Fig. 3

Dual COX/SDH histological staining to detect respiratory chain deficiency attributable to mtDNA deletions in vastus lateralis muscle. a Cross-sectional images from a representative control subject demonstrating uniform, normal-COX staining (left) and a COPD patient with respiratory-deficient fibers highlighted (red arrows, middle) as well as the lack of staining (right) reflecting depletion of mitochondria in muscle fibers. b Proportions of COX-normal (COX⁺/SDH⁺), COX-deficient (COX⁻/SDH⁺), and mitochondria-depleted (COX^low/SDH^low) fibers presented as individual percentages in controls (n = 14) and COPD subjects (n = 21). (Inset) Higher proportion of abnormal fibers (combined COX⁻/SDH⁺ and mitochondria-depleted fibers) in COPD patients (957 of 8136 fibers) compared to control subjects (158 of 5182 fibers). Graphs show mean ± SEM (***P < 0.001). Scale bar is 50 μm