Sickle chimeras with genetically reduced FII levels have improved cardiopulmonary pathology and function. (A) CMR on representative HbA/FII^WT, HbS/FII^WT, and HbS/FII^lox/− mice at 1 year following bone marrow transplantation. A representative view of the ventricles is shown with RV in the same plane, which is indicated by the red arrows. (B-C) LV and RV end-diastole volumes in chimeric mice; symbols represent the value of each individual mouse and the bars denote the average. (D) RV hypertrophy is measured as a ratio of RV wall weight/LV + septum weights (Fulton Index) in HbS/FII^WT (n = 12), HbS/FII^lox/− (n = 15), HbA/FII^WT (n = 6), HbA/FII^lox/− (n = 7) mice. Cohorts were analyzed by Mann-Whitney U test. Statistical significance between FII^WT and FII^lox/− chimeras is indicated by asterisks: **P < .01, *P < .05. (E) α-SMA staining in lung tissue. Images are representative of 5 to 7 mice per group. Mice used as transplant recipients were of similar ages (8-10 weeks) with equal numbers of males and females distributed among the experimental groups. Fully chimeric sickle or normal mice were followed for a year after transplantation.