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Published on: January 7, 2016
In vitro Activation of Mouse Oocytes through Intracellular Ca2+ Regulation
Nining Handayani1, Budi Wiweko2,3,4, Sarah Chairani Zakirah2,4
1Reproductive Science Master Program of Biomedical Science, Faculty of Medicine, University of Indonesia, Jakarta, Indonesia.
Background:
Ca2+ signaling pathway is suggested to play an essential role in mediating oocyte maturation.
Aims:
The aim of this study was to evaluate intracellular Ca2+ of resistant immature oocytes that failed to resume meiosis following subsequent in vitro culture reach metaphase II after calcium ionophore A23187 activation.
Settings And Design:
This in vitro analytical experimental study was conducted at Animal Science Laboratory of Indonesian Medical Education and Research Institute (IMERI), Human Reproductive Infertility and Family Planning of IMERI, and Electrophysiology Imaging of Terpadu Laboratory, Faculty of Medicine, University of Indonesia.
Methods:
A total of 308 oocytes classed as resistant immature following in vitro culture were randomly allocated to control (n = 113) and treatment groups (n = 195). The oocyte activation group was exposed to A23187 solution for 15 min and then washed extensively. Maturation was evaluated by observing the first polar body extrusion 20‒24 h after A23187 exposure. Ca2+ imaging was conducted using a confocal laser scanning microscope to identify the dynamic of Ca2+ response.
Statistical Analysis:
SPSS 20, Chi-square, and Mann-Whitney U-test were used in this study.
Results:
Activation of resistant immature oocytes with A23187 significantly increased the number of oocyte maturation compared with the control group (P < 0.001). Furthermore, fluorescent intensity measurements exhibited a significant increase in the germinal vesicle stage when activated (P = 0.005), as well as the metaphase I stage, even though differences were not significant (P = 0.146).
Conclusion:
Artificial activation of resistant immature oocyte using chemical A23187/calcimycin was adequate to initiate meiosis progress.
Insights
Calcium ionophore A23187 effectively activates resistant immature oocytes, promoting maturation. This chemical activation is sufficient to initiate meiotic progression in oocytes that previously failed to mature in vitro.
Area of Science:
- Reproductive Biology
- Cell Signaling
- In Vitro Fertilization (IVF)
Background:
- Calcium (Ca2+) signaling is crucial for oocyte maturation.
- Some immature oocytes resist standard in vitro maturation protocols.
- Understanding mechanisms to overcome oocyte maturation resistance is vital for fertility treatments.
Purpose of the Study:
- To assess the efficacy of calcium ionophore A23187 in activating resistant immature oocytes.
- To evaluate the subsequent meiotic progression to metaphase II after A23187 activation.
- To analyze intracellular Ca2+ dynamics during activation and maturation.
Main Methods:
- Resistant immature oocytes (n=308) were divided into control and A23187 treatment groups.
- Oocytes were exposed to calcium ionophore A23187 for 15 minutes.
- Maturation was assessed by first polar body extrusion; Ca2+ imaging used confocal microscopy.
Main Results:
- A23187 significantly increased oocyte maturation rates compared to controls (P < 0.001).
- Fluorescent intensity showed a significant Ca2+ increase at the germinal vesicle stage post-activation (P = 0.005).
- A trend towards increased Ca2+ at metaphase I was observed, though not statistically significant (P = 0.146).
Conclusions:
- Artificial activation using A23187 (calcimycin) successfully initiated meiosis in resistant immature oocytes.
- Chemical activation with A23187 is adequate to overcome maturation resistance.
- This method offers a potential strategy for improving IVF outcomes in cases of oocyte maturation failure.
