Effect of IL13 on MPLW515L Megakaryocytes

Myelofibrosis (MF) is a disease associated with high unmet medical needs since allogeneic stem cell transplantation is not an option for most patients and JAK inhibitors are generally effective for only 2-3 years and do not delay disease progression. MF is characterized by the presence of dysplastic megakaryocytic hyperplasia and progression to fulminant disease, which is associated with progressively increasing marrow fibrosis. Despite evidence of an inflammatory milieu in MF that contributes to 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-? and collagen biosynthesis. Analysis of samples from patients with myelofibrosis similarly revealed elevated levels of IL-13 in plasma and increased IL-13 receptor expression by marrow megakaryocytes. 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 the numbers of marrow T cells and mast cells, which are known sources of IL-13. Together, our data demonstrate that IL-13 is involved in disease progression in MF and that inhibition of the IL-13/IL-4 signaling pathway might serve as a novel therapeutic target to treat MF. Overall design: Cells transduced with MPLW515l retroviruses and cultured for 4 days in stemspan media in the presence or absence of murine IL-13