Predictive value of in vitro and in vivo assays in bone and cartilage repair - What do they really tell us about the clinical performance?

The continuous increase of life expectancy leads to an expanding demand for repair and replacement of damaged and degraded organs and tissues. Recent completion of a first version of the human genome sequence is a great breakthrough for the field of pharmaceutics. It is conceivable that new developments in pharmaceutical research will result in a large number of novel and improved medicines. A similar development is expected in the field of biomaterials designed for bone and cartilage repair and replacement. Spinal fusions and repairs of bone defects caused by trauma, tumors, infections, biochemical disorders and abnormal skeletal development, are some examples of the frequently performed surgeries in the clinic. For most of these surgeries, there is a great need for bone graft substitutes. Similarly, the number of patients worldwide experiencing joint pain and loss of mobility through trauma or degenerative cartilage conditions is considerable, and yet, few approaches employed clinically are capable of restoring long-term function to damaged articular cartilage1, 2. Therefore, new materials and techniques need to be developed.