Whether that correlation means that fetal male DNA helps protect women against AD is unclear, however. "To me, this suggests that the presence of fetal cells in the female brain prevents disease," says cardiologist Hina Chaudhry of Mount Sinai School of Medicine in New York City.
In a study published online in Circulation Research late last year, Chaudhry and colleagues found that fetal cells in mice migrated to the mother's heart, differentiated into functioning cardiac cells, and accelerated repair to damaged heart tissue. So, Chaudhry says, a similar thing could be happening when fetal cells migrate to the brain. "I would bet these cells are getting into the maternal brain and are able to differentiate into neurons."
A 2010 study in Stem Cells and Development showed that fetal cells can migrate to the brain of a mother mouse and mature into neurons, Nelson says. But, she adds, it remains unclear if something similar is happening in humans-and it's also difficult to reach any firm conclusions about a potential link between microchimerism and AD. Part of the problem is that her team had little information about the pregnancy histories of the women in their study. "We have to say we really don't know," she says. "I hope that kind of work can be done in the future, but it's very difficult to do with human samples."
- - -
This is adapted from ScienceNOW, the online daily news service of the journal Science. http://news.sciencemag.org