Fig. 1

MMPs and chondrogenic differentiation of MSCs. The upregulation of reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) during the late stages of chondrogenic differentiation downregulates the expression of MT1-MMP (MMP-14), MMP-2, and MMP-9, and directly inhibits them through its enzymatic activity. Expression of MMP-2 is upregulated by the increase in P38 activity resulting in stimulation of the chondrogenic differentiation of MSCs. MMP-2 also regulates the association of FAK and β1 integrin through its degradation of fibronectin. This degradation results in the inhibition of MAPK pathway through P38 to stop the production of more MMP-2 at late stages of the process. ECM extracellular matrix, MMP matrix metalloproteinase, FAK focal adhesion kinase