HSP90 maintains boar spermatozoa motility and mitochondrial membrane potential during heat stress

Immunophenotype profile by flow cytometry reveals different subtypes of extracellular vesicles in porcine seminal plasma

BACKGROUND

Porcine seminal plasma (SP) is endowed with a heterogeneous population of extracellular vesicles (sEVs). This study evaluated the immunophenotypic profile by high-sensitivity flow cytometry of eight sEV subpopulations isolated according to their size (small [S-sEVs] and large [L-sEVs]) from four different SP sources, namely three ejaculate fractions (the first 10 mL of the sperm rich fraction [SRF-P1], the remaining SRF [SRF-P2], and the post-SRF [PSRF]) and entire ejaculate (EE).

METHODS

Seminal EVs were isolated using a size exclusion chromatography-based protocol from six SP pools (five ejaculates/pool) of each SP source and characterized using complementary approaches including total protein (BCA™assay), particle size distribution (dynamic light scattering), morphology (transmission electron microscopy), and purity (albumin by Western blot). Expression of CD9, CD63, CD81, CD44 and HSP90β was analyzed in all sEV subpopulations by high-sensitivity flow cytometry according to MIFlowCyt-EV guidelines, including an accurate calibration, controls, and discrimination by CFSE-labelling.

RESULTS

Each sEV subpopulation exhibited a specific immunophenotypic profile. The percentage of sEVs positive for CD9, CD63, CD81 and HSP90β differed between S- and L-sEVs (P < 0.0001). Specifically, the percentage of sEVs positive for CD9 and CD63 was higher and that for CD81 was lower in S- than L-sEVs in the four SP sources. However, the percentage of HSP90β-positive sEVs was lower in S-sEVs than L-sEVs in the SRF-P1 and EE samples. The percentage of sEVs positive for CD9, CD63, and CD44 also differed among the four SP sources (P < 0.0001), being highest in PSRF samples. Notably, virtually all sEV subpopulations expressed CD44 (range: 88.04-98.50%).

CONCLUSIONS

This study demonstrated the utility of high-sensitivity flow cytometry for sEV immunophenotyping, allowing the identification of distinct sEV subpopulations that may have different cellular origin, cargo, functions, and target cells.

Temperature Elevation during Semen Delivery Deteriorates Boar Sperm Quality by Promoting Apoptosis

Semen delivery practice is crucial to the efficiency of artificial insemination using high-quality boar sperm. The present study aimed to evaluate the effect of a common semen delivery method, a Styrofoam box, under elevated temperatures on boar sperm quality and functionality and to investigate the underlying molecular responses of sperm to the temperature rise. Three pooled semen samples from 10 Duroc boars (3 ejaculates per boar) were used in this study. Each pooled semen sample was divided into two aliquots. One aliquot was stored at a constant 17 °C as the control group. Another one was packaged in a well-sealed Styrofoam box and placed in an incubator at 37 °C for 24 h to simulate semen delivery on hot summer days and subsequently transferred to a refrigerator at 17 °C for 3 days. The semen temperature was continuously monitored. The semen temperature was 17 °C at 0 h of storage and reached 20 °C at 5 h, 30 °C at 14 h, and 37 °C at 24 h. For each time point, sperm quality and functionality, apoptotic changes, expression levels of phosphorylated AMPK, and heat shock proteins HSP70 and HSP90 were determined by CASA, flow cytometry, and Western blotting. The results showed that elevated temperature during delivery significantly deteriorated boar sperm quality and functionality after 14 h of delivery. Storage back to 17 °C did not recover sperm motility. An increased temperature during delivery apparently promoted the conversion of sperm early apoptosis to late apoptosis, showing a significant increase in the expression levels of Bax and Caspase 3. The levels of phosphorylated AMPK were greatly induced by the temperature rise to 20 °C during delivery but reduced thereafter. With the temperature elevation, expression levels of HSP70 and HSP90 were notably increased. Our results indicate that a temperature increase during semen delivery greatly damages sperm quality and functionality by promoting sperm apoptosis. HSP70 and HSP90 could participate in boar sperm resistance to temperature changes by being associated with AMPK activation and anti-apoptotic processes.

Seminal prolactin is associated with HSP90 transcript content in ejaculated spermatozoa

OBJECTIVE

Evidence indicates that an imbalance between the production of reactive oxygen species and defense ability of antioxidants has clinical significance in the pathophysiology of male infertility. To investigate the role of seminal prolactin (PRL) in the fertilizing capacity of men, the present study evaluated the associations of seminal PRL levels with semen parameters and heat shock protein 90 (HSP90) transcript abundance in ejaculated spermatozoa.

METHODS

We assessed seminal PRL levels and the abundance of HSP90 transcripts in ejaculated spermatozoa from normozoospermic donors (n=18) and infertile men (n=18). The transcript content of HSP90 in ejaculated spermatozoa was analyzed using real-time polymerase chain reaction.

RESULTS

Seminal PRL concentrations in infertile patients were significantly lower (p=0.004) than in fertile controls. Seminal PRL showed relatively good diagnostic power for discriminating infertile men (area under the curve=0.776; 95% confidence interval, 0.568 to 0.934; p=0.005). Significant positive correlations were seen between seminal PRL levels and sperm count (r=0.400, p=0.016) and progressive motility (r=0.422, p=0.010). Infertile patients showed a significantly higher abundance of sperm HSP90 than fertile controls (p=0.040). Sperm HSP90 transcript abundance was negatively correlated with sperm progressive motility (r=0.394, p=0.018). Men with higher seminal PRL levels exhibited a lower abundance of sperm HSP90 transcripts.

CONCLUSION

Our finding demonstrated associations among semen quality, seminal PRL levels, and the abundance of HSP90 transcripts in ejaculated spermatozoa. Seminal PRL may contribute to male fertility by maintaining the seminal antioxidant capacity and may have the potential to act as a diagnostic and prognostic biomarker.

TMT-based comparative proteomic analysis of Dezhou donkey spermatozoa related to freezability

The freezability difference between donkey ejaculates is a limiting factor of sperm cryopreservation. Our recent study shows that the freezability of donkey semen is related to the seminal plasma proteome. In this study, we aimed to identify the different abundance sperm proteins in good freezability ejaculates (GFEs) and poor freezability ejaculates (PFEs) using a Tandem Mass Tag (TMT) peptide labeling coupled with LC-MS/MS approach. A total of 2682 proteins were identified, among which 58 were significantly up-regulated in GFEs and 16 were down-regulated compared with PFEs. Bioinformatic analysis results revealed that the majority of different abundance proteins (DAPs) participated in copper and calcium binding, regulation of RNA biosynthetic process, positive regulation of innate immune response, and negative regulation of programmed cell death. KEGG pathway enrichment analysis showed the up-regulated proteins in GF group were mainly involved in N-Glycan biosynthesis and protein processing in endoplasmic reticulum. Our study was the first to analyze the proteome of sperm from donkey ejaculates with different freezabilities. The identified candidate proteins might be used to explore the molecular mechanism related to donkey sperm cryotolerance and might improve the screening of jacks with good sperm freezability. SIGNIFICANCE: Cryopreserved semen has been widely used in assisted reproductive technology. However, semen cryopreservation is a damaging process, which can cause oxidative stress, reduce sperm motility and motility. There are differences in sperm freezability reported to exist between or within breeds, and even between fractions coming from the same ejaculate. The freezability difference between donkey ejaculates is a limiting factor of sperm cryopreservation. The mechanisms that affect the freezing difference in sperm quality remain to be investigated, and freezability differences was found to be related to protein composition of spermatozoa. Some protein markers that can indicate good freezability or poor freezability semen have been identified in mammals. Until now, there is no information about the relationship between donkey spermatozoa proteome and freezability. Additional novel biomarkers of semen freezability in donkey spermatozoa are also needed. The identified candidate proteins might be used to explore the molecular mechanism related to donkey sperm cryotolerance and might improve the screening of jacks with good sperm freezability.

Molecular Markers: A New Paradigm in the Prediction of Sperm Freezability

For decades now, sperm cryopreservation has been a pillar of assisted reproduction in animals as well as humans. Nevertheless, the success of cryopreservation varies across species, seasons, and latitudes and even within the same individual. With the dawn of progressive analytical techniques in the field of genomics, proteomics, and metabolomics, new options for a more accurate semen quality assessment have become available. This review summarizes currently available information on specific molecular characteristics of spermatozoa that could predict their cryotolerance before the freezing process. Understanding the changes in sperm biology as a result of their exposure to low temperatures may contribute to the development and implementation of appropriate measures to assure high post-thaw sperm quality. Furthermore, an early prediction of cryotolerance or cryosensitivity may lead to the establishment of customized protocols interconnecting adequate sperm processing procedures, freezing techniques, and cryosupplements that are most feasible for the individual needs of the ejaculate.

Responses of sperm mitochondria functionality in animals to thermal stress: The mitigating effects of dietary natural antioxidants

The reproductive consequences of global warming representing heat stress (HS) have been widely received more attention in the last decades. HS induced significant influence on the male reproductive cell, especially sperm functionally. Reduction in the sperm function induced by HS leads to failure of fertility potential. The main effects of HS on sperm are reducing sperm motility, increased abnormalities and changes in the fluidity of the membrane as well as cell morphology. Moreover, the destruction of mitochondrial function could be the result of adverse influences of HS. The protein contents and enzymes of mitochondria were lowered after the exposure of sperm to HS. Some natural antioxidants were used for improving sperm mitochondrial function under HS conditions. In this review, it was highlighted the potential influences of HS on sperm function through reduction in ATP Synthesis yield, mitochondrial activity, mitochondrial protein contents and mitochondrial enzymes, which involves the interference of mitochondrial remodelling in sperm of animals.

The Physiological and Evolutionary Ecology of Sperm Thermal Performance

Ongoing anthropogenic climate change has increased attention on the ecological and evolutionary consequences of thermal variation. Most research in this field has focused on the physiology and behavior of diploid whole organisms. The thermal performance of haploid gamete stages directly tied to reproductive success has received comparatively little attention, especially in the context of the evolutionary ecology of wild (i.e., not domesticated) organisms. Here, we review evidence for the effects of temperature on sperm phenotypes, emphasizing data from wild organisms whenever possible. We find that temperature effects on sperm are pervasive, and that above normal temperatures in particular are detrimental. That said, there is evidence that sperm traits can evolve adaptively in response to temperature change, and that adaptive phenotypic plasticity in sperm traits is also possible. We place results in the context of thermal performance curves, and encourage this framework to be used as a guide for experimental design to maximize ecological relevance as well as the comparability of results across studies. We also highlight gaps in our understanding of sperm thermal performance that require attention to more fully understand thermal adaptation and the consequences of global change.

Relevance of the Ejaculate Fraction and Dilution Method on Boar Sperm Quality during Processing and Conservation of Seminal Doses

During boar semen processing and distribution, maximizing the work protocols in the laboratories becomes essential for the conservation of seminal doses. One of the recent implementations in the boar studs to improve efficiency has been semi-automatic semen collection systems, which do not allow to discard fractions of the ejaculate. The objective of this work was to evaluate the dilution method and vibrations (simulating delivery transport) effect on sperm quality (motility, viability, morphology, thermo-resistance test) according to the fraction of ejaculate collected. Two different fractions of the ejaculate were obtained [rich fraction (RF); total fractions (TF)] from six boars, and two dilution methods applied [pouring the extender over the semen (control; ES); pouring the semen over the extender (reverse; SE)]. The seminal doses (2000 × 10⁶ sperm/50 mL) were preserved for 5 days. The results showed that the fraction collected affects sperm quality (better total and progressive motility, and faster sperm in TF; p < 0.05) regardless of the dilution method applied. However, these differences diminished after submitting the semen to the thermo-resistance test, with only differences in sperm viability being observed (p < 0.05). When seminal doses were subjected to vibrations, the sperm viability was more affected in the TF than in the RF group (p < 0.05). In conclusion, using the TF ejaculate leads to comparable results to the RF in sperm quality during storage regardless of the dilution method applied. However, the vibrations of seminal doses are more affected in doses prepared with TF than with RF, although more factors should be included to approach the real conditions during transport.

Influence of different cellular concentrations of boar sperm suspensions on the induction of capacitation and acrosome reaction

We aimed to analyze the influence of different cellular concentrations of boar sperm suspensions on the induction of capacitation and acrosome reaction. When spermatozoa were incubated at 100 or 200 mill/ml, significant increases in protein tyrosine phosphorylation in the p32 protein were observed, compared to those at 50 mill/ml. In addition, sperm concentration-dependent increases were observed in plasma membrane lipid disorganization (50 mill/ml vs. 200 mill/ml), induction of the acrosome reaction (50 mill/ml vs. 100 mill/ml and 200 mill/ml), and sperm viability (50 mill/ml vs. 100 mill/ml and 200 mill/ml). Our data indicate that an increase in sperm concentration stimulates the induction of capacitation and acrosome reaction in boars.

Effect of Boar Sperm Proteins and Quality Changes on Field Fertility

Simple Summary

Artificial insemination with extended liquid boar semen is widely used in the swine industry. The identification of the relationship between boar sperm characteristics and fertility could be of substantial importance to reproduction management. This study evaluated the relationship between boar sperm characteristics and sperm/seminal plasma proteins with main parameters of field fertility. Immotile spermatozoa and spermatozoa with biochemically active plasma membranes affected the number of live-born piglets and litter size of ≥12 piglets. The proteins osteopontin 70 and glutathione peroxidase 5, both separately and in combination, affected the farrowing rate. The combination of immotile sperm and protein osteopontin 70 explained the variation regarding litter size with ≥12 piglets. In conclusion, the evaluation of semen quality variables combined with the evaluation of specific sperm or seminal plasma proteins could provide useful information on in vivo fertilizing capacity of semen doses.

Abstract

This study aimed to evaluate boar sperm characteristics and proteins, in relation to their importance regarding in vivo fertility. Sixty-five ejaculates were used and 468 sows (parity ≥ 2) were inseminated. Sperm CASA kinetics, morphology, viability, DNA fragmentation, mitochondrial membrane potential, sperm membrane biochemical activity (HOST) and sperm proteins (Heat Shock Protein 90-HSP90, glutathione peroxidase-5-GPX5, Osteopontin 70-OPN70) were assessed and related to field fertility (number of live-born piglets—NLBP, litter size ≥ 12 piglets—LS, farrowing rate—FR). Statistical analysis was conducted with simple and multiple regression models. Simple regression analysis showed that immotile sperm (IM) significantly affected the NLBP and LS, explaining 6.7% and 6.5% of their variation, respectively. The HOST positive spermatozoa significantly affected the NLBP and LS, explaining 24.5% and 7.8% of their variation, respectively. Similarly, sperm with activated mitochondria significantly affected the NLBP, explaining 13.5% of its variation. Moreover, the OPN70 affected LS and FR, explaining 7.5% and 10.8% of their variation, respectively. Sperm GPX5 protein affected FR, explaining 6.7% of its variation. Multiple regression analysis showed that the combination of IM and/OPN70 explains 13.0% of the variation regarding LS, and the combination of GPX5 and OPN70 explains 13.6% of the variation regarding FR. In conclusion, the estimation of parameters IM, membrane biochemical activity, mitochondrial membrane potential, OPN and GPX5 can provide useful information regarding semen doses for field fertility.

Macrophage ubiquitin-specific protease 2 contributes to motility, hyperactivation, capacitation, and in vitro fertilization activity of mouse sperm

Macrophages are innate immune cells that contribute to classical immune functions and tissue homeostasis. Ubiquitin-specific protease 2 (USP2) controls cytokine production in macrophages, but its organ-specific roles are still unknown. In this study, we generated myeloid-selective Usp2 knockout (msUsp2KO) mice and specifically explored the roles of testicular macrophage-derived USP2 in reproduction. The msUsp2KO mice exhibited normal macrophage characteristics in various tissues. In the testis, macrophage Usp2 deficiency negligibly affected testicular macrophage subpopulations, spermatogenesis, and testicular organogenesis. However, frozen-thawed sperm derived from msUsp2KO mice exhibited reduced motility, capacitation, and hyperactivation. In addition, macrophage Usp2 ablation led to a decrease in the sperm population exhibiting high intracellular pH, calcium influx, and mitochondrial membrane potential. Interrupted pronuclei formation in eggs was observed when using frozen-thawed sperm from msUsp2KO mice for in vitro fertilization. Administration of granulocyte macrophage-colony stimulating factor (GM-CSF), whose expression was decreased in testicular macrophages derived from msUsp2KO mice, restored mitochondrial membrane potential and total sperm motility. Our observations demonstrate a distinct role of the deubiquitinating enzyme in organ-specific macrophages that directly affect sperm function.

Stress response pathways in the male germ cells and gametes

The unfolded protein response (UPR) is a conserved and essential cellular pathway involved in protein quality control that is activated in response to several cellular stressors such as diseases states, ageing, infection and toxins. The cytosol, endoplasmic reticulum (ER) and mitochondria are continuously exposed to new proteins and in situations of aberrant protein folding; one of three lines of defence may be activated: (i) heat-shock response, (ii) mitochondrial UPR and (iii) ER UPR. These pathways lead to different signal transduction mechanisms that activate or upregulate transcription factors that, in turn, regulate genes that increase the cell's ability to correct the conformation of poorly folded proteins or, ultimately, lead to apoptosis. Despite the recent progress in understanding such biological processes, few studies have focused on the implications of the UPR in male infertility, highlighting the need for a first approach concerning the presence of these components in the male reproductive system. In testis, there is a high rate of protein synthesis, and the UPR mechanisms are well described. However, the presence of these mechanisms in spermatozoa, apparently transcriptionally inactive cells, is contentious, and it is unclear how sperm cells deal with stress. Here, we review current concepts and mechanisms of the UPR and highlight the relevance of these stress response pathways in male fertility, especially the presence and functional activation of those components in male germinal cells and spermatozoa.

Differential proteome between ejaculate and epididymal sperm represents a key factor for sperm freezability in wild small ruminants

Epididymal sperm shows higher cryoresistance than ejaculated sperm. Although the sperm proteome seems to affect cell cryoresistance, studies aiming at identifying proteins involved in sperm freezing-tolerance are scarce. The aims of this study were to investigate differences of sperm freezability and proteome between epididymal and ejaculated sperm in three mountain ungulates: Iberian ibex, Mouflon and Chamois. Sperm samples were cryopreserved in straws by slow freezing. Tandem mass tag-labeled peptides from sperm samples were analyzed by high performance liquid chromatography coupled to a mass spectrometer in three technical replicates. The statistical analysis was done using the moderated t-test of the R package limma. Differences of freezability between both types of sperm were associated with differences of the proteome. Overall, epididymal sperm showed higher freezability than ejaculated sperm. Between 1490 and 1883 proteins were quantified in each species and type of sperm sample. Cross species comparisons revealed a total of 76 proteins that were more abundant in epididymal than in ejaculated sperm in the three species of study whereas 3 proteins were more abundant in ejaculated than epididymal sperm in the three species of study (adjusted P < 0.05; |log₂| fold-change > 0.5). Many of the proteins that were associated with higher cryoresistance are involved in stress response and redox homeostasis. In conclusion, marked changes of sperm proteome were detected between epididymal and ejaculated sperm. This work contributes to update the sperm proteome of small ruminants and to identify candidate markers of sperm freezability.

Boar spermatozoa proteomic profile varies in sperm collected during the summer and winter

Boar sperm quality is less during the summer as a result of the different photoperiod or ambient temperatures as compared with the winter. The present study was conducted to elucidate possible variations in proteomic profiles of boar spermatozoa collected during the summer and winter. Effects of season on sperm viability, total motility, progressive motility, acrosome status, mitochondrial membrane potential and plasma membrane lipid organization were also analyzed. Only sperm viability and mitochondrial membrane potential were less during the summer (P <  0.05). Spermatozoa were processed and evaluated using the nano LC-MS/MS QTof procedures. A total of 1028 characterized proteins were identified in sperm collected during both seasons of the year (False Discovery Rate < 0.01) and, among the total, 85 proteins differed in sperm collected in the winter and summer, with there being a lesser abundance of these proteins when there were ejaculate collections during the summer (q-value ≤ 0.05). The results from enrichment assessments for these protein networks utilizing UniProtKB procedures for determining reproductive processes indicates there were 23 proteins that were less abundant in the summer than winter. These proteins have essential functions in spermatogenesis, sperm motility, acrosome reaction and fertilization. These results are the first where there was ascertaining of proteomic differences in boar spermatozoa collected in the summer and winter. These results might help to explain the decreased sperm quality and prolificity when semen of boars is used for artificial insemination that is collected during the season of the year when ambient temperatures are relatively greater.

Endogenous and Exogenous Antioxidants As a Tool to Ameliorate Male Infertility Induced by Reactive Oxygen Species

Significance: Antioxidants are essential for the maintenance of cellular redox homeodynamics in the male reproductive tract, playing a key role in fertilizing potential. Reactive oxygen species (ROS), at physiological levels, are essential for sperm function and fertilization. Under pathological conditions, abnormal production of ROS may occur. Redox control is primarily regulated by the inner antioxidant system. However, these endogenous antioxidants may be present at abnormal amounts or may be insufficient. Exogenous antioxidants obtained through the diet may have an important role, particularly in specific pathological conditions. This review addresses the regulation of redox homeodynamics in the male reproductive tract by endogenous and exogenous antioxidants and the importance of their cooperation for the maintenance of fertility. Recent Advances: Many studies have shown the importance of antioxidants for the preservation of male fertility, mostly under pathological conditions. Excessive antioxidants can inhibit ROS-induced signaling pathways that are essential for the reproductive system. The challenge is to keep the balance between oxidants and antioxidants to maintain ROS-amount at physiological concentration. Critical Issues: Although antioxidant therapies are gaining popularity and showing promising results in the improvement of male fertility, there is a lack of knowledge regarding the type of exogenous antioxidant, the doses and time to be administered. Future Directions: It would be of great importance to find a way to restore redox homeostasis under stress conditions. Understanding the poorly studied mechanisms by which exogenous antioxidants cooperate with the inner cellular antioxidant system to counteract free radicals may help in the development of new fertility therapies.

First Insights on the Presence of the Unfolded Protein Response in Human Spermatozoa

The unfolded protein response (UPR) is involved in protein quality control and is activated in response to several stressors. Although in testis the UPR mechanisms are well described, their presence in spermatozoa is contentious. We aimed to investigate the presence of UPR-related proteins in human sperm and the impact of oxidative stress induction in UPR activation. To identify UPR-related proteins in human sperm, a bioinformatic approach was adopted. To explore the activation of UPR, sperm were exposed to hydrogen peroxide (H₂O₂) and motility, vitality, and the levels of UPR-related proteins were assessed. We identified 97 UPR-related proteins in human sperm and showed, for the first time, the presence of HSF1, GADD34, and phosphorylated eIF2α. Additionally, the exposure of human sperm to H₂O₂ resulted in a significant decrease in sperm viability and motility and an increase in the levels of HSF1, HSP90, HSP60, HSP27, and eIF2α; all proteins involved in sensing and response to unfolded proteins. This study gave us a first insight into the presence of UPR mechanisms in the male gamete. However, the belief that sperm are devoid of transcription and translation highlight the need to clarify if these pathways are activated in sperm in the same way as in somatic cells.

Effect of boar semen supplementation with recombinant heat shock proteins during summer

Artificial insemination (AI) in pigs is mainly performed with refrigerated boar semen. There is a marked negative seasonal effect on the quality of boar sperm, mainly due to relatively greater ambient temperatures; to counteract this thermal stress, sperm cells possess natural defensive mechanisms such as Heat Shock Proteins (HSPs) that prevent protein denaturation. Thus, the objective of this research was to improve the quality of commercial boar semen collected during the summer when ambient temperatures are greater using recombinant HSPs. For this purpose, different concentrations (0.1, 0.5 and 1 μg/ml) of recombinant heat shock proteins (HSPD1, HSPA8 or HSP86) were added to commercial boar semen and there was cooling for 48 h at 17 °C. After this storage period, sperm quality was assessed by analyzing sperm viability, mitochondrial membrane potential and plasma membrane lipid organization using flow cytometry; additionally, sperm motility was examined using a CASA system. Also, in vitro fertilization (IVF) using HSP-supplemented boar semen was performed and the quality of the embryos produced was evaluated using quantitative real-time polymerase chain reaction (qPCR) analyzing the relative abundance of mRNA transcripts for genes encoding for embryo quality-related proteins (BAX, TFAM, POLG and POG2). Sperm quality variables, blastocyst rates and the abundance of mRNA transcripts for the selected genes were not affected by the presence of recombinant HSPs at any concentration. These results indicate that the supplementation of commercial seminal doses with recombinant HSPs does not improve boar sperm quality or fertility during the summer months when ambient temperatures are greater.

Influence of warming and reanimation conditions on seminiferous tubule morphology, mitochondrial activity, and cell composition of vitrified testicular tissues in the domestic cat model

Understanding critical roles of warming and reanimation is critical to improve the survival of vitrified testicular tissue in domestic cats. The objective was to study structural and functional properties of testicular tissues from prepubertal domestic cats after standard vitrification followed by two warming protocols (directly at 37°C or with a 5-second pre-exposure to 50°C) and three reanimation time points (immediately, 24 h and 5 days post-warming). In Experiment 1, tissues were evaluated for histo-morphology and mitochondrial activity immediately or 24 h after warming protocols. In Experiment 2, cell viability, DNA fragmentation, and germ cell composition were assessed immediately, 24 h, or 5 days after optimal warming. Preservation of seminiferous tubule structure was better using warming at 50°C for five seconds, and survival of somatic as well as germinal cells was higher compared to direct warming at 37°C for one minute. Short term in vitro culture (for reanimation) also proved that cellular composition and functionality were better preserved when warmed for a short time at 50°C. Collective data showed that short warming at 50°C led to better quality of seminiferous tubule structure and cell composition after vitrification and short-term culture. In addition, data suggest clear directions to further understand and optimize testicular tissue survival after fertility preservation procedures.

Calmodulin inhibitors increase the affinity of Merocyanine 540 for boar sperm membrane under non-capacitating conditions

We aimed to test whether the calmodulin (CaM) inhibitors, calmidazolium (CZ) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), can be used to assess lipid disorder by flow cytometry using Merocyanine 540 (M540). Boar spermatozoa were incubated in non-capacitating conditions for 10 min at room temperature with 1 μM CZ, 200 μM W-7, or 1 mM 8-bromoadenosine 3′,5′-cyclic monophosphate (8-Br-cAMP). Then, sperm were 1) directly evaluated, 2) centrifuged and washed prior to evaluation, or 3) diluted with PBS prior to evaluation. Direct evaluation showed an increase in high M540 fluorescence in spermatozoa treated with the inhibitors (4.7 ± 1.8 [control] vs. 70.4 ± 4.0 [CZ] and 71.4 ± 4.2 [W-7], mean % ± SD, P < 0.001); washing decreased the percentage of sperm showing high M540 fluorescence for W-7 (4.8 ± 2.2, mean % ± SD) but not for CZ (69.4 ± 3.9, mean % ± SD, P < 0.001), and dilution showed an increase in high M540 fluorescence for both CZ and W-7; 8-Br-cAMP did not induce a rise in sperm showing high M540 fluorescence. Therefore, special care must be taken when M540 is used in spermatozoa with CaM inhibitors.