Definition - What does Vacuole mean?

A vacuole in a human egg is a round structure that appears in the cytoplasm of the egg and is typically considered to be an abnormality. They appear visually like craters in what should otherwise be a smooth surface.

Egg vacuolization can be an indicator of quality and can lead to a decrease in fertilization and embryo development.

FertilitySmarts explains Vacuole

The vacuoles found in eggs are thought to be due to the collection and swelling of the smooth endoplasmic reticulum, a change which occurs when eggs age.

In addition, the effectiveness of the stimulation protocol used during the egg retrieval process where medications are used to stimulate the maturation of eggs can also have an impact on quality. The appearance of vacuoles may also be associated with estradiol levels that are too high, creating overly mature eggs.

The presence of vacuoles in the cytoplasm has been shown to impact the ability to develop good quality blastocysts.

Larger or numerous vacuole have been associated with lower fertilization rates or failed fertilization during assisted reproductive treatment. This can be because it can be difficult to inject the sperm into the egg without hitting a vacuole during intracytoplasmic sperm injection (ICSI), and it is likely that the presence of a large vacuole could make it difficult for the sperm for and the egg’s pronuclei to move toward each other during fertilization.

If the egg is fertilized, the vacuoles that persist beyond the fusion of the cells can interfere with cleavage (the division of cells in the embryo) which lowers the rate of blastocyst formation or can cause embryonic arrest.

Vacuoles have also been seen in sperm, they can lead to lowered fertilization rates and lower rated of pregnancy, but the area is not as well researched as the egg.

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