A particular defect in the cells of older female mice may explain female infertility in older human females. These findings can one day help develop a new fertility treatment that can help women carry to term.
Infertility is something that many couples across the world have to deal with. Human females, like other mammal females, are born with a definite number of egg cells. At around the age of 35, a woman's fertility starts to decrease. The quality of the eggs begins to decrease as well. Once a woman hits a certain age, it becomes another problem in trying to get pregnant. She may not be able to get pregnant at all or be unable to carry to term. There's also a higher risk of the fetus developing genetic abnormalities.
An abnormal number of chromosomes in egg cells can cause female infertility. Eggs with this defect are aneuploid eggs, and they increase in number as a woman ages. Aneuploid eggs cause infertility problems, miscarriage, and conditions like Down's syndrome in the fetus.
Prior to this new research, scientists believed that the loss of cohesion in chromosomes causes the formation of aneuploid eggs. The new research doesn't disprove this theory, but it does point to another problem.
Researchers found that microtubules in egg cells of older mice were defective. These microtubules are responsible for the sorting and segregation of chromosomes during cell division. Defective microtubules behave erratically and sort chromosomes in all directions instead of in a symmetrical fashion. According to the study, more than 50% of egg cells in older mice have erratic microtubules.
To be sure of these findings, the researchers placed a nucleus from a younger cell in an older cell. They found that it really is maternal age that causes the defects in the microtubules regardless of the age of the chromosomes.
These results will also likely be the same in humans, since defective microtubules also develop in human egg cells.
In the future, these findings may help in developing fertility treatments that can possibly focus on rejuvenating egg cells. It may take years before the development of these treatments, but we've at least taken a step forward in solving the problems of age-related female infertility.
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