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Wellness Corner - October 2016 Microchimera: A Little Piece of Your Heart

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Wellness Corner - October 2016
Microchimera: A Little Piece of Your Heart

Have you ever wondered why mothers are so crazy for their babies? Why those Olympians’ mothers cannot watch their child stick a landing or cross the finish line? Why so many moms report feeling a physical connection to their children decades after having given birth?

Here’s why

During every pregnancy, fetal cells cross the placenta and enter the mother’s bloodstream. They hang around for awhile, and some eventually become part of the mother’s tissues. The longer a woman is pregnant, the more fetal cells make the journey.  Ultimately, some portion of each fetus’ genetic information is integrated into a mother’s body creating what scientists call a “microchimera” – that is, a mixture of cells from one individual  that is genetically distinct from the individual in which they reside. (As a side note, this word comes from the Ancient Greek monster Khimaira with the body and head of a lion, a goat’s head rising from its back, the udders of a goat, and a serpent tail).

Once a mother delivers her baby – within about 30 days – her immune system generally cleans things up and removes the fetal cells that are still circulating in her bloodstream – but not true for the ones who’ve integrated into her tissues. Those may slip by undetected. There was even a study in 2012 that found cells with Y chromosomes (i.e. boy cells, remember chromosomally-speaking boys are XY and girls are XX) in multiple areas of the brains of deceased women!

This all as some amazing implications for medicine

First, it is revolutionizing how we approach genetic testing in prenatal care. In fact, there are currently two tests on the market that can detect fetal DNA in a mother’s body as early as ten weeks (that’s 2 ½ months into a pregnancy) – giving a very accurate chromosomal analysis and gender identification. These tests are being used more and more widely in our local clinics and health centers, particularly for pregnant women who are at increased risk of genetic abnormalities (age over 35, or personal history of a baby with a chromosomal abnormality). 

I am betting these non-invasive tests will virtually replace more invasive testing like amniocentesis and chorionic villous sampling. They allow women to know (not definitively but pretty darn close) whether or not her child has a chromosomal abnormality early enough for her to make decisions about terminating a pregnancy before she is finished with the first trimester.

The other implications are a little further off, but potentially even more interesting. Some scientists are postulating that the presence of fetal cells still circulating in a mother’s bloodstream can prevent another pregnancy from happening “too soon” (i.e. delaying a little brother’s arrival) by leading to early miscarriage. Or that perhaps the fetal cells are part of the signalling for lactation to begin. 

Others are studying the role of fetal microchimerism in autoimmune disease. We know that women have higher rates of autoimmune disease than men do – and these illnesses (e.g. lupus, rheumatoid arthritis, scleroderma) often first appear in middle age. It may be that the foreign genetic material in a mother’s bloodstream contributes to a complex cascade of events that lead to the formation of autoantibodies (antibodies that attack your own body). How this exactly might happen has not been worked out. At minimum, these cells have been detected in the tissues of women with lupus and systemic sclerosis/scleroderma. It is important to note  that microchimera have also been detected in plenty of healthy women and women with non-autoimmune illnesses. So the relationship is not exactly clear. 

Last, there is some hypothesizing that these same fetal cells, which we know are are pluripotent (meaning they, like stem cells, can become ANY type of cell) may actually be able to serve some powerful repair functions inside a woman. That is, they might help a mother recover from some illness or diseases that she would otherwise not been able to  recover from because the fetal cells have so much potential and can generate new “better” tissue within her tissues.

Pretty amazing, right? Just confirms what many of us believe to be true – wherever your children wander, they do leave little bits of them behind, and some of those bits may actually be part of your very own heart.