Vienna, Austria – A “forgotten organ” can be key to protecting the health of women and their unborn babies during pregnancy. That discovery comes when an international team of scientists say they have solved one of the immune system’s greatest mysteries. Their study shows that miscarriage and diabetes in pregnant women can be prevented by making sure the thymus, a small gland behind the breastbone, is firing on all cylinders.
According to the Mayo Clinic, between 10 and 20 percent of all pregnancies end in a miscarriage.
Researchers say that female sex hormones instruct the thymus to produce specialized cells called “tregs” to address physiological changes during pregnancy. However, in order for Tregs to do their job, there must be a receptor called RANK. This particular receptor is located in a region of the thymus called the epithelium.
Solve a medical puzzle
While scientists have known for some time that the thymus is a central organ of the human immune system, how it changes during pregnancy to support the mother and fetus has been a mystery for decades.
“We knew that RANK was expressed in the thymus, but its role in pregnancy was unknown,” said the study’s lead author, Professor Josef Penninger, in a media release.
“The lack of RANK prevented the production of Tregs in the thymus during pregnancy,” adds Dr. Magdalena Paolino from the Karolinska Institutet in Sweden. “This resulted in fewer Tregs in the placenta, which led to increased miscarriage rates.”
Researchers got a better understanding of the organ’s role during pregnancy by removing RANK receptors in mice. The results show that RANK deficient mice are more likely to miscarry. Even if the mothers did not have a miscarriage, researchers say their pups were prone to diabetes and were overweight later in life. The study shows that giving Tregs produced by normal pregnancies to RANK-deficient mice reversed all of their health problems.
Rewiring the thymus to protect pregnancies
The researchers also looked at women who had diabetes during their pregnancy. Like the mice, pregnant women with diabetes had lower numbers of Tregs in their placenta. This suggests that the forgotten organ plays an important role in ensuring healthy pregnancy for women.
“The thymus changes massively during pregnancy and how such rewiring of entire tissue contributes to a healthy pregnancy was one of the remaining puzzles in immunology,” explains Prof. Penninger.
“Our many years of work not only solved this puzzle – pregnancy hormones rewire the thymus via RANK – but also uncovered a new paradigm for its function. Not only does the thymus alter the mother’s immune system so that it does not reject the fetus, but the thymus also controls the mother’s metabolic health. “
The study’s authors believe that new treatments that target the thymus could ensure a healthy pregnancy, especially in women with diabetes.
“The discovery of this new mechanism that underlies gestational diabetes may offer new therapeutic targets for the mother and fetus in the future,” says co-author Dr. Alexandra Kautzky-Willer from the Medical University of Vienna.
“This research is changing our view of the thymus as the active and dynamic organ needed to ensure pregnancy,” concludes Dr. Penninger.
The results appear in the journal Nature.
SWNS writer Tom Campbell contributed to this report.