Michael Furey, Virginia Tech professor emeritus of mechanical and biomedical engineering, recently conducted the first study of wear in human cartilage. Furey will report his research and results at the 231st American Chemical Society National Meeting in Atlanta March 26-30.
Furey has been studying lubrication and wear of cartilage for 20 years. Many years ago, he took a one-year sabbatical to work at the Boston Children's Hospital Medical Center to carry out studies of cartilage wear using bovine cartilage. He demonstrated the importance of fluid biochemistry on wear. In one example, a complex protein isolated by David Swann reduced cartilage wear by 90 percent when added to a saline reference fluid-a level equaling that of normal bovine synovial fluid.
For the last eight years, Furey and Hugo P. Veit, professor of pathobiology in the Virginia – Maryland Regional College of Veterinary Medicine at Virginia Tech, and their students have continued the research on the biochemistry of cartilage wear based on bovine cartilage.
While Furey and his group at Virginia Tech had been developing methods of measuring cartilage wear, Mats Brittberg of the Cartilage Research Unit of Goteborg University had developed methods of cartilage repair, including autologous chondrocyte implantation (ACI). But the Swedish group had no idea how long the repair would last -- days, weeks, months, years? Thus, three years ago a collaboration was born to conduct what the two groups believe is the first research of human cartilage wear under controlled "in vitro" conditions.
Brittberg's ACI method involves taking small samples of healthy cartilage from a patient's damaged joint, culturing the tissue in a Petri dish under controlled conditions to allow millions of chondrocyte cells to grow, and then injecting these cartilage cells into the specially-prepared damaged region. The Swedish ACI process has been used on thousands of patients and Brittberg continues his work on developing improvements in cartilage repair. "But the basic and important question remained: How long will the repair last?" Furey said.
"Funding from the Carilion Biomedical Institute supported a collaborative study with the Swedish group," said Furey. "Mats sent us cartilage biopsies from eight Swedish patients -- a sample of healthy cartilage and repaired cartilage from each. Since the specimens were very small -- only two millimeters (mm) in diameter compared to our usual six mm diameter bovine specimens -- new techniques and holders were developed by Nils Steika, the graduate student on the project and a mechanical engineering major."
"The results showed that Brittberg's ACI method produced repairs of excellent durability," said Furey.
"But additional research is needed in this area of tissue engineering. Conventional repair methods such as abrasion arthroplasty gave significantly higher wear than that of normal cartilage. Articular cartilage, consisting of about 80 percent water, is deceptively simple. But it is very complex and still not completely understood.
"In general, papers from the medical area are strong on joint, arthritis, and biochemistry but weak on mechanics, particularly tribology -- the study of friction, wear, and lubrication," said Furey. "On the other hand, many papers on this topic in the engineering area, although strong on mechanics, are weak on or omit biochemistry. Our group has an advantage in that we fully appreciate the importance of tribology and of biochemistry in the process," he said. "For example, we have shown time and time again that there is absolutely no correlation between cartilage wear and friction -- a point that is often missed by researchers on this topic".
Furey will present the paper, " Biotribology: Lubrication and wear of articular cartilage" (COLL 423) at 9:35 a.m., Wednesday, March 29 at the OMNI CNN Center in the Sycamore room as part of the two-day Tribology Symposium of the ACS Division of Colloid and Surface Chemistry. Co-authors of the paper are Hugo Veit, Mats Brittberg, and Furey's former students, 2004 master's degree graduate Nils A. Steika, now with Automation Creation Inc of Blacksburg, and 1999 Ph.D. graduate LaShaun Berrien, now with the Henry M. Jackson Foundation for the Advancement of Military Medicine in Rockville, Md.
Studies aimed at exploring possible connections between tribology and mechanisms of synovial joint lubrication and degeneration (e.g., osteoarthritis) have been carried out using bovine and human cartilage and techniques designed for "in vitro" measurements of cartilage wear and friction under controlled conditions. The results clearly demonstrate the importance of biochemistry of the fluid as well as of the cartilage on wear and damage under reciprocating sliding contact conditions. For example, certain constituents isolated from bovine synovial fluid by Swann significantly reduce cartilage wear when added to a buffered saline solution. Furthermore, pretreatment of cartilage with collagenase-3, an enzyme found in osteoarthritic joints, increased wears by almost 3-fold. In a recent collaborative study of the wear-resistance of repaired articular cartilage, 16 specimens from the knee joints of eight Swedish patients were examined in our biotribology device. It was found that the Autologous Chondrocyte Implantation (ACI) method of cartilage repair developed by the Goteborg group gave less wear than that of "normal" cartilage from the same joint. In line with our previous experience, there is no correlation between cartilage wear and friction. Plans for further studies of biotribology are briefly outlined.
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