Science Fact: Osteoarthritis, the most common form of arthritis, is also the leading cause of disability in the United States, followed closely by back or spine problems. More than one in five U.S. adults suffer from disability, a number that leaps to over 50% for adults 65 and older.
Cartilage is a flexible connective tissue found throughout our bodies, most prominently in the nose and ears. Today our interest in cartilage arises from its use in the body to separate bones, specifically in joints and in the spine.
Joints: Cartilage separates the bones in joints such as knees and hips; it not only cushions the separation, but produces a lubricating protein, appropriately called lubricin, that reduces friction. When the cartilage wears out, bone contacts bone and the likely result is debilitating pain leading to knee or hip replacement.
Spine: Cartilage also makes up the discs that separate the vertebrae of our spines; degeneration of these discs is a major cause of back pain, particularly in older people. Although artificial replacements for spinal discs can be surgically implanted, the procedure has attracted controversy and the procedure is still considered experimental in the U.S.
Given the importance of cartilage and its propensity to wear out, it’s not surprising that there’s considerable research into producing an artificial cartilage that can replace or even improve on the natural substance. The principal driver of this research is osteoarthritis, perhaps because joint cartilage has a simpler structure, is easier to access, and poses less risk of nerve damage than working with spinal discs. Moreover, there’s strong hope that by replacing cartilage when it begins to wear out, the more drastic step of replacing the entire joint can be avoided.
Three different paths are converging today, with the promise of genuine help for osteoarthritis in the foreseeable future:
– Lubrication: Teflon was tried as a lubricant but it turned out to leave debris in the joints that led to inflammation and bone wear. More recent work uses nanotechnology, specifically engineered polymers described as “molecular brushes”.
– Supporting Lattice: Combinations of polymers can be woven three-dimensionally into structures that could retain their shape under the high stresses experienced in knee and hip joints. Most recently, researchers have been using 3-D printers to weave together polymers and cartilage cells.
– Flexible Strength: Hydrogels are polymers containing a high percentage of water, somewhat resembling Jell-O. They are being used in artificial cartilage research to provide flexibility and toughness.
The media have reported some promising new work from Duke University. The researchers are infusing a woven structure with specially designed hydrogels and have produced physical properties close to or better than natural cartilage. The durability of these new structures needs to be proven, but they may well form the basis for an osteoarthritis treatment that can postpone joint replacement or even make it unnecessary.
Science Speculation: Once again, the word of the day is interdisciplinary. Our bodies are so miraculously constructed that our best efforts to repair and replace its parts will seem hopelessly backward just a few years from now. The work at Duke involved five researchers associated with the Departments of Mechanical Engineering & Materials Science and the Department of Orthopaedic Surgery in Biomedical Engineering. When the sufferings of osteoarthritis and disc degeneration are alleviated – and today it looks more like “when” rather than “if” – it’s likely to come from sophisticated and creative teamwork between biomedicine, engineered materials, nanotechnology and composite materials. Moreover, before a complete solution is in sight, molecular biology and stem cell research may also participate.
Has modern technology helped you or someone you know who has osteoarthritis?
Drawing Credit: adapted from evilestmark & Viscious-Speed, on openclipart.org