The impact of photobiomodulation therapy on the survival and differentiation of periodontal ligament mesenchymal stem cells exposed to zoledronic acid

This study assessed the effects of photobiomodulation therapy (PBMT) with different laser wavelengths on the viability and differentiation of periodontal ligament mesenchymal stem cells (PDLMSCs) exposed to zoledronic acid (ZA). In this in vitro study, PDLMSCs were cultured with 5 µM ZA for 48 h and randomly assigned to 6 groups of positive and negative controls, and PBMT with 635 nm (2 and 4 J/cm²) and 980 nm (2 and 4 J/cm²) lasers. Cell viability was assessed by the methyl thiazolyl tetrazolium (MTT) assay after 24 and 72 h, and mineralized nodule formation was evaluated by Alizarin red staining. Mineralization was assessed by alkaline phosphatase (ALP) activity and expression analysis of osteocalcin (OCN), osteopontin (OPN), and RUNX2 by real-time polymerase chain reaction (PCR). Data were analyzed by one-way ANOVA and Tukey test (α = 0.05). ZA exposure in no-irradiation group decreased viability, ALP activity, mineralized nodule formation, and expression of osteogenic genes (P < 0.05). Cell viability in 980 nm (4 J/cm²) group at 24 h and in 635 nm (4 J/cm²) and 980 nm (2 and 4 J/cm²) groups at 72 h was significantly higher than that in ZA group (P < 0.05). Mineralized nodule formation in both 980 nm groups was significantly higher than that in ZA group (P < 0.001). PBMT with 635 nm laser caused significant downregulation of OCN and OPN with 4 J/cm² and upregulation of OPN with 2 J/cm² (P < 0.05) energy density. PBMT with 980 nm laser (2 and 4 J/cm²) caused significant upregulation of OCN, OPN, and RUNX2 (P < 0.05). PBMT with 980 nm laser (4 J/cm²) in presence of ZA increased PDLMSC viability, ALP activity, mineralized nodule formation, and expression of osteogenic genes.