Every driver knows two cars can’t occupy the same parking space.
Guided by a similar principle, arthritis researchers at the University of Florida and Harvard University hope to use gene therapy to help joint cells pump out a harmless protein that parks in receptor sites, leaving a notorious inflammatory agent “circling the lot” and unable to cause pain, swelling and possible joint damage.
Now a major roadblock to the research apparently has been cleared, said Elvire Gouze, a UF College of Medicine assistant research professor of orthopedics and rehabilitation who arrived from Harvard in March.
Findings in rats presented today at the Third International Meeting on Gene Therapy in Rheumatology and Orthopaedics in Boston showed - for the first time - that gene therapy could generate long-term production of the human version of the anti-arthritic protein known as interleukin-1 receptor antagonist, or IL-1ra, Gouze said. The finding suggests that scientists can now turn their attention to practical issues, such as how best to deliver the IL-1ra gene and control its production.
“Now we can start to think about how we can do it,” Gouze said. “We’re dealing with a chronic disease and if it (the gene expression) isn’t long-term, you’re not going to be able to achieve anything.”
Rheumatoid arthritis is a chronic disease in which immune system cells malfunction and attack healthy joints, causing pain, stiffness, swelling and even permanent disability, according to the American College of Rheumatology. More than 2 million Americans suffer from rheumatoid arthritis, 75 percent of them women. Its cause is unknown and although there is no cure, current treatments can reduce the severity of symptoms. The UF and Harvard researchers believe that gene therapy eventually could offer a less-costly, more-effective and longer-lasting option with fewer side effects than current methods, such as daily injections of a synthetic form of IL-1ra.
In patients with the disease, a protein called interleukin-1 is produced unnecessarily and parks in receptor sites on the cells lining the inside of joint capsules, tough, fibrous containers that surround the moving parts of human joints, said Steve Ghivizzani, a UF associate professor of orthopedics and rehabilitation involved in the research. Once in place, the protein starts a series of chemical reactions that lead to inflammation of the joint cell. Interleukin-1 is one of the most important inflammatory agents used in the human body, and normally helps the body fight disease.
IL-1ra has no apparent function except to occupy the same receptor sites used by interleukin-1, making it an ideal weapon in the fight against rheumatoid arthritis, Ghivizzani said. The study used two viruses as delivery vehicles to bring genes that produce IL-1ra to cells that line the inside of the joint capsule.
“The idea was, what if you could modify the cells that line the internal surface of the capsule so that they were little factories and constantly produced elevated levels of IL-1ra and released it into the joint?” Ghivizzani said. “There are companies poised to undertake this kind of stuff, so it’s not a pipe dream at all.”
The study was funded by a four-year, $1.2 million grant from the National Institute for Arthritis, Musculoskeletal and Skin Diseases. Ghivizzani is co-holder of a patent issued in 2000 on gene delivery to joints, along with researchers at Harvard and the University of Pittsburgh.
Studies in rats, mice and rabbits have shown that IL-1ra causes no harm to joints, even in large amounts, he said.
“The beauty of it is IL-1ra has no stimulatory activity, so you can make as much as you want,” Ghivizzani said. “If you overproduce it, no problem.”
In people with rheumatoid arthritis, the joint cells produce three to five times as much IL-1ra as they produce of the inflammatory protein, but for the treatment to be effective researchers believe they would need to widen the ratio to 50-to-1 or even greater, said Christopher Evans, a Harvard School of Medicine professor of orthopedic surgery who also was involved in the study.
“In order for inhibition to occur there needs to be a very large excess of IL-1ra,” Evans said.
The team used about 250 male rats, genetically modified to have no immune systems. Three groups of rats were used - a control group that received no gene therapy, and two groups that received the modified gene, each delivered through a different virus carrier.
Researchers injected the carrier into the capsule of each rat’s rear knee joint. IL-1ra production was highest during the first week, but declined for about six weeks until it stabilized at 25 percent to 30 percent of the initial level and remained at that level for the lifetimes of the animals.
“We had exactly the same profile of expression (in both gene therapy groups), which meant that joint tissues were capable of expressing a therapeutic gene indefinitely, and that the type of virus used for gene delivery did not make a difference,” Gouze said.
Development of gene therapy treatments for pathologies associated with arthritis using IL-1ra could be one aspect of a huge boom in biotech treatments for orthopedic conditions, said Paul D. Robbins, a professor of molecular genetics and biochemistry at the University of Pittsburgh. Robbins performed pioneering IL-1ra gene therapy studies in the early 1990s. Ghivizzani was a researcher in Robbins’ laboratory before going on to Harvard but did not collaborate with him on the current study.
“I think orthopedics is going to be one of the areas where gene therapy is going to be very successful,” Robbins said, “because you’re taking a natural healing process that may be slow or not as effective for whatever reason and making it better by gene transfer.” http://www.napa.ufl.edu