How your kids might help you in ways you never imagined

We’re publishing the shortlisted entries to the 2012 Wellcome Trust Science Writing Prize. Here, Rhea Chatterjea on how pregnancy doesn’t just take, but gives as well.

If you broke your arm when you were 6, you were probably back playing on the monkey bar within a few months. But if you break your hip at the age of 80, you’re unlikely to ever regain full mobility.

The ease with which the human body repairs injured tissue may, in part, be down to its reserve of fetal stem cells. These cells have the ability to quickly migrate to damaged regions and regenerate lost tissues. However, our reserve of these cells decreases with age and their propensity to participate in repair declines significantly. But what if we could use a fetal cell transfusion to aid in repair of injured tissue? Better still, what if we could use fetal cells to cure pathologies such as autoimmune conditions and heart failure?

Researchers at the Mount Sinai School of Medicine in New York have found that when a pregnant mouse has a heart attack, cells from the fetus are able to travel to the mother’s heart and perhaps help in recovery. These experiments follow observations that women who experience cardiac failure during pregnancy have the highest recovery rate compared to any other cardiac failure patient group. The finding that fetal cells are able to cross the placenta and enter the maternal circulation is not new. But what is intriguing is that these cells are able to persist in human mothers beyond pregnancy.

In 1996, a key study by Dr Diana Bianchi at Tufts University found fetal cells in a mother, 27 years after she had last given birth. Interestingly, although fetal cells are genetically unique from the mother, and preserve some paternal characteristics, they are not eliminated by the maternal immune system. Instead, they seem to be able to contribute to maternal tissues, persisting in the lungs, bone marrow and spleen for example. This phenomenon of persistent fetal cells in the mother is termed fetal microchimerism.

Further research in the past two decades gave rise to another puzzling discovery – women with systemic sclerosis, an autoimmune disease of connective tissue, had increased levels of fetal microchimerism. In autoimmune conditions, the body’s immune system starts attacking its own cells. Subsequently, fetal cells were found in skin lesions of patients with systemic sclerosis, and in affected joints of patients with rheumatoid arthritis. While it has been well known for many decades that women have an increased predisposition for autoimmune conditions, especially after childbearing years, the reason behind this increased risk is unknown. The observations of fetal cells in patients with autoimmune conditions led scientists to question if the fetal cells were involved in the disease process. Are fetal microchimeric cells the missing link between females and the increased risk of autoimmune disease?

Studies like the one at the Mount Sinai School of Medicine are adding to mounting evidence, however, that fetal cells may not be involved in causing disease at all. Instead, scientists are suggesting that fetal cells may be detected at higher frequencies in patients with certain autoimmune conditions because they are more readily recruited to the damaged tissue to aid in repair.

In the Mount Sinai study, fetal cells were shown to develop into cardiac muscle cells with the ability to beat and possibly contribute to heart function. This provides promising evidence that fetal cells could one day be used to promote recovery and regeneration of damaged tissue.

Before doctors start injecting fetal cells into patients however, there are several obstacles that need to be overcome. First, more studies need to be conducted to conclusively establish that fetal cells are indeed not detrimental to maternal health in any way and that they truly are involved in repair and regeneration. At present, both ideas are controversial and being heavily debated. Second, the exact types of fetal cells involved in tissue repair have yet to be ascertained, and although some cell types can be extracted from the placenta after delivery, not all cell types are readily available. Additionally, just like in blood transfusions or organ donations, fetal cells may be rejected by the immune system if the donor and recipient are not accurately matched. Before we fully understand the interactions between the maternal immune system and the fetal cells, fetal cell transfusions are unlikely to become a therapeutic option.

Nevertheless, it is a wondrous idea that our cells may be living and replicating in our mothers and shows that the mother-child bond is a stronger relationship than one could ever imagine.

Rhea Chatterjea

References

1. Artlett CM, Smith JB, & Jimenez SA (1998). Identification of fetal DNA and cells in skin lesions from women with systemic sclerosis. The New England journal of medicine, 338 (17), 1186-91 PMID: 9554859
2. Kara RJ, Bolli P, Karakikes I, Matsunaga I, Tripodi J, Tanweer O, Altman P, Shachter NS, Nakano A, Najfeld V, & Chaudhry HW (2012). Fetal cells traffic to injured maternal myocardium and undergo cardiac differentiation. Circulation research, 110 (1), 82-93 PMID: 22082491
3. Bianchi DW, Zickwolf GK, Weil GJ, Sylvester S, DeMaria MA (1996). Male fetal progenitor cells persist in maternal blood for as long as 27 years post-partum Proc Natl Acad Sci USA , 93, 705-708 DOI: 10.1073/pnas.93.2.705

This is an edited version of Rhea’s original essay. Views expressed are the author’s own.

Find out more about the Wellcome Trust Science Writing Prize in association with the Guardian and the Observer and read our ‘How I write about science‘ series of tips for aspiring science writers.

Over the next couple of months, we’re publishing the shortlisted essays from the 2012 competition. Read all, and the 2011 essays, in our archive.

Image credit: Flickr/nanny snowflake