IN VIVO TRACKING OF NEURAL STEM CELLS AND THEIR PROGENY BY LENTIVIRAL VECTORS: EVALUATION OF THE POTENTIAL CONTRIBUTION TO THE THERAPY OF INHERITED NEURODEGENERATIVE DISORDERS

Metachromatic Leukodystrophy (MLD) is a severe neurological disorder due to a defect in the gene coding for the Arylsulfatase A (ARSA) enzyme. Absence of ARSA activity leads to accumulation of sulfatide within lysosomes of oligodendrocytes in the central nervous system (CNS) and within Schwann cells in the peripheral nervous system. Subsequently, death of the affected cells leads to the demyelination ,characteristic of this pathology. In its more severe form the disease leads to infirmity and, soon after the beginning of the symptoms, to death. There is no therapy available. Gene therapy could be a therapeutic approach for this disease. We recently demonstrated that a single intracranial injection of a lentiviral vector expressing the ARSA gene into the brain parenchyma of the murine model of MLD results in long-term expression of active enzyme in a large sector of the brain with reversion of the disease phenotype and life-long protection from the pathology. Among the mechanisms potentially involved in the spreading of the therapeutic effect, one must consider the possibility that neural stem cells transduced at the injection site could provide a source of a gene corrected progeny capable to migrate to distant diseased areas. The neural stem cells are undifferentatied cells that are present throughout the brain and that have not yet turned into specialized nerve cells. With proper stimulation these cells are capable both of dividing and of differentiating into mature cells. The aim of this project is to assess the influence of gene-mediated correction of the metabolic defect in driving repair through expansion, differentiation, and migration of these genetically corrected neural stem cells and their progeny. This study will shed light on the fundamental biology of stem cell and could have tremendous implications for the design of new gene therapy strategies of neurodegenerative disorders.