Functional genomics of osteoarthritis: on the way to evaluate disease hypotheses.

Functional genomics is a challenging new way to address complex diseases such as osteoarthritis on a molecular level. This complements previous research and will open up new areas of so far unrecognized molecular networks. In this respect, articular cartilage is a good target for functional genomics as it contains only one cell type to which all expression signals can be attributed to. Despite considerable limitations at present, such as a low sensitivity and insensitivity to alternative splicing, posttranscriptional regulation, and posttranslational modification, cDNA-array technology provides a powerful tool to obtain an overview on gene expression patterns hardly achievable with other techniques. This has been shown to be true for known genes as well as for the identification of new genes of interest. Therefore, gene expression analysis will help to identify single genes depending on the disease and experimental conditions investigated. However, the expression pattern of the plethora of expressed genes will paint a picture (network) of disease context, maybe even more pushing forward our understanding of complex diseases such as osteoarthritis.