functional (hypoosmotic test) sperm membrane integrity was assessed. Total motility, VCL, and LIN were also assessed in thawed samples during 3 h of incubation (38 °C). The results showed that hydroxytoluene butylate at 10 mM in Tris-Glucose extender with 8% LDL improved velocity parameters immediately post-thaw compared with Tris-Glucose egg yolk extender, as well as prevented the reduction of total motility and VCL after incubation. There was no benefit of adding ascorbic acid and trehalose. Moreover, for the first time, it was shown the motility impairment promoted by ascorbyl palmitate to ram sperm.

Contributions of seminal plasma proteins to fertilizing ability of bull sperm: A meta-analytical review

Seminal plasma is a dynamic, intricate combination of fluids from the testicles, epididymides, seminal vesicles, bulbourethral glands, and prostate, containing molecules that modulate sperm functions, post-fertilization events, and the female reproductive tract physiology. Significant variations in sperm parameters and fertility status of bulls relate to differences in the seminal plasma proteome. In this framework, a meta-analytical study was conducted examining 29 studies (published between 1990 and 2021) to ascertain the effects of seminal fluid proteins on parameters associated with bull fertility and the influence of distinct methodologies on such effects. Our results revealed that seminal proteins ameliorate sperm parameters, such as motility, integrity, capacitation, and fertilizing ability, and favours sperm protection. Seminal binder of sperm proteins and beta-defensin 126 highly favoured sperm protection when cells were collected from the epididymis by retrograde flux and analysed under room temperature conditions. Furthermore, seminal proteins improved the motility and quality of Bos taurus sperm collected by artificial vagina, mainly in the presence of heparin-binding proteins. The key limitations faced by this meta-analysis were the paucity of studies evaluating the effects of whole seminal fluid proteins and the limited number of studies conducted in vivo. In conclusion, the present meta-analytical study confirms that seminal proteins improve fertility-related parameters in the bovine species. However, methodological strategies used by authors are diverse, with distinct endpoints and methods. Thus, the translational aspects of seminal plasma research should be taken into consideration to precisely define how seminal proteins can be harnessed to advance reproductive biotechnology.

Assisted reproductive techniques for canines: preservation of genetic material in domestic dogs

Assisted reproductive techniques (ARTs), such as artificial insemination, in vitro fertilization, and cryopreservation of gametes/zygotes, have been developed to improve breeding and reproduction of livestock and for the treatment of human infertility. Their widespread use has contributed to improvements in human health and welfare. However, in dogs, only artificial insemination using frozen semen is readily available as an ART to improve breeding and control genetic diversity. A recent priority in sperm cryopreservation is the development of alternatives to egg yolk, which is widely used as a component of the sperm extender. Egg yolk can vary in composition among batches and is prone to contamination by animal pathogens. The latter can be a problem for international exchange of cryopreserved semen. Low-density lipoprotein and skim milk are promising candidates for use as extenders, to ensure fertility after artificial insemination. Although not tested for its effects on fertility following artificial insemination, polyvinyl alcohol may also be a useful alternative to egg yolk as an extender. The development of cryopreservation techniques for canine embryos lags behind that for other mammals, including humans. However, given the success of non-surgical embryo transfer in 2011, studies have sought to refine this approach for practical use. Research on sperm cryopreservation has yielded satisfactory results. However, investigation of other approaches, such as cryopreservation of oocytes and gonadal tissues, remains insufficient. Techniques for the efficient induction of estrus may aid in the development of successful canine ARTs.

Antioxidant effects of supplementation of 3,4-dihydroxyphenyl glycol on sperm parameters and oxidative markers following cryopreservation in canine semen

Supplementing the extender with antioxidants with low molecular weight can enhance the quality of the post-thaw sperm during the freezing process. This study was aimed at determining the impacts of 3,4-dihydroxyphenyl glycol (DHPG) on the spermatozoa of the canine undergoing freeze-thawing process. In this study, 24 ejaculates were obtained from three mixed-breed dogs and were diluted in a Tris-based extender. The diluted semen was divided into aliquots for supplementation of 10, 30, 50 and 70 µg/ml of DHPG, control (without antioxidant) and control sham (DMSO). After being extended, the semen was equilibrated at a temperature of 4°C and then transferred to the straws and kept 4 cm above the liquid nitrogen for 20 min and was finally immersed in the liquid nitrogen. They were cryopreserved for seven days; then, sperm parameters including sperm motility evaluation, motility characteristics, viability, DNA and plasma membrane integrity, total antioxidant capacity (TAC), reduced glutathione content (GSH), antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT] and glutathione peroxidase [GPx]) activity malondialdehyde (MDA) levels were evaluated. This study showed that spermatozoa cryopreservation with 50, 30 and 70 µg/ml of DHPG concentrations had better progressive motility, Curvilinear Velocity, Linearity, viability, intact plasma membrane and the levels of TAC, GPx and GSH were higher than the control group. The 50, 30 and 70 µg/ml of DHPG concentrations led to the significant decrease of DNA damage compared to the control group. Total motility, average path velocity, straight-line velocity and CAT activity were significantly improved in 30 and 50 µg/ml of DHPG concentrations, compared to the control group. Also, the 50 and 30 µg/ml of DHPG concentrations, decreased MDA levels compared to the other groups, significantly. In conclusion, our study showed that the addition 50 µg/ml of DHPG to the canine semen extender improved the semen characteristics and oxidative markers in the cryopreservation process.

A comparison of liquid and lyophilized egg yolk plasma to low density lipoproteins for freezing of canine spermatozoa

The current study aimed to explore the potential usefulness of liquid or lyophilized egg yolk plasma (EYP) as a substitute for low-density lipoproteins (LDL) for cryopreservation of canine spermatozoa. In the first experiment, a total of 20 ejaculates harvested from six Beagles were frozen in extenders containing 6% LDL (control) or liquid or lyophilized EYP at one of three concentrations (20%, 40% or 60%). Motility parameters were assessed 10 min after thawing using computer-assisted sperm analysis. For both liquid and lyophilized EYP, the 40% concentration yielded motility similar (p > 0.05) to that observed with the control extender. In the second experiment, 12 ejaculates collected from the same six dogs were frozen in 6% LDL (Control), 40% liquid EYP or 40% lyophilized EYP extenders. Spermatozoal membrane integrity (hypo-osmotic swelling test [HOSt] and SYBR14/propidium iodide [PI] staining), acrosome integrity (FITC-Pisum sativum agglutinin staining) and DNA integrity (acridine orange staining) characteristics were evaluated 10 min after thawing. Both liquid and lyophilized 40% EYP-based extenders successfully preserved all assessed integrity parameters as efficiently as the control. Results of this study suggest that lyophilized EYP is a viable alternative to LDL in freezing extenders for dog semen.

Highly efficient extraction and purification of low-density lipoprotein from hen egg yolk

Low-density lipoprotein (LDL) from hen egg yolk has high nutritional value and plays an important role in the fields of biology, medicine, and materials. To develop fundamental research about LDL, a highly efficient extraction method is necessary. We found that 30% saturated ammonium sulfate can extract more crude LDL than 40% saturation. We selected polyethylene glycol (PEG; nonionic type) to obtain crude LDL. Three factors were employed, namely, degree of polymerization, concentration of PEG, and pH of egg yolk plasma. The optimized condition was 5% PEG 4,000 and plasma pH 6.0, and the best extraction efficiency was 68.1 ± 0.5 g lipid /100 g DM and 69.9 ± 2.0% protein. The crude LDL oil of PEG precipitation was very significantly higher (P < 0.01) than ammonium sulfate precipitation (ASP), while there was no significant difference in protein, which indicates that PEG can extract more crude LDL. When ascorbic acid was added, hydrosulfuryl (SH) groups and lipids oxidation degree of crude LDL extracted by PEG (PEG-LDL) was very significantly lower than ASP (P < 0.01). We also obtained both purified LDL and yolk immunoglobulin (IgY) with an appropriate purification column. This paper proposes a highly efficient method to extract LDL with high activity using PEG and ensures co-purification of LDL and IgY.

Cryoprotective effect of low-density lipoproteins on post thaw semen quality in Hariana bull

The study aimed to evaluate the cryoprotective effect of low-density lipoprotein in Hariana bull semen. Four adult Hariana bull (3-4 years) after thorough andrological examination were selected for experiment. Semen was collected from each bull twice a week; total of 32 ejaculates (8 from each bull) were collected during the experiment. Collected sample from each bull was divided into 5 equal aliquots. Four aliquots were diluted separately with a Tris-based extender containing different concentration of low-density lipoproteins viz. 7% (T-1), 8% (T-2), 9% (T-3) and 10% (T- 4) as treatment while routinely used extender containing 20% hen egg yolk was used as control (C) to achieve final concentration of 125 million spermatozoa/ml. The diluted samples were cryopreserved and evaluated after 7 days. A significantly higher value of percent live sperms, sperm positive for hypo osmotic swelling test, sperms with intact acrosome and sperms exhibiting pattern F (uncapacitated sperm) were significantly higher in T-3 as compared to other treatment groups and control. The kinematic characters exhibited by sperm i.e forward progression %, VCL (μm/sec), VSL (μm/sec), VAP (μm/sec), Lin (%), Str (%), BCF (Hz) and ALH (μm) were significantly higher in T-3 as compared to other treatment group and control. In conclusion, extender containing 9% low density lipoproteins has better capacity to maintain the sperm character in post thaw Hariana bull semen and can be a preferred concentration to be utilized for cryopreservation with improved conception rate.