Ovarian Stem Cells

The central dogma of female reproductive endocrinology is that the ovaries possess a finite number of eggs. This egg number is at its zenith when the woman is still just a female fetus inside her mother’s womb. Through monthly attrition (the “biological clock“), in which many more eggs per month are lost than merely the one which ovulates, this number is essentially zero by the time a woman approaches age 50.

But is this true? Are women born with all the eggs they will ever have, or do they possess the ability to make more? A team of scientists led by Dr. Jonathan Tilly at Massachusetts General Hospital and Evelyn Telfer at the University of Edinburgh challenged this staid dogma. They recently published their findings in the journal Nature Medicine, reporting how the mouse ovarian stem cells (OSC) they isolated were able to be placed back into ovarian tissue and make mature eggs. This finding, if true, suggests that one day menopause may be a thing of the past.

However, the newest research led by Kui Lu at the University of Gothenburg in Sweden has dampened these high hopes, saying their OSC contenders never seemed to proliferate or to mature into anything resembling oocytes. Therefore the world of infertility specialists is essentially now broken up into two camps: those who believe OSCs exist and those who don’t.

Both teams of scientists have to be congratulated on their vision and the expertise they have demonstrated while pursuing this topic. It is expensive, slow, meticulous work, all the while undertaken knowing that your findings will be ruthlessly scrutinized by other scientists in the field. Let’s face it: no one wants to admit that the central tenets of physiology to which they have long adhered might be fallacious.

I like to think that OSCs are real, and there is certainly a difference in at least the appearance of the cells described by Dr. Tilly and those described by Dr. Lu as the OSC contenders. Perhaps they are not actually describing the same cell subtypes. Dr. Tilly’s group believes the cells scrutinized by Dr. Lu’s team were nothing more than immature oocytes rather than true OSCs.

Given the clinical ramifications of these findings, as well as the truly fascinating scientific interest, this line of research will only heat up rather than cool down. We will likely know in the next five years not only if these OSCs truly do exist deep down in the ovarian tissue of menopausal women, but if they do, whether they can be activated to differentiate into eggs that can ultimately be ovulated to facilitate pregnancies.

At that time I guess shall be looking for a new occupation, or perhaps I could just go back into obstetrics given the presumably amazing surge in the pregnancy rate of older women!

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