Monday, September 28, 2015

Fetal microchimerism and maternal health: A review and evolutionary analysis of cooperation and conflict beyond the womb

We have a review and evolutionary analysis of the role of microchimerism in maternal health. It's open access for all to read and please share your thoughts on. My personal take-home, after completing this paper, is that there is still so much biology to understand. Perhaps my favorite part of the whole paper is that we start by stating how little we know:

The function of fetal cells in maternal tissues is unknown

Certainly there are associations, and many labs are focused on understanding the role of fetal cells in the pregnant body, and after pregnancy. At the minimum, microchimerism appears to have been present since placentation first evolved, with advances in sensitivity and specificity of techniques, we are understanding that microchimerism is likely common across eutherian (placental) mammals, and especially in our favorite eutherian, humans. But it is fantastic to me that there is no answer (and in my opinion will never be) to, "Are microchimeric cells good?" At the best, we can say that it depends. And for the pregnant body and post-pregnant body, the role of fetal cells likely depends heavily on the specific interaction of the fetal cells with the immune system.

Levels of explanationDefinitionExplanations for fetal microchimerism

ProximateThe immediate cause of the pathologyPlacentation allows for the transfer of small numbers of cells between the fetus and the mother
DevelopmentalHow the pathology arose as a result of events during an individual's lifeEvidence suggests that fetal cell microchimerism begins before the placental is completely formed, likely beginning with the initiation of placentation itself [26, 111]
EvolutionaryHow natural selection and other mechanisms of evolution (drift, migration) have left the body vulnerable to the pathologyMaternal-fetal genomic conflict, through genetic imprinting may have allowed for selection of higher proportions of fetal cell microchimerism
PhylogeneticWhen, in evolutionary history, did the vulnerability to the pathology arise?Microchimerism has thus far only been detected in eutherian mammals [14, 27-29], suggesting it arose at least in the common ancestor of eutherian mammals, approximately 93 million years ago [112]

With some very talented help, we made the video abstract below:

  1. Amy M. Boddy1,2,*
  2. Angelo Fortunato2
  3. Melissa Wilson Sayres3,4,† and
  4. Athena Aktipis1,2,3,†
Article first published online: 28 AUG 2015
DOI: 10.1002/bies.201500059

The presence of fetal cells has been associated with both positive and negative effects on maternal health. These paradoxical effects may be due to the fact that maternal and offspring fitness interests are aligned in certain domains and conflicting in others, which may have led to the evolution of fetal microchimeric phenotypes that can manipulate maternal tissues. We use cooperation and conflict theory to generate testable predictions about domains in which fetal microchimerism may enhance maternal health and those in which it may be detrimental. This framework suggests that fetal cells may function both to contribute to maternal somatic maintenance (e.g. wound healing) and to manipulate maternal physiology to enhance resource transmission to offspring (e.g. enhancing milk production). In this review, we use an evolutionary framework to make testable predictions about the role of fetal microchimerism in lactation, thyroid function, autoimmune disease, cancer and maternal emotional, and psychological health.

Popular coverage:
New York Times:
National Geographic:
Smithsonian Magazine:
Medical Daily:

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