Autophagy impairment is associated with enhanced satellite cell activation in muscle biopsies from younger late-onset Pompe disease patients

Late-onset Pompe disease (LOPD) is caused by α-glucosidase (GAA) deficiency, leading to glycogen accumulation resulting in progressive muscular weakness and respiratory insufficiency. Glycogen overload, vacuolation, and autophagic accumulation are the histological hallmarks of the disease. However, markers capable of tracking the progression of LOPD across different disease stages remain insufficiently characterized. We performed a comprehensive myopathologic analysis of eleven LOPD muscle biopsies from untreated patients (age range 7-69 years) and compared them to eleven biopsies from histologically normal age-matched controls. The cohort was divided into two groups considering the age at muscle biopsy below or above 33 years: (1) younger LOPD and (2) older LOPD, respectively. We quantified periodic acid-Schiff-positive fibers, vacuolated fibers using a novel vacuolation severity score, autophagic markers, and satellite cell behavior. We observed prominent vacuolization, glycogen overload, and autophagic bodies in younger LOPD. Moreover, this group showed higher regenerative features accompanied by an increase in the percentages of active satellite cells compared to older LOPD. In conclusion, autophagy impairment correlates with enhanced satellite cell activation in muscle biopsies from younger LOPD patients. These findings suggest that stimulating satellite cell activity may hold therapeutic potential for addressing LOPD progression in its early stages.