RESUMO
CONTEXT: Previous studies showed that nerve growth factor (NGF) induces the expression of functional FSH receptors (FSHR) in preantral follicles of the developing rat ovary. OBJECTIVE: The objective of this study was to determine whether NGF can affect granulosa cell (GC) function in human periovulatory follicles using intact human ovaries and isolated human GCs. PATIENTS AND INTERVENTIONS: Human GCs were obtained from in vitro fertilization patients and normal ovaries from women with elective pelvic surgery for nonovarian indications. RESULTS: In normal ovaries, NGF and trkA (NGF's high-affinity receptor) were detected by immunohistochemistry in GCs of preantral and antral follicles. NGF and trkA are also present in thecal cells of antral follicles. Both freshly collected and cultured GCs contained immunoreactive NGF and trkA in addition to their respective mRNAs. Human GCs respond to NGF with increased estradiol (E(2)) secretion and a reduction in progesterone output. Exposure of human GCs to NGF increased FSHR mRNA content within 18 h of treatment, and this effect was blocked by the trk tyrosine kinase blocker K-252a. Also, cells preexposed to NGF released significantly more E(2) in response to hFSH than cells not pretreated with the neurotropin, showing that the NGF-induced increase in FSHR gene expression results in the formation of functional FSHRs. CONCLUSIONS: These results suggest that one of the functions of NGF in the preovulatory human ovary is to increase the secretion of E(2) while preventing early luteinization via an inhibitory effect on progesterone secretion. NGF stimulates E(2) secretion both directly and by increasing the formation of FSHRs.
Assuntos
Estradiol/metabolismo , Células da Granulosa/metabolismo , Fator de Crescimento Neural/farmacologia , Receptor trkA/fisiologia , Receptores do FSH/biossíntese , Feminino , Humanos , Progesterona/metabolismo , RNA Mensageiro/análise , Receptores do FSH/genéticaRESUMO
Mammalian ovarian function is regulated by both hormonal inputs and direct neural influences. Recent studies have shown that, in addition to the extrinsic innervation, the ovaries of nonhuman primates and a strain of rats contain a discrete population of intrinsic neurons. In the present study, we used histological and immunohistochemical approaches to identify the presence of neuronal cell bodies in the fetal and neonatal human ovary. Neurons containing neurofilament immunoreactivity were detected in the hilum and medulla of the ovary at all ages studied, ranging from 24 weeks of gestation to 10 months of postnatal age. Most of them coexpressed the low affinity neurotrophin receptor (p75NTR), and some were catecholaminergic, as determined by their content of immunoreactive tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis. The presence of intrinsic neurons in the human ovary, similar to those previously found in other species, indicates that they may be engaged in regulating common, phylogenetically conserved, ovarian functions. It also raises the possibility that their dysfunction may contribute to the manifestation of particular ovarian pathologies.
Assuntos
Neurônios/citologia , Ovário/inervação , Animais , Biomarcadores , Tamanho Celular , Feminino , Feto , Humanos , Imuno-Histoquímica/métodos , Proteínas de Neurofilamentos/análise , Neurônios/química , Ovário/química , Ovário/citologia , Ovário/embriologia , Receptor de Fator de Crescimento Neural , Receptores de Fator de Crescimento Neural/análise , Tirosina 3-Mono-Oxigenase/análiseRESUMO
Previous studies have shown the presence of neuronal perikarya in the primate ovary, but not in the ovary from Sprague-Dawley rats. We report here that while such intrinsic neurons are indeed absent in this strain of rats, they can be visualized in the ovary from Wistar rats. The neurons, identified by their morphology and by the expression of NeuN (a neuron-specific nuclear protein), were detected at all postnatal intervals examined, from 14 h after birth to 50 days of age. While they were present in the ovarian hilum and medulla at all ages studied, neurons first appeared in the ovarian cortex during the juvenile period (postnatal days 10-20). In all cases, the size of the neuronal soma increased significantly during prepubertal development, reaching maximal values before puberty. Some neurons were catecholaminergic, as indicated by their content of immunoreactive tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine biosynthesis. Some showed neuropeptide Y (NPY) immunoreactivity. TH-positive neurons were seen either in isolation or clustered in ganglion-like structures in both the ovarian cortex and medulla. These results indicate that ovarian neurons are not present in all strains of rats, but when present, the chemical phenotype of some of them is of a sympathetic nature, similar to that described in primates.
Assuntos
Neurônios/química , Neurônios/enzimologia , Ovário/inervação , Animais , Feminino , Imuno-Histoquímica , Neuropeptídeo Y/análise , Ovário/crescimento & desenvolvimento , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Tirosina 3-Mono-Oxigenase/análiseRESUMO
Platelet-activating factor (PAF) is a lipid mediator that has a range of biological effects on various cells and tissues. PAF-like activity has been detected in the spent media of two-cell to morula stage hamster embryos, leading to the suggestion that PAF may be the embryonic signal that hastens embryo transport to the uterus in this species. The present study was undertaken to examine whether the PAF receptor (PAFr) gene is expressed in hamster oviduct, and to identify the cell types in which the gene is expressed. DNA fragments complementary to the coding region of mRNA encoding hamster PAFr were cloned by reverse transcription-polymerase chain reaction (RT-PCR), identified by sequencing and used to prepare hamster specific cRNA probes. The presence of mRNA transcripts encoding the PAFr receptor in the oviduct was investigated by subjecting oviduct mRNA to RT-PCR. Southern blot analysis of the RT-PCR products verified the identity of the presumptive PAFr cDNAs. The cloned cDNA fragment of hamster PAFr was found to be highly conserved with respect to the receptor of other species, having 94.3% sequence similarity to the rat PAFr receptor. Hybridization histochemistry demonstrated that PAFr is expressed in the subepithelial cells and occasionally in the epithelium. In conclusion, expression of PAFr in the hamster oviduct is compatible with the proposed paracrine role of early embryo-derived PAF.