Scientists find ‘forgotten’ organ that protects women and unborn babies during pregnancy

VIENNA, Austria — A “forgotten organ” may hold the key to protecting the health of women and their unborn babies during pregnancy. This revelation comes as an international team of scientists say they’ve solved one of the immune system’s greatest mysteries. Their study shows that making sure the thymus, a small gland behind the sternum, is firing on all cylinders can prevent miscarriages and diabetes in pregnant women.

According to the Mayo Clinic, between 10 and 20 percent of all pregnancies end in a miscarriage.

Researchers say female sex hormones instruct the thymus to produce specialized cells called “Tregs” in order to tackle physiological changes during pregnancy. For Tregs to do their job however, a receptor called RANK, must be present. This special receptor is located in a region of the thymus called the epithelium.

Solving a medical mystery

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 remained a mystery for decades.

“We knew RANK was expressed in the thymus, but its role in pregnancy was unknown,” the study’s senior author Professor Josef Penninger says in a media release.

“The absence of RANK prevented the production of Tregs in the thymus during pregnancy,” Dr. Magdalena Paolino of the Karolinska Institutet in Sweden adds. “That resulted in less Tregs in the placentas, leading to elevated rates of miscarriage.”

The researchers gained a better understanding of the organ’s role during pregnancy by removing RANK receptors in mice. The results reveal that RANK-deficient mice are more likely to have a miscarriage. Even if the mothers didn’t have a miscarriage, researchers say their pups were prone to diabetes and being overweight later in life. The study finds giving Tregs produced by normal pregnancies to RANK-deficient mice reverses all of their health issues.

Rewiring the thymus to protect pregnancies

Researchers also examined women who suffer from diabetes during their pregnancies. Like the mice, pregnant women with diabetes had a lower number of Tregs in their placentas. This suggests the forgotten organ plays a vital role in ensuring women have a healthy pregnancy.

“The thymus changes massively during pregnancy and how such rewiring of an entire tissue contributes to a healthy pregnancy has been one of the remaining mysteries of immunology,” Prof. Penninger explains.

“Our work over many years has now not only solved this puzzle – pregnancy hormones rewire the thymus via RANK – but uncovered a new paradigm for its function. The thymus not only changes the immune system of the mother so it does not reject the fetus, but the thymus also controls metabolic health of the mother.”

Study authors believe new treatments which target the thymus could ensure a healthy pregnancy, especially among women with diabetes.

“The discovery of this new mechanism underlying gestational diabetes potentially offers new therapeutic targets for mother and fetus in the future,” co-author Dr. Alexandra Kautzky-Willer from the Medical University of Vienna says.

“This research changes our view of the thymus as an active and dynamic organ required to safeguard pregnancies,” Dr. Penninger concludes.

The findings appear in the journal Nature.

SWNS writer Tom Campbell contributed to this report.