Researchers from Ohio State University have found that the stress response works in unexpected ways in pregnant mice. Their findings may go on to inform nutritional recommendations for mothers experiencing stress during pregnancy.
In previous work, researchers found that prenatal stress contributes to life-long anxiety and cognitive difficulties in the offspring of mice and that these issues are linked to changes in microbial communities in both mother and offspring. In the current study, the researchers sought to identify the immune cells and microbes most likely to trigger inflammation in the fetal brain that leads to these issues.
For the study, the researchers examined pregnant mice during their second and early third trimesters. To induce stress among them, they subjected the mice to two hours of restraint for seven days. The researchers also observed a control group that did not undergo the same stressors during gestation.
In the end, they found that stress activated steroid hormones throughout the body in mice- signaling a suppressed immune system. Unexpectedly, however, they found that stress resulted in lower-than-expected populations of immune cells in reproductive tissue, meaning that the uterus was resisting the effects of stress.
“The dogma would be that we’re going to see an influx of immune cells to the placenta. The fact that it’s suppressed speaks to the powerful anti-inflammatory response of the mom. And that makes sense – a fetus is basically a foreign object, so in order to maintain pregnancy, we need to have some level of immunosuppression,” says Tamar Gur, one of the study’s authors.
Maternal microbes affect the brains and immune systems of developing offspring as they produce a variety of chemicals that the body uses to manage physiological processes. As such, the researchers also examined the colon of both the stressed mice and control mice. In doing so, they found that a certain family of microbes linked to immune function was markedly decreased in those that underwent stress during gestation.
To combat this, the researchers said that taking prebiotics and probiotics during gestation may help reduce the effects of this stress-induced microbial deficiency and restore a healthier microbial environment, although further research is needed to confirm this.
In future studies, the researchers plan to continue examining immune cells in the fetal brain and monitor how gene expression changes in placenta cells when under stress.