Expression of β‐NGF and high‐affinity NGF receptor (TrKA) in llama ( Lama glama ) male reproductive tract and spermatozoa

Seasonal variation of NGF in seminal plasma and expression of NGF and its cognate receptors NTRK1 and p75NTR in the sex organs of rams

Nerve growth factor (NGF) has long been known as the main ovulation-inducing factor in induced ovulation species, however, recent studies suggested the NGF role also in those with spontaneous ovulation. The first aim of this study was to evaluate the presence and gene expression of NGF and its cognate receptors, high-affinity neurotrophic tyrosine kinase 1 receptor (NTRK1) and low-affinity p75 nerve growth factor receptor (p75NTR), in the ram genital tract. Moreover, the annual trend of NGF seminal plasma values was investigated to evaluate the possible relationship between the NGF production variations and the ram reproductive seasonality. The presence and expression of the NGF/receptors system was evaluated in the testis, epididymis, vas deferens ampullae, seminal vesicles, prostate, and bulbourethral glands through immunohistochemistry and real-time PCR (qPCR), respectively. Genital tract samples were collected from 5 adult rams, regularly slaughtered at a local abattoir. Semen was collected during the whole year weekly, from 5 different adult rams, reared in a breeding facility, with an artificial vagina. NGF seminal plasma values were assessed through the ELISA method. NGF, NTRK1 and p75NTR immunoreactivity was detected in all male organs examined. NGF-positive immunostaining was observed in the spermatozoa of the germinal epithelium, in the epididymis and the cells of the secretory epithelium of annexed glands, NTRK1 receptor showed a localization pattern like that of NGF, whereas p75NTR immunopositivity was localized in the nerve fibers and ganglia. NGF gene transcript was highest (p < 0.01) in the seminal vesicles and lowest (p < 0.01) in the testis than in the other tissues. NTRK1 gene transcript was highest (p < 0.01) in the seminal vesicles and lowest (p < 0.05) in all the other tissues examined. Gene expression of p75NTR was highest (p < 0.01) in the seminal vesicles and lowest (p < 0.01) in the testis and bulbourethral glands. NGF seminal plasma concentration was greater from January to May (p < 0.01) than in the other months. This study highlighted that the NGF system was expressed in the tissues of all the different genital tracts examined, confirming the role of NGF in ram reproduction. Sheep are short-day breeders, with an anestrus that corresponds to the highest seminal plasma NGF levels, thus suggesting the intriguing idea that this factor could participate in an inhibitory mechanism of male reproductive activity, activated during the female anestrus.

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.

Predictive characteristics of male fertility in alpacas with special reference to seminal NGF

Recent studies document the LH-releasing pathway of nerve growth factor (NGF) in male camelids and that the LH response to seminal NGF is associated with elevated plasma testosterone concentration. Results provide rationale for the hypothesis that NGF in semen is associated with male fertility. In Experiment 1, the association between the amount of NGF in the ejaculate and characteristics of the male reproductive system was examined in alpacas. The concentration of NGF was measured by radioimmunoassay in semen samples collected from male alpacas (n = 47) and correlated with sperm morphology and motility, and measurements of the male reproductive anatomy. Most ejaculates had NGF concentrations that, based on previous studies, triggered ovulation in female camelids, however, we only found a positive correlation between NGF concentration with sperm concentration, thread formation and total NGF, and a negative correlation with pH. In Experiment 2, a retrospective analysis was carried out to determine if breeding performance during the previous season was related to recent concentrations of seminal NGF in male alpacas (n = 22). Birth rates tended to be correlated with sperm concentration and total amount of NGF in the ejaculate (P = 0.09). Experiment 3 was a prospective study to determine the relationship between seminal NGF (n = 8 male alpacas) and ovulation and pregnancy rates in a breeding trial. No association was detected between seminal NGF concentration and ovulation rate, pregnancy rate, or LH response in the female. We conclude that among the breeding males used in our study, the abundance of seminal NGF was correlated with sperm concentration and thread formation, however, it was not predictive of male fertility in alpacas. Examination of males not previously selected as breeding stock may be expected to include a broader range of seminal NGF and provide a more comprehensive understanding of the relationship between seminal NGF and male fertility.

Cooling of alpaca spermatozoa using an extender with the addition of different percentages of seminal plasma

The objective of this study was to evaluate the effect of the addition of different percentages of seminal plasma (SP) during the cooling at 5 °C of alpaca spermatozoa from vas deferens. Fifteen pools of sperm from vas deferens were evaluated and then divided into four aliquots that were diluted to a final concentration of 30 × 106 sperm/ml with either: (1) Tris with 20% egg yolk (T-EY) (control, 0% SP), (2) T-EY with 10% SP, (3) T-EY with 25% SP, and (4) T-EY with 50% SP. Samples were cooled at 5 °C and the following sperm parameters were evaluated after 24 and 48 h of storage: motility, viability, membrane function, acrosome integrity, morphology, and chromatin condensation. Motility was also evaluated after 72 h of storage. A significant decrease in progressive and total sperm motility was observed in samples cooled with 50% SP with respect to all diluted samples, while these parameters were preserved in samples cooled with 0%, 10%, and 25% SP. The percentages of sperm viability, normal morphology, and highly condensed chromatin did not change after the cooling process and were similar between cooled samples. Although a significant decrease was observed in the percentage of spermatozoa with functional membranes and with an intact acrosome in all refrigerated samples compared to raw sperm, the greatest decrease was observed in samples cooled with 50% SP. No advantage was observed from the addition of SP to alpaca spermatozoa obtained from vas deferens and being cooled. In addition, to preserve the sperm motility of cooled samples for up to 72 h, it should be recommended to include a 10% SP in the extender.

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.

Cryopreservation modifies the distribution of the prostate-derived lectin SL15 on the llama (Lama glama) sperm

Lectin-like molecules play a key role in mammalian sperm functionality. These multifunctional proteins have been proven to be involved in sperm capacitation, sperm motility, and viability, formation of the oviductal sperm reservoir, and in sperm-oocyte interaction. In a previous study, we reported the presence of a novel seminal plasma lectin, sperm lectin 15 kDa (SL15), adsorbed to the llama sperm. In order to gain knowledge in the understanding of SL15 and its functions, the aims of this study were to (a) elucidate the presence and localization of SL15 in the llama male reproductive tract and sperm, and (b) determine whether the sperm cryopreservation process of cooling and freeze-thawing affects the SL15 levels and distribution on llama sperm. We found that SL15 protein was expressed along the male reproductive system: testis, epididymis, prostate, and bulbourethral glands, being the prostate the main site of SL15 secretion. SL15 was localized on the sperm head, following different localization patterns. In order to understand if sperm cryopreservation induces modifications in the SL15 adsorption pattern, immunocytochemistry and flow cytometry analysis were carried out on fresh, 24 h cooled, and frozen-thawed sperm. Both cooled and frozen sperm showed particular SL15 patterns, that were not observed in the freshly ejaculated, indicating loss of SL15. Flow cytometry analysis also exhibited a decrease of SL15 in the cooled sperm (P < 0.05), whereas a tendency to decrease was found in frozen-thawed sperm (P < 0.1) when compared with freshly ejaculated sperm. This study extends the knowledge about the SL15 in the llama male physiology and provides evidence that cryopreservation-related techniques disrupt SL15 adsorption to the sperm membrane, possibly affecting sperm functionality and fertility.

Expression of Nerve Growth Factor and Its Receptor TrkA in the Reproductive System of Adult Zebrafish

Nerve growth factor (NGF), a member of the neurotrophin family, has emerged as an active mediator in different crucial events in the peripheral and central nervous system. At the same time, several studies showed that this neurotrophin can also play a role in non-neuronal tissues (e.g., among gonads). In spite of a large number of studies present in mammals, investigations devoted to NGF and its receptor TrkA in the reproductive system of other animal models, such as teleost fish, are scarce. To increase our knowledge of NGF and its receptor in a vertebrate gonads model, the present report describes the expression patterns of ngf and trka mRNA in the testis and ovary of adult zebrafish. By using chromogenic and fluorescence in situ hybridization, we demonstrate that in the testis of adult zebrafish, ngf and its receptor trka are mainly expressed in spermatogony B and spermatocytes. In the ovary of this fish, ngf and trka are expressed at different stages of oocyte development. Altogether, these results show that this neurotrophin and its receptor have an important role in the reproductive system that is conserved during vertebrate evolution.

Physiology and modulation factors of ovulation in rabbit reproduction management

Rabbit is an induced ovulatory species, so ovulation takes place after mating. Traditionally, exogenous and synthetic hormonal factors (administered by intramuscular and intravaginal route) such as GnRH and analogues, or different physical procedures (i.e. stimulation by intravaginal cannula) have been used to induce ovulation in females when artificial insemination is applied in rabbit farms. Restriction and public rejection of the use of hormones is leading to the study of the seminal plasma components with potential action on ovulation induction. The aim of the present review is to collect and summarise the strategies used in recent years to trigger ovulation and improve rabbit fertility management with respect to more animal-friendly manipulation methods. Furthermore, special attention has been paid to the use of a semen component (as endogen molecule) such as beta nerve growth factor (β-NGF) in male and female rabbit reproductive physiology. This neurotrophin and its receptors (TrKA and p75NTR) are abundantly distributed in both male and female rabbit reproductive tracts, and it seems to have an important physiological role in sperm maturation and behaviour (velocity, apoptosis and capacitation), as well as a modulatory factor of ovulation. Endogen β-NGF is diluted in the seminal doses with the extenders; hence it could be considered an innovative and alternative strategy to avoid the current exogenous (by intramuscular route) and stressful hormonal treatments used in ovulation induction. Their addition in seminal dose could be more physiological and improve animal welfare in rabbit farms.

Cooled storage of semen from livestock animals (Part II): Camelids, goats, and sheep

This review is part of the Festschrift in honor of Dr. Duane Garner and provides an overview of current techniques in cooled storage of semen from livestock animals such as camelids, goats, and sheep. Facing worldwide environmental changes and a trend towards more conscious and healthy eating behaviors, the development of a stable animal breeding industry is a significant challenge for the near future. In the present review, factors influencing semen handling in camelids, goats and sheep are described and relevant methods as well as current trends to improve liquid-storage of cooled semen are discussed, including extenders, additives, cooling rates, and storage temperatures. The species-specific physiology and resulting challenges are taken into consideration. While the main problem for camelid semen processing is the relatively greater viscosity as compared with that of some other animals, the deciding factor for successful artificial insemination (AI) in goats and sheep is the site (i.e., cervical or vaginal) of semen placement in the reproductive tract. Due to the type of cervical anatomy, the penetration of the cervix when using AI instruments is rather difficult. Furthermore, the seminal plasma of small ruminants affects the interaction with milk-based extenders and egg yolk which results in species-specific regimens for cooled liquid-preservation. Comparing all three species, the greatest pregnancy rates were obtained by AI with goat semen after cooled liquid-storage for several days.

Spermatozoa Obtained From Alpaca vas deferens. Effects of Seminal Plasma Added at Post-thawing

The viscous seminal plasma (SP) is currently a major impediment to the handling of ejaculate and the development of some biotechnologies in South American camelids. The vas deferens-collected spermatozoa of alpacas is a useful technique to avoid this problem. On the other hand, SP contains a large protein component that has been implicated in the function of spermatozoa within the female reproductive tract. In this sense, the low fertility achieved using transcervical insemination with frozen-thawed spermatozoa in alpacas could be improved by adding SP. This study aimed to evaluate the effect of the whole SP on some in vitro parameters of alpaca spermatozoa after the freezing-thawing-process and the fertility after artificial insemination. It would contribute to a better understanding of the interaction between thawed sperm cells and SP. Spermatozoa were obtained by surgically diverted vas deferens. The samples were diluted with a Tris-based extender, packaged in straws, and frozen. At thawing, each straw was divided into two post-thawing conditions: with the addition of 10% of PBS (control) or with 10% SP (treatment). The sperm cells were evaluated using dynamic parameters, sperm cell morphology, and morphometry. Fertility was assessed by an artificial insemination trial. All in vitro parameters were analyzed by ANOVA. A heterogeneity test was scheduled for the fertility trial. After the freezing-thawing process, motility and plasma membrane functionality was improved when SP was added. No differences were found for post-thaw viability between the control and treatment samples. The percentage of normal cells was higher with SP at post-thawing, and a decrease of the presence of bent tailed spermatozoa with a droplet in the SP group was observed. The length of the head spermatozoa was 3.4% higher in the samples with PBS compared to those in which SP was added. Females pregnant at day 25 post-insemination were 0/12 (with SP inside the straw) and 1/10 (without SP inside the straw). In conclusion, the presence of 10% SP at post-thawing improves sperm cells' motility, functionality, and morphology, indicating that it would be beneficial to improve the frozen-thawed alpaca's physiology spermatozoa. More fertility trials must be developed to increase this knowledge.

Evidence for the LH-releasing pathway of seminal plasma NGF in male camelids

In the female camelid, systemic administration of NGF induces a preovulatory LH surge that results in ovulation, but the effects of seminal NGF in the male are unknown. In the present study, we tested the hypothesis that the LH-releasing pathway of NGF is present in male camelids. In Experiment 1, male llamas and alpacas were treated with NGF or GnRH (n = 2 llamas and 3 alpacas) and blood samples were collected from 1 h before to 3 h after treatment. Plasma LH concentrations increased after treatment in a surge-like fashion in both GnRH- and NGF-treated groups, but concentrations reached a maximum 2.5 times higher and remained elevated for at least 2 h longer in the NGF-treated group (treatment-by-time interaction, P = 0.01). In Experiment 2, we evaluated the LH and testosterone response to NGF vs saline treatment (n = 3 llamas and 3 alpacas). The LH response to NGF was similar to that in Experiment 1, and plasma testosterone concentrations were higher in the NGF group than in the saline group at 2, 4 and 6 h after treatment (P < 0.05). Results support the hypothesis that the LH-releasing pathway for NGF exists in male South American camelids. The LH response to NGF sustained circulating testosterone concentrations in llamas, suggesting a moderate role of NGF in testosterone secretion.

New Insights Into the Role of β-NGF/TrKA System in the Endometrium of Alpacas During Early Pregnancy

One striking reproductive feature in South American camelids is that more than 90% of gestations are established in the left uterine horn (LUH). This phenomenon could be related to a differential vascular irrigation of the LUH. An increase of vascularization in llama endometrium was observed after systemic administration of Beta Nerve Growth Factor (β-NGF), a neurotrophin present in the uterus and placenta of various mammals that is involved in pregnancy development. We hypothesized that the β-NGF signaling pathway is related to embryo implantation in the LUH in camelids. The aim of this study was to characterize the spatial expression of β-NGF and its high-affinity receptor, TrKA, between LUH and right uterine horn (RUH) of non-pregnant (NP) and early pregnant alpacas (15 and 30 days of gestation, 15 and 30P, respectively). In addition, β-NGF, TrKA, and Vascular Endothelium Growth Factor A (VEGFA) temporal gene expression patterns and counting of blood vessels were evaluated among groups. The β-NGF and TrKA were localized in the luminal, glandular, and vascular epithelium of the alpaca uterus and in the embryonic membranes of the 30-days-old conceptus. β-NGF and TrKA immunosignal were stronger in 15P females than that of NP and 30P. In addition, TrKA signal was higher in the LUH luminal epithelium of NP and 15P alpacas than that of NP-RUH and 15P-RUH. β-NGF mRNA relative abundance was higher in the 30P-RUH than that of NP-RUH; whereas TrKA mRNA abundance only differed between 15P-RUH and NP-LUH. VEGFA mRNA relative abundance was higher in NP females compared to the LUH of 15P and 30P alpacas, and lower to their right counterparts. The number of vessels per field was higher in 15P than that of 30P. A positive correlation was observed between the number of vessels per field and β-NGF immunosignal in 15P-LUH. In contrast, the area occupied by vessels was higher in 30P alpacas than of NP and 15P females. The changes of β-NGF/TrKA expression pattern in the peri-implantation endometria between LUH and RUH and their localization in the extraembryonic membranes support the implication of the neurotrophin during implantation and pregnancy development in South American Camelids.

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.

Effect of mating on mRNA and protein expression of beta nerve growth factor and its receptor, TrKA, in the oviduct of llama (Lama glama)

Copulation produces different stimuli in the female reproductive tract in camelids, which lead to ovulation. Expression of β-nerve growth factor (β-NGF) and its specific receptor, tropomyosin receptor kinase A (TrKA), was studied comparing the oviductal microenvironment of mated and nonmated llamas. β-NGF and TrKA were expressed in the llama ampulla, isthmus, and utero-tubal-junction (UTJ), and they were mainly colocalized in the apical region of the oviductal mucosa. A TrKA immunosignal was also found in muscle cells and blood vessels, with the highest mark in UTJ muscle cells of copulated females. Both β-NGF and TrKA transcripts were expressed in the three oviductal segments. Relative TrKA abundance did not differ between mated and nonmated females, but relative β-NGF abundance was higher in the UTJ of copulated females (p < .05). β-NGF might not be secreted into the oviductal fluid (OF) since the protein was not found in the OF of mated or nonmated females. Therefore, it can be concluded that the llama oviduct expresses the β-NGF/TrKA system and that an increase in β-NGF gene expression in the UTJ 24 h after copulation along with an increase in TrKA protein expression may indicate an important role in the gamete transport and fertilization process in llamas.

Incubation of frozen-thawed llama sperm with seminal plasma

Seminal plasma is intimately connected to sperm physiology and particularly in South American Camelids, has demonstrated to be involved in multiple physiological reproductive events. Different percentages of seminal plasma (0%, 10% and 50%) were added to thawed llama semen samples with the objective of evaluating the interaction with cryopreserved sperm over time (0, 1.5 and 3 hr at 37°C). A total of 20 ejaculates from five adult llama males (n = 5; r = 4) were evaluated. A significant decrease in sperm motility, membrane function and live sperm was observed in all thawed samples (0%, 10% and 50%) at 0 hr when compared to raw semen. Neither morphology nor chromatin condensation was altered in all thawed samples (p > .05), but a significant increase in the percentage of spermatozoa with fragmented DNA was observed after thawing all samples versus raw semen. When evaluating thawed samples over time, a significant decrease of motility and membrane function was observed, while the percentages of total live sperm were preserved over the 3 hr of incubation in all final concentrations evaluated. To conclude, the addition of 10% or 50% of seminal plasma was incapable of preserving motility or membrane function of frozen-thawed llama sperm during 3 hr of incubation.

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.

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.