Nerve growth factor promotes human sperm motility in vitro by increasing the movement distance and the number of A grade spermatozoa

Nerve growth factor alleviates arsenic-induced testicular injury by enhancing the function of Sertoli cells

Sertoli cells (SCs) maintain testicular homeostasis and promote spermatogenesis by forming the blood-testis barrier (BTB) and secreting growth factors. The pro-proliferative and anti-apoptotic effects of nerve growth factor (NGF) on SCs have been proved previously. It is still unclear whether the damage effect of arsenic on testis is related to the inhibition of NGF expression, and whether NGF can mitigate arsenic-induced testicular damage by decreasing the damage of SCs induced by arsenic. Here, the lower expression of NGF in testes of arsenic exposed mice (freely drinking water containing 15 mg/l of NaAsO2) was observed through detection of Western blot and Real-time PCR. Subsequently, hematoxylin and eosin (HE) staining, Evans blue staining and transmission electron microscopy were used to evaluate the pathology, BTB permeability and tight junction integrity in testes of control mice, arsenic exposed mice (freely drinking water containing 15 mg/l of NaAsO2) and arsenic + NGF treated mice (freely drinking water containing 15 mg/l of NaAsO2 + intraperitoneal injection with 30 μg/kg of NGF), respectively. Evidently, spermatogenic tubule epithelial cells in testis of arsenic exposed mice were disordered and the number of cell layers was reduced, accompanied by increased permeability and damaged integrity of the tight junction in BTB, but these changes were less obvious in testes of mice treated with arsenic + NGF. In addition, the sperm count, motility and malformation rate of mice treated with arsenic + NGF were also improved. On the basis of the above experiments, the viability and apoptosis of primary cultured SCs treated with arsenic (10 μM NaAsO2) or arsenic + NGF (10 μM NaAsO2 + 100 ng/mL NGF) were detected by Cell counting kit-8 (CCK8) and transferase-mediated DUTP-biotin nick end labeling (TUNEL) staining, respectively. It is found that NGF ameliorated the decline of growth activity and the increase of apoptosis in arsenic-induced SCs. This remarkable biological effect that NGF inhibited the increase of Bax expression and the decrease of Bcl-2 expression in arsenic-induced SCs was also determined by western blot and Real-time PCR. Moreover, the decrease in transmembrane resistance (TEER) and the expression of tight junction proteins ZO-1 and occludin was mitigated in SCs induced by arsenic due to NGF treatment. In conclusion, the above results confirmed that NGF could ameliorate the injury effects of arsenic on testis, which might be related to the function of NGF to inhibit arsenic-induced SCs injury.

Association between mitochondrial DNA genotype and sperm motility in humans

The relationship between genetic alterations in mitochondrial DNA (mtDNA) and progressive motility (PR) and rapid progressive motility (grade A) of ejaculated human spermatozoa remains unclear. In this study, we explored the association between human mtDNA genotype and sperm PR and grade A by analyzing mtDNA copy number, loci, haplogroup, rearrangement, deletions, and duplications and sperm motility parameters. Human sperm mtDNA copy number, loci and haplogroups were not associated with human sperm motility PR or A grade. However, the cumulative frequency of human sperm mtDNA rearrangements (including deletions and duplications) in participants with high PR and grade A ratio was higher than in participants with low PR and grade A ratio. Additional studies are needed to understand the relationship between mtDNA genotypes, including deletions and duplications, and human sperm motility.

NGF, EPO, and IGF-1 in the Male Reproductive System

Several studies have demonstrated interesting results considering the implication of three growth factors (GFs), namely nerve growth factor (NGF), erythropoietin (EPO), and the insulin-like growth factor-I (IGF-1) in the physiology of male reproductive functions. This review provides insights into the effects of NGF, EPO, and IGF-1 on the male reproductive system, emphasizing mainly their effects on sperm motility and vitality. In the male reproductive system, the expression pattern of the NGF system varies according to the species and testicular development, playing a crucial role in morphogenesis and spermatogenesis. In humans, it seems that NGF positively affects sperm motility parameters and NGF supplementation in cryopreservation media improves post-thaw sperm motility. In animals, EPO is found in various male reproductive tissues, and in humans, the protein is present in seminal plasma and testicular germ cells. EPO receptors have been discovered in the plasma membrane of human spermatozoa, suggesting potential roles in sperm motility and vitality. In humans, IGF-1 is expressed mainly in Sertoli cells and is present in seminal plasma, contributing to cell development and the maturation of spermatozoa. IGF-1 seems to modulate sperm motility, and treatment with IGF-1 has a positive effect on sperm motility and vitality. Furthermore, lower levels of NGF or IGF-1 in seminal plasma are associated with infertility. Understanding the mechanisms of actions of these GFs in the male reproductive system may improve the outcome of sperm processing techniques.

A Possible Role for Nerve Growth Factor and Its Receptors in Human Sperm Pathology

Nerve growth factor (NGF) signalling affects spermatogenesis and mature sperm traits. In this paper, we aimed to evaluate the distribution and the role of NGF and its receptors (p75NTR and TrKA) on the reproductive apparatus (testis and epididymis) and sperm of fertile men (F) and men with different pathologies, namely varicocele (V) and urogenital infections (UGIs). We collected semen samples from 21 individuals (31-40 years old) subdivided as follows: V (n = 7), UGIs (n = 7), and F (n = 7). We submitted the semen samples to bacteriological analysis, leucocyte identification, and analysis of sperm parameters (concentration, motility, morphology, and viability). We determined the seminal plasma levels of NGF, interleukin 1β (IL-1β), and F2-isoprostanes (F2-IsoPs), and the gene and protein expression of NGF receptors on sperm. We also used immunofluorescence to examine NGF receptors on ejaculated sperm, testis, and epididymis. As expected, fertile men showed better sperm parameters as well as lower levels of NGF, F2-IsoPs, and IL-1β compared with men with infertility. Notably, in normal sperm, p75NTR and TrKA were localised throughout the entire tail. TrKA was also found in the post-acrosomal sheath. This localisation appeared different in patients with infertility: in particular, there was a strong p75NTR signal in the midpiece and the cytoplasmic residue or coiled tails of altered ejaculated sperm. In line with these findings, NGF receptors were intensely expressed in the epididymis and interstitial tissue of the testis. These data suggest the distinctive involvement of NGF and its receptors in the physiology of sperm from fertile men and men with infertility, indicating a possible role for new targeted treatment strategies.

Serum Nerve Growth Factor Levels as a Predictor of Bull Candidate Semen Quality of Madura Cattle

Madura cattle are the germplasm of native cattle on the verge of extinction because of crossbreeding. Therefore, the present study was aimed to determine the serum nerve growth factor (NGF) concentration as a predictor of fresh ejaculate fertility parameters in Madura bull candidates. Eleven Madura bull candidates used for frozen semen production were selected for the study. Blood samples were collected using a vacutainer from the jugular vein for analyzing serum NGF and testosterone levels. Meanwhile, semen collection was conducted using an artificial vagina for sperm motility, viability, and concentration assessment. Data were analyzed to determine the correlation among variables and the linear regression of NGF concentration to other significant variables. The result showed that NGF had a significant correlation (p < 0.05) with testosterone levels, sperm motility, viability, and concentration. A significant correlation was observed between testosterone levels, sperm concentration, and sperm viability. The regression equation among significantly correlated variables was determined. For artificial insemination, suitable bull ejaculates for obtaining frozen semen should reach at least 2.12 ng/mL of NGF levels, with sperm viability, sperm concentration, and testosterone levels of more than 78.63%, 1,462.177 million/mL ejaculate, and 25.67 ng/mL, respectively. This is the first study to identify NGF as a predictor of male fertility in bull candidates of Madura cattle. Therefore, NGF levels could be used as a marker of male fertility in Madura bull cattle candidates. Thus, based on the minimum NGF levels, the ejaculate of Madura bull candidate that meets the requirements for frozen semen production could predict fertility.

The Effect of Interaction NGF/p75NTR in Sperm Cells: A Rabbit Model

Background: Nerve Growth Factor (NGF) plays an important role in the reproductive system through its receptor’s interaction (p75NTR). This paper aims to analyze the impact of NGF p75NTR in epididymal and ejaculated rabbit semen during in vitro sperm storage. Methods: Semen samples from 10 adult rabbit bucks were collected four times (n = 40) and analyzed. NGF was quantified in seminal plasma, and the basal expression of p75NTR in sperm was established (time 0). Moreover, we evaluated p75NTR, the apoptotic rates, and the main sperm parameters, at times 2–4 and 6 h with or without the administration of exogenous NGF. Results: Based on the level of p75NTR, we defined the threshold value (25.6%), and sperm were divided into High (H) and Normal (N). During sperm storage, p75NTR of H samples significantly modulated some relevant sperm parameters. Specifically, comparing H samples with N ones, we observed a reduction in motility and non-capacitated cell number, together with an increased percentage of dead and apoptotic cells. Notably, the N group showed a reduction in dead and apoptotic cells after NGF treatment. Conversely, the NGF administration on H sperm did not change either the percentage of dead cells or the apoptotic rate. Conclusion: The concentration of p75NTR on ejaculated sperm modulates many semen outcomes (motility, apoptosis, viability) through NGF interaction affecting the senescence of sperm.

IGF-I and NGFβ enhance in vitro progressive motility and vitality of human spermatozoa

PURPOSE

Progressive motility (PM) and vitality are positively associated with fertilization ability of spermatozoa. Here, the effects of IGF-I and NGFβ on PM and vitality of human spermatozoa were investigated.

METHODS

Forty-three volunteers gave semen samples after 2-3 days of sexual abstinence. Each sample was processed with density gradient centrifugation and sperm washing. The pellet was divided into 3 aliquots. An aliquot containing one million of progressively motile spermatozoa was incubated for an hour (37°C) in standard culture medium (control group), and two aliquots with the same number of progressively motile spermatozoa were incubated in medium supplemented with IGF-I or NGFβ. Two concentrations of IGF-I (100 ng/ml and 1000 ng/ml) and NGFβ (0,5 ng/ml and 5 ng/ml) were tested.

RESULTS

Both growth factors significantly increased PM and vitality in comparison with control either at the low or the high concentration. IGF-I seemed to be more effective than NGFβ. The effects did not seem to be dose dependent with the exception of the effect of IGF-I on vitality.

CONCLUSIONS

The enhancement of PM and vitality of human spermatozoa by IGF-I and NGFβ opens new ways for the improvement of sperm processing. Further research is needed to determine the most effective concentrations.

Endosialin defines human stem Leydig cells with regenerative potential

STUDY QUESTION

Is endosialin a specific marker of human stem Leydig cells (SLCs) with the ability to differentiate into testosterone-producing Leydig cells (LCs) in vitro and in vivo?

SUMMARY ANSWER

Endosialin is a specific marker of human SLCs which differentiate into testosterone-producing LCs in vitro and in vivo.

WHAT IS KNOWN ALREADY

Human SLCs have been identified and isolated using the marker platelet-derived growth factor receptor α (PDGFRα) or nerve growth factor receptor (NGFR). However, the specificity was not high; thus, LCs and germ cells could be mistakenly sorted as SLCs if PDGFRα or NGFR was used as a marker for human SLCs isolation.

STUDY DESIGN, SIZE, DURATION

Firstly, we re-evaluated the specificity of PDGFRα and NGFR for SLCs in adult human testes. Then we analysed the previously published single-cell sequencing data and found that endosialin may identify human SLCs. Subsequently, we sorted endosialin+ cells from four human donors and characterized their self-renewal and multipotent properties. To assess whether endosialin+ cells have the potential to differentiate into functional LCs in vitro, these cells were stimulated by differentiation-inducing medium. We next assessed the in vivo regenerative potential of human endosialin+ cells after xenotransplantation into the testes of immunodeficient mice.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single-cell sequencing analysis, immunofluorescence and flow cytometry were used to characterize human testis tissues. In vitro colony formation, multipotent differentiation (adipogenic, osteogenic and chondrogenic) and Leydig cell-lineage induction were used to assess stem cell activity. Xenotransplantation into 3-week-old immunodeficient mice was used to determine in vivo regenerative potential. Endpoint measures included testosterone measurements, cell proliferation, immunofluorescence, flow cytometry and quantitative RT-PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

The results indicate that endosialin is a specific marker of SLCs compared with PDGFRα and NGFR. Additionally, endosialin+ cells isolated from human testes show extensive proliferation and differentiation potential in vitro: their self-renewal ability was inferred by the formation of spherical clones derived from a single cell. Moreover, these cells could differentiate into functional LCs that secreted testosterone in response to LH in a concentration-dependent manner in vitro. These self-renewal and differentiation properties reinforce the proposal that human testicular endosialin+ cells are SLCs. Furthermore, transplanted human endosialin+ cells appear to colonize the murine host testes, localize to peritubular and perivascular regions, proliferate measurably and differentiate partially into testosterone-producing LCs in vivo.

LARGE SCALE DATA

NA.

LIMITATIONS, REASONS FOR CAUTION

Owing to the difficulty in collecting human testis tissue, the sample size was limited. The functions of endosialin on SLCs need to be elucidated in future studies.

WIDER IMPLICATIONS OF THE FINDINGS

A discriminatory marker, endosialin, for human SLCs purification is a prerequisite to advance research in SLCs and logically promote further clinical translation of SLCs-based therapies for male hypogonadism.

STUDY FUNDING/COMPETING INTEREST(S)

A.P.X. was supported by the National Key Research and Development Program of China (2017YFA0103802 and 2018YFA0107200). C.D. was supported by the National Natural Science Foundation of China (81971314) and the Natural Science Foundation of Guangdong Province, China (2018B030311039). The authors declare no conflict of interest.

Effects of NGF Addition on Llama (Lama glama) Sperm Traits After Cooling

To provide new insights into the mechanisms through which seminal plasma proteins can protect sperm from damage caused during refrigeration, we evaluate the possibility that β-NGF can contribute to the improvement of sperm quality after cooling. First, β-NGF was detected in refrigerated sperm and compared with unrefrigerated sperm by western blotting of the proteins adsorbed by sperm, showing that native β-NGF is still present even 24 h after cooling only as an active form. Then, the effect of exogenous β-NGF on sperm quality after cooling was evaluated. A total of 12 ejaculates from male llamas (three ejaculates per male), were obtained by electro-ejaculation, diluted 4:1 with buffer Hepes-balanced salt solution and centrifuged at 800 × g for 8 min to remove the seminal plasma. Sperm were suspended in Tris-citrate-fructose-egg yolk diluent for a final concentration of 30 ×10⁶/ml and cooled at 5°C for 24 h. After refrigeration, the extended sperm were equilibrated for 5 min at 37°C and divided into the following subgroups: sperm samples without treatment (control) and sperm samples supplemented with exogenous human β-NGF (10, 100, and 500 ng/ml). At 5, 30, and 60 min of incubation sperm were evaluated for sperm viability (using eosin/nigrosin stain), sperm motility and vigor (observed under light microscopy), and mitochondrial activity (using the JC-1 fluorescent marker). Vigor data were analyzed with the nonparametric Kruskal-Wallis test. The rest of the variables were analyzed with a mixed models approach. Mean comparisons were performed using Fisher's LSD test with a confidence level of 95%. A principal components analysis was performed to analyze the relationships between variables. Treatment of 24 h cooled sperm with 10 or 100 ng/ml of human β-NGF increased the percentage of total motility and vigor (p < 0.05). Besides, an incubation time of 60 min would be adequate to improve sperm quality, since all variables are positively related. The significant improvement observed in the motility and vigor of post-refrigerated sperm suggests that supplementation with exogenous β-NGF may be profitable for the improvement of cooled llama sperm.

Nerve Growth Factor (NGF) and Animal Reproduction

Stimuli that lead to the release of gonadotropin-releasing hormone (GnRH) and pituitary gonadotropins and, consequently, ovulation in mammals fall into two broad categories. In the first, high plasma oestrogen concentrations induce the events that trigger ovulation, a characteristic of spontaneous ovulators. In the second, nerve stimuli occurring during mating reach the hypothalamus and trigger the release of GnRH and ovulation with a neuroendocrine reflex that characterizes induced ovulators.In this review, we will give an overview of the distribution of NGF and its expression in the different tissues of the male accessory sex glands, the main sites of NGF production. Next, we will highlight the role of NGF in sperm function and its potential cryopreserving role in artificial insemination techniques. Finally, we will evaluate the functions of NGF in ovulation, particularly in induced ovulators. Overall, the information obtained so far indicates that NGF is widely distributed in organs that regulate the reproductive activity, in both males and females. In spontaneous ovulators, NGF exerts mainly a luteotrophic action, while, in induced ovulators it is the main ovulation-inducing factor. A better understanding of the role of NGF in reproduction would be of great interest, since it could help finding innovative therapeutic aids to improve mammalian fertility.

Nerve growth factor receptor role on rabbit sperm storage

The influence of NGF in male reproduction in some animal species and humans has already been assessed. Many of these effects are mediated by the distribution and abundance of tropomyosin receptor kinase A (TrKA) and p75 neurotrophin (p75NTR) receptors on sperm cells. The aim of this research was to investigate the role of NGF and its receptors, TrKA and p75NTR, in rabbit sperm outcomes during in vitro storage. Major semen traits (kinetic parameters, apoptotic, necrotic and live sperm) were recorded in rabbit semen samples from 0 to 12 h of storage (every 4 h). Three experimental hypotheses were formulated: i) sperm storage changes NGF receptor abundance in rabbit sperm; ii) TrKA and p75NTR differently modulate NGF signalling (assessed by the neutralisation of receptors); iii) NGF-receptor interactions show different responses during storage (evaluated by the addition of exogenous NGF). The results demonstrate that: (i) the receptor number changed in a time-dependent manner with a significant increase in p75NTR after 8-12 h of storage; ii) the neutralisation of NGF receptors largely affected VCL, apoptotic, necrotic and live cells during sperm storage, i.e. blockade of TrKA significantly increased speed, capacitation, necrosis and apoptosis, whereas blockade of p75NTR improved motility and live cells; iii) the addition of exogenous human NGF (100 ng/mL) at different time points of storage (0, 4, 8 h) differently influenced sperm traits i.e. NGF addition at time 0 positively affected all the pro-vital traits (kinetic, live cells) whereas, after 4-8 h, the effect of NGF was null or negative. In conclusion, NGF affects kinetic and other physiological traits (capacitation, apoptosis and necrosis) of rabbit sperm in a time-dependent manner. Most of these modifications are modulated by the receptors involved (TrKA or p75NTR), which changed considerably during sperm storage (increase of p75NTR).

Ceramide induces a multicomponent intracellular calcium increase triggering the acrosome secretion in human sperm

Exocytosis of spermatozoon's secretory vesicle, named acrosome reaction (AR), is a regulated event that plays a central role in fertilization. It is coupled to a complex calcium signaling. Ceramide is a multitasking lipid involved in exocytosis. Nevertheless, its effect on secretion is controversial and the underlying cellular and molecular mechanisms remain unknown. Human spermatozoa are useful to dissect the role of ceramide in secretion given that the gamete is not capable to undergo any trafficking mechanisms other than exocytosis. We report for the first time, the presence of sphingolipid metabolism enzymes such as neutral-sphingomyelinase and ceramide synthase in sperm. Ceramidases are also present and active. Both the addition of cell-permeable ceramide and the rise of the endogenous one, increase intracellular calcium acting as potent inducers of exocytosis. Ceramide triggers AR in capacitated spermatozoa and enhances the gamete response to progesterone. The lipid induces physiological ultrastructural changes in the acrosome and triggers an exocytosis-signaling cascade involving protein tyrosine phosphatase 1B and VAMP2. Real-time imaging showed an increment of calcium in the cytosol upon ceramide treatment either in the absence or in the presence of extracellular calcium. Pharmacological experiments demonstrate that at early stages the process involves ryanodine receptors, CatSper (calcium channel of sperm), and store-operated calcium channels. We set out the signaling sequence of events that connect ceramide to internal calcium mobilization and external calcium signals during secretion. These results allow the coordination of lipids and proteins in a pathway that accomplishes secretion. Our findings contribute to the understanding of ceramide's role in regulated exocytosis and fertilization.

Role of nerve growth factor in the reproductive physiology of female rabbits: A review

Rabbit does are reflex ovulators such that coitus is needed to release GnRH and elicit the LH surge that triggers the ovulation of mature oocytes. However, the mechanisms eliciting ovulation in this species remain unclear. One of the most promising recently discovered candidates with a role in female reproductive physiology is nerve growth factor beta (β-NGF). This neurotrophin and its high-affinity receptor TrkA and low affinity receptor p75, is present in all compartments of the ovary, oviduct and uterus suggesting a physiologic role in ovarian folliculogenesis, steroidogenesis, ovulation, luteogenesis and embryo development. Besides, evidence exists that β-NGF found in seminal plasma could exert a modulatory role in the female hypothalamus-pituitary-ovarian axis contributing to the adrenergic and cholinergic neuronal stimulus of GnRH neurons in an endocrine manner during natural mating. Probably, the paracrine and local roles of the neurotrophin in steroidogenesis and ovulation reinforce the neuroendocrine pathway that leads to ovulation. This review updates knowledge of the role of β-NGF in rabbit reproduction, including its possible contribution to the mechanisms of action that induce ovulation, and discusses perspectives for the future applications of this neurotrophin on rabbit farms.

In vitro effect of nerve growth factor on the main traits of rabbit sperm

BACKGROUND

The nerve growth factor (NGF), a member of the neurotrophins family, plays an important role not only in the nervous but also in other non-nervous systems such as the reproductive system. The aim of the paper is to study the in vitro effect of NGF on rabbit sperm functions.

METHODS

Ten adult rabbit bucks were collected five times, and pooled semen samples have been analysed. NGF was quantified in seminal plasma, and the distribution of NGF receptors (TrKA and p75NTR) in sperm was established. Moreover, the dose-effect of NGF on motility rate and track speed was evaluated. Successively, the effect of the neutralisation of NGF receptors was assessed to verify the specific role of each receptor. Untreated sperm were used as control.

RESULTS

Our study identified several interesting results: i) We detected NGF in seminal plasma and TrKA and p75NTR in sperm surface. In particular, TrKA is localised in the head and p75NTR in the midpiece and tail of rabbit sperm. ii) Once the optimal dose of NGF (100 ng/mL) was established, its addition affected both kinetics and other physiological traits (capacitation, apoptosis and necrosis) of rabbit sperm. (iii) The neutralisation of TrKA and p75NTR receptors affected sperm traits differently. In particular, sperm speed, apoptosis and capacitation seemed mainly modulated via p75NTR receptor, whereas motile, live cells, necrosis and acrosome reaction were modulated via TrKA.

CONCLUSION

For the first time, we showed the presence of p75NTR in rabbit sperm. NGF affects kinetic and other physiological traits of rabbit sperm. Most of these changes are modulated by the receptors involved (TrKA or p75NTR). Considering that some seminal disorders in human have been correlated with a lower NGF concentration and no studies have been done on the possible involvement of NGF receptors, these findings also provide new insights on human fertility.

The effects of di-butyl phthalate exposure from medications on human sperm RNA among men

Endocrine disruptors, such as phthalates, are suspected of affecting reproductive function. The Mesalamine and Reproductive Health Study (MARS) was designed to address the physiological effect of in vivo phthalate exposure on male reproduction in patients with Inflammatory Bowel Disease (IBD). As part of this effort, the effect on sperm RNAs to DBP exposure were longitudinally assessed using a cross-over cross-back binary design of high or background, exposures to DBP. As the DBP level was altered, numerous sperm RNA elements (REs) were differentially expressed, suggesting that exposure to or removal from high DBP produces effects that require longer than one spermatogenic cycle to resolve. In comparison, small RNAs were minimally affected by DBP exposure. While initial study medication (high or background) implicates different biological pathways, initiation on the high-DBP condition activated oxidative stress and DNA damage pathways. The negative correlation of REs with specific genomic repeats suggests a regulatory role. Using ejaculated sperm, this work provides insight into the male germline's response to phthalate exposure.

Recombinant rabbit beta nerve growth factor production and its biological effects on sperm and ovulation in rabbits

In some induced-ovulating species, beta nerve growth factor (β-NGF) has important roles in ovulation, though data for rabbits are still inconclusive. In this study we first synthesized functional recombinant β-NGF from rabbit tissue (rrβ-NGF) to address the following objectives: 1) to compare rabbit β-NGF amino acid sequence with those of other induced- or spontaneous-ovulating species; 2) to assess the effects of rrβ-NGF on rabbit sperm viability and motility, and 3) to examine the in vivo ovulation inducing effect of rrβ-NGF added to the seminal dose in rabbit does. The NGF gene in rabbit prostate tissue was sequenced by Rapid Amplification of cDNA Ends and annotated in GenBank (KX528686). Recombinant rβ-NGF was produced in CHO cells and purified by affinity chromatography. Once confirmed by Western blotting and mass spectrometry (MALDI-TOF) that the amino acid sequence of the recombinant protein corresponded to β-NGF, its functionality was validated in PC12 cells in a successful dose-response study over 8 days. The amino acid sequence of prostate rabbit NGF differed to that of other species mainly in its receptor binding sites. In all the spontaneous ovulating species examined, compared with rabbit, alanine and proline residues, which interact with the high-affinity receptor, were replaced by a serine. In rabbits, asparagine and methionine were substituted by lysine at the low-affinity receptor binding site. In time- and dose-response experiments, the in vitro addition of rrβ-NGF to the ejaculate did not affect sperm viability whereas sperm motility parameters were enhanced by the addition of 1 μg/mL of the neuropeptide. Addition of this same concentration of rrβ-NGF to the seminal dose administered via the intravaginal route in does induced ovulation with a delayed LH peak, leading to a plasma progesterone increase, gestation and delivery. Our findings suggest that rrβ-NGF could be a useful option for biotechnological and reproduction assisted techniques in rabbits but further studies are needed.

Major seminal plasma proteome of rabbits and associations with sperm quality

The present study was conducted to describe the major seminal plasma proteome of rabbits and potential associations between seminal proteins and semen criteria. Semen samples were collected from 18 New Zealand adult rabbits, and seminal plasma proteins were analyzed by 2-D SDS-PAGE and tandem mass spectrometry. Sperm motility, vigor, concentration, morphology and membrane sperm viability were evaluated. Rabbits ejaculated 364 ± 70 million sperm/ml, with 81 ± 6.1% motile cells, 3.8 ± 0.2 vigor and 66.7 ± 2.5% sperm with normal morphology. Based on the viability and acrosome integrity assay, there were 65.8 ± 2.5% live sperm with intact acrosome and most spermatozoa had both intact acrosome and functional membrane. On average, 2-D gels of rabbit seminal plasma had 232 ± 69.5 spots, as determined by PDQuest software (Bio Rad, USA). Mass spectrometry allowed the identification of 137 different proteins. The most abundant proteins in rabbit seminal plasma were hemoglobin subunit zeta-like, annexins, lipocalin, FAM115 protein and albumin. The intensity of the spots associated with these five proteins represented 71.5% of the intensity of all spots detected in the master gel. Multiple regression models were estimated using sperm traits as dependent variables and seminal plasma proteins as independent ones. Also, sperm motility had positive association with beta-nerve growth factor and cysteine-rich secretory protein 1-like and a negative one with galectin-1. The percentage of rabbit sperm with intact membrane was related to seminal plasma protein FAM115 complex and tropomyosin. Then, the population of morphologically normal sperm in rabbit semen was positively linked to carcinoembryonic antigen-related cell adhesion molecule 6-like and down regulated by seminal plasma isocitrate dehydrogenase. Based on another regression model, the variation in the percentage of live sperm with intact acrosome was partially explained by the amount of leukocyte elastase inhibitor and the peptidyl-prolyl cis-trans isomerase A in the rabbit seminal fluid. The current study reports the identification of 137 proteins of rabbit seminal plasma. Major proteins of seminal secretion relate primarily to prevention of damages caused by lipid peroxide radicals and oxidative stress, membrane functionality, transport of lipids to the sperm membrane and temperature regulation. Moreover, finding seminal plasma proteins as indicators of semen parameters will improve assisted reproductive technologies.

Characterization of β-Nerve Growth Factor-TrkA system in male reproductive tract of rabbit and the relationship between β-NGF and testosterone levels with seminal quality during sexual maturation

β-Nerve Growth Factor (β-NGF) is a neurotrophin which acts through its receptors TrkA and p75, performing important actions in male reproductive physiology and its presence in seminal plasma (SP) has been related to male fertility. The aim of the present study was to evaluate the gene expression profile and the immunolocalization of β-NGF and its high-affinity receptor TrkA in sex organs in rabbits during sexual maturation period. β-NGF concentration for both SP and blood plasma (BP) and BP testosterone levels were determined as well as the seminal parameters during such period. Ten New Zealand White x California young rabbits were trained to semen collection since 20 weeks of age and routinely done once a week with two ejaculations per session. At 22 and 37 weeks of age, semen collection was carried out three times a week and seminal parameters were evaluated. Four males were randomly assigned and slaughtered in each age (n = 8); sex organs (prostate, bulbourethral glands and epididymis) were dissected and collected to determine β-NGF and TrkA gene expression and immunolocalization. SP and BP were also taken at each semen collection session to evaluate β-NGF concentration, and testosterone levels were also assessed in BP. The highest β-NGF mRNA expression was observed in prostate compared to bulbourethral glands and epididymis. These two last tissues showed residual β-NGF mRNA expression and limited localization of the neurotrophin. The prostate epithelial cells and lumen were strongly stained with regard to the other sex organs indicating that immunolocalization of β-NGF rely mainly in the prostate. TrkA gene expression was lower but constant and differentially immunolocalized in the sex organ tissues. Finally, β-NGF concentration in SP and BP remained unchanged in accordance to age, while some seminal characteristics such as sperm concentration, percentage of live sperm and mass and progressive motility were enhanced as endowed by BP testosterone variation. β-NGF and its cognate TrkA receptor are expressed and immunolocalized in the male reproductive tract in the two ages studied, independently of the circulating levels of testosterone and β-NGF.