Evaluation of heat shock protein 70 and toll-like receptor 4 expression in gingival crevicular fluid in response to orthodontic forces

Evaluation of pain intensity with prostaglandin E2 biomarker and visual analog scale during initiation of orthodontic treatment: A prospective study

OBJECTIVES

The aim of this study was to assess subjectively and objectively, at which timepoint the patient undergoing fixed orthodontic treatment will have maximum pain during the initiation of orthodontic treatment.

MATERIALS AND METHOD

A total of 22 patients (21 ± 2.7 years, [15 female and 7 male]) requiring extraction of maxillary first premolar participated in the study. Following bonding, an initial archwire of 0.016" NiTi was placed with a distal force of 100 g applied to the canines. The concentration of prostaglandin E2 (PGE2) in the gingival crevicular fluid was assessed at four time points: 1 hour before (T0); 24 hours (T1); 48 hours (T2); 72 hours (T3) after initial archwire placement. The pain intensity was recorded with visual analog scale.

RESULTS

The concentration of PGE2 increased from T0 to T1. The highest concentration was observed at T2 following which there was a mild decline at T3. Statistically significant difference in the PGE2 concentration was observed between T0 to T1 and T1 to T2. The visual analogue scale (VAS) scores increased from T0 to T1. The highest score was observed at T2 followed by a decline at T3. A statistically significant difference in the VAS score was noted between T0 to T1 and T2 to T3. On correlating PGE2 and VAS score, a weak negative correlation was noted between T0 to T1 and no correlation was noted between T1 to T2 and T2 to T3.

CONCLUSION

The patients experience maximum pain between 24 hours (T1) and 48 hours (T2) following initial archwire placement. The highest concentration of PGE2 and VAS score was observed at 48 hours (T2).

Ribosomal Stress Couples with the Hypoxia Response in Dec1-Dependent Orthodontic Tooth Movement

This study characterized the effects of a deficiency of the hypoxia-responsive gene, differentiated embryonic chondrocyte gene 1 (Dec1), in attenuating the biological function of orthodontic tooth movement (OTM) and examined the roles of ribosomal proteins in the hypoxic environment during OTM. HIF-1α transgenic mice and control mice were used for hypoxic regulation of periodontal ligament (PDL) fibroblasts. Dec1 knockout (Dec1KO) and wild-type (WT) littermate C57BL/6 mice were used as in vivo models of OTM. The unstimulated contralateral side served as a control. In vitro, human PDL fibroblasts were exposed to compression forces for 2, 4, 6, 24, and 48 h. HIF-1α transgenic mice had high expression levels of Dec1, HSP105, and ribosomal proteins compared to control mice. The WT OTM mice displayed increased Dec1 expression in the PDL fibroblasts. Micro-CT analysis showed slower OTM in Dec1KO mice compared to WT mice. Increased immunostaining of ribosomal proteins was observed in WT OTM mice compared to Dec1KO OTM mice. Under hypoxia, Dec1 knockdown caused a significant suppression of ribosomal protein expression in PDL fibroblasts. These results reveal that the hypoxic environment in OTM could have implications for the functions of Dec1 and ribosomal proteins to rejuvenate periodontal tissue homeostasis.

Impact of phosphorylation of heat shock protein 27 on the expression profile of periodontal ligament fibroblasts during mechanical strain

PURPOSE

Orthodontic tooth movement is a complex process involving the remodeling of extracellular matrix and bone as well as inflammatory processes. During orthodontic treatment, sterile inflammation and mechanical loading favor the production of receptor activator of NF-κB ligand (RANKL). Simultaneously, expression of osteoprotegerin (OPG) is inhibited. This stimulates bone resorption on the pressure side. Recently, heat shock protein 27 (HSP27) was shown to be expressed in the periodontal ligament after force application and to interfere with inflammatory processes.

METHODS

We investigated the effects of phosphorylated HSP27 on collagen synthesis (COL1A2 mRNA), inflammation (IL1B mRNA, IL6 mRNA, PTGS2 protein) and bone remodeling (RANKL protein, OPG protein) in human periodontal ligament fibroblasts (PDLF) without and with transfection of a plasmid mimicking permanent phosphorylation of HSP27 using real-time quantitative polymerase chain reaction (RT-qPCR), western blot and enzyme-linked immunosorbent assays (ELISAs). Furthermore, we investigated PDLF-induced osteoclastogenesis after compressive strain in a co-culture model with human macrophages.

RESULTS

In particular, phosphorylated HSP27 increased gene expression of COL1A2 and protein expression of PTGS2, while IL6 mRNA levels were reduced. Furthermore, we observed an increasing effect on the RANKL/OPG ratio and osteoclastogenesis mediated by PDLF.

CONCLUSION

Phosphorylation of HSP27 may therefore be involved in the regulation of orthodontic tooth movement by impairment of the sterile inflammation response and osteoclastogenesis.