Fibronectin silencing remodels the fibrotic bone marrow niche
Bone marrow (BM) fibrosis is a defining feature of Primary Myelofibrosis, yet the extracellular matrix (ECM) that sustains the fibrotic niche remains largely untargeted therapeutically. Fibronectin (FN), a key organizer of ECM architecture and growth factor signaling, accumulates in the fibrotic BM niche and correlates with disease severity. Here, we investigated whether systemic FN depletion can disrupt pathological remodeling of the BM niche. We developed a chemically modified antisense oligonucleotide targeting FN1 (FN ASO), which reduced FN expression and assembly and impaired transforming growth factor-{beta}1 (TGF-{beta}1)-induced activation of mesenchymal stromal cells. Systemic FN ASO administration efficiently depleted circulating and BM FN in mice and was well tolerated during short-term treatment. In two complementary models of BM fibrosis, FN silencing reduced FN matrix organization, stromal activation, active TGF{beta}-1, reticulin, and collagen deposition. In Jak2V617F-driven disease, transcriptomic profiling further revealed attenuation of ECM, TGF-{beta}1, and mesenchymal remodeling programs, accompanied by changes in inflammatory signaling. Collectively, these findings identify FN as an active organizer of the fibrotic BM niche and show that its systemic silencing uncouple ECM organization from profibrotic stromal signaling, providing rationale for targeting FN in myelofibrosis with broader therapeutic relevance to fibrosis-driven diseases.