FSH Receptor Knockout Mice Research Articles

Catalase can protect spermatozoa of FSH receptor knock‐out mice against oxidant‐induced DNA damage in vitro

The aetiology of sperm DNA damage is likely multi-factorial with abnormal compaction of nuclear DNA, abortive apoptosis and oxidative stress implicated as potential causes of DNA damage. The objective of this study was to evaluate DNA damage in spermatozoa from wild-type (WT) and FSH receptor knock-out (FORKO) mice, compare the relative susceptibility of spermatozoa from these animals to oxidative DNA damage, and examine the protective effect of the antioxidant catalase on sperm DNA damage. Epididymal spermatozoa from FORKO mice (n = 5) and WT controls (n = 5) were extracted and incubated with or without catalase. Sperm DNA damage was assessed immediately after epididymal extraction (time 0 control) and following 2-h incubation at 37 °C. DNA damage was measured by the sperm chromatin structure assay and the results expressed as the %DNA fragmentation index or %DFI. Freshly retrieved epididymal spermatozoa from WT mice had a significantly lower mean (±SD) %DFI than that of FORKO mice (2.7 ± 1.8 vs. 6.4 ± 2.9%, p < 0.05). Prolonged (2-h) incubation of FORKO mice spermatozoa resulted in a significant increase in %DFI compared with the time 0 control (17.9 ± 9.2% vs. 6.4 ± 2.9%, respectively, p < 0.05) and the addition of catalase protected these spermatozoa from DNA damage (9.8 ± 4.1 vs. 17.9 ± 9.2%, respectively, p < 0.05). However, incubation of WT mice spermatozoa did not increase %DFI significantly (5.8 ± 5.0 vs. 2.7 ± 1.8, respectively, p > 0.05) and the addition of catalase (vs. no catalase) did not result in a significant reduction in %DFI (5.8 ± 5.0 vs. 7.7 ± 6.5%, respectively, p > 0.05). These data indicate that catalase may protect sperm nuclear DNA from oxidative stress in vitro. The data also demonstrate the differential susceptibility of WT and FORKO mice spermatozoa to oxidative stress.

Poor ovarian response to gonadotrophin stimulation is associated with FSH receptor polymorphism

Similarities in the phenotype observed in women with FSH receptor mutation and in FSH receptor knockout mice have clearly established a critical role of this protein in normal gonadal function. Two common single nucleotide polymorphisms in the exonic region of the FSH receptor gene have been shown to be associated with altered ovarian response in subjects undergoing gonadotrophin treatment. Recent in-vitro studies have shown that the A allele at the −29 position in the 5′ untranslated region of the FSH receptor gene is associated with impaired transcriptional activity. Differential expression of the FSH receptor and its function may be one of the factors responsible for altered ovarian response. These observations prompted a study of the association between FSH receptor genotype at the −29 position and ovarian response in women undergoing gonadotrophin treatment. Analysis of the data revealed that the subjects with AA genotype at the −29 position required the highest amount of exogenous FSH for ovulation induction, and oestradiol concentrations before the day of human chorionic gonadotrophin administration were significantly lower ( P = 0.015) compared with the GA genotype. The number of pre-ovulatory follicles and retrieved oocytes were lowest in the subjects with AA genotype. These results indicate that the AA genotype at position −29 may be associated with the poor ovarian response.

Ovarian Dysfunction and Related Hyperandrogenemia in FSH Receptor Knockout (FORKO) Female Mice

To assess hormonal imbalances ovarian dysfunction and related metabolic abnormalities during partial or complete absence of the FSH receptor in ovarian granulosa cells. Androgens important for normal ovarian function and produced by the thecal and stromal compartments are used by the granulosa cells for production of estrogens. Androgen overproduction has significant adverse consequences for reproduction and other related metabolic disturbances. We compared wild type, haploinsufficient and null FSH-R female mice at different ages. The design of the targeting construct ensures elimination of all types of FSH-R in a single manipulation. In this study we have assessed ovarian sex steroids and LH levels at different ages in genetically altered females with complete or partial disruption of the FSH-receptor gene. Follicular structure, molecular markers and metabolic parameters were also examined. Some effects of antiandrogen treatment were also examined. Null females (FORKO mice) are sterile producing excess androgen as early as 3 weeks with sustained high levels in adult life. Concomitantly estradiol levels are very low and progesterone is also reduced. Surgery confirmed the ovary as the sole source of androgen. Androgen excess was associated with extensive hypertrophy of the theca and stromal cells with early elevated levels of LH in circulation. Follicular structure and dynamics were drastically altered in various ways in FORKO mice resulting in early loss of oocytes. These phenomena were also reproducible in haploinsufficient females that showed early reproductive senescence. In addition to ovarian dysfunction early androgen excess (coupled with estrogen deficiency) led to abdominal obesity, abnormal lipid profiles, glucose intolerance, hyperinsulinemia and presumptive insulin resistance in the mutants, many phenomena that occur in PCO women with hyperandrogenemia. Flutamide treatment ameliorated some of the ovarian pathologies. We postulate that androgen excess acts as precursor for ovarian dysfunction and induces insulin resistance in FORKO mice. As these are hall marks of polycystic ovarian disease and metabolic syndromes in women additional investigations in this model are needed to explore mechanisms and treatment options

Alterations in Ovarian Surface Epithelium and Age Dependent Propensity for Ovarian Tumors in FSH Receptor Knockout (FORKO) Female Mice

One theory of ovarian cancer in women suggests that incessant ovulation causes changes in the surface epithelium leading to transformation. Others postulate that the high levels of FSH during post menopause activates putative receptors on the OSE inducing proliferation. Our objective was to systematically study ovarian changes including the appearance of tumors in an animal model where ovulation never occurs due to the complete absence of the follitropin receptor (FORKO mice) in granulosa cells.

Intercellular Communication Between Sertoli Cells and Leydig Cells in the Absence of Follicle-Stimulating Hormone-Receptor Signaling1

Effective interactions among the various compartments of the testis are necessary to sustain efficiency of the spermatogenic process. To study the intercellular communication between the Sertoli and Leydig cells in the complete absence of FSH receptor signaling, we have examined several indices of Leydig cell function in FSH receptor knockout (FORKO) mice. The serum testosterone levels were reduced in the 3- to 4-mo-old adult FORKO males compared to wild-type mice despite no significant alteration in circulating LH levels. Treatment with ovine LH resulted in a dose-dependent increase in serum testosterone levels in all three genotypes (+/+, +/-, and -/-). However, the response in FORKO males was significantly reduced. Similarly, the total intratesticular testosterone per testis was also lower, but the intratesticular testosterone per milligram of testis was significantly elevated in the FORKO males. Western blot analysis revealed an apparent higher expression of the enzyme 3beta-hydroxysteroid dehydrogenase (3beta-HSD) as well as LH-receptor density in the testis of FORKO males. Immunohistochemistry also showed an increase in the intensity of 3beta-HSD staining in the testicular sections of FORKO males. Although LH receptor binding increased per unit weight in FORKO mice, the total LH binding remained the same in all genotypes. Taken together, the results of the present study suggest that, in the absence of FSH receptor signaling, the testicular milieu is altered to affect Leydig cell response to LH such that circulating testosterone is reduced in the adult mutant. Studies are currently under way to understand the mechanisms underlying this phenomenon.