Cytoskeleton Structure in Mouse Sperm and Testes After 30 Days of Hindlimb Unloading and 12 Hours of Recovery

Abstract

Background/Aims: Changes in the external mechanical field result in cytoskeleton reorganization and the formation of adaptive patterns in different types of cells, including somatic cells and sex cells. The aim of this research was to study the protein and mRNA content of cytoskeletal and sperm-specific genes in the sperm and testis cells of mice. Methods: Mice were subjected to 30 days of antiorthostatic suspension to simulate weightlessness, followed by 12 h of recovery, while receiving essential phospholipids at a dosage of 500 mg/kg/day (30HSE and 30HSE+12h groups) or a similar dosage of a placebo (30HS and 30HS+12h groups). Accordingly, reference groups (CE group and C group) were formed. The total number and the percentage of motile spermatozoa were calculated using a Makler chamber. To analyze the number of viable spermatozoa and the permeability of their membranes, eosin staining was used as well as Diff-Quick for a morphological evaluation. Relative protein and mRNA content was estimated in a western blot and quantitative PCR assay, respectively. Results: The relative protein expression levels of actin (beta and gamma) and two alpha-actinin isoforms (1 and 4) remained constant in the sperm of all study groups, except for the 30HS+12h group, where the alpha-actinin-4 level was 13% higher than in the reference group (p < 0.1). In the testis cells, the relative actin isoform content was equivalent to that in the spermatozoa. However, in the testis cells, the ACTN1 mRNA content was 17% higher in the 30HS group than in the C group (p < 0.05), and decreased after 12 h of recovery. In contrast, the ACTN4 mRNA content was 20% lower in the 30HS group than in the reference group (p < 0.05) and increased after the 12-h recovery period. At the same time, in the group administered the essential phospholipids, the relative ACTN1 and ACTN4 mRNA content did not differ from those of the reference group. The relative beta-tubulin content was similar in the reference C group and the reference CE group, which was administered the essential phospholipids. In the 30HS and 30HS+12h groups, the beta-tubulin content decreased by 19% and 22% (p < 0.05), respectively, and they also decreased in the groups administered the essential phospholipids (30HSE and 30HSE+12h groups, by 27% and 33%, respectively, p < 0.05). In the testis tissue, the relative tubulin content did not change in any of the experimental groups. At the same time, the relative mRNA content of the genes encoding the studied cytoskeletal proteins increased, which may indicate the protein content was regulated mainly at the translational level. Conclusion: The spermogram parameters and the content of the sperm-specific proteins and the associated mRNAs revealed a decrease in the number of mature spermatozoa in mice suspended under conditions of weightlessness. Moreover, the decrease was prevented by the administration of essential phospholipids.

Sperm Motility of Mice under Simulated Microgravity and Hypergravity

“…For sperm collection, we used both caudal epididymides from each male mouse and received sperm as described previously [ 10 ]. Briefly, immediately after extraction, the epididymis was placed in 1.2 mL α-MEM medium with 10% bovine serum heated to 37 °C.…”

“…After a 30-day antiorthostatic suspension of mice, we observed various changes in the spermogram of the mice: a decrease in the number of motile spermatozoa, a significant decrease in the proportion of viable sperm and a normal sperm morphology. According to the data on the sperm-specific protein levels, there was a shift towards immature forms, as well as various changes in the content of cytoskeletal proteins and the expression of the corresponding genes [ 10 ].…”

Drosophila melanogaster Sperm under Simulated Microgravity and a Hypomagnetic Field: Motility and Cell Respiration

“…In contrast, in mammals, the speed of sperm movement decreased. This result has been shown in experiments with animals that underwent antiorthostatic suspension [ 22 , 38 ] and during exposure of isolated sperm of humans and mice to simulated microgravity conditions [ 39 , 40 ].…”

“…We previously suggested that cell mechanoreception can be realized through deformation of the membrane and cortical cytoskeleton, leading to the initiation of various signaling pathways with increases and decreases in external mechanical stress [ 41 , 42 ]. Moreover, a change in the lipid composition of membranes and a decrease in cholesterol, which leads to rearrangements of the cortical cytoskeleton and an increase in the resistance of these structures to deformations, allowed us to prevent the effects of simulated microgravity in various cases, including for mouse sperm [ 22 , 43 ]. However, in this study, even with the use of essential phospholipids, the increased linear speed of the tail of the sperm of the fruit fly was maintained, although it was not as pronounced.…”

“…Moreover, similar changes occur in germ cells, which can be especially significant for the subsequent formation and development of the embryo. In space flight and in model experiments on Earth, the number of mature sperm cells decreased in rodents [ 18 , 19 , 20 , 21 ], and changes in their mobility, the structure of the cytoskeleton and the mRNA levels of various genes were observed, including changes in the epigenetic regulation of expression [ 22 , 23 , 24 , 25 ].…”