Cells that are not our own may unlock secrets about our health

During pregnancy, maternal and fetal cells migrate back and forth across the placenta, with fetal cells entering the mother’s bloodstream and tissues. They can settle in maternal organs such as the thyroid, liver, lungs, brain and heart — and can persist there for decades. Conversely, maternal cells can enter the fetus and be passed down to future generations, essentially creating a lifelong connection between mothers, their offspring and their descendants.

In other words, we all carry little pieces of our family with us.

This phenomenon, called microchimerism, is often characterized by cells of different genetic origin that circulate within the body and can occur either naturally through pregnancy or artificially through organ transplantation and blood transfusions. Microchimeric cells can be transferred from a fetus to its mother, from the mother to her children and even back and forth between multiples within the womb.

What microchimeric cells do

Microchimeric cells can play complex roles in a person’s body, often beneficial as well as harmful. They can help heal wounds, repair tissue and regulate the immune system, but they have also been linked to pregnancy complications as well as autoimmune diseases such as scleroderma and rheumatoid arthritis, and certain cancers like leukemia.

Microchimerism is not new. Its existence has been well documented since its discovery in the late 19th century, but it has recently made a resurgence in popular mainstream media.

However, what microchimeric cells do, how they move between bodies and what their role is in health outcomes remain largely unknown.

“These cells are extremely rare, making up less than 1 percent of the total cells in our body, and are difficult to detect,” said Kristine Joy Chua, a biological anthropologist in the University of Notre Dame’s Department of Anthropology. Her work focuses on the social and biological factors that affect pregnancies and pregnant mothers.

According to Chua, “Maternal and fetal cells have similar DNA because they come from the same source genetically. The challenge lies in detecting them and isolating them independently.”

The Microchimerism, Human Health & Evolution Project

Their rarity has fueled skepticism within the scientific community, with researchers questioning whether these cells matter or have any meaningful impact on human health. Despite these critiques, microchimerism researchers have continued to examine and learn about them, synthesizing their efforts in a recent publication co-led by Chua in the journal Advanced Science.

It is the first publication by the Microchimerism, Human Health & Evolution Project, a multidisciplinary microchimerism consortium, that sought to identify the field’s most pressing questions to advance microchimerism research. The project team surveyed 29 leading experts in the field of microchimerism and found that, as a community, they need to define what these cells are, examine why they exist and persist, set protocols for how to collect and detect them in the lab, and analyze their function and role in health and disease.

Potential benefits of microchimeric cells

With the development of more advanced modern technologies, experts are more confident that they may circumvent previous difficulties in research design or execution to better understand what microchimeric cells do. Doing so can bring researchers one step closer to developing diagnostic and therapeutic tools.

For example, the experts noted the potential to harness the stem cell-like properties of microchimeric cells, which could allow these cells to morph into organ-specific cells that could be used restoratively in patients with thyroid or liver damage.

“They could also be used as a biomarker for those who are at risk for certain pregnancy complications such as pre-eclampsia, spontaneous abortion and placental dysfunction,” Chua explained. “Based on the quantity of these cells or their phenotype, it is possible that these cells have real implications for how we look at maternal health and intervention.”

Microchimeric cells can also explain the intergenerational health of a family — how and where particular diseases and health deficiencies are passed along, especially immune-related disorders. “If we can better understand how diseases start in a person’s body, perhaps that could inform how we prevent some of these complications, potentially leading to better health,” Chua suggested.

The future of the research

In addition to certain methodological constraints, the authors noted additional challenges that appear to be relevant to all scientists studying reproductive biology and pregnancy. These include ethical constraints related to biosample collection from pregnant individuals, concerns over formal consent and addressing these concerns on a global scale. They also called for more research priorities to shift toward pregnancy and women’s health, more broadly, along with a more developed research community to advance the field.

They hope that by assembling this consortium of scientists, they will be able to establish new and innovative collaborations, train future researchers in standardized methods for studying microchimerism and create pipelines to allow for the sharing of ideas — all in an effort to continue growing the microchimerism community.

Chua said she hopes more anthropologists will join her to further the study of microchimerism and its role in pregnancy and intergenerational health.

“We know that pregnancy outcomes are not just a product of our biology, but also of our social environment,” she said. “Together, they shape how the body reacts to being pregnant and giving birth. We cannot forget about the social environment — it is a component that requires more attention in microchimerism research.”

Funding support is provided from the John Templeton Foundation and the Intramural Research Program of the National Human Genome Research Institute, National Institutes of Health.

Contact: Tracy DeStazio, associate director of media relations, 574-631-9958 or tdestazi@nd.edu