Pioneering fertility study alters perceptions of egg reproduction

A pioneering study conducted by a scientist in Massachusetts has found that women continuously replenish eggs in the ovary, which sweeps away the belief that women only have a limited stock of eggs.

The experiment, conducted at Massachusetts General Hospital, found that eggs in a women's womb are continuously replenished from precursor cells in the ovary. This challenges the long term 'bank account' doctrine, which suggests that women are given a set amount of eggs at birth which is not renewable.

Lead author of the study Jonathan Tilly had originally challenged this perception eight years ago, and has now confirmed his results and further developed his ideas. His team isolated egg-producing stem cells in human ovaries and then coaxed them into developing oocytes. They then pinpointed the oocyte stem cells by using antibodies which latched onto a protein "handle" located on the side of these cells. The team tagged the stem cells with a fluorescent green protein, and the cells were injected into biopsied human ovarian tissue which was then grafted beneath the skin of mice.

The graft produced a budding of oocytes, some of which glowed with the fluorescent tag and others did not, which suggests that they were already present in the tissue before the injection. Tilly said: "If we can guide the process correctly, I think it opens up a chance that sometime in the future, we might get to the point of actually having an unlimited source of human eggs."

Published by Fiona Griffiths