Effect of silver nanoparticles on the osteogenesis of mesenchymal stem cells and their role in fracture healing

Abstract

Background：Silver nanoparticles (AgNps) have been widely used in wound healing. The differential effects of AgNps on keratinocytes and skin fibroblasts have also been demonstrated by our group. One interesting finding from our previous research suggested that AgNps could promote skin stem cell proliferation and might have effects on stem cells differentiation. As mesenchymal stem cells (MSCs) are the most easily available source of stem cells, our aim here was to explore the effect of AgNps on MSCs proliferation and differentiation in-vitro and in-vivo.

For my experiments, BrdU assay was used to test human mesenchymal stem cells (hMSCs) proliferation mediated by AgNps. Secondly, after having tested the appropriate AgNps concentration and frequency, the differentiation inducing property of AgNps was investigated using classical osteogenesis methods of ALP activity assay and alizarin. Furthermore, PCR assay and proteomics by liquid chromatography–mass spectrometry (LC/MS) were used to find out the possible signaling mechanism of AgNPs. Lastly, an in-vivo femoral fracture model was used to test for pro-healing effects after incubation with AgNps.

The key findings from this study: 1.AgNps stimulated the proliferation of hMSCs at appropriate concentrations and were capable of promoting osteogenic differentiation of hMSCs when sustainedly stimulated by AgNps at the concentration of 8 μM, its cells viability, ALP activity and the amount of calcium deposition were significantly more than the control group. 2.Furthermore, TGF-β/BMP signaling pathway was involved as its proteins and genes were significantly up-regulated when interacted with AgNps and down-regulated when blocked with TGF-β receptor 1 inhibitor.

3.Lastly, AgNps were also benefit for mMSCs’ proliferation and osteogenesis, and the in vivo data also showed that animals in the AgNps only (0.2 mM and 0.4 mM) groups achieved faster healing than control.

In conclusion, we found that AgNps could promote MSCs proliferation in a dose dependent manner, and also had effects on MSCs osteogenesis. Furthermore, it would appear that TGF-β/BMP signaling pathway was involved in silver nanoparticle-promoted osteogenic differentiation of human mesenchymal stem cells. Lastly, we confirmed that AgNps could be beneficial for bone healing. AgNps may become a potential drug for bone healing in the clinical setting.