Lowered Expression of MicroRNAs 221 and 222 Mediate Apoptosis Induced by High Glucose in Human Periodontal Ligament Cells

Impaired periodontal healing is a common complication of diabetes mellitus (DM), frequently related to hyperglycemia. MicroRNAs 221 and 222 have been studied as biomarkers for inflammatory diseases, including diabetes, but their role in the periodontal ligament (PL) is unknown. The effects of high glucose on human PL cells death were studied, as well as the expression of microRNA-221 and microRNA-222, potentially modulated by DM. Cells were obtained from the premolar teeth of young humans and cultured for 7 days under different glucose concentrations (5 or 30 mM). MicroRNAs-221/222 expressions were evaluated by real-time RT-PCR and apoptosis by TUNEL assays. Caspase-3 expression was studied by western blotting and immunocytochemistry. High glucose increased apoptosis and caspase-3 protein expression by about 3×. MicroRNA-221 and microRNA-222 expressions decreased by nearly 40% under high glucose. MicroRNA-221 and microRNA-222 inhibition using antagomiRs increased apoptosis by 2–3×, while the expression of caspase-3, a validated target for these microRNAs, was increased by 50%. The overexpression of both microRNAs using miR mimics in high glucose cells did no effect on apoptosis but increased caspase-3 expression by 30%. In conclusion, high glucose induces apoptosis of human PL cells potentially through a reduction of microRNA-221 and microRNA-222 expression and elevation of caspase-3.