Autophagy (cellular self-consumption) is an adaptive stress response and an important aspect of adaption to mechanical loading. If mechanical forces are associated with autophagy regulation in periodontal ligament (PDL) fibroblasts is still unknown. The aim of this study was to analyze the influence of force magnitude on autophagy regulation and subsequently on cell death in human PDL fibroblasts. Autophagy-associated genes were analyzed with a specific PrimePCR assay after 24 h of stimulation with high (STSH) and low magnitudes (STSL) of static tensile strain applied to PDL fibroblasts. Based on the results, targets were selected for further real-time PCR analysis. The autophagic flux was assessed by immunoblotting for autophagy marker microtubule-associated protein 1, light chain 3, and by autophagosome staining. Cell death was determined by TUNEL assay and Cell Death Detection ELISAPLUS. Autophagy was induced pharmacologically by rapamycin and inhibited by chloroquine. For statistical analysis, the Kruskal Wallis test followed by the post-hoc Dunnett’s test was used. Static tensile strain had regulatory effects on mRNA expression of multiple autophagy-associated targets. Stimulation with STSH induced mRNA expression changes in more autophagy-associated targets than STSL. The autophagic flux was induced by STSH while STSL had no significant effect on autophagosome formation. Furthermore, autophagy inhibition led to increased cell death. Low magnitudes of tensile strain seem to have cell-protective properties. Taken together, our findings provide novel insights about autophagy regulation by biomechanical loading in human PDL fibroblasts. Our results suggest a gradual response of autophagy to static tensile strain in human PDL fibroblasts.
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The authors would like to thank Dr. Michaela Rinneburger, Dr. Benedikt Kleineidam, Ms. Ramona Menden, Ms. Silke van Dyck, and Ms. Inka Bay for their valuable support.
This study was supported by the Medical Faculty of the University of Bonn, the German Research Foundation (DFG, ME 4798/1-1) and the German Orthodontic Society (DGKFO).
Conflict of interest
The authors declare that they have no conflict of interest.
Research involving human participants and/or animals
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
PDL cells were taken after the approval of the Ethics Committee of the University of Bonn was given (#117/15). Patients or their legal guardians provided written informed consent before PDL cells were harvested.
Informed consent was obtained from all individual participants included in the study.
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Memmert, S., Damanaki, A., Weykopf, B. et al. Autophagy in periodontal ligament fibroblasts under biomechanical loading. Cell Tissue Res 378, 499–511 (2019). https://doi.org/10.1007/s00441-019-03063-1
- Periodontal ligament
- Biomechanical loading
- Orthodontic tooth movement
- Cell death