to have direct effects on nerve cells, the results of these experiments suggest a possible contribution of direct effects of HGF on nerve integrity.

HGF also acts as a neurotrophic factor.56,57 We examined the therapeutic effects of HGF on brain injury in a rat permanent middle cerebral artery occlusion model because an ideal therapeutic approach to treat ischemia may have both aspects of enhancement of collateral formation and prevention of neuronal death.58−61 Gene transfer of the HGF plasmid into the brain by injection into the cerebrospinal fluid via the cisterna magna resulted in a significant decrease in the infarcted brain area after 24 hours of ischemia.61 Consistently, the neurological deficit was significantly attenuated in rats transfected with the HGF gene at 24 hours after the ischemic event. Stimulation of angiogenesis was also detected in rats transfected with the HGF gene compared with controls. Of importance, no cerebral edema or destruction of the blood-brain barrier was observed in rats transfected with the HGF gene. In particular, the reduction of brain injury by HGF may provide a new therapeutic option to treat cerebrovascular disease.

Gene therapy will be useful for treatment of many diseases, including peripheral arterial disease, myocardial infarction, and heart transplantation rejection among others. Since the first federally approved human gene therapy protocol started on 14 September 1990 for adenosine deaminase deficiency, more than 4000 patients have been treated using gene therapy approaches. Although there are still many unsolved issues in the clinical application of gene therapy, it now appears to be not far from reality and it is time to take a hard look at practical issues that will determine the real clinical potential, including further innovations in gene transfer methods, well-defined disease targets, cell-specific targeting strategies, and effective and safe delivery systems.

Acknowledgments

This work was partially supported by a Grant-in-Aid from the Program for Promotion of Fundamental Studies in Health Sciences of the National Institute of Biomedical Innovation (NIBIO), the Organization for Pharmaceutical Safety and Research, a Grant-in-Aid from the Ministry of Public Health and Welfare, a Grant-in-Aid from the Japan

380 R. Morishita & T. Ogihara

Promotion of Science, and through Special Coordination Funds of the Ministry of Education, Culture, Sports, Science and Technology, the Japanese Government.

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