Although generally not as efficient as viral vectors, such nonviral systems have the potential advantages of being less toxic, nonrestrictive in cargo DNA size, potentially targetable, and easy to produce in relatively large amounts. More important, lipidic vectors generally lack immunogenicity, allowing repeated in vivo transfection using the same vector. The use of proteins like active recombinase to stimulate searching for homology and forming stable DNA heteroduplexes between oligonucleotides and chromosomal DNA may improve the gene targeting events. The chimeric molecules have been demonstrated to be effective in the alteration of single nucleotides in episomal and genomic DNA in cell culture, as well as genomic DNA of cells in situ. This is a potentially powerful strategy for gene repair for the multitude of hepatic genetic diseases caused by point mutations.
Stem cells are multi-purpose embryonic cells from which each organ is originally formed.
Inserting corrective genes into these cells, once they are identified could prove more effective than using viruses and other vectors for DNA insertion. A number of genetic disorders result in irreversible damage to the fetus before birth. In these cases, as well as when patients may benefit from therapy before symptoms are manifested, in utero gene therapy could be beneficial. Some successes with in utero gene transfer have been reported in animals. But stem cell technology is in its infancy, and a number of technical and ethical questions need to be answered before any clinical tests are allowed.