OBJECTIVETo observe the effect of superparamagnetic iron oxide (SPIO) on the differentiation of rat bone marrow stem cells (BMSCs) into chondrocytes in vitro and explore the possible mechanism.

METHODSCCK8 assay was performed to examine the cytotoxicity of SPIO (1 and 5 µg/mL) on cultured SD rat BMSCs. Prussian blue staining and fluorescence excitation assay were used to assess the binding of the SPIO to BMSCs after the cells had been cultured in chondrocytes-induced medium in the presence of SPIO (1 and 5 µg/mL) for 9 days. The mRNA levels of COL2 α2, aggrecan and MMP13 in the cell culture were examined using Q-PCR, and the chondrogenic differentiation of the BMSCs was analyzed using alcian blue staining and immunofluorescence staining for COL2 α2. The protein levels of COL2 α2, aggrecan, MMP13, Ihh and PTHrP in the cells were examined using Western blotting.

RESULTSCCK8 assay showed no significant toxicity of SPIO on BMSCs. Compared with the control cells, the cells cultured in the presence of SPIO showed increased expressions of COL2 α2 and aggrecan and decreased expression of MMP13 at both mRNA and protein levels with also significantly increased expressions of Ihh and PTHrP proteins.

CONCLUSIONSPIO can promote the differentiation of rat BMSCs into chondrocytes and up-regulate the Ihh/PTHrP signal pathway, suggesting the potential of SPIO as a new therapeutic agent for chondrocyte-related diseases.