Recent advances in gene therapy of GI and liver diseases.

Gene therapy toward the digestive organs has made substantial progress. The strategies applied include ex vivo and in vivo delivery. The ex vivo pathway does not require a tissue-specific vector while the in vivo pathway is advantageous for tissues not obtainable or hard to culture. The specific vectors of gene delivery for the liver and gastrointestinal tract include (1) viral vectors: retrovirus, adenovirus, and adeno-associated virus are the three most common currently used. (2) liposomes: when cationic substances are incorporated, DNA can be coated on the surface and carried into cells. (3) receptor-mediated gene therapy: natural and physiological and tissue-specific ligands were incorporated and modified to carry foreign DNA into the cells. They are tissue-specific and relatively nontoxic. The innovations focus on the prolongation of gene expression and a more efficient gene delivery.