Using the gene-editing tool CRISPR, researchers have found a way to rewire mouse stem cells to fight inflammation caused by arthritis and other chronic conditions.

Such stem cells, known as SMART cells (Stem cells Modified for Autonomous Regenerative Therapy), develop into cartilage cells that produce a biologic anti-inflammatory drug that could replace arthritic cartilage and simultaneously protect joints and other tissues from damage that occurs with chronic inflammation. The researchers initially worked with skin cells taken from the tails of mice and converted those cells into stem cells. 

Then, using the gene-editing tool CRISPR in cells grown in culture, they removed a key gene in the inflammatory process and replaced it with a gene that releases a biologic drug that combats inflammation.

"Our goal is to package the rewired stem cells as a vaccine for arthritis, which would deliver an anti-inflammatory drug to an arthritic joint but only when it is needed," said Farshid Guilak, Professor at Washington University School of Medicine, and senior author of a study published online in the journal Stem Cell Reports.

"To do this, we needed to create a 'smart' cell," Guilak said. Many current drugs used to treat arthritis attack an inflammation-promoting molecule called tumour necrosis factor-alpha (TNF-alpha).  But the problem with these drugs is that they are given systemically rather than targeted to joints. As a result, they interfere with the immune system throughout the body and can make patients susceptible to side effects such as infections. "We want to use our gene-editing technology as a way to deliver targeted therapy in response to localised inflammation in a joint, as opposed to current drug therapies that can interfere with the inflammatory response through the entire body," Guilak said.