# Matrix Stiffness Governs Fibroblasts’ Regulation of Gingival Immune Homeostasis

## TL;DR

This study shows that the stiffness of the gum tissue's matrix affects immune responses, offering a new way to treat periodontal disease.

## Contribution

The study identifies a 'mechano-epigenetic' checkpoint linking matrix stiffness to immune regulation in periodontal disease.

## Key findings

- Stiff hydrogels suppressed inflammatory responses in fibroblasts compared to soft hydrogels.
- Restoring matrix stiffness reduced inflammation via non-canonical NFκB signaling and DNA methylation.
- Ex vivo crosslinking of gum tissue increased stiffness and reduced inflammatory cytokines.

## Abstract

Periodontal disease is characterized by inflamed gingival tissues and degradation of the gingival extracellular matrix (ECM), yet the role of mechanical cues remains poorly understood. Gingival ECM in periodontal disease showed reduced fibrillar collagen compared to healthy samples. We hypothesized that ECM softening in periodontal disease contributes to inflammation by dysregulating gingival fibroblasts (GFs). A mechanically tunable hydrogel model of the gingival ECM was developed to investigate the mechano‐immune crosstalk. Stiff and soft collagen‐alginate hydrogels matched the rheological properties of healthy and diseased gingival biopsies respectively. Human donor GFs encapsulated in these stiff hydrogels showed significantly suppressed toll‐like receptor‐mediated inflammatory responses compared to those in soft hydrogels. The non‐canonical NFκB pathway and epigenetic nuclear organization directed stiffness‐dependent inflammatory responses of GFs. The direct impact of mechanical cues on immune responses was investigated ex vivo by co‐culture of donor‐derived 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 the production of inflammatory cytokines. Gingival mechano‐immune regulation offers a novel approach to biomaterial‐based treatments for periodontitis.

This study identifies a “mechano‐epigenetic” checkpoint in which matrix stiffness governs the immune responses of gingival fibroblasts. Using biomimetic hydrogels and human gingival explants, the studies revealed that restoring extracellular matrix stiffness actively suppresses inflammation via non‐canonical NF‐κB signaling and DNA methylation, offering a novel therapeutic paradigm.