(Ivanhoe Newswire) -- New research shows gene therapy is possible and safe to treat patients with rheumatoid arthritis.

Researchers from the University of Pittsburgh conducted the world’s first human study of gene therapy on patients with rheumatoid arthritis. The study included nine women who received genetically modified cells that were injected into their knuckles, where arthritis was rampant. It was the first time a gene was injected into human joint. The study was conducted between 1996 and 1999.

Results show gene therapy can target joint inflammation, and it opens the door for new gene-based therapies for millions of arthritis sufferers. Researchers from the University of Pittsburgh say they used the same vector as a recent French study for X-linked severe combined immunodeficiency. In the French study, three children later developed leukemia. However, researchers from Pitt say the vector -- a virus that carries the gene into cells -- is the only similarity between the two trials. The studies had different targets. In the arthritis trial, the cells were removed after one week during a routine joint replacement surgery. Pitt researchers were concerned with the safety but say no clinical side effects have been reported up to five years later.

Researchers found joints treated with gene therapy did well. Cells that contained large amounts of the gene were found near a specific type of tissue and produced significantly less of the inflammation-provoking substances than cells found in joints that did not receive the gene.

Authors of the study write, “It is possible to transfer a potentially therapeutic gene safely to human rheumatoid joints and to obtain intraarticular, transgene expression. This conclusion justifies additional efficacy studies and encourages further development of genetic approaches tot the treatment of arthritis and related disorders.”