Quantitative analysis of repair tissue biopsies following chondrocyte implantation.

Outcome measures for cartilage repair techniques include clinical assessment of functional status, magnetic resonance imaging, mechanical indentation in situ and second-look biopsies, which are used for detailed ex vivo histological and immunohistochemical assessment. Biopsy analysis is considered an important outcome measure, despite being highly invasive, since it provides a visual record of the spatial organization of matrix proteins and cells. We propose that the value of second-look biopsies would be significantly enhanced if accurate quantification of cartilage matrix molecules could also be obtained. The goal of our work has been to develop a combined method for histological and biochemical analysis of a single biopsy. We have developed a method of cutting frozen sections of cartilage and recovering the uncut tissue for subsequent biochemical analysis. We have also developed a range of miniaturized assays that can be performed after cartilage digestion with trypsin. In this way we are now able to analyse biopsies with a wet weight as low as 5 mg using both histological and biochemical methods, so obtaining the maximum amount of information from the minimum volume of tissue. This new approach will allow a more accurate assessment of the quality of cartilage repair tissue than histological analysis alone.