New insights of the role of β-NGF in the ovulation mechanism of induced ovulating species

Abstract

The type of stimuli triggering GnRH secretion has been used to classify mammalian species into two categories: spontaneous or induced ovulators. In the former, ovarian steroids produced by a mature follicle elicit the release of GnRH from the hypothalamus, but in the latter, GnRH secretion requires coital stimulation. However, the mechanism responsible for eliciting the preovulatory LH surge in induced ovulators is still not well understood and seems to vary among species. The main goal of this review is to offer new information regarding the mechanism that regulates coitus-induced ovulation. Analysis of several studies documenting the discovery of β-NGF in seminal plasma and its role in the control of ovulation in the llama and rabbit will be described. We also propose a working hypothesis regarding the sites of action of β-NGF in the llama hypothalamus. Finally, we described the presence of β-NGF in the semen of species categorized as spontaneous ovulators, mainly cattle, and its potential role in ovarian function. The discovery of this seminal molecule and its ovulatory effect in induced ovulators challenges previous concepts about the neuroendocrinology of reflex ovulation and has provided a new opportunity to examine the mechanism(s) involved in the cascade of events leading to ovulation. The presence of the factor in the semen of induced as well as spontaneous ovulators highlights the importance of understanding its signaling pathways and mechanism of action and may have broad implications in mammalian fertility.

Protein signatures of seminal plasma from bulls with contrasting frozen-thawed sperm viability

“…In humans, seminal plasma stimulates the expression of pro-inflammatory genes in the cervix and vaginal epithelia and transcripts associated with cell proliferation, vascularization and angiogenesis in the endometrium 25 , 26 . Moreover, a seminal molecule, β-nerve growth factor, acts on the female reproductive tract to help trigger hormonal responses that cause ovulation in species of induced ovulation, such as rabbits and alpacas 27 , 28 . The attributes of seminal fluid molecules make them suitable targets of studies to elucidate factors controlling specific aspects of sperm function and male fertility.…”

Effect of Exposure to Seminal Plasma Through Natural Mating in Cattle on Conceptus Length and Gene Expression

“…Female exposure to SP has been shown to improve embryo development and survival in mice (Bromfield et al, 2014), humans (Crawford et al, 2015), pigs (O'Leary et al, 2004) and golden hamsters (O et al, 1988). In addition, in llamas and rabbits, species with induced ovulation, SP has been reported to stimulate ovulation through nerve growth factor (Silva et al, 2011;Ratto et al, 2012Ratto et al, , 2019Adams and Ratto, 2013). It is thought that the beneficial effect of SP on the embryo is due in part to the immunoregulatory role.…”

Semen Modulates the Expression of NGF, ABHD2, VCAN, and CTEN in the Reproductive Tract of Female Rabbits

“…Rabbits (Oryctolagus cuniculus) are considered to be game, vermin, laboratory animals, pets, or livestock, and are principally consumed in Mediterranean Europe [1]. Unlike many other livestock species, rabbits are induced ovulators, requiring the generation of genital-somatosensory signals during coitus to activate midbrain and brainstem noradrenergic neurons and generate the preovulatory peak of gonadotropin-releasing hormone (GnRH) [2,3]. This mating-induced output of GnRH, which is of a far greater magnitude than what has been reported for other species, causes an immediate release of luteinizing hormone from the anterior pituitary that results in ovulation [2].…”

“…The nerve growth factor (NGF) not only participates in the differentiation, plasticity, and phenotype of sensory and sympathetic neurons [20], but has also been proposed as a key ovulation-inducing factor in rabbits and other induced ovulators, due to its presence in the SP [3,[21][22][23][24]. In the genital tract, NGF may display different effects, from activating sperm motility via its cytoskeleton influence, as it occurs during neuronal growth, to preventing embryo rejection through the inhibition of local immune responses [20].…”