Effects of spinal cord injury on spermatogenesis and the expression of messenger ribonucleic acid for Sertoli cell proteins in rat Sertoli cell-enriched testes.
The study was an examination of the effects of spinal cord injury (SCI) on spermatogenesis and Sertoli cell functions in adult rats with Sertoli cell-enriched (SCE) testes. The effects of SCI on the seminiferous epithelium were characterized by abnormalities in the remaining spermatogenic cells during the first month after SCI. Three days after SCI, serum testosterone levels were 80% lower, while serum FSH and LH levels were 25% and 50% higher, respectively, than those of sham control SCE rats. At this time, the levels of mRNA for androgen receptor (AR), FSH receptor (FSH-R), and androgen-binding protein (ABP) were normal whereas those for transferrin (Trf) had decreased by 40%. Thereafter, serum testosterone levels increased, but they remained lower than those of the sham control rats 28 days after SCI; and serum FSH and LH levels returned to normal. The levels of mRNA for AR, ABP, and Trf exhibited a biphasic increase 7 days after SCI and remained elevated 28 days after SCI. FSH-R mRNA levels were also elevated 90 days after SCI. Unexpectedly, active spermatogenesis, including qualitatively complete spermatogenesis, persisted in > 40% of the tubules 90 days after SCI. These results suggest that the stem cells and/or undifferentiated spermatogonia in SCE testes are less susceptible to the deleterious effects of SCI than the normal testes and that they were able to proliferate and differentiate after SCI. The presence of elevated levels of mRNA for Sertoli cell FSH-R and AR, as well as of that for the Sertoli cell proteins, in the SCE testes during the chronic stage of SCI suggests a modification of Sertoli cell physiology. Such changes in Sertoli cell functions may provide a beneficial environment for the proliferation of the stem cells and differentiation of postmeiotic cells, thus resulting in the persistence of spermatogenesis in these testes. (+info)
Comparative expression of luteinizing hormone and follicle-stimulating hormone receptors in ovarian follicles from high and low prolific sheep breeds.
Expression of gonadotropin receptors and granulosa cell sensitivity to gonadotropin hormones by small (1-3 mm) and large (3.5-7 mm) follicles were compared in Romanov (ROM, ovulation rate = 3) and Ile-de-France (IF, ovulation rate = 1) ewes in the early and late follicular phase. In healthy follicles, LH receptor levels in granulosa cells increased with increasing follicular size (p < 0. 001) while FSH receptor levels decreased (p < 0.05). In granulosa cells of large follicles, LH receptor (LHR) mRNA levels were greater in the late than in the early follicular phase (p < 0.001, p < 0.05, for ROM and IF, respectively). In the early follicular phase, LHR levels in granulosa (p < 0.001) and theca cells (p < 0.05) of small follicles were greater in ROM than in IF ewes. FSH receptor mRNA levels in granulosa cells of small and large ROM follicles were greater than in the corresponding IF follicles (p < 0.05). Finally, a greater responsiveness (increase in cAMP secretion) to both FSH and hCG was observed by granulosa cells collected during the early follicular phase from ROM vs. IF ewes. Data provide evidence that the greater ovulation rate in the ROM as compared to the IF breed is associated with a greater gonadotropin responsiveness during the early follicular phase. (+info)
Generating FSH antagonists and agonists through immunization against FSH receptor N-terminal decapeptides.
Follicle-stimulating hormone (FSH) via interaction with G-protein coupled specific receptors plays a central role in the control of gametogenesis in mammals of both sexes. In females, FSH is crucial for follicle growth, follicle maturation and ovulation. FSH receptors, together with luteinizing hormone-chorionic gonadotropin and thyrotropin receptors belong to a subfamily of structurally related receptors within the seven transmembrane receptor family. Among several other regions, the N-terminus of these receptors is believed to be responsible for important specific hormone-receptor contact sites. Recombinant filamentous phages displaying at their surface three overlapping N-terminal decapeptides of the FSH receptor, peptides A18-27, B25-34 and C29-38 were constructed. Ewes and female mice were immunized against the three FSH receptor (FSHR) recombinant phages. Immunoglobulins purified from immunized animals were analyzed for their biochemical properties on a Chinese hamster ovary cell line expressing the porcine FSH receptor. AntiA and antiB immunoglobulins (IgGs) behave as antagonists for 125I-FSH binding and for FSH-dependent cAMP production, while antiC IgGs did not compete for hormone binding. By contrast, antibodies against the C29-38 peptide displayed FSH agonist activity and stimulated the FSH receptor, whereas antiA and antiB IgGs did not. Furthermore, when the FSHR phages were used as peptidic vaccines, they induced a reversible inhibition of ovulation rate in ewes, and impaired fertility in female mice. (+info)
Expression of granulosa cell-specific genes and induction of apoptosis in conditionally immortalized granulosa cell lines established from H-2Kb-tsA58 transgenic mice.
Granulosa cell lines have been established from H-2Kb-tsA58 transgenic mice. Using immunocytochemistry, significant amounts of insulin-like growth factor-I (IGF-I) were found in all cell lines investigated, whereas estrogen and progesterone receptor expression could be detected in only some of the lines. All cell lines showed low basal production of the gonadal steroids estradiol and progesterone. The genes for the ovarian paracrine regulators IGF-I and basic fibroblast growth factor were expressed, as well as the genes for anti-Mullerian hormone and for the P450 side-chain cleavage enzyme (P450scc). Expression of P450scc could be shown to be up-regulated in the cell lines under conditions mimicking the hormonal environment of the luteinizing granulosa cells in vivo. Inactivation of the temperature-sensitive SV40 T antigen by a shift of the cell lines to the nonpermissive temperature of 39.5 degrees C led to massive induction of apoptosis in several cell lines. These cell lines will allow a detailed study of the mechanisms regulating the expression of granulosa cell-specific functions, as well as the induction of granulosa cell apoptosis. (+info)
Molecular cloning of the mouse follicle-stimulating hormone receptor complementary deoxyribonucleic acid: functional expression of alternatively spliced variants and receptor inactivation by a C566T transition in exon 7 of the coding sequence.
The gonadotropin receptors, i.e., those of LH and FSH (FSHR), are pivotal elements in the regulation of gonadal function. Recently, extensive efforts have been made to elucidate the structure-function relationship of these receptors as well as the modulatory mechanism(s) of their function. In the present study, we report 1) characterization of the mouse (m) FSHR cDNA coding sequence and 2) the functional consequences of coexpression of several splice variants of the mFSHR. In addition, we evaluate 3) the impact on mFSHR function of a C566T transition in exon 7 of the coding sequence, a substitution analogous to the inactivating mutation in the human FSHR gene responsible for a hereditary form of hypergonadotropic ovarian failure. Molecular cloning of the mFSHR cDNA was carried out by reverse transcription-polymerase chain reaction (RT-PCR) using 129/Sv mouse testicular RNA and primers complementary to the rat or the partially characterized mouse FSHR sequence. Overlapping partial fragments of receptor cDNA were amplified, sequenced, and engineered to produce the entire cDNA coding sequence, subcloned into the pSG5 expression vector. Using a similar approach, 4 different receptor splice variants, selectively lacking exons 2, 2 and 5, 5 and 6, and 2, 5, and 6 of the coding region, were cloned. Finally, PCR-based site-directed mutagenesis was used to generate the C566T mutant of mFSHR. Sequence analysis showed an open reading frame of 2076 base pairs for the mFSHR cDNA, predicting a putative 17-amino acid signal peptide and a 675-amino acid mature receptor protein, and overall sequence homology of 94% with rat, 87% with human, and 85-84% with bovine, and ovine FSHRs. Functional expression in human embryonic kidney (HEK 293) and mouse granulosa (KK-1) cells demonstrated for the cloned receptor high-affinity binding to recombinant human (rh) FSH and ability to elicit cAMP, inositol trisphosphate (IP3), and progesterone responses. In contrast, transient transfection studies showed that despite successful transcription, the exon-lacking FSHR variants were unable to bind rhFSH either in intact or in solubilized HEK 293 cells, or to elicit cAMP or progesterone responses in KK-1 cells. Furthermore, cotransfections of the splice variants in the context of an ovarian cell line stably expressing the full-length mFSHR failed to demonstrate modulatory effects on the holoreceptor function. Finally, transient expression of the C566T mFSHR mutant in HEK 293 cells revealed that, in accordance with observations on human FSHR, this substitution profoundly impaired the ligand binding and cAMP and IP3 responses to rhFSH stimulation. In conclusion, the present data indicate that, despite extensive splicing of the mFSHR message, a potential role of the exon-lacking receptor transcripts in modulating FSH actions is unlikely. In addition, we provide evidence for mFSHR inactivation by a C566T transition in exon 7 of the coding sequence, thus paving the way for further development of animal models of hypergonadotropic ovarian failure. (+info)
Follicle-stimulating hormone receptor and its messenger ribonucleic acid are present in the bovine cervix and can regulate cervical prostanoid synthesis.
The hypothesis that FSH regulates the bovine cervical prostaglandin E(2) (PGE(2)) synthesis that is known to be associated with cervical relaxation and opening at the time of estrus was investigated. Cervical tissue from pre-estrous/estrous, luteal, and postovulatory cows were examined for 1) the presence of bovine (b) FSH receptor (R) and its corresponding mRNA and 2) the effect of FSH on the PGE(2) regulatory pathway in vitro. The presence of bFSHR mRNA in the cervix (maximal during pre-estrus/estrus) was demonstrated by the expression of a reverse transcription (RT) polymerase chain reaction (PCR) product (384 base pairs) specific for bFSHR mRNA and sequencing. Northern blotting revealed three transcripts (2.5, 3.3, and 3.8 kilobases [kb]) in cervix from pre-estrous/estrous cows. The level of FSHR (75 kDa) was significantly higher (p < 0.01) in Western blots of pre-estrous/estrous cervix than in other cervical tissues. There was a good correlation between the 75-kDa protein expression and its corresponding transcript of 2.55 kb throughout the estrous cycle as described by Northern blot analysis as well as RT-PCR. Incubation of FSH (10 ng/ml) with pre-estrous/estrous cervix resulted in a 3-fold increase in the expression of FSHR and a 2-fold increase in both G protein (alpha(s)) and cyclooxygenase II. FSH (5-20 ng/ml) significantly increased (p < 0.01) cAMP, inositol phosphate (p < 0.01), and PGE(2) (p < 0.01) production by pre-estrous/estrous cervix but not by cervix at the other stages. We conclude that bovine cervix at the time of the peripheral plasma FSH peak (pre-estrus/estrus) contains high levels of FSHR and responds to FSH by increasing the PGE(2) production responsible for cervical relaxation at estrus. (+info)
Autoradiographic analysis of follicle-stimulating hormone and human chorionic gonadotropin receptors in the ovary of immature rats treated with equine chorionic gonadotropin.
The gonadotropin-primed immature rat has become the most common model for the study of follicular development and ovulation. In this study, prepubertal female rats, 23 and 24 days old, were injected s. c. with 5 IU eCG, and ovaries were collected for topical autoradiography of FSH and hCG receptors at 48 or 24 h post-eCG, respectively (i.e., Day 25). In a baseline group, on Day 25 (before eCG), even the smallest preantral follicles with 1 layer of granulosa cells (GCs; primary follicles) possessed FSH receptors, but hCG receptors were found only on the theca of follicles with 2 or more layers of GCs. Human CG receptors were especially prominent in the interstitium that intimately surrounds preantral follicles without any distinction between theca and interstitial cells. There was a discrete theca surrounding antral follicles. Occasionally antral follicles had hCG receptors in the interstitium, but the adjacent theca was negative, suggesting that these follicles might be destined for atresia. By 24 h post-eCG, a now-discrete theca layer with hCG receptors surrounded all preantral follicles except for the primary follicles, which never responded to eCG. The interstitium was hypertrophied and epithelioid, as was the theca surrounding nonatretic preantral and antral follicles. Increased mitotic activity characterized the growing preantral follicle, and for the first time, FSH binding in GCs of antral follicles was greater than in the preantral population. By 48 h post-eCG, the primary follicles were still unresponsive to eCG. FSH receptors were even more pronounced in the GCs of large antral follicles, although hCG receptors were present in the GCs of only one third of the antral follicles, reflecting the small dose of eCG administered. By 48 h post-eCG, receptors in the interstitium were barely detectable. Using this model, the following study considers the functional in vitro changes in steroidogenesis in follicles from the smallest preantral follicles to the largest antral follicles. (+info)
A role of insulin-like growth factor I for follicle-stimulating hormone receptor expression in rat granulosa cells.
The present study was undertaken to identify the mechanisms underlying the effect of insulin-like growth factor I (IGF-I) on FSH receptor (FSHR) in rat granulosa cells. Treatment with FSH produced a substantial increase in FSHR mRNA level, as was expected, while concurrent treatment with increasing concentrations of IGF-I brought about dose-dependent increases in FSH-induced FSHR mRNA, with a maximal response 2.8-fold greater than that induced by FSH alone. IGF-I, either alone or in combination with FSH, did not affect intracellular cAMP levels, whereas it enhanced the effect of 8-bromo (Br)-cAMP on FSHR mRNA production. Taken together, these findings suggest that the ability of IGF-I to enhance FSH action concerning the induction of FSHR is exerted at sites distal to cAMP generation. We then investigated whether the effect of IGF-I and FSH on FSHR mRNA levels was the result of increased transcription and/or altered mRNA stability. The rates of FSHR mRNA gene transcription, assessed by nuclear run-on transcription assay, were not increased by the addition of IGF-I. On the other hand, the decay curves for the 2. 4-kilobase (kb) FSHR mRNA transcript in primary granulosa cells significantly altered the slope of the FSHR mRNA decay curve in the presence of IGF-I and increased the half-life of the FSHR mRNA transcript. These data suggest a possible role for changes in FSHR mRNA stability in the IGF-I-induced regulation of FSHR in rat granulosa cells. Treatment with activin produced a substantial increase in FSHR mRNA level, as was expected, and concurrent treatment with IGF-I did not affect activin-induced FSHR mRNA. Our data suggest that the IGF-I effect on FSHR expression is related to cAMP production induced by FSH and may maintain FSHR mRNA level because of prolonged FSHR mRNA stability. (+info)