Superparamagnetic iron oxide (SPIO) nanoparticles labeled endothelial progenitor cells (EPCs) administration inhibited heterotopic ossification in rats.

Heterotopic ossification (HO) is a painful disease characterized by unwanted bone ectopic formation outside of the skeleton after injury. SPIO nanoparticles therapy has been widely used in diverse orthopedic diseases. However, the effect of SPIO nanoparticles on heterotopic ossification remains unknown. Here, we prepared the SPIO nanoparticles carrying mothers against decapentaplegic homolog 7 (SMAD7) and evaluated their mechanism function to HO in a rat model. The results revealed that SPIO nanoparticles containing SMAD7 treatment lead to a decrease in epithelial-mesenchymal transition (EMT) relevant protein expression in vitro. Moreover, SPIO nanoparticles labeled EPCs transplantation effectively prevented heterotopic ossification and inhibited endothelial-mesenchymal transition (EndMT) in HO rats. In addition, SPIO nanoparticles labeled EPCs transplantation suppressed osteogenic and adipogenic differentiation of embryonic fibroblasts (EFs) in HO rats. Our results demonstrated that administration of SPIO nanoparticles labeled EPCs could inhibit heterotopic ossification in rats, which might be a potential therapy method for a medical intervention to treat HO in clinic.