Patrick Guilfoile: Men on the brain
Pregnancy has many effects on the female body. For example, weight gain, hormonal changes and quirks in food preference are associated with carrying a fetus.
In general, these effects are not permanent. However, in recent years, scientists have identified an interesting legacy of pregnancy. In many women, cells or DNA from the fetus end up lodging in tissues and organs and apparently remain there for a lifetime. Tissues previously shown to contain fetal DNA or fetal cells include the heart, lymph nodes, liver, skin, and intestines, among others.
Researchers from the Fred Hutchison Cancer Institute and the University of Washington took this previous work one-step further. They studied the brains of 59 women who died, and who donated their brains for study. The scientists took small pieces of tissue from various regions of the women’s brains, and searched for signs of male DNA. Males have a Y-chromosome and females do not, so any indication of a Y-chromosome in the brains of these women would be a sign of male DNA.
The researchers found male (Y-chromosome) DNA in the brains of 37 of the 59 women (63%). Since it was unknown whether most of the women had been pregnant with male children, it suggests that a very substantial fraction of women who gave birth to a son would have acquired DNA or cells from their child during pregnancy. (At least one woman who did not have a male child also had evidence of male DNA in the brain, but it is possible that she could have had a miscarriage of a male fetus.) Likely, cells from female fetuses also traverse the placenta and end up in the mother’s tissues, but these female cells are harder to identify.
The significance of finding fetal cells and DNA in the brains (and other tissues) of women is not yet clear. There has been a suggestion that this might contribute to the greater prevalence of autoimmune disorders like rheumatoid arthritis in women. The continued exposure to the foreign cells from a fetus might over-stimulate the immune system and cause it to recognize the woman’s own cells as being foreign. There has also been a suggestion that these male cells or male DNA might trigger the immune system to more easily track down and eliminate cancer cells, thereby reducing the risk of malignancy. There has also been an indication that fetal cells may move to an injured area and aid in tissue repair, thereby contributing to the health of the mother.
The jury is still out on whether these fetal cells have a net benefit or are more likely to cause harm for the mother. However, for women who feel they always carry their children with them in their hearts and minds, that idea now appears to be literally true.
More information is available in the following article (freely available online): Chan WFN, Gurnot C, Montine TJ, Sonnen JA, Guthrie KA, et al. (2012) Male Microchimerism in the Human Female Brain. PLoS ONE 7(9): e45592. doi:10.1371/journal.pone.0045592.
PATRICK GUILFOILE has a Ph.D. in bacteriology and is currently an interim associate vice president at Bemidji State University.