Figure 1.
High Expression of FXN-HA in Cardiomyocytes Is Associated with Impaired Succinate Dehydrogenase (SDH) Enzymatic Activity despite Functional Rescue of Mck Mice Treated with AAVRh.10-CAG-hFXN-HA
(A–C) Histological analysis of heart tissue sections collected from the Mck mice treated at 5 weeks of age with the AAVRh.10-CAG-hFXN-HA vector and sacrificed at 12 weeks. Representative images are from the Mck mouse treated with 5 × 1013 vg/kg and expressing the highest level of hFXN-HA (10,927 ng/mg) and from another Mck mouse treated with 2.5 × 1013 vg/kg and with lower hFXN-HA level (695 ng/mg). For controls, heart tissue sections from 12-week-old NaCl-injected wild-type (WT) mice and 9-week-old untreated Mck mice were also analyzed. The corresponding vector copies per diploid genome (VCN) and tissue concentration in human FXN ([hFXN] in ng per mg of total protein) are reported. The same time exposure was used for all animals. (A) Co-staining and co-localization analysis of hFXN-HA overexpression and SDH enzymatic activity. Acquisitions of a single microscopic field at low and high magnification are shown, to compare the distribution of hFXN-HA expression hotspots and SDH activity impairment. (B) Hematoxylin and eosin (H&E) and wheat germ agglutinin (WGA) staining. (C) DAB-enhanced Perls labeling of iron deposits with methyl green counterstaining. (D–F) Longitudinal echocardiography analysis of the same Mck mice, represented here as individual kinetics. Data are represented as mean ± SD for WT control mice (n = 7) and untreated Mck mice (n = 10). For untreated Mck mice, historical data were plotted. Statistical analyses are reported in Table S2. (D) Left ventricle (LV) shortening fraction (SF). (E) Cardiac blood output (CO) measured at the aorta and normalized to body weight (BW). (F) LV mass normalized to BW. See also Figures S1A–S1C for the extended echocardiography analysis of this cohort of mice. See also Figures S1D–S1H for the echocardiography follow-up, until 25 weeks of age, of a second cohort of Mck mice treated at 5 weeks of age at 5 × 1013 vg/kg. Figure partially adapted from Belbellaa et al.15