Activation of adenosine monophosphate-activated protein kinase (AMPK) enhances energy metabolism, motility, and fertilizing ability of cryopreserved spermatozoa in domestic cat model

Characterization of freezability-associated metabolites in boar semen

Sperm cryopreservation maintains the diversities of porcine genetic resources and improves utilization efficiency of boar semen in artificial insemination practices. Freezability of boar semen presents remarkable differences among individuals. However, metabolic markers for boar semen freezability in both sperm and seminal plasma largely remain unknown. The present study thus aims to determine differences in metabolites of sperm and seminal plasma between poor (PF) and good (GF) freezability semen from a Chinese native pig and screen potential markers for semen freezability. A total of 72,048 metabolites in sperm and 66,551 metabolites in seminal plasma were identified by liquid chromatography-mass spectrometry, respectively. The proportion of lipid molecules among all metabolites in both sperm and seminal plasma was the maximum regardless of negative or positive mode. Furthermore, we identified 21 differentially expressed metabolites (DEMs) in sperm and 185 DEMs in seminal plasma between PF and GF group. Additionally, clustering analysis showed that DEMs in sperm and seminal plasma exhibited significant changes between PF and GF group. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that DEMs in sperm were mainly enriched in metabolic pathways of amino acids and caffeine. DEMs in seminal plasma were associated with AMPK and cAMP signaling pathways. Taken together, these results demonstrate that sperm and seminal plasma of native pigs present differential metabolome between PF and GF semen.

Influence of hydrogel encapsulation during cryopreservation of ovarian tissues and impact of post-thawing in vitro culture systems in a research animal model

Objective

Using domestic cats as a biomedical research model for fertility preservation, the present study aimed to characterize the influences of ovarian tissue encapsulation in biodegradable hydrogel matrix (fibrinogen/thrombin) on resilience to cryopreservation, and static versus non-static culture systems following ovarian tissue encapsulation and cryopreservation on follicle quality.

Methods

In experiment I, ovarian tissues (n=21 animals; 567 ovarian fragments) were assigned to controls or hydrogel encapsulation with 5 or 10 mg/mL fibrinogen (5 or 10 FG). Following cryopreservation (slow freezing or vitrification), follicle viability, morphology, density, and key protein phosphorylation were assessed. In experiment II (based on the findings from experiment I), ovarian tissues (n=10 animals; 270 ovarian fragments) were encapsulated with 10 FG, cryopreserved, and in vitro cultured under static or non-static systems for 7 days followed by similar follicle quality assessments.

Results

In experiment I, the combination of 10 FG encapsulation/slow freezing led to greater post-thawed follicle quality than in the control group, as shown by follicle viability (66.9%±2.2% vs. 61.5%±3.1%), normal follicle morphology (62.2%±2.1% vs. 55.2%±3.5%), and the relative band intensity of vascular endothelial growth factor protein phosphorylation (0.58±0.06 vs. 0.42±0.09). Experiment II demonstrated that hydrogel encapsulation promoted follicle survival and maintenance of follicle development regardless of the culture system when compared to fresh controls.

Conclusion

These results provide a better understanding of the role of hydrogel encapsulation and culture systems in ovarian tissue cryopreservation and follicle quality outcomes using an animal model, paving the way for optimized approaches to human fertility preservation.

Protective Effect of Chlorogenic Acid on Human Sperm: In Vitro Studies and Frozen-Thawed Protocol

The study evaluated the chlorogenic acid (CGA) antioxidant potential on oxidative stress (OS) induced in vitro in human spermatozoa and during cryopreservation procedure. Swim-up selected spermatozoa were treated with 100 µM CGA, 100 µM H₂O₂ to induce lipid peroxidation (LPO), and with both compounds and the effects on mitochondrial membrane potential (MMP) by JC-1, DNA integrity by acridine orange (AO), and sperm ultrastructure by transmission electron microscopy (TEM), were evaluated. CGA antioxidant activity was assessed by measuring malondialdehyde (MDA) and F₂-isoprostanes (F₂-IsoPs) in the media. The CGA protective activity and the immunolocalization of Phospho-AMPKα (Thr172) were explored in frozen-thawed sperm. CGA was not toxic for sperm motility, DNA integrity and MMP. The increase in MDA (p < 0.05) and F₂-IsoPs (p < 0.001), DNA damage (p < 0.01) and low MMP (p < 0.01) levels after H₂O₂ treatment were reduced in presence of CGA as well as the percentage of broken plasma membranes (p < 0.01) and altered acrosomes (p < 0.01) detected by TEM. Treated frozen-thawed spermatozoa showed increased sperm motility (p < 0.01), DNA integrity (p < 0.01), MMP (p < 0.01), reduced MDA (p < 0.01) and increased sperm percentage with Phospho-AMPKα labelling in the head (p < 0.001). CGA can be used to supplement culture media during semen handling and cryopreservation where OS is exacerbated.

Rosmarinic acid improves boar sperm quality, antioxidant capacity and energy metabolism at 17°C via AMPK activation

Boar sperm are susceptible to oxidative damage caused by reactive oxygen species (ROS) during storage. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an important therapeutic target, because it is a cellular metabolism energy sensor and key signalling kinase in spermatozoa. We evaluated the effects of rosmarinic acid (RA), an antioxidant, on boar sperm during liquid storage to determine whether it protects boar sperm via AMPK activation. Boar ejaculates were diluted with Modena extender with different concentrations of RA and stored at 17°C for 9 days. Sperm quality parameters, antioxidant capacity, energy metabolism, AMPK phosphorylation and fertility were analysed. Compared with the control, 40 μmol/L significantly improved sperm motility, plasma membrane integrity and acrosome integrity (p < .05). The effective storage time of boar sperm was up to 9 days. On the third and seventh days, the sperm with RA exhibited increased total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, adenosine triphosphate (ATP) content, mitochondrial membrane potential (ΔΨm) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, whereas malondialdehyde (MDA) content was significantly decreased (p < .05). Western blot showed that RA, as well as AICAR (AMPK activator), promoted AMPK phosphorylation, whereas Compound C (AMPK inhibitor) inhibited this effect. The sperm-zona pellucida binding experiment showed that 40 μmol/L RA increased the number of sperm attached to the zona pellucida (p < .05). These findings suggest meaningful methods for improved preservation of boar sperm in vitro and provide new insights into the mechanism by which RA protects sperm cells from oxidative damage via AMPK activation.

Identification of new protein biomarkers associated with the boar fertility using iTRAQ-based quantitative proteomic analysis

In this study, we performed the isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis in the spermatozoa of Landrace boars with different fertility potentials and investigated the ability of sperm acrosome associated 4 (SPACA4) and IZUMO family member 2 (IZUMO2) to predict the reproductive perform of boars. The iTRAQ results revealed that 202 proteins were up-regulated and 43 proteins were down-regulated in the spermatozoa from high fertility boars. SPACA4 and IZUMO2 protein levels were significantly up-regulated in the spermatozoa from high fertility boars. SPACA4 and IZUMO2 expression were specifically detected in the adult boar testis. SPACA4 levels were positively correlated with Sow's farrowing rate and reproductive efficiency, but not litter size. IZUMO2 were positively correlated with litter size, Sow's farrowing rate and reproductive efficiency. Treating the boar semen with SPACA4 or IZUMO2 antibodies for 30 min and 60 min failed to affect the sperm motility; while treating the semen with SPACA4 antibody significantly reduced the fertilization and cleavage rates. Similar results for fertilization and cleavage rates were found in IZUMO2 antibody-treated semen. Collectively, our results indicated that protein levels of SPACA4 and IZUMO2 in the spermatozoa were positively related to the reproductive performance of Landrace boars.

Cold case: Small animal gametes cryobanking

Germplasm preservation of animals, whether they are valuable domestic breeds or rare species, is the main goal of gamete cryobanking. Dogs and cats act as models for this purpose thanks to the wide availability of biological material which can be employed to experiment protocols that can then be applied to wild animals. This review is focused on spermatozoa, oocytes and gonadal tissues cryobanking in small domestic animals, which is still an unsolved case. Like in a courtroom, evidences of cryoinjuries affecting cellular structures will be presented, penalties as loss of functionality due to cellular alterations will be described, and appeal as strategies to protect gametes from damages or rescue their functionality will be discussed. Differences and similarities between single cell or tissue cryopreservation will be highlighted, together with the rationale for the choice of one type of preservation or another and the fundamental principles which they are based on. The deep analysis of different aspects that still hamper the success of cryopreservation in small animals can help clarify where research is most needed. Therefore, as in a cold case, investigation should remain open in order to hopefully find the solution and make these procedures more and more efficient in the future.