Calcifying nanoparticles induce apoptosis and calcification in bone marrow mesenchymal stem cells via the...

Pathological calcification is a common feature of many diseases. Calcifying nanoparticles (CNPs) are considered potential inducers of this abnormal calcification, but their specific effects on bone marrow mesenchymal stem cells (BMSCs) remain unclear. BMSCs are key cells in bone formation and repair, and their aberrant apoptosis and calcification are closely related to disease progression.

To explore whether CNPs can induce apoptosis and calcification in BMSCs and analyzed the relationship between these processes. The differential effects of CNPs and nanoscale hydroxyapatites (nHAPs) in inducing apoptosis and calcification in BMSCs were also compared.

CNPs obtained in the early stage were identified by electron microscopy and particle size analysis. BMSCs were cultured with various treatments, including different concentrations of nHAPs, CNPs [2 McFarland (MCF) turbidity, 4 MCF, 6 MCF], and a transforming growth factor (TGF)-β inhibitor (SB431542) for 72 hours. The isolated CNPs exhibited the expected sizes and shapes.

Exposure to CNPs and nHAPs suppressed cell proliferation and promoted apoptosis in a concentration-dependent manner, with CNPs exhibiting significantly stronger effects. Alizarin Red staining indicated an increase in calcium deposition with exposure to increasing concentrations of nHAPs and CNPs. Quantitative reverse-transcription polymerase chain reaction results indicated that medium concentrations of nHAPs and CNPs significantly enhanced the expression of pro-apoptotic and pro-calcification markers, whereas the expression of anti-apoptotic Bcl-2 was reduced compared with untreated controls. Western blotting results showed that medium concentrations of CNPs and nHAPs increased the expression of osteopontin, bone morphogenetic protein-2, TGF-β/Smad, Bax, and caspase-3 and decreased Bcl-2 expression compared with controls.

CNPs and nHAPs induced apoptosis and calcification in BMSCs, with CNPs being the most potent. Additionally, the TGF-β inhibitor SB431542 significantly reduced the occurrence of apoptosis and calcification. A correlation was found between apoptosis and calcification, which is likely mediated through the TGF-β/Smad signaling pathway.