The role of primary cilia in articular cartilage and growth plate

Primary cilia are now considered an important organelle required for many key steps during developmental processes including skeletal development. Articular cartilage and growth plate are two cartilage compartments whose functions are important postnatally. Articular cartilage is a think cartilage layer which serves as a cushion to protect the joint space, whereas growth plate is important for postnatal long bone growth. Both articular cartilage and growth plate need to be developed properly to ensure the normal bone function. Here, we show an important role of primary cilia in development of both articular cartilage and growth plate using genetic modified mouse model in which primary cilia are specifically deleted in chondrocytes. The function of primary cilia in regulation of Hedgehog signaling is required in both articular cartilage and growth plate. We also show the activity of Hedgehog signaling is required differently in these two types of cartilage tissue. In conclusion, our study not only reveals a crucial role of primary cilia in postnatal cartilage maintenance, but also demonstrates that Hedgehog signaling is the key step downstream of primary cilia for this regulation.