917. Engineered Cell Therapy for Sustained Local Myocardial Delivery of Non-Secreted Proteins

Abstract

Top of pageAbstract The increasing prevalence of congestive heart failure is spurring the development of novel therapy - stem cell therapy. Arguably stem cell therapy directed at trying to regenerate damaged myocardial tissue would be benefited by having the ability to locally deliver specific transcription factors and other usually non-secreted proteins to direct stem cells differentiated into cardiac myocytes and induce cardiac myocyte hypertrophy. Unfortunately, the local delivery of transcription factors is limited by the fact that transcription factors are not normally secreted nor taken up into neighboring cells. In an attempt to develop a strategy for delivering transcription factors to myocardial tissue, we determined if cell based therapy is an effective means of delivering normally cellular bound proteins to the surrounding myocardial tissue. The herpes simplex virus type 1 (HSV-1) tegument protein VP22 has been shown to mediate intercellular protein trafficking to mammalian cells and to localize a VP22 chimeric protein to the nucleus. These characteristics make VP22 an intriguing cargo carrying protein for the delivery of functional proteins to myocardial tissue via a cell based gene transfer strategy. In order to evaluate the efficacy of VP22 fusion protein intercellular trafficking in the heart, fusion constructs of VP22 and the enhanced green fluorescence protein (eGFP) were prepared and stably transfected into rat cardiac fibroblasts (RCF). In vitro studies where untransfected RCF were co-cultured with RCF stably expressing GFP or VP22-eGFP showed that there was a fourteen-fold greater number of untransfected RCF cells being GFP positive 48 h later when co-culture was done with VP22-eGFP RCF. In the rat model, transplantation of VP22-eGFP expressing RCF led to VP22-eGFP fusion protein delivery to an area of myocardial tissue that was 20 fold greater than that observed when eGFP RCF were transplanted. This area appeared to reach a steady state between 7 and 10 days after transplantation. The VP22-eGFP area consisted of eGFP positive endothelium, smooth muscle cells and cardiac myocytes with delivery to an area of approximately 1 mm2 of myocardial tissue. Our data provide the first insight into the feasibility and the effectiveness of VP22 intercellular trafficking combined with autologous cell transplantation in myocardial tissue. Our data suggests that a strategy using VP22 as a cell-based therapeutic tool for the treatment of cardiac disease or directing stem cell differentiation may be feasible.