Harvard, MGH researchers track egg cell production to marrow

Harvard researchers have found new evidence that female mammals can produce egg cells throughout life and have traced their production out of the ovary and into the bone marrow in findings that could both reshape science's understanding of female reproduction and provide new avenues for treatment of infertility.
In a series of experiments on sterile female mice, researchers from Massachusetts General Hospital (MGH), a Harvard teaching hospital, were able to restore egg production by transplanting bone marrow from fertile mice. The researchers believe that egg stem cells in the donor bone marrow established themselves in the sterile mice and began producing egg cells, also called oocytes.

Stem cells are precursor cells that develop into specific kinds of tissues, replenishing blood, skin, and other kinds of cells in the body.

The results, which build upon a study published last year, further erode the long-held belief that female mammals are born with a lifetime supply of egg cells that they slowly use up until the supply is exhausted.

If further experiments bear out the study's results and the processes discovered in mice hold true for humans, the findings could have far-reaching ramifications for treatment of human infertility and solve the mystery surrounding reported cases of spontaneous restoration of fertility in sterile women who've undergone bone marrow transplants.

Fertility expert Kutluk Oktay, an associate professor at Cornell University's Weill Medical College, said the research was "revolutionary" and said the most shocking finding was that the bone marrow, not the ovary itself, was the site of egg cell replenishment.

"It's nearly impossible to digest for many scientists," Oktay said.