Monday, August 31, 2015

The alien within: Fetal cells influence maternal health during pregnancy (and long after)

http://www.eurekalert.org/pub_releases/2015-08/asu-taw082515.php

Public Release: 28-Aug-2015
The alien within: Fetal cells influence maternal health during pregnancy (and long after)
Arizona State University

Parents go to great lengths to ensure the health and well-being of their developing offspring. The favor, however, may not always be returned.

Dramatic research has shown that during pregnancy, cells of the fetus often migrate through the placenta, taking up residence in many areas of the mother's body, where their influence may benefit or undermine maternal health.

The presence of fetal cells in maternal tissue is known as fetal microchimerism. The term alludes to the chimeras of ancient Greek myth--composite creatures built from different animal parts, like the goat-lion-serpent depicted in an Etruscan bronze sculpture.

According to Amy Boddy, a researcher at Arizona State University's Department of Psychology and lead author of a new study, chimeras exist. Indeed, many humans bear chimerical traits in the form of foreign cells from parents, siblings or offspring, acquired during pregnancy.

"Fetal cells can act as stem cells and develop into epithelial cells, specialized heart cells, liver cells and so forth. This shows that they are very dynamic and play a huge role in the maternal body. They can even migrate to the brain and differentiate into neurons," Boddy says "We are all chimeras."

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Fetal cells may do more than simply migrate to maternal tissues. The authors suggest they can act as a sort of placenta outside the womb, redirecting essential assets from the maternal body to the developing fetus. Cells derived from the fetus--which can persist in maternal tissues for decades after a child is born--have been associated with both protection and increased susceptibility to a range of afflictions, including cancer and autoimmune diseases like rheumatoid arthritis.

But, as co-author Wilson Sayres, cautions, "it's not only a tug of war between maternal and fetal interests. There is also a mutual desire for the maternal system to survive and provide nutrients and for the fetal system to survive and pass on DNA."

If some degree of fetal microchimerism exerts a beneficial effect on maternal and offspring survival, it will likely be selected for by evolution as an adaptive strategy.

A review of existing data on fetal microchimerism and health suggests that fetal cells enter a cooperative relationship in some maternal tissues, compete for resources in other tissues and may exist as neutral entities--hitchhikers simply along for the ride. It is likely that fetal cells play each of these roles at various times.

For example, fetal cells may contribute to inflammatory responses and autoimmunity in the mother, when they are recognized as foreign entities by the maternal immune system. This may account in part for higher rates of autoimmunity in women. (For example, women have three times higher rates of rheumatoid arthritis, compared with men.)

Fetal cells can also provide benefits to mothers, migrating to damaged tissue and repairing it. Their presence in wounds--including caesarian incisions--points to their active participation in healing. In other cases, fetal cells from the placenta are swept through the bloodstream into areas including the lung, where they may persist merely as bystanders.

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Finally, the authors note, fetal microchimerism may be one piece of a subtle and dizzyingly complex puzzle. Cell traffic is actually bi-directional, with the fetus receiving cells from the mother. Fetal cells from maternal tissue may cross the placental barrier during subsequent pregnancies, potentially influencing the health of later offspring. To further complicate matters, cells from later fetuses can also cross the placenta to enter the microchimeric arena, perhaps introducing sibling rivalries for the mother's limited resources.

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