Expression of nerve growth factor and its receptors trkA and p75 and inhibin alpha-subunit in the ovarian interstitial cells of lactating golden hamsters

Role of neurotrophins in pregnancy, delivery and postpartum

Neurotrophins (NTs) are a family of polypeptides whose functions have been extensively studied in the past two decades. In particular, Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF) play a major role in the development, nutrition and growth of the central and peripheral nervous system and in the pathogenesis of neurodegenerative, cardiometabolic and (auto)immune diseases. However, NGF and BDNF have subtle functions for follicular development, implantation, and placentation. This short narrative review summarizes the existing evidence, published between 2000 and 2019, about the role of NTs in many different conditions that might affect women during and after pregnancy such as preeclampsia, gestational diabetes, obesity, depression, anxiety, smoking and alcohol abuse. Literature suggests that the dysregulation of synthesis and release of NTs may lead to decisive effects on both maternal and fetal health. Some piece of evidences was found about a possible association between NGF/BDNF and breastfeeding. Additional studies on human models are necessary to further characterize the role of NTs in life-changing experiences like labor and delivery.

Testicular expression of NGF, TrkA and p75 during seasonal spermatogenesis of the wild ground squirrel (Citellus dauricus Brandt)

The nerve growth factor (NGF) not only has an essential effect on the nervous system, but also plays an important role in a variety of non-neuronal systems, such as the reproductive system. The aim of this study was to compare the quality and quantity in expression of NGF and its receptors (TrkA and p75) in testes of the wild ground squirrel during the breeding and nonbreeding seasons. Immunolocalization for NGF was detected mainly in Leydig cells and Sertoli cells in testes of the breeding and nonbreeding seasons. The immunoreactivity of TrkA was highest in the elongated spermatids, whereas p75 in spermatogonia and spermatocytes in testes of the breeding season. In the nonbreeding season testes, TrkA showed positive immunostainings in Leydig cells, spermatogonia and primary spermatocytes, while p75 showed positive signals in spermatogonia and primary spermatocytes. Consistent with the immunohistochemical results, the mean mRNA and protein level of NGF and TrkA were higher in the testes of the breeding season than in non-breeding season, and then decreased to a relatively low level in the nonbreeding season. In addition, the concentration of plasma gonadotropins and testosterone were assayed by radioimmunoassay (RIA), and the results showed a significant difference between the breeding and nonbreeding seasons with higher concentrations in breeding season. In conclusion, these results of this study provide the first evidence on the potential involvement of NGF and its receptor, TrkA and p75 in the seasonal spermatogenesis and testicular function change of the wild ground squirrel.

Immunolocalization of NGF and its receptors in ovarian surface epithelium of the wild ground squirrel during the breeding and nonbreeding seasons

The ovarian surface epithelium (OSE) plays an important role in normal ovarian physiology. During each reproductive cycle, the OSE takes part in the cyclical ovulatory ruptures and repair. The aim of this study was to investigate the immunolocalization of nerve growth factor (NGF) and its receptors, tyrosine kinase A (TrkA) and p75, in the OSE cells of the wild ground squirrels during the breeding and nonbreeding seasons. There were marked variations in ovarian weight and size between the breeding and the nonbreeding seasons. Histologically, cuboidal cells and squamous cells were identified in the OSE of both seasons. Yet, stronger immunostaining of NGF, TrkA and p75 were observed in cuboidal cells and squamous cells in the breeding season as compared to the nonbreeding season. In addition, plasma gonadotropin concentrations were higher in the breeding season than in the nonbreeding season, suggesting that the expression patterns of NGF, TrkA and p75 in the OSE were correlated with changes in plasma gonadotropins. These findings suggested that NGF and its receptor TrkA and p75 may be involved in the regulation of seasonal changes in the OSE of wild ground squirrel.

Seasonal changes in expression of nerve growth factor and its receptors TrkA and p75 in the ovary of wild ground squirrel (Citellus dauricus Brandt)

The aim of this study was to investigate the presence of nerve growth factor (NGF) and its receptors tyrosine kinase A (TrkA) and p75 in the ovaries of the wild ground squirrels during the breeding and nonbreeding seasons. In the breeding period, NGF, TrkA and p75 were immunolocalized in granulosa cells, thecal cells, interstitial cells and luteal cells whereas in the nonbreeding period, both of them were detected only in granulosa cells, thecal cells and interstitial cells. Stronger immunostaining of NGF, TrkA and p75 were observed in granulosa cells, thecal cells and interstitial cells in the breeding season compared to the nonbreeding season. Corresponding for the immunohistochemical results, immunoreactivities of NGF and its two receptors were greater in the ovaries of the breeding season then decreased to a relatively low level in the nonbreeding season. The mean mRNA levels of NGF, TrkA and p75 were significantly higher in the breeding season than in the nonbreeding season. In addition, plasma gonadotropins, estradiol-17β and progesterone concentrations were significantly higher in the breeding season than in the nonbreeding season, suggesting that the expression patterns of NGF, and TrkA and p75 were correlated with changes in plasma gonadotropins, estradiol-17β and progesterone concentrations. These results indicated that NGF and its receptors, TrkA and p75 may be involved in the regulation of seasonal changes in the ovarian functions of the wild ground squirrel.

Expression of nerve growth factor and its receptors TrkA and p75 in the uterus of wild female ground squirrel (Citellus dauricus Brandt)

In this study, we investigated the presence of nerve growth factor (NGF) and its receptors tyrosine kinase A (TrkA) and p75 in the uterus of the wild ground squirrels during the estrous period, early pregnancy and non-breeding period. In the estrous period and early pregnancy, NGF and TrkA were immunolocalized in stromal cells, luminal epithelial cells, glandular cells and smooth muscle cells whereas in the non-breeding period, both of them were detected only in luminal epithelial cells and glandular cells, but not in stromal cells or smooth muscle cells. Stronger immunostaining of NGF and TrkA was observed in luminal epithelial cells and glandular cells in the estrous period and early pregnancy as compared to the non-breeding period. p75 was immunolocalized only in luminal epithelial and glandular cells during the estrous period, early pregnancy and non-breeding period. The intensity of the immunohistochemical signals for p75 did not vary significantly in the estrous period, early pregnancy and non-breeding period. The mean mRNA levels of NGF and TrkA and p75 were significantly higher in the estrous period and early pregnancy as compared to the non-breeding period. Besides, plasma estradiol-17β and progesterone concentrations were higher in the estrous period and early pregnancy than in the non-breeding period, suggesting that the expression patterns of NGF and TrkA are correlated with changes in plasma estradiol-17β and progesterone concentrations. These results indicate that NGF and its receptor TrkA may be involved in the regulation of seasonal changes in the uterine functions of wild female ground squirrels.