The mucous surface of the gastrointestinal tract is a large and complex area of ââhuman anatomy, a microenvironment very sensitive to inflammation and other disorders which are, at a minimum, pain in the gut, but can also portend a more serious illness.
Researchers from University of Colorado School of Medicine and Rice University have teamed up on an important discovery that promises to advance earlier diagnosis – and potentially better treatment – for inflammatory bowel disease (IBD). They have developed a non-invasive diagnosis that is shown primarily as a biomarker of active disease. The results of the study were recently published in the Proceedings of the National Academy of Sciences.
Sean colgan, PhD, Levine-Kern professor of medicine and immunology at the University of Colorado School of Medicine, said researchers have long known that intestinal tissue becomes more acidic with active inflammation. Detect this change in pH in vivo can be done with probes, but the results are often not very accurate and the probes are difficult to use, Colgan said.
“Color change when the pH decreases”
âI had seen Jeff Tabor (PhD, Rice University) giving a talk and, by the way, he mentioned, ‘We have this bacteria that can sense pH, and it changes color as the pH goes down. So I said, “Why don’t we incorporate your bacteria into our model (mice) and see if we can detect active inflammation by basically looking at the change in fluorescent bacteria in the fecal samples.”
Researchers at Rice University have designed a strain of the harmless gut bacteria E. coli to detect gastrointestinal acidosis. The body produces fluorescent molecules that allow researchers to see it with standard optical equipment. Under normal conditions (left), it produces glowing molecules. When it encounters acidic conditions (right), it glows green and the brightness of the glow reflects the level of acidity.
Rice researchers used synthetic biology to produce the modified strain of the gut bacteria E. coli. Kathryn Brink, a doctoral candidate at Tabor’s lab, spliced ââsensory circuits in bacteria and sent them to Colgan’s lab.
Ian Cartwright, PhD, postdoctoral fellow in Colgan’s lab, said Brink “has done a lot of work cutting and pasting specific sequences of DNA” – the type of gene editing pioneered by CRISPR technology – to create the modified organism that the CU Anschutz team then colonized in mice.
âIt’s a great type of proof of concept experiment where they have this organism that should theoretically be able to detect the pH of tissues in an animal,â Cartwright said. “We were able to put it in a mouse and show that not only did it express more GFP (green fluorescent protein) when under acidic conditions, but we were also able to correlate inflammation in the tissue with this expression of GFP. . So we really went from a theoretical âit should workâ to showing that it can work. “
Colgan, who has studied inflammatory bowel disease for 25 years, said synthetic biology allows more practical applications of possible treatments for IBD – the cause of which remains a mystery. âWe can integrate these (synthetics) faster now with some of the models that we have,â he said. “I think we are more advanced now with the integration of synthetic biology.”
Difference between IBD and IBS
IBD, which includes Crohn’s disease and ulcerative colitis, is signaled by increased acidosis in the intestines, while irritable bowel syndrome (IBS), one of the most diagnosed diseases in the United States, causes pain but not inflammatory.
So, for people with intestinal distress, a non-invasive pH-sensing diagnosis would be beneficial for what it shows – a color change, possibly in the toilet water, although it would require a lot of refinement to achieve. this type of diagnosis – or does not. t show – as in no color change.
It’s possible to imagine this diagnostic strain of bacteria, for example, being placed in a yogurt product, according to Colgan. âThe patient eats the yogurt regularly and then monitors their fecal samples for disease outbreaks,â he said.
CU Anschutz and Rice jointly hold the patent application for the application of the modified bacteria. Human clinical trials should be the next step.
At any one time, Colgan said, about 90 drugs are being tested for IBD. Biologic drugs, given by infusion, are the most effective drugs, he said, but a significant need remains as an estimated 50% of patients with IBD do not have effective treatment.
âI think with a few more refinements, you could imagine that this (latest application of synthetic biology) could take a path of personalized medicine,â Colgan said.