In vitro Chondrogenic Hypertrophy Induction of Mesenchymal Stem Cells To investigate underlying mechanism of chondrogenic hypertrophy, we need proper in vitro hypertrophic model of mesenchymal stem cells (MSCs). This protocol describes our defined method for induction of in vitro chondrogenic hypertrophy of human umbilical cord blood-derived MSCs (hUCB-MSCs). By adding thyroid hormone (T3; triiodothyronine) and minimum osteogenic-inducing factors to culture medium, we could induce hypertrophy of hUCB-MSCs in vitro. Hypertrophic induction was validated using immunohistochemical analysis, Western blotting and reverse transcriptase polymerase chain reaction.