Primary myelofibrosis (PMF) is associated with bone marrow fibrosis; mouse models show that transforming growth factor-beta (TGF-β) and platelet-derived growth factors (PDGFs) are involved in fibrosis and that the source of myofibroblasts is CAR/LepR+ cells [69]. Here, TGFB1 is linked to primary myelofibrosis.