Substrate stiffness modulates human gingival fibroblast paracrine signaling to promote osteogenic differentiation of human periodontal ligament cells

Background: Human gingival fibroblasts (HGFs) are stromal cells that maintain periodontal tissue structure and extracellular matrix (ECM) dynamics. ECM stiffness serves as a physical cue that regulates HGF behavior and secretory profiles. This study investigated how substrate stiffness modulates the secretome of HGFs and observed the subsequent effects of this secretome on the osteogenic differentiation of human periodontal ligament cells (HPDLCs). Methods: HGFs isolated from healthy donors were cultured on polydimethylsiloxane substrates, representing soft or hard periodontal tissue under normal and lipopolysaccharide (LPS)-induced inflammatory conditions. The expression of cytokines and chemokines was analyzed using qRT-PCR and ELISA, with p38 MAPK inhibitors used to identify stiffness-associated signaling involvement. HPDLCs were treated with conditioned medium from HGFs (HGF-CM) under osteogenic induction, osteogenic marker expression was examined using qRT-PCR and immunofluorescence, with mineralization assessed by Alizarin red S staining. To establish mechanistic causality, functional blocking was conducted using a C-X-C motif chemokine receptor 4 (CXCR4) inhibitor. Results: ) and confirmed a subsequent decrease in matrix mineralization. Conclusion: Substrate stiffness modulated the paracrine behavior of HGFs, with CXCL12 serving as a representative example of a stiffness-responsive factor. These alterations in the HGF-derived secretome were associated with altered osteogenic and inflammatory responses in HPDLCs. These findings support the influence of the physical microenvironment on fibroblast-periodontal ligament cell interactions on anti-inflammatory response and periodontal tissue stabilization.