A new study published in the journal Cell, challenges the theory that mammals such as mice and humans generate egg cells only as fetuses, to be born with all the eggs they will ever have. Scientists said in their study published on Thursday, that stem cells from bone marrow may serve as a source of egg cells at least in mice, leading to the possibility of new fertility treatments for humans.
The scientists believe that they also found evidence that the egg-generating stem cells found in adult mouse ovaries, also exist in human bone marrow. Jonathan Tilly, director at Massachusetts General Hospital and Harvard Medical School, who led the study, said that the study could usher in a new era in the clinical management of female infertility and menopause. He believed that this could lead to new treatment approaches based not on regenerative medicine through adult stem cells rather than drugs. Also a little long way off is the possibility of patients whose ovaries have been destroyed or surgically removed, being helped in their quest to have children. The study also indicates that adult stem cells found in bone marrow might turn out to be a source of eggs for therapeutic cloning.
So far one of the key limitations to research on human embryonic stem cells is the need for female donors to undergo surgery to provide eggs for the process, besides a law severely restricting funding of such work. However, when earlier this year, the scientists reported a puzzling problem of sterilized female mice spontaneously regenerating their ovaries and egg cells, they could find little evidence of oocyte stem cells that could have caused it. It was only when they looked in the bone marrow, a rich source of adult stem cells that they found markers or protein signatures of germ cells that are capable of giving rise to eggs and sperm.
Dr. Tilly said that the findings were a surprise as "Everyone had missed finding female germline stem cells because they are not in the ovaries, where everyone would have looked for them". After giving the sterilized mice bone marrow transplants, the scientists found the mice to have new egg cells and follicles within 24 hours, and two months later they could hardly make out the sterilized mice from unsterilized mice.
However, the scientists need to conclusively prove that the mice can produce babies with their new egg cells. But preliminary tests have established that these egg-precursor cells exist in human bone marrow and blood and fertility treatments may now consist of drugs that encourage the cells to migrate to the ovary to restock a woman’s declining supply of eggs.
The study reports suggest that stem cells may not only be the future of treating deadly diseases but also the future of human procreation amidst falling female fertility. But as long as laws prevent these tests from being replicated on test human cases, it is likely that the surprising results of the new study may remain confined to labs and mice.
