What Is Articular Cartilage?
The matrix of cartilage is comprised of collagens, proteoglycans, and non-collagenous proteins. While cartilage is a highly-organized structure, about 85% of cartilage is water -- decreasing to about 70% in older people. Chondrocytes are the only cells found in cartilage. Chondrocytes produce and maintain the cartilage matrix.
Articular cartilage serves as the cushion and shock absorber within the joint as it lines the ends of the two bones that form the joint. Cartilage damage can be caused by several conditions including:
Joints affected by cartilage damage become painful, stiff, and have limited range of motion.
The enormous problem is that cartilage is unable to heal itself. Consequently, articular cartilage has become the focus of many researchers and tissue engineers who strive to be able to grow new cartilage and transplant it in place of damaged or worn cartilage.
Have Researchers Made Progress With Cartilage Regeneration?
Several techniques have been developed:
- debridement or abrasion - surgeon arthroscopically removes loose cartilage which causes bleeding at the bone surface and growth of fibrocartilage (fibrous cartilage or scar tissue) but the fibrocartilage may not be strong enough
- microfracture - surgeon arthroscopically clears the affected area and makes several perforations in the bone to stimulate bleeding and growth of fibrocartilage
- mosaicplasty or osteochondral autograft transplantation surgery - surgeon removes plug of bone with cartilage covering from healthy area of the joint and transplants it to the damaged area
- periosteal flap - surgeon removes a portion of the periosteum (connective tissue covering all bones) from shin and transplants it to the area of cartilage damage
- autologous chondrocyte implantation - surgeon arthroscopically removes small portion of cartilage from knee; tissue is sent to a lab to be cultured; second surgery required so lab-grown cells can be implanted at the site of the damaged cartilage
- osteochondral allografts - donor bone is used to repair the damaged cartilage
All of the procedures yield mixed results. There are still many questions that plague attempts at cartilage regeneration. More clinical trials are needed to find definitive answers and to develop procedures that relieve arthritis symptoms and produce a durable replacement for damaged cartilage.
What's the Latest Breakthrough for Cartilage Regeneration?
Bioengineers at Rice University have discovered that intense pressure (comparable to the pressure someone would feel more than half mile below the surface of the ocean) stimulates cartilage cells to grow new tissue -- and that new tissue possesses nearly all of the properties of natural cartilage.
The Musculoskeletal Bioengineering Laboratory at Rice University has studied cartilage for more than a decade. The combination of hydrostatic pressure and growth factors are used to produce the tissue that is strikingly similar to natural cartilage. The researchers believe this development holds promise for arthritis treatment. However, the process has only been tried with cells from cows and has not yet been tested on live animals. The lead researcher forewarns that it will be several years before the process would be ready for clinical testing in humans.
Cartilage regeneration '20,000 Leagues Under the Sea'. Rice University. June 4, 2008.
Cartilage Regeneration: An Overview. Hospital for Special Surgery. 6/4/2003.