... And Another Makes Stem Cells Regenerate Cartilage

People whose joint cartilage is destroyed by an overactive immune system—a disease called osteoarthritis—can currently choose between painkillers and surgery as treatment options. Drug developers, who have primarily been working to find compounds that stop cartilage destruction, may now wish to focus on a strategy that pushes stem cells to produce more cartilage cells. Researchers led by Peter G. Schultz, at Scripps Research Institute, and Kristen Johnson, at the Genomics Institute of the Novartis Research Foundation, have found a small molecule called kartogenin, which causes mesenchymal stem cells found in joints to differentiate into chondrocyte cells that can build cartilage where it has been destroyed (Science, DOI: 10.1126/science.1215157). The team tested the molecule in rodent arthritis models and found that cartilage repair was induced without any negative side effects. Working out the biochemistry of kartogenin’s mode of action, the team learned that the molecule binds to a protein called filamin A, thereby blocking its interaction with a transcription factor called CBFβ and leading to the production of new chondrocyte cells.