Indian hedgehog: its roles and regulation in endochondral bone development

Normal endochondral bone development requires the coordination of chondrocyte proliferation and differentiation. Indian hedgehog (Ihh) is a morphogen produced by chondrocytes in the early stage of terminal differentiation and plays several key roles in this process. Ihh regulates growth of adjacent proliferative chondrocytes and can also regulate the rate of differentiation of chondrocytes indirectly through its stimulation of parathyroid hormone-related protein (PTHrP). In this review, we focus on recent studies that have identified new functions of Ihh and how Ihh itself is being regulated.