Nerve growth factor-β effects on post-thaw bull semen quality: Effects of nerve growth factor-β added to extenders for cryopreservation of electro-ejaculated and epididymal bull semen

Review: Unveiling the effect of beta-nerve growth factor on the reproductive function in llamas and cows

The actions of the beta-nerve growth factor (β-NGF) on the neuroendocrine and reproductive system have challenged classical views on the control of reproductive function. After endometrial absorption, β-NGF triggers ovulation and promotes the development of functional corpora lutea in camelids. In this article, we review evidence showing that, in camelids, β-NGF exerts its actions by acting in both the hypothalamus and the ovary. In the hypothalamus, β-NGF may induce gonadotropin-releasing hormone (GnRH) release by interacting with neurons or glial cells expressing receptors for β-NGF. The LH surge occurs under the influence of ovarian estradiol and requires the release of GnRH into the portal vessels to reach the pituitary gland. In the ovary, β-NGF may be promoting the differentiation of follicular to luteal cells by modifying the steroidogenic profile of ovarian follicular cells in both camelids and ruminants. Although the mechanisms for these actions are largely undetermined, we aim to offer an update on the current understanding of the effects of β-NGF controlling reproductive function in camelids and ruminants.

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).

Insights into nerve growth factor-β role in bovine reproduction - Review

Nerve growth factor-β (NGF), initially recognized as a neurotrophin involved in regulating neuronal survival and differentiation, was also later revealed as a ubiquitous seminal plasma protein in mammals. In South American camelids, NGF was initially named ovulation-inducing factor and a dose-dependent luteotropic effect was also reported in llamas. Although NGF was present in the seminal plasma of bulls, the first studies only indicated a potential role on regulation of sperm physiology. The breakthrough discovery of NGF ability to induce ovulation in camelids led to a series of studies investigating the potential functions of NGF within the female reproductive system. In the bovine, a potential luteotropic effect of NGF was perceived as potential tool to overcome the current issues with early embryonic losses attributed at least in part to luteal insufficiency and failed maternal recognition of pregnancy. The aims of this review are to discuss recent advancements in the understanding of the biological roles of NGF in the bovine species. The insights of recent studies with NGF administered in cattle include enhancement of steroidogenesis, luteal formation, and function through increased release of LH, and downstream effect of increased expression of interferon-stimulated genes. In addition, a positive association with sire conception rates; the determination that is produced in the ampulla and vesicular glands of bulls and that is secreted into the sperm-rich fraction of the ejaculate; and the absence of improved post-thaw sperm motility, viability, acrosome integrity, or chromatin stability in ejaculated or epididymal derived sperm supplemented with purified NGF is also discussed.