Evidence of Lysosomal β-Hexosaminidase Enzymatic Activity Associated with Extracellular Vesicles: Potential Applications for the Correction of Sandhoff Disease

Extracellular vesicles (EVs) can be isolated from biological fluids and cell culture medium. Their nanometric dimension, relative stability, and biocompatibility have raised considerable interest for their therapeutic use as delivery vehicles of macromolecules, namely nucleic acids and proteins. Deficiency in lysosomal enzymes and associated proteins is at the basis of a group of genetic diseases known as lysosomal storage disorders (LSDs), characterized by the accumulation of undigested substrates into lysosomes. Among them, GM2 gangliosidoses are due to a deficiency in the activity of lysosomal enzyme beta-hexosaminidase, leading to the accumulation of the GM2 ganglioside and severe neurological symptoms. Current therapeutic approaches, including enzyme replacement therapy (ERT), have proven unable to significantly treat these conditions. Here, we provide evidence that the lysosomal beta-hexosaminidase enzyme is associated with EVs released by HEK cells and that the EV-associated activity can be increased by overexpressing the alpha-subunit of beta-hexosaminidase. The delivery of EVs to beta-hexosaminidase-deficient fibroblasts results in a partial cross-correction of the enzymatic defect. Overall findings indicate that EVs could be a source of beta-hexosaminidase that is potentially exploitable for developing therapeutic approaches for currently untreatable LSDs.