Absence of seasonal changes in FSHR gene expression in the cat cumulus–oocyte complex in vivo and in vitro

Abstract

Domestic cat oocytes are seasonally sensitive to FSH. Compared with those collected during the breeding season, oocytes from the nonbreeding (NB) season require more FSH during in vitro maturation to achieve comparable developmental competence. This study tested the hypothesis that this seasonal variation was due to altered expression of FSH receptors (FSHR) and/or FSH-induced genes. Relative expression levels of FSHR mRNA and FSH-enhanced gene estrogen receptor b (ESR2) were measured by qPCR in whole ovaries and immature cumulus-oocyte complexes (COCs) isolated from cat ovaries during the natural breeding vs NB seasons. Expression levels of FSH-induced genes prostaglandin-endoperoxide synthase 2 (PTGS2), early growth response protein-1 (EGR1), and epidermal growth factor receptor (EGFR) were examined in mature COCs from both seasons that were a) recovered in vivo or b) matured in vitro with conventional (1 mg/ml) or high (10 mg/ml) FSH concentrations. Overall, FSHR mRNA levels were lower in whole ovaries during the NB compared with breeding season but were similar in immature COCs, whereas ESR2 levels did not differ in either group between intervals. We observed changes in PTGS2, EGR1, and EGFR mRNA expression patterns across maturation in COCs within but not between the two seasons. The lack of seasonal differentiation in FSH-related genes was not consistent with the decreased developmental capacity of oocytes fertilized during the NB season. These findings reveal that the seasonal decrease in cat oocyte sensitivity to FSH occurs both in vivo and in vitro. Furthermore, this decline is unrelated to changes in expression of FSHR mRNA or mRNA of FSH-induced genes in COCs from antral follicles.

FSHR and LHR Expression and Signaling as Well as Maturation and Apoptosis of Cumulus-Oocyte Complexes Following Treatment with FSH Receptor Binding Inhibitor in Sheep

“…The extrusion of the first polar body is a principal sign of oocyte IVM and nucleus maturation. The previous studies have confirmed that addition of 10µg/mL FSH and 10 µg/mL LH has been shown to increase the IVM rate of ovine oocytes [5]. Supplementation in IVM media with 1.5 µg/mL rbFSH yielded a high degree of cumulus expansion of sheep oocytes [17].…”

“…FSHR is an important mediator in human and animals’ reproduction [4]. FSH-FSHR interaction activates a cascade of intracellular signaling events leading to the production of steroidogenesis that are involved in modulating the proliferation and differentiation of ovarian granulosa cells [5]. …”

The corpus luteum of the domestic cat: Histologic classification and intraluteal hormone profile

“…Knowledge of feline reproduction is expanding each year with the introduction of new methods that allow, for e.g., the study of gonadal function on a molecular level [1][2][3] and introduction of species-specific approaches for assisted reproduction of endangered felids [4][5][6][7]. However, we are still lacking knowledge about fundamental aspects of feline reproduction, especially, on luteal function.…”

Short-term hypertonic exposure enhances in vitro follicle growth and meiotic competence of enclosed oocytes while modestly affecting mRNA expression of aquaporin and steroidogenic genes in the domestic cat model

“…With the exception for Fshr the gene-specific primers were designed by Beacon designer software package (Premier Biosoft, Palo Alto, California, USA). Fshr primer sequences were those previously reported by Hobbs et al [34]. All primer sequences used in the present study are shown in Table 1.…”