Scientists now are closer to understanding why older women become less fertile, suffer a miscarriage or have a baby with Down's syndrome. This could be ground breaking in infertility treatment in the older women in their late 30s and early 40s.
The study was led by Dr Mary Herbert, an expert in reproductive biology at Newcastle University's Institute for Ageing and Health, and published in the journal Current Biology.
It has been seen for many years that older women tend to produce abnormal eggs that lead to chromosomal abnormalities in the babies. The reasons have not been clear till now. This study shows that these problems arise from a woman's declining stock of proteins called Cohesins, which act as binding agents to hold chromosomes together by keeping them inside a ring. They are vital to ensure that chromosomes split evenly when cells divide. Cohesins decline with age said Herbert and her colleagues as they studied eggs taken from both young and old mice. With the decline of this protein the chromosomes are less tightly held together and they are therefore more likely to result in defective eggs, which can cause problems such as miscarriage and Down's syndrome.
The important form of cell division called meiosis causes the division of the reproductive cells to sperms and eggs, each of which only have half the total number of chromosomes in humans i.e. 23 instead of 46. In women the attachments that hold chromosomes together have to be maintained by Cohesins until the egg divides just before ovulation. If there is too little cohesin, the structure can be too “floppy” for division to happen equally leading to chromosomal abnormalities.
Herbert said, “Reproductive fitness in women declines dramatically from the mid-30s onwards. Our findings point to Cohesin being a major culprit in this…. More work was needed to understand why Cohesin declines over women's reproductive years, and such knowledge could lead to ways being developed to stop that loss from occurring.
Other doctors like Dr Peter Bowen-Simpkins, the medical director of the London Women's Clinic network of private fertility clinics and spokesman for the Royal College of Obstetricians and Gynaecologists, found this discovery an “exciting” one. He said, “This breakthrough could mean the difference between success and failure – them having a baby or not – for the fast-growing number of women who are trying to conceive after their late 30s.”
Adam Balen, professor of reproductive medicine and surgery at the Leeds Centre for Reproductive Medicine agreed that this finding was “very interesting”. “This is a neat explanation as to why we see mismatches in chromosomes as women get older,” he said. He however warned that it was “far too early to say” if the finding would have any bearing on clinical care for older women with fertility problems.
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