Kisspeptin Protein in Seminal Plasma Is Positively Associated with Semen Quality: Results from the MARHCS Study in Chongqing, China

Identification of potential candidate miRNAs related to semen quality in seminal plasma extracellular vesicles and sperms of male duck (Anas Platyrhynchos)

Semen quality is an important indicator that can directly affect fertility. In mammals, miRNAs in seminal plasma extracellular vesicles (SPEVs) and sperms can regulate semen quality. However, relevant regulatory mechanism in duck sperms remains largely unclear. In this study, duck SPEVs were isolated and characterized by transmission electron microscopy (TEM), western blot (WB), and nanoparticle tracking analysis (NTA). To identify the important molecules affecting semen quality, we analysed the miRNA expression in sperms and SPEVs of male ducks in high semen quality group ((DHS, DHSE) and low semen quality group (DLS, DLSE). We identified 94 differentially expressed (DE) miRNAs in the comparison of DHS vs. DLS, and 21 DE miRNAs in DHSE vs. DLSE. Target genes of SPEVs DE miRNAs were enriched in ErbB signaling pathway, glycometabolism, and ECM-receptor interaction pathways (P < 0.05), while the target genes of sperm DE miRNAs were enriched in ribosome (P < 0.05). The miRNA-target-pathway interaction network analyses indicated that 5 DE miRNAs (miR-34c-5p, miR-34b-3p, miR-449a, miR-31-5p, and miR-128-1-5p) targeted the largest number of target genes enriched in MAPK, Wnt and calcium signaling pathways, of which FZD9 and ANAPC11 were involved in multiple biological processes related to sperm functions, indicating their regulatory effects on sperm quality. The comparison of DE miRNAs of SPEVs and sperms found that mir-31-5p and novel-273 could potentially serve as biomarkers for semen quality detection. Our findings enhance the insight into the crucial role of SPEV and sperm miRNAs in regulating semen quality and provide a new perspective for subsequent studies.

Effect of Pre-Incubation of Cryopreserved Sperm with either Kisspeptin or Glutathione to Mitigate Freeze-Thaw Damage

Background

Sperm cryopreservation reduces sperm quality. Kisspeptin (KP) has beneficial effects on sperm functions. This study compares the effect of KP and Glutathione (GSH) on mitigating the detrimental effects of the freeze-thaw cycle on sperm.

Methods

An experimental study was conducted in Birjand (Iran) during 2018-2020. Thirty normal swim-up semen samples were treated with Ham's F10 medium (negative control), 1 mM GSH (positive control), or KP (10 µM) for 30 min before freezing. The motility, acrosome reaction, capacitation, and DNA quality of the frozen-thawed sperms were assessed according to the WHO guidelines. Statistical analysis was performed using paired t test, one-way analysis of variance, and least significant difference.

Results

Pre-incubation with KP significantly increased the percentage of sperm motility (34.00±6.7, P=0.003) compared to the control (20.44±7.4) and GSH-treated (31.25±12.2) aliquots. The frequency of non-capacitated spermatozoa was significantly higher in the KP-treated group (98.73%) than in the control (96.46%) and GSH-treated (96.49%) aliquots (P<0.001). The percentage of acrosome-intact spermatozoa in the KP-treated group (77.44%) was significantly higher than the control (74.3%) and GSH-treated (74.54%) groups (P<0.001). The sperm frequency with normal histone in the KP-treated group (51.86%) and with normal protamine (65.39%) was significantly higher than the controls (P=0.001 and P=0.002, respectively). The percentage of TUNEL-positive sperm was significantly lower in the KP-treated group (9.09±2.71) than both GSH-treated (11.22±2.73) and control (11.31±2.2) groups (both P=0.002).

Conclusion

Pre-incubation with KP protects sperm motility and DNA integrity from the detrimental effect of the freeze-thaw cycle. KP is suitable as a pre-treatment to control sperm quality during freezing-thawing.

CRISPR/Cas9-editing of KISS1 to generate pigs with hypogonadotropic hypogonadism as a castration free trait

Introduction: Most male pigs are surgically castrated to avoid puberty-derived boar taint and aggressiveness. However, this surgical intervention represents a welfare concern in swine production. Disrupting porcine KISS1 is hypothesized to delay or abolish puberty by inducing variable hypogonadotropism and thus preventing the need for castration. Methods: To test this hypothesis, we generated the first KISS1-edited large animal using CRISPR/Cas9-ribonucleoproteins and single-stranded donor oligonucleotides. The targeted region preceded the sequence encoding a conserved core motif of kisspeptin. Genome editors were intracytoplasmically injected into 684 swine zygotes and transferred to 19 hormonally synchronized surrogate sows. In nine litters, 49 American Yorkshire and 20 Duroc liveborn piglets were naturally farrowed. Results: Thirty-five of these pigs bore KISS1-disruptive alleles ranging in frequency from 5% to 97% and did not phenotypically differ from their wild-type counterparts. In contrast, four KISS1-edited pigs (two boars and two gilts) with disruptive allele frequencies of 96% and 100% demonstrated full hypogonadotropism, infantile reproductive tracts, and failed to reach sexual maturity. Change in body weight during development was unaffected by editing KISS1. Founder pigs partially carrying KISS1-disruptive alleles were bred resulting in a total of 53 KISS1 ^+/+, 60 KISS1 ^+/-, and 34 KISS1 ^-/- F1 liveborn piglets, confirming germline transmission. Discussion: Results demonstrate that a high proportion of KISS1 alleles in pigs must be disrupted before variation in gonadotropin secretion is observed, suggesting that even a small amount of kisspeptin ligand is sufficient to confer proper sexual development and puberty in pigs. Follow-on studies will evaluate fertility restoration in KISS1 KO breeding stock to fully realize the potential of KISS1 gene edits to eliminate the need for surgical castration.

Hypothalamic-Pituitary-Gonadal Axis Disorders Impacting Fertility in Both Sexes and the Potential of Kisspeptin-Based Therapies to Treat Them

Impaired function of the hypothalamic-pituitary-gonadal (HPG) axis can lead to a vast array of reproductive disorders some of which are inherited or acquired, but many are of unknown etiology. Among the clinical consequences of HPG impairment, infertility is quite common. According to the latest report from the World Health Organization, the global prevalence of infertility during a person's lifetime is a staggering 17.5% which translate into 1 out of every 6 people experiencing it. In both sexes, infertility is associated with adverse health events, and if unresolved, infertility can cause substantial psychological stress, social stigmatization, and economic strain. Even though significant advances have been made in the management and treatment of infertility, low or variable efficacy of treatments and medication adverse effects still pose a significant problem. However, the discovery that in humans inactivating mutations in the gene encoding the kisspeptin receptor (Kiss1R) results in pubertal failure and infertility has expanded our understanding of the mechanisms underlying the neuroendocrine control of reproduction, opening up potential new therapies for the treatment of infertility disorders. In this chapter we provide an overview of common infertility disorders affecting men and women, their recommended treatments, and the potential of kisspeptin-based pharmacotherapies to treat them.

Expression of Kisspeptin in the Adult Hamster Testis

Kisspeptins, products of KISS1 gene, are ligands of the G-protein coupled receptor (GPR54), and the kisspeptin-GPR54 signaling has an important role as an upstream regulator of gonadotropin releasing hormone (GnRH) neurons. Interestingly, extrahypothalamic expressions of kisspeptin/GPR-54 in gonads have been found in primates and experimental rodents such as rats and mice. Hamsters, another potent experimental rodent, also have a kisspeptin-GPR54 system in their ovaries. The presence of testicular kisspeptin-GPR54 system, however, remains to be solved. The present study was undertaken to determine whether the kisspeptin is expressed in hamster testis. To do this, reverse transcription-polymerase chain reactions (RT-PCRs) and immunohistochemistry (IHC) were employed. After the nest PCR, two cDNA products (320 and 280 bp, respectively) were detected by 3% agarose gel electrophoresis, and sequencing analysis revealed that the 320 bp product was correctly amplified from hamster kisspeptin cDNA. Modest immunoreactive (IR) kisspeptins were detected in Leydig-interstitial cells, and the weak signals were detected in germ cells, mostly in round spermatids and residual bodies of elongated spermatids. In the present study, we found the kisspeptin expression in the testis of Syrian hamster. Further studies on the local role(s) of testicular kisspeptin are expected for a better understanding the physiology of hamster testis, including photoperiodic gonadal regression specifically occurred in hamster gonads.

The Kisspeptin System in Male Reproduction

The kisspeptin system includes the cleavage products Kiss1 precursor and kisspeptin receptor (Kiss1R). It was originally discovered and studied in cancer metastasis, but the identification of KISS1/KISS1R gene mutations causing hypogonadotropic hypogonadism (HH) revealed unexpected effects in reproduction. Nowadays, the kisspeptin system is the main central gatekeeper of the reproductive axis at puberty and adulthood, but it also has a widespread functional role in the control of endocrine functions. At the periphery, Kiss1 and Kiss1R are expressed in the testes, but the need for kisspeptin signaling for spermatogenesis and sperm quality is still unclear and debated. This brief manuscript summarizes the main findings on kisspeptin and male reproduction; upcoming data on sperm maturation are also discussed.

Differential Expression of Kisspeptin System and Kisspeptin Receptor Trafficking during Spermatozoa Transit in the Epididymis

The hypothalamus–pituitary–testis axis controls the production of spermatozoa, and the kisspeptin system, comprising Kiss1 and Kiss1 receptor (Kiss1R), is the main central gatekeeper. The activity of the kisspeptin system also occurs in testis and spermatozoa, but currently the need of peripheral kisspeptin to produce gametes is not fully understood. Hence, we characterized kisspeptin system in rat spermatozoa and epididymis caput and cauda and analyzed the possible presence of Kiss1 in the epididymal fluid. The presence of Kiss1 and Kiss1R in spermatozoa collected from epididymis caput and cauda was evaluated by Western blot; significant high Kiss1 levels in the caput (p < 0.001 vs. cauda) and constant levels of Kiss1R proteins were observed. Immunofluorescence analysis revealed that the localization of Kiss1R in sperm head shifts from the posterior region in the epididymis caput to perforatorium in the epididymis cauda. In spermatozoa-free epididymis, Western blot revealed higher expression of Kiss1 and Kiss1R in caput (p < 0.05 vs. cauda). Moreover, immunohistochemistry revealed that Kiss1 and Kiss1R proteins were mainly localized in the secretory epithelial cell types and in contractile myoid cells, respectively. Finally, both dot blot and Elisa revealed the presence of Kiss1 in the epididymal fluid collected from epididymis cauda and caput, indicating that rat epididymis and spermatozoa possess a complete kisspeptin system. In conclusion, we reported for the first time in rodents Kiss1R trafficking in spermatozoa during the epididymis transit and Kiss1 measure in the epididymal fluid, thus suggesting a possible role for the system in spermatozoa maturation and storage within the epididymis.

Characterization and proteomics of chicken seminal plasma extracellular vesicles

In mammals, seminal plasma extracellular vesicles (SPEVs) can regulate sperm motility and capacitation. The characteristics and functions of SPEVs in avians have been rarely reported. In this study, chicken SPEVs were isolated and characterized by transmission and scanning electron microscopy (TEM/SEM) and nanoparticle tracking analysis (NTA); furthermore, seven extracellular vesicle (EVs) marker proteins were detected by Western blot (WB). TEM revealed that chicken SPEVs had a classic bilayer membrane structure. NTA confirmed that the size of SPEVs was 30-250 nm, and concentration ranged from 8.0 E + 11-8.5 E + 11 particles/ml. There were 3073 SPEVs proteins identified by deep sequencing, including 2794 intracellular proteins and 279 extracellular proteins. The overlap rate of proteomes between chicken SPEVs and vesicles reported in the Vesiclepedia database reached 86%, and 360 new proteins that had not been reported by the ExoCarta and Vesiclepedia databases were identified in chicken SPEV proteomes. Gene Ontology (GO) analysis revealed that chicken SPEV proteins were mainly enriched in supplying energy and transporting protein. There were 4 IFT family proteins speculated to play an important role in sperm composition and function. Our data were compared with two previously published studies on the proteomics of chicken seminal plasma (SP) and hen uterine fluid, and some overlapping proteins described in chicken SPEVs had been identified in hen uterine fluid (545) and chicken SP (284). In conclusion, these findings will increase our understanding of the content and composition of proteome in SPEVs and provide new insights into the important role of the SPEV regulation in sperm functions.

Kisspeptin Receptor on the Sperm Surface Reflects Epididymal Maturation in the Dog

Alongside the well-known central modulatory role, the Kisspeptin system, comprising Kiss1, its cleavage products (Kisspeptins), and Kisspeptin receptor (Kiss1R), was found to regulate gonadal functions in vertebrates; however, its functional role in the male gamete and its localization during maturation have been poorly understood. The present study analyzed Kisspeptin system in dog testis and spermatozoa recovered from different segments of the epididymis, with focus on Kiss1R on sperm surface alongside the maturation during epididymal transit, demonstrated by modification in sperm kinetic, morphology, and protamination. The proteins Kiss1 and Kiss1R were detected in dog testis. The receptor Kiss1R only was detected in total protein extracts from epididymis spermatozoa, whereas dot blot revealed Kiss1 immunoreactivity in the epidydimal fluid. An increase of the Kiss1R protein on sperm surface along the length of the epididymis, with spermatozoa in the tail showing plasma membrane integrity and Kiss1R protein (p < 0.05 vs. epididymis head and body) was observed by flow cytometry and further confirmed by epifluorescence microscopy and Western blot carried on sperm membrane preparations. In parallel, during the transit in the epididymis spermatozoa significantly modified their ability to move and the pattern of motility; a progressive increase in protaminization also occurred. In conclusion, Kisspeptin system was detected in dog testis and spermatozoa. Kiss1R trafficking toward plasma membrane along the length of the epididymis and Kiss1 in epididymal fluid suggested a new functional role of the Kisspeptin system in sperm maturation and storage.

Role of Kisspeptin on Hypothalamic-Pituitary-Gonadal Pathology and Its Effect on Reproduction

Kisspeptin is a neuropeptide that plays a significant role in human reproduction by its action on the hypothalamic-pituitary-gonadal (HPG) axis and functions through a G-protein-coupled receptor called G-protein-coupled receptor 54/kisspeptin 1 receptor (GPR54/KISS1R). It is encoded by the kisspeptin 1 (KISS1) gene that is mainly expressed in the hypothalamus. Kisspeptins are also recognized as vital aspects of maturation and proper function of the reproductive system in both males and females. It also plays its role in the onset of puberty, sexual patterns, desires, ovum development in women, sperm quality in men, feedback mechanisms, pregnancy, and lactation. Studies proved the pathological role of kisspeptin dysregulation in disorders like polycystic ovarian syndrome (PCOS) and infertility. Mutations in the KISS1 gene also contribute to precocious puberty or hypogonadotropic hypogonadism, depending upon the nature of mutations. Levels of kisspeptin also aid in the identification of a few pregnancy-related complications like preeclampsia, intrauterine growth restriction, and act as a marker of miscarriage. Due to the wide range of effects that kisspeptin has on the reproductive axis, investigations are being carried out to develop it as a diagnostic marker, treat diseases like hypogonadism and PCOS, and solve infertility issues.

Seminal Plasma Proteome as an Indicator of Sperm Dysfunction and Low Sperm Motility in Chickens

Molecular mechanisms underlying sperm motility have not been fully explained, particularly in chickens. The objective was to identify seminal plasma proteins associated with chicken sperm motility by comparing the seminal plasma proteomic profile of roosters with low sperm motility (LSM, n = 4) and high sperm motility (HSM, n = 4). Using a label-free MS-based method, a total of 522 seminal plasma proteins were identified, including 386 (∼74%) previously reported and 136 novel ones. A total of 70 differentially abundant proteins were defined, including 48 more-abundant, 15 less-abundant, and seven proteins unique to the LSM group (specific proteins). Key secretory proteins like less-abundant adhesion G-protein coupled receptor G2 (ADGRG2) and more-abundant serine peptidase inhibitor Kazal-type 2 (SPINK2) in the LSM suggested that the corresponding secretory tissues played a crucial role in maintaining sperm motility. Majority (80%) of the more-abundant and five specific proteins were annotated to the cytoplasmic domain which might be a result of higher plasma membrane damage and acrosome dysfunction in LSM. Additionally, more-abundant mitochondrial proteins were detected in LSM seminal plasma associated with lower spermatozoa mitochondrial membrane potential (ΔΨm) and ATP concentrations. Further studies showed that the spermatozoa might be suffering from oxidative stress, as the amount of spermatozoa reactive oxygen species (ROS) were largely enhanced, seminal malondialdehyde (MDA) concentrations were increased, and the seminal plasma total antioxidant capacity (T-AOC) were decreased. Our study provides an additional catalogue of chicken seminal plasma proteome and supports the idea that seminal plasma could be as an indicator of spermatozoa physiology. More-abundant of acrosome, mitochondria and sperm cytoskeleton proteins in the seminal plasma could be a marker of sperm dysfunction and loss of motility. The degeneration of spermatozoa caused by the reduced seminal T-AOC and enhanced oxidative stress might be potential determinants of low sperm motility. These results could extend our understanding of sperm motility and sperm physiology regulation.

Kisspeptin and Testicular Function-Is it Necessary?

The role of kisspeptin in stimulating hypothalamic GnRH is undisputed. However, the role of kisspeptin signaling in testicular function is less clear. The testes are essential for male reproduction through their functions of spermatogenesis and steroidogenesis. Our review focused on the current literature investigating the distribution, regulation and effects of kisspeptin and its receptor (KISS1/KISS1R) within the testes of species studied to date. There is substantial evidence of localised KISS1/KISS1R expression and peptide distribution in the testes. However, variability is observed in the testicular cell types expressing KISS1/KISS1R. Evidence is presented for modulation of steroidogenesis and sperm function by kisspeptin signaling. However, the physiological importance of such effects, and whether these are paracrine or endocrine manifestations, remain unclear.

Tachykinins and Kisspeptins in the Regulation of Human Male Fertility

Infertility is a global disease affecting one out of six couples of reproductive age in the world, with a male factor involved in half the cases. There is still much to know about the regulation of human male fertility and thus we decided to focus on two peptide families that seem to play a key role in this function: tachykinins and kisspeptins. With this aim, we conducted an exhaustive review in order to describe the role of tachykinins and kisspeptins in human fertility and their possible implications in infertility etiopathogenesis. Many advances have been made to elucidate the roles of these two families in infertility, and multiple animal species have been studied, including humans. All of this knowledge could lead to new advances in male infertility diagnosis and treatment, but further research is needed to clarify all the implications of tachykinins and kisspeptins in fertility.

Reproductive functions of Kisspeptin/KISS1R Systems in the Periphery

Kisspeptin and its G protein-coupled receptor KISS1R play key roles in mammalian reproduction due to their involvement in the onset of puberty and control of the hypothalamic-pituitary-gonadal axis. However, recent studies have indicated a potential role of extra-hypothalamic kisspeptin in reproductive function. Here, we summarize recent advances in our understanding of the physiological significance of kisspeptin/KISS1R in the peripheral reproductive system (including the ovary, testis, uterus, and placenta) and the potential role of kisspeptin/KISS1R in reproductive diseases. A comprehensive understanding of the expression, function, and potential molecular mechanisms of kisspeptin/KISS1R in the peripheral reproductive system will contribute to the diagnosis, treatment and prevention of reproductive diseases.