Approaches to Gene Therapy in the CNS: Intracerebral Grafting of Fibroblasts Genetically Modified to Secrete Nerve Growth Factor
Considerable effort in recent years has been applied towards the development of methods for the genetic modification of mammalian cells to correct disease phenotypes in vivo, an approach that has been named gene therapy (1). In an ideal gene therapy system, the new genetic information would be applied directly to the affected tissue. This direct approach has not yet been attempted, because the current methods of gene transfer are limited to replicating cells. Because of this and other technical limitations, approaches to gene therapy in animal models of human disease have relied on removing mitotic cells from the target tissue, genetically modifying them in culture, and then returning the cells to the animal. Most of these studies have used genetic transducing vectors derived from murine retroviruses to introduce foreign genes (transgenes) into target cells, because retrovirus vectors offer several advantages over other current methods of gene transfer (2): 1) infection by retrovirus vectors is extremely efficient for a broad range of cell types and species, with up to 100% of the target cells expressing the transgene; 2) the viral genomes have a relatively large capacity for foreign DNA; and 3) infection generally causes little or no genetic or metabolic damage to recipient cells. Other methods of gene transfer, which utilize biochemical or physical means to introduce transgenes into cells, suffer from serious limitations in comparison. The first methods developed involve incubating cells with DNA complexed with DEAE-dextran (3) or calcium phosphate (4). More recent methods use direct microinjection (5), electric fields (electroporation) (6), liposomes (lipofection) (7), and tungsten microprojectiles (8).
KeywordsGene Therapy Nerve Growth Factor Cholinergic Neuron Medial Septum Lysosomal Storage Disease
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