Background and objective: Periodontitis is a chronic inflammatory disease characterized by the destruction of the periodontium. The strontium ion (Sr2+ ) can prevent the bone loss associated with periodontitis and promote the regeneration of the bone. The mechanisms by which the Sr2+ works remain poorly understood. We aim to investigate the effects of the Sr2+ ion on cell proliferation, inflammatory regulation and osteogenic differentiation of human periodontal ligament cells (hPDLCs) in pathological conditions.
Material and methods: hPDLCs were obtained from premolars that came from the orthodontic extraction. The hPDLCs were treated with Sr2+ and/or lipopolysaccharide (LPS), which was applied as the pathological condition of periodontitis. The effect of the dose of Sr2+ on cell proliferation was analyzed using a Cell Counting Kit-8 assay. The gene and protein expression of proinflammatory cytokines were detected by the real-time polymerase chain reaction and enzyme-linked immunosorbent assay. The osteogenic differentiation and mineralization were assessed by the real-time polymerase chain reaction, alkaline phosphatase activity assay and alizarin red staining.
Results: Results demonstrated that Sr2+ in a range of concentrations from 0.02 to 2.5 mmol/L significantly improved the proliferation of hPDLCs. Sr2+ reversed LPS-stimulated proinflammatory cytokine expressions such as tumor necrosis factor alpha, interleukin (IL)-1β, IL-6 and IL-8. Moreover, Sr2+ rescued the LPS-inhibited gene expression of osteogenic differentiation. Although it appeared to suppress the late mineralization, Sr2+ can reverse the LPS-inhibited early osteogenic differentiation of hPDLCs.
Conclusion: These results indicated that Sr2+ could attenuate the LPS-stimulated proinflammatory molecule expression and inhibit early osteogenic differentiation of hPDLCs.
Keywords: human periodontal ligament cells; osteogenic differentiation; periodontitis; proinflammatory cytokines; strontium.
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