Conclusions
Our studies support that JAK2 could be a culprit contributing to the pulmonary vascular remodelling, and therefore, it could be a viable target for prevention and treatment of PAH in clinical settings.
Methods
Smooth muscle cell (SMC)-specific Jak2 deficient mice and their littermate controls were subjected to normobaric normoxic or hypoxic (10% O2 ) challenges for 28 days to monitor the development of PAH, respectively. To further elucidate the potential mechanisms whereby JAK2 influences pulmonary vascular remodelling, a selective JAK2 inhibitor was applied to pre-treat human pulmonary arterial smooth muscle cells (HPASMCs) for 1 hour followed by 24-hour hypoxic exposure.
Results
Mice with hypoxia-induced PAH were characterized by the altered JAK2/STAT3 activity in pulmonary artery smooth muscle cells. Therefore, induction of Jak2 deficiency in SMCs protected mice from hypoxia-induced increase of right ventricular systolic pressure (RVSP), right ventricular hypertrophy and pulmonary vascular remodelling. Particularly, loss of Jak2 significantly attenuated chronic hypoxia-induced PASMC proliferation in the lungs. Similarly, blockade of JAK2 by its inhibitor, TG-101348, suppressed hypoxia-induced human PASMC proliferation. Upon hypoxia-induced activation, JAK2 phosphorylated signal transducer and activator of transcription 3 (STAT3), which then bound to the CCNA2 promoter to transcribe cyclin A2 expression, thereby promoting PASMC proliferation. Conclusions: Our studies support that JAK2 could be a culprit contributing to the pulmonary vascular remodelling, and therefore, it could be a viable target for prevention and treatment of PAH in clinical settings.