IL-13/IL-4 signaling contributes to fibrotic progression of the myeloproliferative neoplasms

Myelofibrosis (MF) is a disease with high unmet medical need since bone marrow transplant is not an option for many patients and JAK inhibitors are generally effective for only 2-3 years. MF is characterized by the presence of dysplastic megakaryocytes and progression to fulminant disease is associated with significantly increased fibrosis in the bone marrow. Despite evidence of an inflammatory state in MF that drives disease progression, the specific factors that promote megakaryocyte growth are poorly understood. Here, we analyzed changes in the cytokine profiles of MF mouse models before and after development of fibrosis coupled with analysis of bone marrow populations by scRNA-seq. We found high IL-13 levels in the bone marrow of MF mice. IL-13 promoted the growth of mutant megakaryocytes and induced the surface expression of TGF-B and collagen biosynthesis. Analysis of samples from patients with myelofibrosis revealed elevated levels of IL-13 in plasma and increased IL-13 receptor expression in megakaryocytes in the bone marrow, indicating that our observations in mice are relevant in human disease. In vivo, IL-13 overexpression promoted disease progression while reducing IL-13/IL-4 signaling reduced several features of the disease including fibrosis. Lastly, we found an increase in T cells and mast cells, which are known sources of IL-13 in MF bone marrow. Together, our data demonstrate that IL-13 is involved in the progression of MF and that inhibition of the IL-13/IL-4 signaling pathway should be investigated as a therapeutic option in MF. Overall design: Bone marrow cells from mice transplanted with Jak2V167F Vav-Cre+ cells at 2 and 6 months after transplant (n = 2 per timepoint)