The matrix-fibroblast interplay as a therapeutic target in idiopathic pulmonary fibrosis (IPF)

Background and objective: Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with poor prognosis. Activated fibroblasts are key effector cells in fibrosis, producing excessive amounts of extracellular matrix (ECM) proteins, a number of soluble factors, additionally to ECM modification. Like in cancer, the microenvironment plays an important role in IPF progression. Whether the ECM conditioned by IPF fibroblasts determines the phenotype of naïve fibroblasts is difficult to explore.

Methods: IPF-derived primary fibroblasts were cultured on Matrigel and then cleared using NH4OH, thus creating the IPF-conditioned matrix (IPF-CM). Normal fibroblast CM served as control. Normal fibroblasts were cultured on these matrixes. Tested parameters: cell count and viability, cell distribution, MMP activity, as well as RNA-seq for gene expression. The effects of the anti-fibrotic drugs (nintedanib and pirfenidone) at physiologically relevant concentrations and various exposure times were analyzed (10 min-24 hours).

Results: Normal fibroblasts cultured on IPF-CM arranged in large aggregates as a result of increased proliferation, migration and differentiation (e.g. elevated Collagen1a and alpha-SMA). Both drugs effectively blocked the large aggregate formation induced by the IPF-CM (p<0.05, 24h), as well as the other cellular responses in a dose dependent manner. The `HIF-1 signaling pathway` was significantly upregulated (P<0.0001).

Conclusion: IPF fibroblasts alter the ECM, thus creating a CM that further propagates an IPF-like phenotype in normal fibroblasts. This assay demonstrated differences in drug activities for approved IPF drugs at clinically relevant concentrations. Thus, the matrix–fibroblast interplay might serve as a relevant assay to explore drug candidates for IPF treatment.