Targeting Fused in Sarcoma (FUS): A Novel Antisense Strategy for Treating Idiopathic Pulmonary Fibrosis [RNA-Seq PCLS]

Fused in Sarcoma (FUS) is a highly conserved RNA-binding protein with essential roles in RNA processing and genomic stability. While extensively studied in the context of neurodegeneration, its involvement in fibrotic diseases—particularly idiopathic pulmonary fibrosis (IPF)—remains largely unexplored. This study investigates the pathological role of FUS in IPF and assesses its viability as a therapeutic target. Specifically, we examine how FUS dysregulation contributes to fibrotic signaling and evaluate whether therapeutic silencing of FUS offers a rational strategy to modulate disease progression. Functional assays were performed on primary lung fibroblasts derived from healthy donors and IPF patients to assess the effects of FUS overexpression and knockdown. Precision-cut lung slices (PCLS) and 3D-alveolosphere cultures from IPF patients were treated with a FUS-targeted antisense oligonucleotide (ASO;ION363). FUS-RNA interactions were mapped using CLIP-Seq, and global transcriptional changes following FUS inhibition were analyzed via RNA sequencing. FUS overexpression in healthy fibroblasts promoted proliferation, while its knockdown attenuated the hyperproliferative phenotype in IPF fibroblasts. IPF cells demonstrated aberrant cytoplasmic mislocalization of FUS. Standard-of-care treatments (pirfenidone, nintedanib) reduced FUS expression in PCLS. CLIP-Seq revealed FUS binding to a distinct set of pro-fibrotic RNAs in IPF. ION363 treatment downregulated fibrotic gene programs, including those linked to ECM remodeling, TGF-β signaling, and epithelial dysfunction. On the contrary, ION363 promoted functional markers and improved morphology in patient derived 3D-alveolospheres. We conclude that FUS is a pivotal regulator of fibrotic signaling in IPF and targeting FUS via ASO represents a promising therapeutic avenue for IPF.