Relationship between the gingival sulcus depth and interleukin-1 isoform concentrations within the adjacent gingival tissue

Decreased MORF leads to prolonged endoplasmic reticulum stress in periodontitis-associated chronic inflammation

The association between inflammation and endoplasmic reticulum (ER) stress has been described in many diseases. However, if and how chronic inflammation governs the unfolded protein response (UPR) and promotes ER homeostasis of chronic inflammatory disease remains elusive. In this study, chronic inflammation resulted in ER stress in mesenchymal stem cells in the setting of periodontitis. Long-term proinflammatory cytokines induced prolonged ER stress and decreased the osteogenic differentiation of periodontal ligament stem cells (PDLSCs). Interestingly, we showed that chronic inflammation decreases the expression of lysine acetyltransferase 6B (KAT6B, also called MORF), a histone acetyltransferase, and causes the upregulation of a key UPR sensor, PERK, which lead to the persistent activation of the UPR in PDLSCs. Furthermore, we found that the activation of UPR mediated by MORF in chronic inflammation contributes to the PERK-related deterioration of the osteogenic differentiation of PDLSCs both in vivo and in vitro. Taken together, our results suggest that chronic inflammation compromises UPR function through MORF-mediated-PERK transcription, which is a previously unrecognized mechanism that contributes to impaired ER function, prolonged ER stress and defective osteogenic differentiation of PDLSCs in periodontitis.

Analysis of vascular distribution and growth factors in human gingival tissue associated with periodontal probing depth

Vascular endothelial growth factor (VEGF) is a key regulator of blood vessel endothelium. Tissue levels of this angiogenesis marker are unknown in human gingival tissue, as is the correlation between vascular growth factors and hypoxia-inducible factor. We examined the expression of VEGF, type III tyrosine kinase receptors (VEGF-R2), platelet-endothelial cell adhesion molecule (CD31) and hypoxia-inducible factor (HIF) mRNA from human gingival tissue of the oral cavity. Tissue samples were from a small quantity of gingival sample biopsy with gingival sulcular depth (GSD) < 2 mm (Group 1), 2 to 4 mm (Group 2), and > 4 mm (Group 3). We found that the levels of VEGF-R2, CD31 and HIF mRNA were higher in the gingival tissue of Group 2 than that of Group 1, and VEGF in the Group 3 was also higher than that of Group 1. The different mRNA levels of these markers may reflect the mRNA levels reflect the vasculature state of gingival tissue based on GSD. VEGF-R2 and HIF also indicate the presence of an elongated blood vessel in the gingival tissue. In the early stage of angiogenesis, VEGF-R2 leads to expression of VEGF, and HIF-1 mediates increased VEGF expression in response to hypoxia in swollen tissues or during the expansion of periodontal tissues, which is useful in the early diagnosis of periodontal diseases.