Physiological roles of relaxin in prefertilizing activities of spermatozoa

Interaction of sperm with endometrium can regulate genes involved in endometrial receptivity pathway in mice: An experimental study

Background

Many researchers consider implantation and endometrial receptivity as pertinent issues in reproductive science. Although, several experiments have been performed and their results evaluated, yet there is no confirmed evidence about the related factors and the role of sperm in endometrial receptivity.

Objective

To investigate the effect of the sperm-endometrium interaction in regulating genes involved in the endometrial receptivity pathway.

Materials and Methods

In this experimental study, 10 male and 30 female NMRI mice were included, and half of the male cases were vasectomized. The subjects were divided into two groups as follows; group 1 (case) comprised of 15 females mated with 5 non-vasectomized male mice, while group 2 (control) consisted of 15 females mated with 5 vasectomized males. Cases were sacrificed and assessed after 36 hr and the endometrial tissue was extracted and kept at -80°C until the next use. The expression of the endometrial receptivity pathway genes, including VEGF, HBEGF, FGF2, EGF, LIF, LIFR, HOXA10, MUC1, PGR, and CSF, was examined in both groups. For statistical analysis, an independent samples test (Mean ± SD) was used.

Results

The mRNA levels of LIF (p = 0.045), LIFR (p = 0.040), MUC1 (p = 0.032), VEGF (p = 0.022), EFG (p = 0.035), and FGF2 (p = 0.040) were significantly upregulated in the case group compared with the control group.

Conclusion

Finally, seminal plasma was observed to be effective in expressing the involved genes in the successful implantation pathway, including LIF, LIFR, MUC1, VEGF, EGF, and FGF2.

Effect of relaxin on semen quality variables of cryopreserved stallion semen

The aim of the study was to ascertain effects of different concentrations of relaxin added to extender medium during the pre-freezing incubation periods on quality variables of stallion frozen-thawed spermatozoa. Semen samples collected from three stallions were filtered, diluted with skim milk, and centrifuged at 600g for 10 min. Sperm pellets were suspended in BotuCrio freezing medium to a final concentration of 50 × 10⁶ sperm/mL. The diluted semen was divided into five experimental groups supplemented with 0 (control), 12.5, 25, 50, or 100 ng/mL of relaxin. The semen samples were transferred into 0.5 mL straws, equilibrated at 5 °C for 30 min, and placed in liquid nitrogen (LN₂) vapour for 15 min before being plunged into LN₂. After thawing, sperm samples were evaluated for motility and velocity variables, mitochondrial membrane potential, apoptosis, and plasma membrane and DNA integrities. For sperm motility variables, there were dose- and time-dependent effects, with the largest values recorded when 12.5 and 25 ng/mL relaxin were used for 0-120 min of incubation. Furthermore, at all of the concentrations at which there were evaluations, relaxin additions to semen diluent led to a marked improvement in sperm mitochondrial membrane potential and a lesser percentage of apoptotic cells compared to the control group. Plasma membranes and DNA integrities were not affected by relaxin supplementations to the diluent. In conclusion, supplementation of relaxin in extender before semen cryopreservation, especially at 12.5 and 25 ng/mL, had a positive effect on the sperm quality variables.

The Drosophila Accessory Gland as a Model for Prostate Cancer and Other Pathologies

The human prostate is a gland of the male reproductive tract, which together with the seminal vesicles, is responsible for most seminal fluid production. It is a common site of cancer, and unlike other glands, it typically enlarges in aging men. In flies, the male accessory glands make many major seminal fluid components. Like their human equivalents, they secrete proteins from several conserved families, including proteases, lectins, and cysteine-rich secretory proteins, some of which interact with sperm and affect fertility. A key protein, sex peptide, is not conserved in vertebrates but plays a central role in mediating long-term effects on females after mating. Although postmitotic, one epithelial cell type in the accessory glands, the secondary cell, continues to grow in adults. It secretes microvesicles called exosomes from the endosomal multivesicular body, which, after mating, fuse with sperm. They also appear to affect female postmating behavior. Remarkably, the human prostate epithelium also secretes exosomes, which fuse to sperm in vitro to modulate their activity. Exosomes from prostate and other cancer cells are increasingly proposed to play fundamental roles in modulating the tumor microenvironment and in metastasis. Here we review a diverse accessory gland literature, which highlights functional analogies between the male reproductive glands of flies and humans, and a critical role for extracellular vesicles in allowing seminal fluid to promote male interests within the female. We postulate that secondary cells and prostate epithelial cells use common mechanisms to control growth, secretion, and signaling, which are relevant to prostate and other cancers, and can be genetically dissected in the uniquely tractable fly model.