Ex vivo transfection of pulmonary artery segments in lung isografts

Gene Therapy: Will the Promise of Optimizing Lung Allografts Become Reality?

Lung transplantation is the definitive therapy for patients living with end-stage lung disease. Despite significant progress made in the field, graft survival remains the lowest of all solid organ transplants. Additionally, the lung has among the lowest of organ utilization rates-among eligible donors, only 22% of lungs from multi-organ donors were transplanted in 2019. Novel strategies are needed to rehabilitate marginal organs and improve graft survival. Gene therapy is one promising strategy in optimizing donor allografts. Over-expression or inhibition of specific genes can be achieved to target various pathways of graft injury, including ischemic-reperfusion injuries, humoral or cellular rejection, and chronic lung allograft dysfunction. Experiments in animal models have historically utilized adenovirus-based vectors and the majority of literature in lung transplantation has focused on overexpression of IL-10. Although several strategies were shown to prevent rejection and prolong graft survival in preclinical models, none have led to clinical translation. The past decade has seen a renaissance in the field of gene therapy and two AAV-based in vivo gene therapies are now FDA-approved for clinical use. Concurrently, normothermic ex vivo machine perfusion technology has emerged as an alternative to traditional static cold storage. This preservation method keeps organs physiologically active during storage and thus potentially offers a platform for gene therapy. This review will explore the advantages and disadvantages of various gene therapy modalities, review various candidate genes implicated in various stages of allograft injury and summarize the recent efforts in optimizing donor lungs using gene therapy.

Gene delivery into ischemic myocardium by double-targeted lipoplexes with anti-myosin antibody and TAT peptide

The treatment of myocardial ischemia using gene therapy is a rather novel but promising approach. Gene delivery to target cells may be enhanced by using double-targeted delivery systems simultaneously capable of extracellular accumulation and intracellular penetration. With this in mind, we have used low cationic liposomes-plasmid DNA complexes (lipoplexes) modified with cell-penetrating transactivating transcriptional activator (TAT) peptide (TATp) and/or with monoclonal anti-myosin monoclonal antibody 2G4 (mAb 2G4) specific toward cardiac myosin, for targeted gene delivery to ischemic myocardium. In vitro transfection of both normoxic and hypoxic cardiomyocytes was enhanced by the presence of TATp as determined by fluorescence microscopy and ELISA. The in vitro transfection was further enhanced by the additional modification with mAb 2G4 antibody in the case of hypoxic, but not normoxic cardiomyocytes. However, we did not observe a synergism between TATp and mAb 2G4 ligands under our experimental condition. In in vivo experiments, we have clearly demonstrated an increased accumulation of mAb 2G4-modified TATp lipoplexes in the ischemic rat myocardium and significantly enhanced transfection of cardiomyocytes in the ischemic zone. Thus, the genetic transformation of normoxic and hypoxic cardiomyocytes can be enhanced by using lipoplexes modified with TATp and/or mAb 2G4. Such complexes also demonstrate an increased accumulation in the ischemic myocardium and effective transfection of hypoxic cardiomyocytes in vivo.

Ischemia-reperfusion-induced lung injury

Ischemia-reperfusion-induced lung injury is characterized by nonspecific alveolar damage, lung edema, and hypoxemia occurring within 72 hours after lung transplantation. The most severe form may lead to primary graft failure and remains a significant cause of morbidity and mortality after lung transplantation. Over the past decade, better understanding of the mechanisms of ischemia-reperfusion injury, improvements in the technique of lung preservation, and the development of a new preservation solution specifically for the lung have been associated with a reduction in the incidence of primary graft failure from approximately 30 to 15% or less. Several strategies have also been introduced into clinical practice for the prevention and treatment of ischemia-reperfusion-induced lung injury with various degrees of success. However, only three randomized, double-blinded, placebo-controlled trials on ischemia-reperfusion-induced lung injury have been reported in the literature. In the future, the development of new agents and their application in prospective clinical trials are to be expected to prevent the occurrence of this potentially devastating complication and to further improve the success of lung transplantation.

Recent progress in gene delivery using non-viral transfer complexes

The delivery of genetic material into cells is a field that is expanding very rapidly. Non-viral delivery methods, especially ones that focus on the use of chemical agents complexed with genetic material, are the focus of this mini-review. More-recent uses of known transfection agents such as poly(ethylenimine), poly(L-lysine), and various liposomes are discussed, and some novel approaches (both chemical and methodical) are reviewed as well. A very brief look at how non-viral gene delivery research is being aimed at the clinic is also included.