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 AND METHODS: A compressive force of 25 g/m² 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 α₅β₁/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 α₅β₁ inhibitor (Ac-PHSCN-NH 2, ATN-161).

RESULTS: Mechanical force increased the expression of integrin α₅β₁, FAK (p-FAK), and COL-1 in HGFs, and induced the formation of stress fibers. Blocking integrin α₅β₁ reduced the expression of FAK (p-FAK), while the expression of COL-1 was not fully inhibited.

CONCLUSIONS: The integrin α₅β₁/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 α₅β₁ pathway.

Keywords: actin cytoskeleton, Focal Adhesion Kinase 1, Gingival Overgrowth, Integrin alpha5beta1, Mechanotransduction, Cellular, Actins, Adolescent, Child, Collagen Type I, Focal Adhesion Protein-Tyrosine Kinases, Gingiva, Phosphorylation, Polylactic Acid-Polyglycolic Acid Copolymer, RNA, Messenger, Stress Fibers, Stress, Mechanical