Women Not Born With Lifetime Supply of Eggs?
Animal Study Shows Mammals Have a Reserve of Egg-Producing Follicles
WebMD News Archive
Finding Challenges Basic Reproductive Biology Beliefs continued...
Researchers found that the number of healthy follicles actually
decreased relatively slowly despite this rapid loss of follicles. That finding
shows that healthy egg-producing follicles must be produced somewhere in young
To test this theory, researchers treated the young mice with a
chemical that kills egg cells and instead found that the mice still produced
viable eggs in adulthood.
Researchers say the results show that a reserve of stem cells
that form the building blocks for reproductive cells must exist in female mice
as they do in male mammals. But more research is needed to determine how they
function and what causes them to decline after adolescence.
Implications for Female Fertility
In an editorial that accompanies the study, Allan C. Spradling
of the Carnegie Medical Institute Laboratory in Baltimore, Md., says the study
raises many interesting and important questions.
For example, the location and the number of these 'reserve' or
germ stem cells in females will need to be determined.
In addition, "the question on everyone's lips will be
whether there are germline stem cells in the human ovary."
Spradling says these cells might have easily been missed in
humans for the same reasons they were missed in mice for so long -- they were
thought to be rare.
He says the work also raises "the strong possibility"
that the rapid decline in female fertility that occurs after age 30 is caused
by the depletion of these 'reserved' cells coupled with an age-related decline
in healthy egg-producing follicles.