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Human gingival fibroblasts (HGFs) are responsible for connective tissue repair and scarring, and are exposed to mechanical forces under physiological and pathological conditions. The exact mechanisms underlying gingival tissue reconstruction under mechanical forces remain unclear. The present study aimfed to investigate the effects of mechanical forces on the proliferation and extracellular matrix synthesis in HGFs by establishing a 3-dimensional (3D) HGF culture model using poly(lactide-co-glycolide) (PLGA) scaffolds. HGFs were cultured in 3D PLGA scaffolds and a mechanical force of 0, 5, 15, 25 or 35 g/cm 2 was applied to HGFs for 24 h. A mechanical force of 25 g/cm 2 induced the highest proliferation rate, and thus was selected for subsequent experiments. Cell viability was determined using the MTT assay at 0, 24, 48 and 72 h. The expression levels of type I collagen (COL-1) and matrix metallopeptidase (MMP)-1 were examined by reverse transcription-quantitative polymerase chain reaction and ELISA, and transforming growth factor (TGF)-β expression was evaluated by ELISA. The application of mechanical force on HGFs cultured on the 3D PLGA scaffolds resulted in a significant increase in cell proliferation and COL-1 expression, as well as a decrease in MMP-1 expression. A TGF-β1 inhibitor was also applied, which attenuated the effects of mechanical force on HGF proliferation, and COL-1 and MMP-1 expression, thus suggesting that TGF-β signaling pathways may mediate the mechanical force-induced alterations observed in HGFs. In conclusion, these findings helped to clarify the mechanisms underlying mechanical force-induced HGF proliferation and ECM synthesis, which may promote the development of targeted therapeutics to treat various diseases, including gingival atrophy caused by orthodontic treatment.

Background:The stability of orthodontic treatment is thought to be significantly affected by the compression and retraction of gingival tissues, but the underlying molecular mechanism is not fully elucidated. The objectives of our study were to explore the effects of mechanical force on the ECM-integrin-cytoskeleton linkage response in human gingival fibroblasts (HGFs) cultured on 3-dimension (3D) lactide-co-glycolide (PLGA) biological scaffold and to further study the mechanotransduction pathways that could be involved. Material/Methods:A compressive force of 25 g/m 2 was applied to the HGFs-PLGA 3D co-cultured model. Rhodamine-phalloidin staining was used to evaluate the filamentous actin (F-actin) cytoskeleton. The expression level of type I collagen (COL-1) and the activation of the integrin a 5 b 1 /focal adhesion kinase (FAK) signaling pathway were determined by using real-time PCR and Western blotting analysis. The impacts of the applied force on the expression levels of FAK, phosphorylated focal adhesion kinase (p-FAK), and COL-1 were also measured in cells treated with integrin a 5 b 1 inhibitor (Ac-PHSCN-NH 2, ATN-161). Results:Mechanical force increased the expression of integrin a 5 b 1 , FAK (p-FAK), and COL-1 in HGFs, and induced the formation of stress fibers. Blocking integrin a 5 b 1 reduced the expression of FAK (p-FAK), while the expression of COL-1 was not fully inhibited. Conclusions:The integrin a 5 b 1 /FAK signaling pathway and actin cytoskeleton appear to be involved in the mechanotransduction of HGFs. There could be other mechanisms involved in the promotion effect of mechanical force on collagen synthesis in addition to the integrin a 5 b 1 pathway.

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