P75. A gene therapy for a gene mutation in human iPS cell using helper-dependent adenoviral vector

Retinitis pigmentosa (RP) is one of the hereditary neurodegenerative diseases, which finally causes photoreceptor cell death. Several kinds of mutations in genes, e.g. rhodopsin, peripherin and cGMP phophodiesterase, are reported to cause the disease, however, the fundamental therapeutic approach has not established yet. Recent progress in the stem cell science has led us to a possibility of applying cell transplantation for this disease. Embryonic stem (ES) cells were the first candidate cell source of the transplantation; however, there were some concerns in using ES cells; immunological responses and ethical issues. On the other hand, induced pluripotent stem (iPS) cells may overcome these problems. Patients may use their own somatic cells to obtain cells for transplantation. However, there is another concern; if the disease were caused by genetic reason, the mutation would be inherited into iPS cells, and would cause the degeneration again. Thus, we try to cure the gene mutation in iPS cells before differentiation and transplantation. It has been reported that gene targeting of human ES or iPS cells is quite difficult compared with that of mouse ES or iPS cells. However, we have recently reported that introducing targeting construct using helper-dependent (HD) adenoviral vector resulted in effective recombination rate. We established iPS cells from skin cells of a RP patient who has a mutation in rhodopsin gene allele. We try to replace the wild type rhodopsin allele into the mutated rhodopsin allele of the iPS cells using a HD adenoviral vector. We also attempt to differentiate the iPS cells into rod photoreceptor cells by the methods reported by other groups, and injected into subretinal space of the eyes of the model mice of retinal degenerative disease. This study could be applicable to the regenerative medicine not only for RP patient, but also for the patients of any kind of neurodegenerative diseases caused by genetic reasons.