Clinical, Radiographic, and Histological Outcomes After Cartilage Repair With Particulated Juvenile Articular Cartilage: A 2-Year Prospective Study.

BACKGROUND: Biological repair of cartilage lesions remains a significant clinical challenge because of the lack of natural regeneration and limited treatment options. HYPOTHESIS: Treatment of articular cartilage lesions in the knee with particulated juvenile articular cartilage (PJAC) will result in an improvement in patient symptoms of pain and function and magnetic resonance imaging (MRI) findings at 2 years compared with baseline. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Patients with symptomatic articular cartilage lesions on the femoral condyles or trochlear groove of the knee were identified for treatment with PJAC. There were 25 patients with a mean age of 37.0 ± 11.1 years and a mean lesion size of 2.7 ± 0.8 cm(2). All patients were assessed preoperatively (baseline) with a knee examination and surveys including the International Knee Documentation Committee (IKDC) subjective knee form, 100-mm visual analog scale (VAS) for pain, and Knee injury and Osteoarthritis Outcome Score (KOOS). Patients were followed at predetermined time points postoperatively through 2 years. Also, MRI was performed at baseline and at 3, 6, 12, and 24 months. At 2 years, patients were given the option of undergoing voluntary diagnostic arthroscopic surgery with cartilage biopsy to assess the histological appearance of the cartilage repair including safranin O staining for proteoglycans and immunostaining for type I and II collagen. RESULTS: Clinical outcomes demonstrated statistically significant increases at 2 years after surgery compared with baseline, with improvements seen as early as 3 months. Over the 24-month follow-up period, the IKDC score increased from a mean of 45.7 to 73.6, KOOS-pain score from 64.1 to 83.7, KOOS-symptoms score from 64.6 to 81.4, KOOS-activities of daily living score from 73.8 to 91.5, KOOS-sports and recreation score from 44.6 to 68.3, and KOOS-quality of life score from 31.8 to 59.9. The MRI results suggested that T2-weighted scores were returning to a level approximating that of normal articular cartilage by 2 years. Histologically, the repair tissue in biopsy samples from 8 patients was composed of a mixture of hyaline and fibrocartilage; immunopositivity for type II collagen was generally higher than for type I collagen, and there appeared to be excellent integration of the transplanted tissue with the surrounding native articular cartilage. Other than elective biopsies, there were no reoperations, although 1 graft delamination was reported at 24 months. CONCLUSION: This study demonstrates a rapid, safe, and effective treatment for cartilage defects. For the patient population investigated, the clinical outcomes of the PJAC technique showed a significant improvement over baseline, with histologically favorable repair tissue 2 years postoperatively.

Enhanced tissue regeneration potential of juvenile articular cartilage.

BACKGROUND: Articular cartilage undergoes substantial age-related changes in molecular composition, matrix structure, and mechanical properties. These age-related differences between juvenile and adult cartilage manifest themselves as markedly distinct potentials for tissue repair and regeneration. PURPOSE: To compare the biological properties and tissue regeneration capabilities of juvenile and adult bovine articular cartilage. STUDY DESIGN: Controlled laboratory study. METHODS: Articular cartilage harvested from juvenile (age, 4 months) and adult (age, 6-8 years) bovine femoral condyles was cultured for 4 weeks to monitor chondrocyte migration, glycosaminoglycan content conservation, and new tissue formation. The cartilage cell density and proliferative activity were also compared. Additionally, the effects of age-related changes on cartilage gene expression were analyzed using the Affymetrix GeneChip array. RESULTS: Compared with adult cartilage, juvenile bovine cartilage demonstrated a significantly greater cell density, higher cell proliferation rate, increased cell outgrowth, elevated glycosaminoglycan content, and enhanced matrix metallopeptidase 2 activity. During 4 weeks in culture, only juvenile cartilage was able to generate new cartilaginous tissues, which exhibited pronounced labeling for proteoglycan and type II collagen but not type I collagen. With over 19,000 genes analyzed, distinctive gene expression profiles were identified. The genes mostly involved in cartilage growth and expansion, such as COL2A1, COL9A1, MMP2, MMP14, and TGFB3, were upregulated in juvenile cartilage, whereas the genes primarily responsible for structural integrity, such as COMP, FN1, TIMP2, TIMP3, and BMP2, were upregulated in adult cartilage. CONCLUSION: As the first comprehensive comparison between juvenile and adult bovine articular cartilage at the tissue, cellular, and molecular levels, the results strongly suggest that juvenile cartilage possesses superior chondrogenic activity and enhanced regenerative potential over its adult counterpart. Additionally, the differential gene expression profiles of juvenile and adult cartilage suggest possible mechanisms underlying cartilage age-related changes in their regeneration capabilities, structural components, and biological properties. CLINICAL RELEVANCE: The results of this comparative study between juvenile and adult bovine articular cartilage suggest an enhanced regenerative potential of juvenile cartilage tissue in the restoration of damaged articular cartilage.