Vascular TSP1-CD47 Signaling Promotes Sickle Cell-Associated Arterial Vasculopathy and Pulmonary Hypertension in Mice.

Pulmonary hypertension (PH) is a leading cause of death in sickle cell disease (SCD). Hemolysis and oxidative stress are contributing factors to SCD-associated PH. We have reported that the protein thrombospondin-1 (TSP1) is elevated in the plasma of patients with SCD and by interacting with its receptor CD47 limits vasodilation of distal pulmonary arteries ex vivo. We hypothesized that the TSP1-CD47 interaction may promote PH in SCD. We found that TSP1 and CD47 are upregulated in the lungs of BERK sickle mice and patients with SCD-associated PH. We then generated chimeric animals by transplanting BERK bone marrow into C57BL/6J (n=24) and CD47 knockout (CD47KO, n=27) mice. Fully engrafted Sickle-to-CD47KO chimeras had lower right ventricular (RV) pressures than Sickle-to-C57BL/6J chimeras as shown by the reduced maximum pressure of the RV (p=0.013) and mean pulmonary artery pressure (p=0.020). The afterload of the Sickle-to-CD47KO chimeras was also lower as shown by the diminished pulmonary vascular resistance (p=0.024) and RV effective arterial elastance (p=0.052). On myography, aortic segments from Sickle-to-CD47KO chimeras had improved relaxation to acetylcholine. We hypothesized that in SCD TSP1-CD47 signaling promotes PH, in part, by increasing ROS generation. Treatment with TSP1 stimulated ROS in human pulmonary artery endothelial cells, which was abrogated by CD47 blockade. Explanted lungs of CD47KO chimeras had less vascular congestion and oxidative footprint. Our results show that genetic absence of CD47 ameliorates SCD-associated PH, which may be due to decreased ROS levels. Modulating TSP1-CD47 may provide a new molecular approach to the treatment of SCD-associated PH.