Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Theory on Genesis of Osteoarthritis Comes with Successful Therapy in Mice

22.05.2013
In the future, joint replacement surgery might be avoidable
Scientists at Johns Hopkins have turned their view of osteoarthritis (OA) inside out. Literally. Instead of seeing the painful degenerative disease as a problem primarily of the cartilage that cushions joints, they now have evidence that the bone underneath the cartilage is also a key player and exacerbates the damage. In a proof-of-concept experiment, they found that blocking the action of a critical bone regulation protein in mice halts progression of the disease.

The prevailing theory on the development of OA focuses on joint cartilage, suggesting that unstable mechanical pressure on the joints leads to more and more harm to the cartilage—and pain to the patient—until the only treatment option left is total knee or hip replacement. The new theory, reported May 19 in Nature Medicine, suggests that initial harm to the cartilage causes the bone underneath it to behave improperly by building surplus bone. The extra bone stretches the cartilage above and speeds its decline.

“If there is something wrong with the leg of your chair and you try to fix it by replacing the cushion, you haven’t solved the problem,” says Xu Cao, Ph.D., director of the Center for Musculoskeletal Research in the Department of Orthopaedic Surgery at the Johns Hopkins University School of Medicine. “We think that the problem in OA is not just the cartilage ‘cushion,’ but the bone underneath,” he adds.

Joints are formed at the intersection of two bones. To prevent the grinding and wearing down of the ends of the bones, they are capped with a thin layer of cartilage, which not only provides a smooth surface for joint rotation but also absorbs some of the weight and mechanical strain placed on the joint. The degeneration of this protective layer causes extreme pain leading to limited mobility.

Gehua Zhen, Courtesy of Nature Medicine

When placed in the bone (green) beneath the cartilage (red) of a rat’s knee joint, antibodies against the protein TGF-beta1 can prevent the damage caused by osteoarthritis. Left, without treatment; right, with treatment.

Cao says degeneration is most frequently initiated by instability in the load-bearing joints of the knee and hip caused by injury or strain, so athletes, overweight people and people whose muscles are weakened by aging are at highest risk of developing OA. The prevalence of the disease is rapidly increasing; it currently affects 27 million Americans and may double by 2030. The only treatment available is pain management, or surgical replacement of the arthritic joint with a prosthetic one.

Cao says that the lack of effective drugs or a complete understanding of the underlying process that causes OA to progress led his group to search for a different underlying cause. “We began to think of cartilage and the bone underneath it, called subchondral bone, as functioning as a single unit,” says Cao. “That helped us to see the ways in which the bone was responding to changes in the cartilage and exacerbating the problem.”

Using mice with ACL (anterior cruciate ligament) tears, which are known to lead to OA of the knee, the researchers found that, as soon as one week after the injury, pockets of subchondral bone had been “chewed” away by cells called osteoclasts. This process activated high levels in the bone of a protein called TGF-beta1, which, in turn, recruited stem cells to the site so that they could create new bone to fill the holes. Cao calls these pockets of new bone formation “osteoid islets.”

But the bone building and the bone destruction processes were not coordinated in the mice, and the bone building prevailed, placing further strain on the cartilage cap. It is this extraneous bone formation that Cao and his colleagues believe to be at the heart of OA, as confirmed in a computer simulation of the human knee.

With this new hypothesis in hand, complete with a protein suspect, the team tried several methods to block the activity of TGF-beta1. When a TGF-beta1 inhibitor drug was given intravenously, the subchondral bone improved significantly, but the cartilage cap deteriorated further. However, when a different inhibitor of TGF-beta1, an antibody against it, was injected directly into the subchondral bone, the positive effects were seen in the bone without the negative effects on the cartilage. The same result was also seen when TGF-beta1 was genetically disrupted in the bone precursor cells alone.

“Our results are potentially really good news for patients with OA,” says Cao. “We are already working to develop a clinical trial to test the efficacy of locally applied TGF-beta1 antibodies in human patients at early stages of OA.” If successful, their nonsurgical treatment could make OA — and the pain and debilitation it causes — halt in its tracks, he says.
Other authors of the report include Gehua Zhen, Xiaofeng Jia, Janet Crane, Simon Mears, Frederic Askin, Frank Frassica, Weizhong Chang, John Carrino, Andrew Cosgarea, Dmitri Artemov, Lee Riley, Paul Sponseller and Mei Wan of the Johns Hopkins University School of Medicine; Chunyi Wen, Jie Yao and William Weijia Lu of the University of Hong Kong; and Yu Li, Qianming Chen, Zhihe Zhao and Xuedong Zhou of Sichuan University.

This work was supported by grants from the National Institute of Diabetes and Digestive and Kidney Diseases (DK057501, DK08098).

Catherine Kolf | Newswise
Further information:
http://www.jhmi.edu

More articles from Life Sciences:

nachricht Decoding the genome's cryptic language
27.02.2017 | University of California - San Diego

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>