Our intestinal lining, or epithelium, rapidly and continually renews itself, replacing its entire cell population every four to five days. Stem cells, which live in tube-like "crypts" deep in the gut lining, are vital to the renewal process, dividing and differentiating into different cell types that replace old cells.

New research by Duke-NUS Medical School and Nanyang Technological University, Singapore (NTU Singapore), has uncovered an unexpected – and precise – communication system that exists in the gut, similar to the way neurons signal one another in the brain.

"Sometimes, when you study the basics closely, you uncover something transformative," said principal research scientist Dr Gediminas Greicius, from Duke-NUS' Cancer and Stem Cell Biology (CSCB) Program and the lead and corresponding author of the study. "This system of targeted signaling was hiding in plain sight, and now that we see it, it reshapes our understanding of the biology of stem cells in the gut."

It comes down to Wnts, signaling molecules that help control the behavior of intestinal stem cells located in the crypts of the intestine. Actually, they're located within a "niche" within a crypt, a highly regulated microenvironment that supports and regulates their behavior. When Wnt signaling is activated, it promotes the growth and division of these stem cells. Wnt signals help maintain a balance between stem cell self-renewal (keeping enough stem cells in the crypts) and differentiation (turning some stem cells into specialized cells that make up the lining of the intestine).

Initially, it was thought that Wnts simply diffused through the tissue, eventually reaching their stem cell targets. However, the present study overturned that hypothesis.

"We discovered that these signals aren't just drifting through tissue," said co-corresponding author Professor David Virshup, a cancer biologist and the Director of the CSCB. "They're being delivered with surprising precision from the niche to the stem cells by specialized cells or telocytes – changing the way we think about cellular communication in the gut, similar to how neurons pass signals to one another in the brain."