Figure 7. FXN mutations in Friedreich’s ataxia are associated with pulmonary vascular disease and endothelial senescence.

(A) Lungs from age- and sex-matched FRDA (n = 3) versus healthy donors (n = 9) stained with CD31⁺ (brown) and hematoxylin counterstain (blue). Scale bar: 50 μm. Quantification of relative pulmonary arteriolar wall thickness in FRDA lungs in comparison to controls. Two-tailed Student’s t test with error bars that reflect weighted averages ± SD. (B–I) Phenotypic experiments performed in male age-matched iPSC-ECs from healthy controls versus patients with FRDA. (B) Colorimetric BrdU incorporation assay (n = 4/group). (C) Chemiluminescent caspase-3/7 activity (n = 3/group). (D) Immunoblot quantification of apoptosis resistance BCL2 protein (n = 3/group). (E and F) Relative CDKN2A transcript and p16^INKA protein expression in male FRDA iPSC-ECs compared with healthy controls (n = 3/group). (G) Representative light microscopic images of β-galactosidase (blue) in male iPSC-ECs. Scale bar: 200 μm. (H) Immunoblot of phosphorylated (γH2AX) and ubiquitinated (Ub-γH2AX) forms of H2AX in FRDA patient iPSC-ECs compared with control (n = 3/group). (I) Proximity ligation assay followed by confocal microscopy showing quantification of associated POLD1 and POLD3 subunits of DNA Pol δ in FRDA iPSC-ECs compared with healthy controls (n = 190 nuclei/group). Scale bars: 10 μm. The same β-actin blot was used as a control for panels D and K. Two-tailed Student’s t test with error bars that reflect mean ± SD.