Crucial role of hematopoietic JAK2 V617F in the development of aortic aneurysms.

JAK2V617F is the most frequent driver mutation in myeloproliferative neoplasms (MPNs) and is associated with vascular complications. However, the impact of hematopoietic JAK2V617F on the aortic aneurysms (AAs) remains unknown. Our cross-sectional study indicated that 9 (23%) out of 39 MPN patients with JAK2V617F exhibited the presence of AAs. Next, to clarify whether the hematopoietic JAK2V617F contributes to the AAs, we applied a bone marrow transplantation (BMT) with the donor cells from Jak2V617F transgenic (JAK2V617F) mice or control wild-type (WT) mice into lethally irradiated apolipoprotein E-deficient mice. Five weeks after BMT, the JAK2V617F-BMT mice and WT-BMT mice were subjected to continuous angiotensin II infusion to induce AA formation. Four weeks after angiotensin II infusion, the abdominal aorta diameter in JAK2V617F-BMT mice was significantly enlarged compared to that in the WT-BMT mice. Additionally, the abdominal AA-free survival rate was significantly lower in the JAK2V617F-BMT mice. Hematopoietic JAK2V617F accelerated aortic elastic lamina degradation as well as activation of matrix metalloproteinase (MMP)-2 and MMP-9 in the abdominal aorta. The numbers of infiltrated macrophages were significantly upregulated in the abdominal aorta of the JAK2V617F-BMT mice accompanied by STAT3 phosphorylation. The accumulation of BM-derived hematopoietic cells carrying JAK2V617F in the abdominal aorta was confirmed by use of reporter GFP-transgene. BM-derived macrophages carrying JAK2V617F showed increases in mRNA expression levels of Mmp2, Mmp9, and Mmp13. Ruxolitinib decreased the abdominal aorta diameter and the incidence of abdominal AA in the JAK2V617F-BMT mice. Our findings provide a novel feature of vascular complications of AAs in MPNs with JAK2V617F.