Immunolocalization of carboxy-terminal type II procollagen peptide in regenerated articular cartilage of osteoarthritic knees after reduction of mechanical stress

The purpose of this study was to investigate the immunolocalization of carboxy-terminal type II procollagen peptide (pCOL-II-C) in the regenerated articular cartilage grown 1-2 years after reduction of mechanical stress by correction of varus deformity with high tibial osteotomy (HTO) for knees with medial compartmental osteoarthritis.The series included 24 knees of 16 patients with a mean age of 70 (56-79) years. Synovial fluid and tissue specimens of the regenerated articular cartilage were obtained at the time of plate removal with arthrotomy. Tissue specimens were decalcified and stained with toluidine blue, safranin O, anti-type I and type II collagen and anti-pCOL-II-C. Pineda's histological grading of articular cartilage repair and Okada's grade of immunostaining were employed to assess the regenerated articular cartilage.In knees with regeneration of articular cartilage, there was a positive linear correlation between the grade of immunostaining and the concentration of synovial fluid pCOL-II-C (r=0.652; P< 0.001). Similarly, a positive linear correlation was observed between the grade of immunostaining and the histological grading score (r=0.683; P< 0.001).The immunostaining and synovial fluid concentration of pCOL-II-C decreased in accordance with the progression of articular cartilage regeneration observed after reduction of mechanical stress by correction of deformity with HTO.