Gene therapy strategies to facilitate organ transplantation

In vivotransfection rat small intestine K-cell with pGIP/Ins plasmid by DOTAP liposome

Gene therapies to produce insulin in diabetic patients have been considered for several years. Genetic engineering of ectopic insulin production and secretion in autologous non-beta-cells has been tested in different tissues. Recently, gut K-cells have been shown to express glucokinase, the glucose sensor of pancreatic beta-cells. K-cells are responsible for the secretion of the glucose-dependent insulinotropic peptide (GIP). Transfection of K-cells by a specific plasmid to produce insulin correlated to glucose level is being considered. Cationic liposomes are non-viral gene delivery to lung, spleen, liver and intestinal cells. DOTAP-GIP/Ins plasmid complex was used for transfection of K-cells in vivo. RT-PCR assay of human insulin mRNA revealed that the transfection of insulin gene by DOTAP liposome is an efficient tool. The genetic engineering of ectopic insulin production and secretion in autologous non-beta-cells is an appropriate method. The potential of the transmission of a constructed plasmid, which contains human insulin gene under the control of GIP promoter, to gut K-cells could be considered for treatment of diabetes.

In vivo molecular imaging characterizes pulmonary gene expression during experimental lung transplantation

Experimental gene therapy is a promising strategy to prevent ischemia-reperfusion (I/R) injury and allograft rejection after lung transplantation, and methods will eventually be needed to characterize pulmonary transgene expression in vivo in humans. Therefore, we studied positron emission tomography (PET) as a means of performing in vivo molecular imaging in rodent models of lung transplantation. Rats were transfected endotracheally with adenovirus encoding a fusion gene of a mutant Herpes simplex virus-1 thymidine kinase and the green fluorescent protein gene (the former serving as an imaging reporter gene). Twenty-four hours after transfection, lungs were transplanted in groups representing normal transplantation, I/R injury and acute allograft rejection. Imaging was obtained either 24 h after transplantation to study reperfusion injury or 4 days after transplantation to study graft rejection. After imaging, lungs were excised and analyzed for thymidine kinase activity. Imaging detected transgene expression in transplanted lungs even in the presence of acute rejection or I/R injury. The PET imaging signal correlated with in vitro lung tissue assays of thymidine kinase activity (r(2) = 0.534). Thus, noninvasive molecular imaging with PET is a feasible, sensitive and quantitative method for characterizing pulmonary transgene expression in experimental lung transplantation.

Prolonged islet allograft survival by adenovirus-mediated transfer of sICAM-1/Ig immunoadhesin gene

Administration of monoclonal antibodies directed against the leukocyte function-associated antigen 1 (LFA-1)-intercellular adhesion molecule 1 (ICAM-1) pathway showed that these costimulatory molecules play a key role in allograft rejection. Here, adenoviral gene transfer of an immunoadhesin, sICAM-1/Ig, was used to prolong islet allograft survival in a mouse model, and was compared with anti-LFA-1 antibody administration. A replication-deficient recombinant adenoviral vector encoding a chimeric protein, in which the extracellular domain of ICAM-1 is covalently linked to the C(H)2-C(H)3 domains of an IgG1, was used for gene transfer. C3H murine islets were transplanted under the kidney capsule of streptozotocin-induced diabetic BALB/c mice. Experimental groups underwent adenovirus vector administration either in vivo (intravenous injection) or ex vivo (gene transfer to the graft), and control groups received either an empty vector (Ad.null) or an anti-LFA-1 monoclonal antibody. Graft survival was significantly prolonged by in vivo sICAM-1/Ig gene transfer as compared with both Ad.null and anti-LFA-1 groups, but not by ex vivo gene transfer. Histological examination of the grafts showed the presence of a mononuclear infiltrate within functioning grafts, suggesting that the homing of alloreactive T cells was not altered. In vitro T cell proliferation experiments indicated that sICAM-1/Ig exerted agonist effects on both CD4(+) and CD8(+) T cells.

Molecular therapeutics of liver disease

Fundamental advances in biomedical research will revolutionize the prevention and treatment of liver disease during the early twenty-first century. Recent progress in gene-, cell-, and recombinant protein-based therapeutics will contribute to this revolution, although formidable obstacles currently prevent the clinical application of these novel therapies. Eventually, these obstacles will be overcome, and molecular therapeutics of liver disease will become a clinical reality. As a result, the new millennium will be a very interesting time to practice hepatology.