Live-cell Raman imaging of Pompe disease reveals extensive sarcoplasmic accumulations of precipitated glycogen

Abstract Pompe disease is a genetic myopathy characterised by inadequate levels of lysosomal acid α-1,4-glucosidase (GAA). This deficiency leads to the abnormal accumulation of glycogen in lysosomes, primarily affecting skeletal muscle cells. As research and treatment options progress, accurate methods for evaluating glycogen storage are crucial. We employed Raman spectroscopy to analyse glycogen accumulation in primary muscle cells from patients with late-onset Pompe disease (LOPD) and healthy individuals. Our findings indicated a significant increase in glycogen in Pompe-derived muscle cells compared to controls, with unique glycogen signatures detected at the subcellular level. Notably, glycogen existed in two forms: small, round stores encased in lipids, recognised as lysosomes, and larger, more loosely defined areas of cytoplasmic glycogen. Moreover, precipitated glycogen was also noted. These results provide new insights into glycogen localisation and condition in Pompe disease, serving as a valuable tool for assessing therapeutic approaches targeting glycogen storage disorders.