Related Experiment Videos
FSH-induced resumption of meiosis in mouse oocytes: effect of different isoforms
C Yding Andersen1, L Leonardsen, A Ulloa-Aguirre
1Laboratory of Reproductive Biology, Section 5712, Juliane Marie Center for Children, Women and Reproduction, University Hospital of Copenhagen, Blegdamsvej 9, DK-2100 Copenhagen, Denmark.
Abstract:
The ability of different isoforms of follicle stimulating hormone (FSH) to induce the resumption of meiosis in cultured mouse oocytes was evaluated. Oocytes were cultured in the presence of hypoxanthine to prevent spontaneous resumption of meiosis. Using serial dilutions of the isoform fractions representing less acidic isoforms (pI 6. 43-5.69), mid-acidic (pI 5.62-4.96) and acidic (pI 4.69-3.75), the concentration which caused 50% of the oocytes to resume meiosis and undergo germinal vesicle breakdown (GVBD) after a culture period of 24 h (i.e. ED(50%) GVBD) was determined. The FSH concentration of the isoform fractions was determined by radioimmunoassay, radio-receptor assay or through cAMP release in a Chinese hamster ovary-cell line expressing the human FSH-receptor. Determined by radioimmunoassay, the (ED(50%) GVBD) values were: less acidic 6.4 +/- 0.3 IU/l (mean +/- SD), mid-acidic 6.1 +/- 0.7 IU/l and acidic 12.2 +/- 0.7 IU/l. The less and mid-acidic isoforms were significant lower than the acidic (P < 0.0005). Similar relationships between the isoform fractions were obtained by the two other FSH assays. The results demonstrate that FSH isoforms with a pI of >5.0 induced resumption of meiosis significantly more efficiently than acidic isoforms. Less and mid-acidic isoforms may exert an important physiological function by inducing the resumption of meiosis in oocytes from pre-ovulatory follicles during the mid-cycle gonadotrophin surge.
Insights
Less acidic follicle stimulating hormone (FSH) isoforms are more effective at inducing meiosis resumption in mouse oocytes. These findings suggest a key physiological role for less acidic FSH isoforms in ovulation.
Area of Science:
- Reproductive Biology
- Endocrinology
- Cell Biology
Background:
- Follicle-stimulating hormone (FSH) plays a critical role in reproductive processes.
- FSH exists in various isoforms with differing acidic properties.
- Understanding isoform-specific activity is crucial for reproductive research.
Purpose of the Study:
- To evaluate the efficacy of different follicle stimulating hormone (FSH) isoforms in inducing meiosis resumption in cultured mouse oocytes.
- To determine the dose-response relationship (ED50%) for various FSH isoforms.
- To elucidate the physiological relevance of FSH isoforms in oocyte maturation.
Main Methods:
- Mouse oocytes were cultured with hypoxanthine to inhibit spontaneous meiosis resumption.
- Serial dilutions of less acidic, mid-acidic, and acidic FSH isoform fractions were used.
- The concentration inducing 50% germinal vesicle breakdown (GVBD) was determined after 24 hours.
- FSH concentrations were quantified using radioimmunoassay, radio-receptor assay, and cAMP release assays.
Main Results:
- Less acidic (pI 6.43-5.69) and mid-acidic (pI 5.62-4.96) FSH isoforms showed significantly higher potency in inducing GVBD compared to acidic isoforms (pI 4.69-3.75).
- The ED50% GVBD values for less acidic, mid-acidic, and acidic isoforms were 6.4 ± 0.3, 6.1 ± 0.7, and 12.2 ± 0.7 IU/l, respectively (radioimmunoassay).
- Similar trends were observed across different FSH quantification methods, confirming the differential activity of isoforms.
Conclusions:
- FSH isoforms with a pI > 5.0 are significantly more efficient in inducing oocyte meiosis resumption than acidic isoforms.
- Less and mid-acidic FSH isoforms likely play a crucial physiological role in initiating oocyte maturation during the mid-cycle gonadotropin surge.
- These findings highlight the importance of FSH isoform heterogeneity in regulating ovulation.