Periodontitis is a chronic inflammatory disease that results in the destruction of periodontal soft tissue and the resorption of alveolar bone. Evidence indicates that in diabetic patients, hyperglycemia suppresses periodontal ligament stem cell (PDLSC) functions and leads to difficulties in periodontal repair. The present study aimed to explore the mechanisms by which high‐glucose concentrations aggravate cell viability reduction in human CD146‐positive PDLCs (CD146+PDLCs) under tumor necrosis factor‐alpha (TNF‐alpha) induction. CD146+PDLCs were isolated from periodontal ligament tissues and treated in the absence or presence of 10 ng/ml of TNF‐alpha and 30 mM glucose. Cell viability was detected using Cell Counting Kit‐8 assays and Luminescent Cell Viability Assays. Western blotting and real‐time polymerase chain reaction were performed to determine tumor necrosis factor‐alpha receptor‐1 (TNFR‐1) protein and messenger RNA expression. Bisulfite and MassArray methylation analyses were used to analyze the methylation status of the TNFR‐1 gene. Our results indicated that cell viability was reduced after treatment with a combination of both high‐glucose concentration and TNF‐alpha. Treatment with 30 mM glucose suppressed DNA methyltransferase (DNMT) activities and DNMT1 protein expression, and this was accompanied by the upregulation of TNFR‐1. Additionally, we found that the CpG island located within the TNFR‐1 gene was hypomethylated under 30 mM glucose conditions. S‐adenosylmethionine, an established methyl donor, reversed TNFR‐1 upregulation and restored cell viability against high‐glucose concentration and TNF‐alpha. In conclusion, the present findings suggest that high‐glucose‐induced CpG island hypomethylation within the TNFR‐1 gene plays an essential role in TNFR‐1 upregulation, and this further enhances the cell viability reduction of CD146+PDLCs caused by TNF‐alpha.

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The aim of this study was to explore the effects of platelet‐rich plasma on gingipain‐caused changes in cell morphology and apoptosis of osteoblasts. Mouse osteoblasts MC3T3‐E1 cells were treated with gingipain extracts from Porphyromonas gingivalis in the presence or absence of platelet‐rich plasma. Apoptosis was detected with terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling staining. F‐actin was determined by phalloidin‐fluorescent staining and observed under confocal microscopy. Western blot analysis was used to detect integrin β1, F‐actin, and G‐actin protein expressions. A knocking down approach was used to determine the role of integrin β1. The platelet‐rich plasma protected osteoblasts from gingipain‐induced apoptosis in a dose‐dependent manner, accompanied by upregulation of integrin β1. Platelet‐rich plasma reversed the loss of F‐actin integrity and decrease of F‐actin/G‐actin ratio in osteoblasts in the presence of gingipains. By contrast, the effects of platelet‐rich plasma were abrogated by knockdown of integrin β1. The platelet‐rich plasma failed to reduce cell apoptosis and reorganize the cytoskeleton after knockdown of integrin β1. In conclusion, platelet‐rich plasma inhibits gingipain‐induced osteoblast apoptosis and actin cytoskeleton disruption by upregulating integrin β1 expression.