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Effects of Compressive and Tensile Strain on Macrophages during Simulated Orthodontic Tooth Movement.

ABSTRACT: During orthodontic tooth movement (OTM) to therapeutically correct the position of misaligned teeth, thus improving oral health and quality of life, fibroblasts, macrophages, and other immune cells within the periodontal ligament (PDL), which connects a tooth to its surrounding bone, are exposed to compressive and tensile strain. While it is known that PDL fibroblasts are critically involved in the biological regulation of OTM by a mechanotransductively triggered release of cytokines, it is unclear whether macrophages also react to pressure and tension in a similar manner thus impacting on or mediating OTM. RAW264.7 macrophages were seeded onto conventional 6-well cell culture plates for pressure or on Bioflex plates for tension assays and preincubated for 24?h. For in vitro simulation of physiological orthodontic compressive or tensile strain for 2?h, 4?h, 24?h, and 48?h, glass discs (2?g/cm2) were placed or adherent macrophages isotropically stretched for 16%, respectively. We determined cell number, cytotoxicity, and gene/protein expression of Vegf-a/VEGF-A (macrophage-mediated angiogenesis), Mmp-8/9 (extracellular matrix reorganization), and Cox-2/PG-E2, Il-6/IL-6, and Tnf-?/TNF-? (proinflammatory mediators) by RT-qPCR and ELISA. Compressive but not tensile strain resulted in a significant reduction in cell number after only 2?h. Mmp-8 and Mmp-9 expression was significantly enhanced within 24?h of compressive and in part tensile strain. Significantly increased Vegf-a/VEGF-A expression was detected within 4?h of pressure, but not during application of tensile strain. Expression of proinflammatory mediators Cox-2/PG-E2, Il-6/IL-6, and Tnf-?/TNF-? was significantly increased as early as 2-4?h after application of compressive or tensile strain. Our results indicate that macrophages respond early on to compressive and tensile strain occurring during OTM with an enhanced gene expression of proinflammatory cytokines, which could affect PDL fibroblasts, osteoblasts, and immune cells triggering or enhancing the biological mechanisms and osteoclastogenesis underlying OTM.

SUBMITTER: Schroder A

PROVIDER: S-EPMC7204109 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Effects of Compressive and Tensile Strain on Macrophages during Simulated Orthodontic Tooth Movement.

Schröder Agnes A Käppler Paul P Nazet Ute U Jantsch Jonathan J Proff Peter P Cieplik Fabian F Deschner James J Kirschneck Christian C

Mediators of inflammation 20200428

During orthodontic tooth movement (OTM) to therapeutically correct the position of misaligned teeth, thus improving oral health and quality of life, fibroblasts, macrophages, and other immune cells within the periodontal ligament (PDL), which connects a tooth to its surrounding bone, are exposed to compressive and tensile strain. While it is known that PDL fibroblasts are critically involved in the biological regulation of OTM by a mechanotransductively triggered release of cytokines, it is uncl ...[more]

PMID: 32410848

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Project description:During orthodontic tooth movement (OTM) mechanical forces trigger pseudo-inflammatory, osteoclastogenic and remodelling processes in the periodontal ligament (PDL) that are mediated by PDL fibroblasts via the expression of various signalling molecules. Thus far, it is unknown whether these processes are mainly induced by mechanical cellular deformation (mechanotransduction) or by concomitant hypoxic conditions via the compression of periodontal blood vessels. Human primary PDL fibroblasts were randomly seeded in conventional six-well cell culture plates with O2-impermeable polystyrene membranes and in special plates with gas-permeable membranes (Lumox®, Sarstedt), enabling the experimental separation of mechanotransducive and hypoxic effects that occur concomitantly during OTM. To simulate physiological orthodontic compressive forces, PDL fibroblasts were stimulated mechanically at 2?g·cm-2 for 48?h after 24?h of pre-incubation. We quantified the cell viability by MTT assay, gene expression by quantitative real-time polymerase chain reaction (RT-qPCR) and protein expression by western blot/enzyme-linked immunosorbent assays (ELISA). In addition, PDL-fibroblast-mediated osteoclastogenesis (TRAP+ cells) was measured in a 72-h coculture with RAW264.7 cells. The expression of HIF-1?, COX-2, PGE2, VEGF, COL1A2, collagen and ALPL, and the RANKL/OPG ratios at the mRNA/protein levels during PDL-fibroblast-mediated osteoclastogenesis were significantly elevated by mechanical loading irrespective of the oxygen supply, whereas hypoxic conditions had no significant additional effects. The cellular-molecular mediation of OTM by PDL fibroblasts via the expression of various signalling molecules is expected to be predominantly controlled by the application of force (mechanotransduction), whereas hypoxic effects seem to play only a minor role. In the context of OTM, the hypoxic marker HIF-1? does not appear to be primarily stabilized by a reduced O2 supply but is rather stabilised mechanically.

Project description:Periodontal accelerate osteogenesis orthodontics (PAOO) is an extension of described techniques that surgically alter the alveolar bone; however, the specific mechanism underlying the technique is not completely understood. The aim of the present study was to evaluate the roles of microRNA (miR)?21 during PAOO. Sprague?Dawley rats were divided into the following four groups: i) Group tooth movement (TM), underwent TM and were administered normal saline (NS); ii) Group PAOO, underwent PAOO + TM and were administered NS; iii) Group agomiR?21, underwent PAOO + TM and were administered agomiR?21; and iv) Group antagomiR?21, underwent PAOO + TM and were administered antagomiR?21. To validate the rat model of PAOO, morphological analyses were performed and measurements were collected. Reverse transcription?quantitative PCR, western blotting and immunohistochemical staining were performed to examine the expression levels of programmed cell death 4 (PDCD4), activin A receptor type 2B (ACVR2b), receptor activator of NF??? ligand (RANKL) and C?Fos. Dual?luciferase reporter assays were performed to validate PDCD4 as a target of miR?21 in vitro. Following 7 days of treatment, the TM distance of group PAOO was longer compared with groups TM and antagomiR?21 (P<0.05), but shorter compared with group agomiR?21 (P<0.05). Tartrate?resistant acid phosphatase staining indicated that following treatment with agomiR?21, osteoclast activity was notably increased, whereas the mRNA and protein expression levels of PDCD4 were notably decreased compared with group PAOO. The mRNA and protein expression levels of RANKL and C?Fos in group agomiR?21 were notably increased compared with group PAOO, whereas group antagomiR?21 displayed the opposite pattern (P<0.05). With regard to ACVR2b, no significant differences were observed among the group agomiR?21 and antagomiR?21 compared with group PAOO. Bioinformatics analysis predicted that PDCD4 was a potential target gene of miR?21, and dual?luciferase reporter assays demonstrated that miR?21 directly targeted PDCD4. In conclusion, the present study demonstrated that miR?21 serves an important role during PAOO?mediated orthodontic TM.

Dataset Information

Effects of Compressive and Tensile Strain on Macrophages during Simulated Orthodontic Tooth Movement.

Publications

Effects of Compressive and Tensile Strain on Macrophages during Simulated Orthodontic Tooth Movement.

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