Researchers from several US universities have discovered a link between an immune system cell called a "macrophage" that helps to fight infections, and the contractions of the colon that push digested food through the digestive tract.
Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders in the world, affecting between 10-20% of the adult population.
The condition causes patients to experience severe abdominal pain, bloating and difficulty in bowel movements, due to irregular contractions of the colon.
However, there is no cure for the condition and doctors don't know what causes it, although stress is thought to be a key factor.
Now researchers have noticed that "good bacteria" orchestrate interactions between macrophages and nerve cells in order to for the contractions happen, and when the quantity of macrophages is depleted in the digestive tract, IBS symptoms will occur.
Their study, entitled "Crosstalk between Muscularis Macrophages and Enteric Neurons Regulates Gastrointestinal Motility", is published in the journal Cell.
The researchers depleted macrophages in the intestines of mice by feeding them antibiotics, and then watched what happened.
"Very little is known about the function of muscularis macrophages, mainly because these cells are difficult to isolate from intestinal tissue," said Milena Bogunovic, assistant professor of microbiology and immunology at Penn State College of Medicine.
"After macrophage depletion, we observed that the normal intestinal movements are irregular, probably because the muscular contractions were poorly coordinated, suggesting that intestinal movements are regulated by macrophages."
The antibiotics caused the communication between macrophages and nerve cells to be interrupted, causing a decrease in BMP2 proteins, which are thought to control organ development, as well as a decrease in the production of CSF1, which supports macrophages.
Good bacteria is essential
When the mice were given "good bacteria", however, the dialogue between the macrophages and the nervous system was reconnected, which shows that the bacterial environment in the intestines plays an important role in how the two types of cells interact.
Much of what the researchers learned confirms what many IBS sufferers know already – gut-balancing drinks containing "good bacteria" like Yakult are absolutely essential, and that special precautions must be taken when taking antibiotics as they can severely upset the stomach.
However, by pinpointing the particular cells that regulate contractions in the colon and how they can malfunction, perhaps an actual cure can be developed, rather than just coping tools.
"By better understanding how the nervous system cells, the muscularis macrophages and signals from inside the intestine interact, we may be able to find new treatments for IBS, or even prevent it," Bogunovic said.
The research was conducted by Penn State College of Medicine, the Icahn School of Medicine at Mount Sinai Hospital, Columbia University College of Physicians and Surgeons, The Rockefeller University and Albert Einstein College of Medicine.