High glucose inhibits the osteogenic differentiation of periodontal ligament stem cells in periodontitis by activating endoplasmic reticulum stress

Periodontitis is a highly prevalent dental disease which is associated with diabetes and is challenging to cure in diabetic patients. However, the mechanism of comorbid diabetes and periodontitis is still unclear. This study aimed to uncover the role of endoplasmic reticulum (ER) stress in high glucose-associated periodontitis.

The osteogenic differentiation ability of PDLSCs cells is inhibited in a high glucose microenvironment, and this effect is realized by ER stress activation. Blocking ER stress can partially restore the reduced osteogenic ability of PDLSCs. These results suggest that high glucose inhibits the osteogenic differentiation ability of PDLSCs by activating ER stress, which ultimately exacerbates periodontitis.

Periodontal tissues were obtained from diabetic patients with periodontitis, periodontitis patients without systemic disease, and healthy teeth. The expressions of ER stress-related factors GRP78, ATF6, PERK and XBP1 were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and immumohistochemical staining. Periodontal ligament stem cells (PDLSCs) from three states of periodontal tissues were isolated and cultured as diabetic PDLSCs (dPDLSCs), inflamed PDLSCs (iPDLSCs) and healthy PDLSCs (hPDLSCs), and the cell stemness was assayed. Different concentrations (8, 11, and 25 mmol/L) of D-glucose were used on hPDLSCs to simulate high glucose microenvironment. The changes of osteogenic ability of PDLSCs were observed, and the expressions of ER stress-related factors in different time point (6, 12, 24, and 72 h) were detected. Finally, GRP78 shRNA lentivirus was used to block ER stress on PDLSCs in the 25 mmol/L D-glucose microenvironment, and the osteogenic ability of PDLSCs was observed.

The results showed that the expressions of GRP78, ATF6, PERK, and XBP1 were highest in the diabetic periodontitis group and lowest in the healthy periodontal tissue group (P<0.05). The clone formation, osteogenic and lipogenic differentiation abilities were lowest in dPDLSCs and highest in hPDLSCs. With the increase of glucose concentration, the osteogensis ability of PDLSCs decreased. After 6 hours of stimulation with D-glucose 25 mmol/L, the ER stress pathways in PDLSCs were effectively activated, and the peak value was reached at 12 hours. The decrease in the osteogensis ability of PDLSCs in a high glucose microenvironment reversed when ER stress was blocked. Conclusions: The osteogenic differentiation ability of PDLSCs cells is inhibited in a high glucose microenvironment, and this effect is realized by ER stress activation. Blocking ER stress can partially restore the reduced osteogenic ability of PDLSCs. These results suggest that high glucose inhibits the osteogenic differentiation ability of PDLSCs by activating ER stress, which ultimately exacerbates periodontitis.