Increased in vitro binding and fertilizing ability of mouse sperm exposed to a synthetic peptide

A systematic review identifying seminal plasma biomarkers and their predictive ability on IVF and ICSI outcomes

The diverse nature and high molecule concentration of seminal plasma (SP) makes this fluid a good potential source for a potential biomarker that could predict assisted reproductive technology (ART) outcomes. Currently, semen quality parameters cannot accurately predict ART outcomes. A systematic literature search was conducted to identify human SP biomarkers with potential predictive ability for the outcomes of IVF and intracytoplasmic sperm injection. Observational cohort and case-control studies describing the association between biomarkers in human SP and the outcome of infertile men attending for ART were included. Forty-three studies were selected, reporting on 89 potential SP biomarkers (grouped as oxidative stress, proteins glycoproteins, metabolites, immune system components, metals and trace elements and nucleic acids). The present review supports 32 molecules in SP as potentially relevant biomarkers for predicting ART outcomes; 23 molecules were reported once and nine molecules were reported in more than one study; IL-18 and TGF-β1-IL-18 ratio were confirmed in distinct studies. This review presents the most comprehensive overview of relevant SP biomarkers to predict ART outcomes to date, which is of clinical interest for infertility investigations and assisted reproduction; nevertheless, its potential is under-exploited. This review could serve as starting point for designing an all-encompassing study for biomarkers in SP and their predictive ability for ART outcomes, and for developing a non-invasive diagnostic tool.

Cascading effects of hypobaric hypoxia on the testis: insights from a single-cell RNA sequencing analysis

Most mammals tolerate exposure to hypobaric hypoxia poorly as it may affect multiple regulatory mechanisms and inhibit cell proliferation, promote apoptosis, limit tissue vascularization, and disrupt the acid-base equilibrium. Here, we quantified the functional state of germ cell development and demonstrated the interaction between the germ and somatic cells via single-cell RNA sequencing (scRNA-seq). The present study elucidated the regulatory effects of hypobaric hypoxia exposure on germ cell formation and sperm differentiation by applying enrichment analysis to genomic regions. Hypobaric hypoxia downregulates the genes controlling granule secretion and organic matter biosynthesis, upregulates tektin 1 (TEKT1) and kinesin family member 2C (KIF2C), and downregulates 60S ribosomal protein 11 (RPL11) and cilia- and flagella-associated protein 206 (CFAP206). Our research indicated that prosaposin-G protein-coupled receptor 37 (PSAP-GPR37) ligands mediate the damage to supporting cells caused by hypobaric hypoxic exposure. The present work revealed that hypoxia injures peritubular myoid (PTM) cells and spermatocytes in the S phase. It also showed that elongating spermatids promote maturation toward the G2 phase and increase their functional reserve for sperm-egg binding. The results of this study provide a theoretical basis for future investigations on prophylactic and therapeutic approaches toward protecting the reproductive system against the harmful effects of hypobaric hypoxic exposure.

Sub-fertility in crossbred bulls: Identification of proteomic alterations in spermatogenic cells using high throughput comparative proteomics approach

The present study was carried out to compare the proteomic profiles of spermatogenic cells of crossbred and zebu cattle in an effort to understand the possible reasons for a higher incidence of sub-fertility in crossbred bulls. The spermatogenic cells collected from the testes of pre-pubertal (6 mo) and adult (24 mo) crossbred and zebu males through fine needle aspiration were proliferated in vitro, and proteomic profiling was done using a shotgun proteomics approach. The age- and species-specific variations in the expression level of proteins were identified in spermatogenic cells. The number of differentially expressed proteins (DEPs) identified in pre-pubertal zebu and crossbred was 546, while 579 DEPs were identified between adult zebu and crossbred bulls. Out of these, 194 DEPS were common to these groups and 40 DEPs displayed a fold change ≥2. However, only 20 proteins exhibited similar expression variation trends (upregulated or downregulated) among pre-pubertal as well as adult zebu and crossbred bulls. Out of these 20 DEPs, 13 proteins were upregulated, and 7 proteins were downregulated in spermatogenic cells of zebu compared to crossbred bulls. Among the upregulated proteins were RPLP2, PAXIP1, calumenin, prosaposin, GTF2F1, TMP2, ubiquitin conjugation factor E4A, COL1A2, vimentin, protein FAM13A, peripherin, GFPT2, and GRP78. Seven proteins that were downregulated in zebu bulls compared to crossbred included APOA1, G patch domain-containing protein 1, NAD P transhydrogenase mitochondrial, glutamyl aminopeptidase, synaptojanin 1 fragment, Arf GAP with SH3 domain ANK repeat and PH domain-containing protein 1, and protein transport protein sec16B. It was inferred that the proteins associated with sperm function and fertilization processes, such as calumenin, prosaposin, vimentin, GRP78, and APOA1 could be studied further to understand the precise cause of subfertility in crossbred bulls.

Prosaposin in seminal plasma on the day of oocyte retrieval is associated with normal fertilization and embryo development in in vitro fertilization cycles

The prospective study including 166 participants aims to evaluate the association between seminal prosaposin and the outcomes of in vitro fertilization (IVF) cycles in humans. The generalized linear model (GLM) was used to analyze the associations between seminal prosaposin concentrations and normal fertilization rates and good embryos proportion. The generalized estimating equation (GEE) was used to evaluate the association between embryo parameters and the prosaposin concentrations. Each model was adjusted for age of the couples, female basal FSH, AFC and BMI, starting dose and oocyte yield of IVF cycles and smoker. GLM models suggested that prosaposin was significantly associated with fertilization rate (P = 0.005) and good embryo proportion (P = 0.038) while none of the semen parameters (sperm concentration, motility, progressive motility, normal morphology rate, postwash sperm concentration and motility) was significantly associated with the parameters in the cohort. Using GEE, it was also shown that prosaposin was positively associated with the occurrence of early cleavage and negatively associated with uneven cleavage pattern on day 3. In both the overall population and the normozoospermia patients, the prosaposin was significantly associated with pregnancy with adjustment with covariates. In conclusion, our data suggested that seminal prosaposin concentration could provide more information regarding normal fertilization and embryo development in IVF than traditional semen parameters.

Creatine enhances the duration of sperm capacitation: a novel factor for improving in vitro fertilization with small numbers of sperm

STUDY QUESTION

Why are many sperm required for successful fertilization of oocytes in vitro, even though fertilization occurs in vivo when only a few sperm reach the oocyte?

SUMMARY ANSWER

Creatine produced in the ovary promotes efficient fertilization in vivo; however, in vitro, creatine is not contained in the in vitro fertilization (IVF) medium.

WHAT IS KNOWN ALREADY

The IVF medium enables capacitation of sperm. However, the IVF medium does not fully mimic the in vivo environment during fertilization. Consequently, fertilization in vitro is more inefficient than in the oviduct.

STUDY DESIGN, SIZE, DURATION

Follicular and oviductal fluids were collected and then analyzed for creatine and glucose levels. To determine the physiological functions of creatine, the creatine antagonist 3-guanidinopropionic acid (GPA) was injected into hormonally primed mice. Using conventional IVF protocols, sperm were pre-incubated in IVF medium with creatine and then co-cultured with 10 ovulated cumulus-oocyte complexes (1-1000 per oocyte) in 50 μl medium droplets.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Glucose and creatine levels were measured using commercial enzymatic assay kits. The effect of creatine in vivo was assessed by mating experiments using mice treated with or without GPA just before ovulation. To assess the functions of sperm incubated in IVF medium containing creatine, we analyzed (1) the motility of sperm using computer-assisted sperm assay, (2) the capacitation level of sperm by western blot analyses, and (3) the condition of sperm acrosomes by peanut agglutinin lectin-FITC staining.

MAIN RESULTS AND THE ROLE OF CHANCE

Oviductal creatine levels were significantly increased following ovulation. Injecting mice with GPA just before ovulation significantly reduced the number of fertilized oocytes. The addition of creatine to IVF medium enhanced sperm capacitation by increasing ATP levels. Successful fertilization was achieved with as few as five sperm/oocyte in the creatine group, and the number of fertilized oocytes was significantly higher than in the control without creatine (P < 0.01).

LIMITATIONS, REASONS FOR CAUTION

In the present study, a pharmacological approach, creatine antagonist (GPA) treatment, but not a knockout mouse model, was used to understand the role of creatine in vivo. The role of creatine in fertilization processes can only be shown in a mouse model.

WIDER IMPLICATIONS OF THE FINDINGS

A modified IVF technique using creatine-containing medium was developed and shown to markedly improve fertilization with small numbers of sperm. This approach has the potential to be highly beneficial for human assisted reproductive technologies, especially for patients with a limited number of good quality sperm.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by JSPS KAKENHI Grant numbers JP24688028, JP16H05017 (to M.S.), and JP15J05331 (to T.U.), the Japan Agency for Medical Research and Development (AMED) (16gk0110015h0001 to M.S.), and National Institutes of Health (NIH-HD-076980 to J.S.R). The authors have nothing to disclose.

Conservation of expression and alternative splicing in the prosaposin gene

Prosaposin is the precursor of four lysosomal activator molecules known as saposins A, B, C and D. It is also secreted and was proposed to be a neurotrophic factor. The neurotrophic function was attributed to the amino terminus of saposin C. In man, mouse and rat prosaposin is transcribed to two major isoforms differing in the inclusion of 9 bps of exon 8 within the saposin B domain. In the present study, we show that there is evolutionary conservation of the prosaposin structure and alternative splicing in chick and zebrafish as well. Moreover, there is conservation in prosaposin expression as tested immunohistochemically in the mouse and chick developing brain. We developed a sensitive assay to quantitate the prosaposin alternatively spliced forms. Our results indicate that, in mouse brain, skeletal and cardiac muscle the exon 8-containing RNA is most abundant, while it is almost absent from visceral and smooth muscle-containing organs. We observed temporal and differential expression of the alternatively spliced prosaposin mRNAs in mouse and chick brain as well as during development. The elevation in the abundance of exon 8-containing prosaposin RNA during mouse and chick brain development may suggest a role for the exon 8-containing prosaposin form in this process.