Gene therapy approaches for mucopolysaccharidosis iiia
- Autores: Alberto Ruzo Matias
- Directores de la Tesis: Fàtima Bosch i Tubert (dir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2010
- Idioma: español
- Tribunal Calificador de la Tesis: Josep Torrent Farnell (presid.), Mercedes Pineda Marfá (secret.), Odile Cohen-Haguenauer (voc.)
- Materias:
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- Resumen
Mucopolysaccharidosis type IIIA (MPSIIIA) is a inherited lysosomal storage disease (LSD) caused by the deficiency of the sulfamidase enzyme, resulting in intralysosomal accumulation of the glycosaminoglycan (GAG) heparan sulfate, which represents the molecular signature of the disease. MPSIIIA is usually diagnosed in the first years of life, when the pathological accumulation of GAG becomes symptomatic. Severe neurodegeneration and other non-neurological alterations lead to death of the affected subjects during adolescence. No effective treatment for MPSIIIA is currently available, and enzyme replacement therapy is typically not effective in improving neurological symptoms of LSDs because of the inability of the therapeutic proteins to cross the blood brain barrier (BBB).
Here we used adeno-associated viral (AAV) vectors to transfer the sulfamidase gene to either the skeletal muscle or the liver of MPSIIIA mice, and tested the efficacy of the approach in reverting the disease phenotype in MPSIIIA mice at 2 months of age, when high levels of GAG accumulation are already present. The intramuscular administration of AAV vectors resulted in only partial correction of the peripheral disease phenotype and no effect on the GAG accumulation in the brain. In contrast, using an AAV8 vector expressing sulfamidase under the control of a liver-specific promoter, we were able to reach very high levels of serum sulfamidase activity. Complete correction of the lysosomal accumulation of GAG was observed in all somatic tissues analyzed. Remarkably, we also documented a 50% reduction of the GAG accumulation throughout the entire brain; this correlated with a slight improvement in the histological alterations of the brain in AAV-treated MPSIIIA mice compared with untreated controls.
Aiming to achieve a further correction of the neurological pathology, we tested the new serotype AAV9, which has recently been described to be highly efficient in crossing the BBB and transducing both neurons and astrocytes in the CNS after systemic delivery. Intravenous administration of sulfamidase-expressing AAV9 vectors resulted in a widespread reversal of lysosomal accumulation in nearly all brain regions, which was parallel to a reduction of neuroinflammatory markers and an improvement of neuromotor alterations of MPSIIIA mice. Intravenous AAV9 treatment also corrected GAG accumulation in all somatic tissues.
In order to decrease the dose of the vector to be administered while maintaining enough CNS correction, we locally delivered AAV9 vectors carrying the sulfamidase gene to the cerebrospinal fluid of MPSIIIA mice, by direct injection into the cisterna magna. Animals treated intracisternally with low doses of the AAV9 vector also displayed complete CNS correction. This treatment mediated normalization of GAG storage in all brain areas, concomitant with a complete reversal of the lysosomal accumulation in neurons, astrocytes and microglia, and the absence of neuroinflammatory process. Intracisternally treated animals showed significant correction of somatic GAG accumulation, due to leakage of the vector to systemic circulation.
Thus, the results described herein may constitute the basis for the development of a new non-invasive therapeutic alternative for MPSIIIA patients, but it can also pave the way for developing novel gene transfer approaches for other similar LSDs involving not only somatic, but also neurologic pathology.
