Gene expression profiling by the cDNA array technology: Molecular portraying of chondrocytes
Many studies have investigated morphological and biochemical changes during osteoarthritic cartilage degeneration. These studies have never allowed to paint a picture of an expression profile in the chondrocytes during the disease process, based on a broad number of genes simultaneously investigated using the same material. cDNA-array technology is a new, very powerful tool for mRNA expression profiling of large numbers of genes at the same time. The major limitation in using this technology for gene expression profiling in diseased versus normal tissue is the inherent heterogeneity of cell populations present in most tissues. Thus, one is not able to distinguish expression signals derived from endothelial cells, neural tissue, inflammatory cell populations, fibroblasts and other cells physiologically or pathologically present in the tissues. In this respect, adult human articular cartilage offers the great advantage that it contains - both in the normal and in the diseased state - only one cell population, the chondrocytes. Therefore, the detected gene expression levels can be fully attributed to the chondrocytes.