Researchers gain insight into how the intestine repairs itself
Two unexpected findings
“Our first finding refers to the type of stem cell involved in the repair of the epithelial cells damaged by the virus,” said Zou. “Previous studies had shown that when CBC stem cells are damaged, the reserve stem cells come to their rescue leading the reconstitution of the damaged epithelium. When rotavirus damages the epithelium, but not the stem cells, we found that the CBCs, not the reserve stem cells, are the primary cell type involved in the restoration of the intestinal epithelium.”
“Until now, CBCs were not considered important for the repair of intestinal epithelium, but our results show that they are crucial for injury repair after rotavirus-induced epithelial cell damage in contrast to previous studies supporting the reserve intestinal stem cells as the cell type involved in epithelial restitution,” said Estes, who is also a member of the Dan L Duncan Comprehensive Cancer Center and holds a joint appointment in gastroenterology and hepatology at Baylor.
The second unexpected finding refers to the source of the signaling molecules – called WNTs – that trigger the growth and activation of stem cells leading to injury repair. Scientists have described two sources of WNT molecules, epithelial cells and mesenchymal cells. Until now, research has considered the mesenchymal and the epithelial WNT to be redundant and not essential on their own.
“We found that the epithelial WNT molecules were essential to signal the stem cells to repair the damage caused by rotavirus infection,” said Zou.
“This was the biggest surprise. The predominant idea in the field is that the epithelial WNTs have no specific function, and here we found the first model indicating that in some cases epithelial WNTs do have a specific function. We show that epithelial and mesenchymal WNTs are not interchangeable, as it was thought before,” Estes said. “I think this finding will be exciting for intestinal stem cell researchers. Now, we are exploring what the infection is doing that triggers WNT production in the epithelium.”
Other contributors to this study include Sarah E. Blutt, Xi-Lei Zeng, Min-Shan Chen, Yuan-Hung Lo, David Castillo-Azofeifa, Ophir D. Klein, Noah F. Shroyer and Mark Donowitz. The contributors are affiliated with one of the following institutions: Baylor College of Medicine, Johns Hopkins University School of Medicine and the University of California, San Francisco.
This work was funded by the National Institutes of Health (NIH) through grants U01 DK103168, U01DK103168-03S1, U01 DK103168-02S1 and F30 DK107173. This project was also supported by the Cellular and Molecular Morphology Core of the Texas Medical Center Digestive Disease Center (funded by NIH P30DK056338), and the Advanced Technology Core Laboratories at Baylor College of Medicine, including the Cytometry and Cell Sorting Core (funded by NIH NIAID P30AI036211, NCI P30CA125123, and NCRR S10RR024574), the Pathology and Histology Core (funded by NCI P30CA125123), and the Integrated Microscopy Core (funded by NIH DK56338 and CA125123, CPRIT RP150578, the Dan L Duncan Comprehensive Cancer Center and the John S. Dunn Gulf Coast Consortium for Chemical Genomics).