# Inflammation-driven periostin in ECRS has contrasting effects on tissue structural integrity and osteitis

## TL;DR

Periostin in ECRS promotes bone thickening but also helps maintain tissue structure, suggesting it could be a key target for treatment.

## Contribution

This study reveals periostin's dual role in promoting osteitis and maintaining tissue integrity in ECRS.

## Key findings

- Periostin levels correlate with osteitis and are increased by Th2 cytokines in nasal fibroblasts.
- Periostin deficiency reduces bone thickening but causes epithelial collapse and lower fibronectin.
- Periostin supports osteogenesis and ECM stability in inflamed sinonasal tissues.

## Abstract

Eosinophilic chronic rhinosinusitis (ECRS) is a severe form of chronic rhinosinusitis characterized by type 2 inflammation, tissue remodeling, and bone thickening, known as osteitis. Periostin, a matricellular protein involved in extracellular matrix (ECM) regulation and T helper 2 (Th2)-mediated inflammation, is markedly elevated in patients with ECRS; however, its pathophysiological role remains unclear.

We investigated the role of periostin in inflammation and tissue remodeling in ECRS using samples from ECRS patients, human nasal epithelial cells and fibroblasts, as well as an ECRS mouse model including periostin knockout mice.

Periostin levels were elevated in ECRS tissues and modestly correlated with osteitis scores. Th2 cytokines increased periostin expression, particularly in nasal fibroblasts. Conditioned medium containing periostin promoted osteogenic differentiation in vitro, whereas neutralizing antibodies reduced the expression of osteogenic markers. In an ECRS mouse model, periostin deficiency led to reduced bone thickening and lower expression of osteogenic markers despite similar eosinophil infiltration. Furthermore, periostin-deficient mice exhibited greater epithelial collapse and reduced fibronectin levels, indicating compromised ECM integrity.

These findings demonstrate that periostin contributes to osteogenesis and maintenance of structural stability in the inflamed sinonasal mucosa. Periostin may be a potential therapeutic target for controlling chronic inflammation and tissue remodeling in ECRS.