3D pellets were formed using 2.5×105 human bone marrow-derived mesenchymal stem cells (hBMSCs). Chondrogenesis was initiated in serum-free chondrogenic differentiation medium. From day 14 onwards, cell pellets were maintained either in the standard chondrogenic differentiation medium or in the presence of T3 (10 nM) or IOP (10 μM). For additional details, see online supplemental methods.