Pregnancy Triggers Lasting Changes in Mouse Small Intestine

A new study from the Francis Crick Institute reveals that pregnancy induces significant growth in the small intestine of mice, with some changes persisting long after birth. This research, published in Cell, sheds light on how reproduction affects organ remodeling in female animals.

The team observed that the small intestine of pregnant mice grew 18% longer by the end of gestation. Remarkably, this elongation remained even 35 days post-lactation, suggesting a semi-permanent change. The intestine grew even longer during a second pregnancy.

While the villi and crypts in the intestine also increased in size during pregnancy, these structures returned to normal shortly after weaning. The team found that these changes occurred independently of dietary alterations, including probiotic intake. 

Genetic analysis revealed significant changes in enterocytes, the nutrient-absorbing cells in the villi. A key finding was the early increase in SGLT3a, a membrane protein responsible for about 45% of villi growth triggered by reproduction.

Irene Miguel-Aliaga, senior author of the study, stated: "We don't often think about organs changing size or appearance in response to triggers in adulthood rather than earlier childhood and adolescent development, but the gut is a striking example of how the body responds to a new challenge at different stages of life, in this case pregnancy."

The researchers hypothesize that maintaining a longer gut after the first pregnancy might prepare the body for subsequent pregnancies. They are now investigating whether similar changes occur in humans and exploring the potential evolutionary advantages of this adaptation.

“Understanding how pregnancy impacts the body in other mammals is a critical first step to understanding this in people. We don’t fully understand why the gut expands in response to pregnancy, but we think it must give an evolutionary advantage and help mice reproduce regularly,” explained first author Tomotsune Ameku.