COPYRIGHT © 2005 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED Molecular and Immuno- histological Characterization of Human Cartilage Two Years Following Autologous

Background: There are only a few studies concerning the cellular, biochemical, and genetic processes that occur during the remodeling of graft tissue after autologous chondrocyte transplantation. The purpose of the present study was to quantify the expression of genes encoding extracellular matrix proteins and regulatory factors that are essen-tial for cell differentiation in cartilage biopsy specimens from patients who had this treatment two years previously. Methods: Two cartilage biopsy specimens from each of four patients who had been treated with autologous chondro-cyte transplantation and from two multiorgan donors were used. Real-time reverse transcriptase-polymerase chain reac-tion analysis was performed to evaluate the expression of types I, II, and X collagen; aggrecan; cathepsin B; and early growth response protein-1 (Egr-1) and Sry-type high-mobility-group box transcription factor-9 (Sox-9) mRNAs. Immunohis-tochemical analysis for matrix proteins and regulatory proteins was carried out on paraffin-embedded sections. Results: Type-I collagen mRNA was expressed in all of the samples evaluated. Type-II collagen was present in autolo-gous chondrocyte transplantation samples but at lower levels than in the controls. Type-X collagen messenger was undetectable. Aggrecan mRNA was present in all of the samples at lower levels than in the controls, while cathepsin-B messenger levels were higher and Egr-1 and Sox-9 mRNAs were expressed at lower levels. The immunohistochemi-cal analysis showed slight positivity for type-I collagen in all of the sections. Type-II collagen was found in all of the samples with positivity confined inside the cells, while the controls displayed a positivity that was diffuse in the extra