Gene therapy/cell therapy for lysosomal storage disease

Lysosomal storage diseases (LSD) are considered to be appropriate disorders for gene therapy/cell therapy. We are attempting to treat one of these dis orders using a mouse model, the Sly mouse. This is an authentic model for h uman beta-glucuronidase deficiency, MPS VII. We have carried out two types of experimental protocols; in vivo gene therapy and ex vivo gene therapy us ing Sly mice. For in vivo gene therapy, we produced a recombinant adenoviru s that expresses human beta-glucuronidase and administered this to Sly mice intravenously. The beta-glucuronidase activities in liver and spleen were elevated to 40% and 20%, respectively, of the heterozygote enzyme level at day 16. Expression persisted for at least 35 days. Pathological abnormaliti es improved in these tissues and urinary glycosaminoglycan excretion was re duced in treated animals. ex vivo gene therapy/cell therapy was carried out using macrophages obtained by cultivation of bone marrow cells. Non-myeloa blated macrophages from normal mice were transplanted into Sly mice, and af ter 7 days donor cells had populated the liver and spleen. The human beta-g lucuronidase (HBG) activity was increased in liver and spleen, although the se enzyme activities subsequently fell by 38 days. The pathological improve ment in Sly mice was evident at day 38 post transplantation. Furthermore, t he macrophages from Sly mice were treated with retrovirus/adenovirus vector expressing HBG activity and the glycosaminoglycan accumulation was markedl y decreased after 5 weeks. These data suggest that genetically engineered m acrophage transplantation may be a very useful form of ex vivo gene therapy for lysosomal storage diseases. We also discuss the possible treatment of the CNS involvement in lysosomal storage diseases by gene therapy/cell ther apy.