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Ulcer-causing Helicobacter bacteria induce stomach stem cell to grow

Reporter: Aviva Lev-Ari, PhD, RN

 

 

 

 

 

The ulcer-causing bacterium Helicobacter pylori can directly interact with stomach stem cells, causing the cells to divide more rapidly, according to a new study by researchers at the Stanford University School of Medicine.

The increased cell division was observed in mice, but the findings could explain why H. pylori is a risk factor for gastric cancer in humans, the researchers said.

They used 3-D microscopy to identified colonies of the bacteria deep within human stomach glands, where stem cells and precursor cells that replenish the stomach’s lining reside.

One of every two people has H. pylori in their stomachs. It’s one of the few organisms capable of surviving the harsh acidic environment. While the majority of people remain asymptomatic, in about 15 percent of those infected the bacteria causes painful ulcers, and in another 1 percent the bacteria contribute to stomach cancer, the third-most lethal cancer worldwide.

Although the infection can be successfully treated with antibiotics, those who develop cancer are often unaware of their condition until the tumor is large enough to interfere with stomach functions. “The bacteria will be brewing for many years, and when the cancer starts to cause symptoms it may be too late,” said Manuel Amieva, MD, PhD, associate professor of pediatrics and of microbiology and immunology.

The researchers came up with the idea of sampling stomach tissues removed during weight-loss surgery. These samples came from healthy stomachs, in which H. pylori was not actively causing ulcers or cancer. After identifying tissue infected with particular strains of H. pylori, they used confocal microscopy to reconstruct 3-D images of the glands from four stomachs with H. pylori. All four showed colonies of the spiral-shaped bacteria clustered about two-thirds of the way into the gland, where fast-dividing precursor cells reside.

Unexpectedly, the researchers found a smaller number of bacterial colonies at the base of the glands, where the stem cells reside. When they went back to their mouse models, they discovered about 30 percent of the glands colonized by H. pylori had bacteria at the base of the glands.

H. pylori affects stem cells.

This unanticipated finding shed light on how H. pylori could influence cells to turn cancerous. Cancer is thought to develop slowly as the cell acquires mutations in the DNA that override cellular controls and increase cell proliferation. Even though H. pylori had been shown to manipulate cellular controls, the mature stomach’s epithelial cells don’t live long enough to acquire mutations.

Source: ekaweb02.eurekalert.org

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