highly significantp<0.001
TGF-β1 driven differentiation of SPIO-labeled MSCs As predicted, without SPIO TGF-β1 induced a typical chondrogenic differentiation of MSCs seeded 3D in collagen sponges ( Figure 3 ): we observed a highly significant over-expression of global type II collagen (495 fold versus ITS condition, p<0.001) and especially for type IIB collagen, which is typically expressed in differentiating and adult cartilage (810 fold, p<0.001).