When the 1-year-old boy arrived from overseas, he was relying on total parenteral nutrition — a way of bypassing the digestive system to provide nutrients and calories completely intravenously — to survive. From the time of his birth, he had experienced unexplainable diarrhea. Answers were desperately needed.
Sequencing his genes in search of clues, neonatologists and collaborators at the Manton Center for Orphan Disease Research at Boston Children’s Hospital identified a new gene mutation responsible for chronic congenital diarrhea — even finding a similar mutation in two other children as well.
Using patient-derived intestinal organoids in the laboratory, the team discovered that the newly-identified gene mutation, WNT2B, appears to stifle intestinal stem cells’ normal function and growth. The findings were published in the American Journal of Human Genetics.
The small intestine is much more than a digestive organ. It’s a major home to our microbiome, it’s a key site where mucosal immunity develops and it provides a protective barrier against a variety of infections. Animal models don’t do justice to the human intestine in all its complexity.
Attempts to better model human intestinal function began with intestinal “organoids,” created from intestinal stem cells. The cells, from human biopsy samples, form hollowed balls or “mini-intestines” bearing all the cell types of the intestinal lining, or epithelium. Recently, intestinal organoids helped reveal how Clostridium difficile causes such devastating gastrointestinal infections.
But while organoids have all the right cells, they don’t fully replicate the environment of a real small intestine. Real intestines are awash in bacteria and nutrients, are fed by blood vessels and are stretched and compressed by peristalsis, the intestines’ cyclical muscular contractions that push nutrients forward.