Three weeks of SMC CYB5R3 knockdown has no effect on cardiopulmonary hemodynamics or cardiac morphology in AS chimeras. (A) Study design for testing role of VSM CYB5R3 on hemodynamics and cardiac remodeling in AS chimeras. Cyb5r3^fl/flMyh11-CreER^T2 and Cyb5r3^wt/wtMyh11-CreER^T2 mice were lethally irradiated (500-550 rad twice) and transplanted with BM (2-4 million cells) from AS donor mice at 5 to 10 weeks of age to create AS/R3^KD and AS/R3^WT chimeras, respectively. At 8 to 10 weeks posttransplantation, peripheral blood was sampled to test engraftment to donor Hb phenotype. Chimeras testing 80% or more engraftment to AS phenotype, assessed by Hb electrophoresis, were fed a tamoxifen diet ad libitum for 2 weeks, and thereafter switched back to regular chow and aged for an additional 3 weeks before measurement of hemodynamics by RV microcatheterization. At 3 weeks CYB5R3 knockdown (solid line), animals were 5 weeks AS phenotype (dashed timeline) and a total age of 19 to 24 weeks. Complete blood counts were assessed at 8 to 10 weeks posttransplant, before and after tamoxifen diet (day −1 and day 14) and again at time of RV catheterization. No differences were noted between AS/R3^KD (blue bar) and AS/R3^WT (red bar) chimeras for RVmaxSP (n = 9-10) (B), heart rate (HR; n = 9-10) (C), RV weight normalized to tibia length (RV/tibia, n = 12-13) (D), LV+S weight normalized to tibia length (LV+S/tibia, n = 12-13) (E), RV end diastolic pressure (n = 9-10) (F), mPAP (n = 9-10) (G), RV dP/dT min (H), RV dP/dT max (n = 9-10) (I), and RV contractile index (n = 9-10) (J). The mean ± SEM is represented.