Dynamized follicle-stimulating hormone affects the development of ovine preantral follicles cultured in vitro

The objective of the present study was to characterize expression of mRNAs encoding FSH and LH receptors during follicular development and at different stages of the first follicular wave in cattle. Following estrus, groups of heifers (3-5 per group) were ovariectomized on the day of initiation of the first follicular wave (as determined by ultrasonography; Day 0), or on Days 2, 4, 6, 8, or 10 after initiation of the first wave. FSH and LH receptor mRNAs were detected within follicles > or = 4 mm and in some smaller follicles by in situ hybridization and were quantified by image analysis. FSH receptor mRNA was expressed in granulosa cells of all growing follicles, starting in some follicles with only one layer of granulosa cells. Irrespective of day of the follicular wave, the level of expression of FSH receptor mRNA in granulosa cells of healthy antral follicles ranging from 0.5 to 14 mm in diameter did not vary significantly with follicular size (r = 0.02, p > 0.10). Expression of LH receptor mRNA was first observed in theca interna cells of follicles shortly after antral formation. Irrespective of day of the follicular wave, the levels of LH receptor mRNA in theca interna cells of healthy antral follicles ranging from 0.5 to 14 mm increased with follicular size (r = 0.39, p 9 mm in diameter and was first observed in the dominant follicles collected on Day 4. Expression of mRNA for LH receptor, but not for FSH receptor, changed (p < 0.01) with the stage of the first follicular wave.(ABSTRACT TRUNCATED AT 250 WORDS)

Oocyte-granulosa cell communication is essential for oocyte development. The aims of this study were: 1) to determine the effect of FSH on expression of Kit ligand (KL), growth/differentiation factor-9, bone morphogenetic protein (BMP)-15, and Kit during growth of oocyte-granulosa cell complexes (OGCs) in vitro; 2) to investigate the role of BMP-15 in regulation of KL expression; and 3) to correlate mRNA expression with oocyte growth. OGCs from 12-d-old mice were cultured for up to 7 d in the presence of FSH [0.05 ng/ml (low), 5 ng/ml (high)] or BMP-15 (10 or 100 ng/ml). Transcripts were quantified using real-time RT-PCR, and oocyte and OGC diameters were measured. FSH regulated KL expression in a biphasic manner, with low FSH decreasing the KL-1/KL-2 ratio, and high FSH increasing the KL-1/KL-2 ratio, compared with controls (P < 0.05). The decrease in KL-1/KL-2 ratio with low FSH was due to increased KL-2 mRNA expression. Both FSH concentrations increased OGC diameter (P < 0.05), but only low FSH promoted oocyte growth (P < 0.05). High FSH also decreased BMP-15 expression (P < 0.05). FSH-stimulated oocyte growth was inhibited by Gleevec, an inhibitor of Kit activity. BMP-15 increased both KL-1 and KL-2 mRNA levels in a dose-dependent manner (P < 0.05) but did not alter the KL-1/KL-2 ratio or promote oocyte growth. When the KL-1/KL-2 ratio was increased by exogenous KL-1, FSH-stimulated oocyte growth was suppressed (P < 0.05), suggesting that lowered KL-1/KL-2 ratio is important for oocyte growth. In summary, the correct concentration of FSH is crucial for appropriate modulation of KL and BMP-15 to promote oocyte growth.