Bio-engineered cartilage repairs osteoarthritic knees

Implantation of bioengineered tissue can result in the progressive maturation of osteoarthritis knee cartilage, according to new findings.The authors write, "articular cartilage injuries are a prime target for tissue engineering, because in adults, the tissue has a slow turnover rate and is avascular, and therefore the lesions do not spontaneously heal. Left untreated, many cartilage injuries replacement of the whole joint with a prosthesis."Using new techniques Dr Anthony Hollander (University of Bristol) and colleagues implanted bioengineered cartilage (Hyalograft C) into the knee joint of 23 patients whose knee damage had been caused by injury or osteoarthritis. The patients included 18 men and 5 women with a mean age of 35.6 years (maximum, 56 years) affected by chondral defects of the knee. The average follow-up time from grafting to biopsy was 16 months (range, 6-30). Lesions were mostly localized on the medial (52%) or lateral (30%) femoral condyle.Biopsies were performed between 6 and 30 months after implantation. Ten patients showed normal distribution of cartilage cells while ten had an abnormal cell organization, the researchers report. Three biopsies showed features of both fibrocartilage and normal hyaline tissue.Hollander's group add that all of the normal hyaline biopsies showed that the defect repair was level with the surrounding cartilage and that all biopsies showed close integration of the cartilage with the underlying bone, whether the repair tissue was hyaline or fibrocartilage.The authors point out that the quality of the hyaline cartilage repair tissue was better in osteoarthritic knees than in non-osteoarthritic knees, "Osteoarthrosis did not inhibit tissue regeneration and may even have enhanced it, suggesting that degenerating tissues are primed for repair and require only the appropriate cellular cues for regeneration of healthy tissue.""It is clear from our study that the joint can support tissue regeneration and maturation. The reason why regeneration occurred in only approximately 50% of patients during the 6- to 30-month follow-up period is not yet known, although the data... indicate that the proportion is likely to increase with time after implantation," Hollander and colleagues add.The investigators propose that cartilage degradation in osteoarthritis may involve an imbalance between anabolic and catabolic processes. The group speculates, "the cells introduced by Hyalograft C shift the balance of this metabolic equation in favour of the anabolic side, resulting in cartilage formation. Injured joints without osteoarthritis may lack the endogenous anabolic pathways and so must rely entirely on the introduced cells to produce a repair."Reference...