[Bone and calcium update; bone research update. Molecular mechanisms regulating chondrocyte differentiation and hypertrophy].

Chondrocyte differentiation process is composed of multiple steps. During the process, hypertrophy of chondrocyte is controlled by various factors including Indian hedgehog (Ihh) and parathyroid hormone related peptide (PTHrP) . PTHrP signals regulate HDAC4-MEF2C axis in chondrocyte. Recently, several co-factors have been found to interact with Sox9. Function of chondrocyte-specific microRNA has been determined. Several types of Cre transgenic mice are available to express Cre at various steps during chondrocyte differentiation. Using these mice, gene functions at specific steps of chondrocyte differentiation are analyzed by generating conditional knockout mice and conditional transgenic mice. It may be possible in future to induce chondrocytes from skin fibroblasts of patients with genetic cartilage diseases by using iPS cell technology, and to analyze molecular mechanism that control differentiation of human chondrocytes.