Can mammals renew their eggs?

I've talked about this subject in the past, and we briefly mention it in the upcoming podcast, but where are we with the question of whether a germline stem cell exists in female mammals? PLOS as a great article which summarizes the ongoing debate on whether a woman is born with a limited pool of eggs that will last for her reproductive life or whether that pool is continuously renewed... Obviously the presence of a hematopoietic stem cell which has the ability to form eggs, as Jonathan Tilly believes, would radically change the way we view conditions such as infertility, menopause and bone marrow transplants. As mentioned in this article, it's still too early to call, considering so little of the work has been replicated. Additionally, while bone marrow transplants in irradiated females is sufficient to reestablish fertility, none of the ovulated eggs match the donor, despite such eggs being supposedly present in the ovary.

In addition to this story being interesting, it highlights how reproducibility is so seldom tested in the current constrained funding environment. In fact it seems that this situation is particularly true of the whole field of stem cell biology...

“What anyone publishes is not really the corpus of scientific knowledge unless it can be verified,” says Gosden. “You don't get a paradigm change until you have a consensus of expert opinion,” he says, and that is certainly not the case here. This follows physicist and science historian Thomas Kuhn's view of scientific revolutions—that many inconsistencies must build up in a field of science before a paradigm shift can occur.

The Kuhn model of paradigm shifts describes how most central ideas in science get revised or overturned, but there is another model that some would argue is equally valid, if rarer: the “lone voice in the wilderness” of a single scientist pushing a revolutionary idea forward. There are notable examples of lone voices who both succeeded and failed in overturning an idea. Stanley Prusiner's hypothesis that aberrant protein structures called prions could cause infection initially lost him his bid for tenure at the University of California at San Francisco and significant funding from the Howard Hughes Medical Institute, but eventually won him a Nobel prize in physiology or medicine in 1997. The cold fusion work of the late 1980s, which was never replicated to the satisfaction of the nuclear physics community, eventually resulted in Martin Fleischmann and Stanley Pons dropping out of academia.

“There's a fine line between being a maverick and a genius prescient person,” says Durant. Currently, Tilly is gingerly straddling that line, which can mean the difference between receiving the highest scientific honors or the scorn of your peers."

Backboner

A couple of years ago, I went to the meeting of the Society for the Study of Reproduction (SSR) where J. Tilly presented his paper on the repopulation of germ cells in the ovary by a circulating stem cell in the blood. It was the first time that I saw both a standing ovation and grumbling from skeptics at a scientific talk. It went against everything we knew about female germ cells, and raised the possibility that woman with bone marrow tranplants or blood transfusion may not be the biological mothers of their own child. I am still not 100% convinced, but the idea that the niche can dictate what a stem cell will become is becoming more and more supported by evidence. This recent report that bone marrow cells injected in the testes can give rise to sperm further substantiates that claim. So maybe females can become, biological fathers? And it is good news for my friend who's spontaneously grown ovaries after watching too much dancing with the stars...