Matrix Stiffness Governs Fibroblast-Driven Immune Homeostasis in Gingival Tissues

Abstract

Periodontal disease is associated with inflamed gingival tissues and degradation of the gingival extracellular matrix (ECM), yet the role of mechanical cues is poorly understood. Gingival ECM in periodontal disease showed a loss of fibrillar collagen compared to healthy samples. We hypothesized that ECM softening in periodontal disease contributes to inflammation due to dysregulated gingival fibroblasts (GFs). A mechanically tunable hydrogel model of the gingival ECM was developed to investigate the mechano-immune crosstalk. Stiff collagen-alginate hydrogels matched the rheological properties of gingival biopsies. Human donor GFs encapsulated in these stiff hydrogels showed significantly suppressed toll-like receptor inflammatory responses compared to soft. Stiffness-dependent inflammatory responses of GFs were directed by the non-canonical NF{kappa}B pathway and epigenetic nuclear organization. The direct impact of mechanical cues on immune responses was investigated with human donor cells ex vivo by co-culture of human GFs with myeloid cells and in human gingival explants. Myeloid progenitors co-cultured with GFs in stiff hydrogels differentiated into immunomodulatory dendritic cells. Ex vivo crosslinking of human gingival tissue increased stiffness and reduced inflammatory cytokines. Gingival mechano-immune regulation provides a new avenue for biomaterials-based treatments in periodontitis.