Womb Natural Killer Cell Discovery Could Lead to Screening For Miscarriage Risk

Source: University of Warwick

Summary: Researchers for the first time identified the functions of natural killer cells found in the lining of the womb and prepare the womb for pregnancy.

Natural Killer cells (NK cells) are a type of lymphocyte that belongs to the innate immune system. It is long known that lining of the womb harbours dynamic uterine natural killer cells but no functions have so far been given to these cells outside of pregnancy. Researchers from University of Warwick and University Hospitals Coventry and Warwickshire (UHCW) NHS Trust for the first time identified two functions of the NK cells. First being the uterine natural killer cells remodel and refresh the lining of the womb at the time of embryo implantation. The second function, the NK cells perform the role of targeting and clearing inflammatory stressed cells, thereby making space for the implanting embryo. The study findings were published in the journal eLife.

Embryo Implantation

Image from a human embryo cultured with decidual cells in the lab. Credit: Jan Brosens

The process isn’t always balanced in each cycle, sometimes enough of the stressed cells are cleared and sometimes too many are targeted and removed which may lead to miscarriage. This imbalance, which may be short-lived or last for multiple cycles, explains the high rate of early pregnancy failure, yet high cumulative live-birth rate that characterizes human reproduction. In late reproductive years, patients suffering recurrent IVF failures or miscarriages, as well as their treating doctors, often refer to this phenomenon as the ‘numbers game’. The findings were based large amounts of experimental and observational data, where the research team conducted an analysis of 2,111 endometrial biopsies. Also, the data suggest that acutely stressed cells in the lining of the womb are responsible for generating the elusive ‘implantation signal‘ in the human uterus.

lining of the womb harbours dynamic uterine natural killer cells

Histological slide, demonstrating uNK cells in the womb lining (brown staining). Credit: Jan Brosens

Prof. Jan Brosens said, “We hope in the future this new information will be used to screen women at risk of reproductive failure. Furthermore, our findings suggest new treatment options for women suffering recurrent miscarriages or recurrent IVF failure.”

More Information: Paul J Brighton et al, “Clearance of senescent decidual cells by uterine natural killer cells in cycling human endometrium”, eLife (2017). DOI: 10.7554/eLife.31274


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