Scientists have found that natural killer (NK) cells that are normally known as defenders of the immune system can actually also help fetal growth in pregnant mice. The work was published yesterday in Immunity from researchers at the University of Science and Technology of China.
Researchers have discovered that a specific subset of natural killer cells in the human uterine lining secrete growth-promoting factors called pleiotrophin and osteoglycin, which are involved in wide-ranging developmental processes. This subset made up a smaller proportion of natural killer cells in the uterine lining of patients who experienced recurrent spontaneous abortion (42%) compared to healthy females (81%). The findings suggest that restricted fetal development in humans may be due to the insufficient secretion of growth-promoting factors by this subset of NK cells.
Right now, in the mouse model, a deficiency in this subset of NK cells has resulted in severe fetal growth restriction and defective development of the fetal skeletal system. However, when these NK cells are transplanted in, the fetal growth impairments issues are reversed.
"Additional studies are needed to explore the most suitable protocols to induce uterus-like natural killer cells that secrete growth-promoting factors in a human system, and to improve the feasibility of applying these uterus-like natural killer cells to patients," co-senior author Zhigang Tian says. "This study provides an avenue for treating fetal growth restriction, recurrent spontaneous abortion with unknown reasons, and age-related fetal loss by improving the uterus microenvironment."
Image: An artistic representation of how decidual NK cells promote fetal growth during early pregnancy. Image courtesy of Bingqing Fu.