Primary Cilia: A Cellular Regulator of Articular Cartilage Degeneration

Figure 1

The structure of primary cilium. The cilium structure mostly contains three parts: the basal body, transition zone, and axoneme. The basal body locates at the ciliary bottom, which is associated with other cellular organelles (such as the nucleus and Golgi body). The transition zone is between the basal body and the axoneme, acting as a “gatekeeper”; it controls the entry and exit of various substances and proteins. The axoneme consists of nine pairs of doublet microtubules and covers with a ciliary membrane, which is the main component of primary cilia sensing the extracellular signal.