Immune Switch in Uterus Linked to Preeclampsia and Early Pregnancy Failure
Researchers at the University of Alabama at Birmingham (UAB) have identified a critical immune pathway involving a molecule called NFAT that plays a key role in successful pregnancies. The discovery, published in Science Translational Medicine, sheds light on potential causes of preeclampsia and early pregnancy failure .
The Role of Uterine Natural Killer Cells
Early pregnancy relies on the successful interaction between the embryo and the mother’s immune system. Uterine natural killer (uNK) cells are specialized immune cells that guide this process, helping the embryo connect with the mother’s blood supply and establish a healthy placenta. The new research reveals that NFAT acts as a “residency switch” for uNK cells, helping them take up residence in the uterus .
How NFAT Impacts Pregnancy
When the NFAT switch is deactivated, fewer uNK cells migrate to the uterus, potentially leading to pregnancy complications. Researchers, led by Paige Porrett, M.D., Ph.D., professor of surgery and obstetrics and gynecology at UAB, found that lower levels of uNK cells were present in uterine tissue samples from women who had received uterine transplants compared to healthy controls .
Uncovering the Mechanism with RNA Sequencing
To understand why uNK cell levels were lower in transplant recipients, the UAB team used single-RNA sequencing. This technology allowed them to analyze the molecular makeup of individual cells, identifying differences in gene expression between transplant recipients and healthy volunteers. The analysis revealed that NFAT plays a crucial role in helping uNK cells remain in the uterine tissue .
The Link to Immunosuppressant Drugs
The research also investigated the impact of tacrolimus (TAC), an immunosuppressant drug commonly used in transplant recipients. TAC blocks NFAT from entering the cell nucleus, preventing it from activating genes that promote immune cell activity. Interestingly, the study found that TAC’s effect on NFAT also impacted uNK cell residency, potentially contributing to the lower levels observed in transplant recipients .
Implications for Preeclampsia and Beyond
Abnormalities in placentation, the process of placenta development, are linked to preeclampsia, a condition affecting 5-8% of all births in the United States . This discovery offers new insights into the biological mechanisms behind preeclampsia, implantation failure, inadequate placental blood flow, and early pregnancy loss .
Dr. Porrett suggests that understanding the role of NFAT in uNK cell residency could have broader implications for immune cell behavior in other contexts, such as fighting infections in the liver .
Future Directions
The UAB research team plans to leverage this new knowledge to develop better tests for identifying women at risk of pregnancy complications and to personalize medical care to improve outcomes. “This improvement in our knowledge will allow us to build better tests and better ways of detecting… To personalize the medical care we provide, right, so that we can identify patients at risk and then ultimately change the plan… So that we can decrease that risk and get them a better outcome,” said Dr. Porrett .