Treatment of lysosomal storage disorders: Cell therapy and gene therapy

Most lysosomal storage diseases have central nervous system (CNS) involvement. No effective treatment is available at present. We investigated the usefulness of brain-directed gene therapy and cell therapy using mouse models of lysosomal storage diseases. For gene therapy to the CNS, a recombinant adenovirus encoding beta-galactocerebrosidase gene was injected into the cerebral ventricle of neonatal twitcher mice, a murine model of Krabbe disease. Improvements in neurological symptoms and a prolonged lifespan were observed. Brain activity of beta-galactocerebrosidase was increased significantly and the concentration of a cytotoxic metabolite, psychosine, was decreased. Pathological observations of the brain were also improved in treated twitcher mice. For cell therapy to the CNS, a neural stem cell line derived from human fetal brain was genetically engineered to overexpress beta-glucuronidase and transplanted into the cerebral ventricles of neonatal MPS VII mice, a model of beta-glucuronidase deficiency. Transplanted human neural stem cells were found to integrate and migrate in the host brain and to produce large amounts of beta-glucuronidase. Brain contents of the substrate of beta-glucuronidase were reduced and widespread clearing of lysosomal storage was observed in treated MPS VII mice. These data suggest that brain-directed gene/cell therapy may be useful in the treatment of neurological alterations in lysosomal storage diseases.