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Human oocyte activation after intracytoplasmic sperm injection
J Tesarik1, M Sousa, J Testart
1Centre of Reproductive Biology and Medicine, American Hospital of Paris, Neuilly sur Seine, France.
Human Reproduction (Oxford, England)
|March 1, 1994
Summary
Intracytoplasmic sperm injection (ICSI) causes an initial calcium rise, but does not activate the oocyte. True oocyte activation and embryonic development require a sperm factor released after injection.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cellular Physiology
Background:
- Oocyte activation is crucial for embryonic development, initiating after fertilization.
- Intracellular free calcium ([Ca2+]i) dynamics are central to oocyte activation.
- Intracytoplasmic sperm injection (ICSI) is a common assisted reproductive technology.
Purpose of the Study:
- To investigate the role of intracellular calcium ([Ca2+]i) changes in human oocytes following ICSI.
- To differentiate between procedural calcium fluctuations and fertilization-induced calcium signaling.
Main Methods:
- Confocal laser scanning microscopy was employed to monitor [Ca2+]i in human oocytes.
- Human oocytes underwent ICSI, with or without sperm, to observe calcium responses.
- Calcium concentration changes were recorded immediately post-injection and over several hours.
Main Results:
- A transient [Ca2+]i increase occurred immediately after microinjection needle penetration, independent of sperm.
- This initial calcium rise did not induce oocyte activation.
- A secondary, sperm-dependent [Ca2+]i increase, either non-oscillatory or oscillatory, was observed 4-12 hours post-injection in activated oocytes.
Conclusions:
- The calcium increase caused by the ICSI procedure itself is not sufficient for oocyte activation.
- Oocyte activation requires the release of specific sperm factor(s) after ICSI.
- The observed secondary calcium patterns are linked to the initiation of embryonic development.