Efficient transgene expression from naked DNA delivered into an arterio-venous fistula model for kidney dialysis.

BACKGROUND: Patients with kidney failure frequently require the formation of an arterio-venous fistula (AVF) in which a vein is connected to an artery resulting in arterialization of the vein to allow adequate blood flow into an external 'artificial kidney'. In most patients, neo-intimal hyperplasia (NIH) ensues, causing narrowing and subsequent occlusion of the vein, leading to significant morbidity. The cellular events causing venous NIH may serve as ideal targets for molecular-based therapies. However, therapeutic gene delivery into the vascular system is seriously impeded by problems related to the low efficacy and toxicity of targeted viral vector delivery. MATERIALS AND METHODS: To explore the feasibility of a plasmid-based vascular gene delivery system, we established a rat AVF model that develops NIH. Plasmids encoding for reporter or therapeutic genes were delivered into the blood vessels at the time or after AVF formation. RESULTS: Intra-luminal injection of plasmid into the AVF resulted in extensive and long-term reporter gene expression at the venous limb mainly at the site of NIH formation. Transgene expression was confined to endothelial cells and myofibroblasts that migrate inwards from the adventitia and form the NIH lesion. There was no detrimental tissue reaction to plasmid delivery, contrasting with the severe inflammatory response observed after adenovirus infection. Intra-vascular delivery of a plasmid carrying the endothelial nitric oxide synthase gene resulted in sustained production of nitric oxide, previously shown to mitigate NIH formation. CONCLUSIONS: These findings open the possibility of vascular transduction with naked DNA bearing therapeutic genes in areas prone to NIH to ameliorate vein graft pathologies using simple and clinically applicable vector delivery methods.

A mouse model for sleeve gastrectomy: applications for diabetes research.

INTRODUCTION: Discovery of enhanced glucose tolerance following bariatric surgery has sparked renewed interest in the investigation of unchartered underlying pathways of glucose homeostasis. Delineation of this pathway may ultimately be the first step in the creation of a novel therapy for type II diabetes. Nevertheless, the technical complexity and formidable nature of these surgeries coupled with the fragile nature of small rodents has made the creation of a mouse model to study these effects incredibly challenging. We have created a simplified sleeve gastrectomy mouse model to study the effects of bariatric surgery on glucose tolerance and beta cell proliferation. METHODS: Nineteen mice were randomized to undergo either sleeve gastrectomy (SG) (9) or sham operation (SH) (10). Weight and serum glucose were measured three times weekly and serum insulin measurements and pancreatic harvest were performed at the time of sacrifice. Five mice from each group were sacrificed after one week and the remainder sacrificed after one month. RESULTS: Survival of mice was 100% for both groups. The SG group demonstrated an initial drop in weight and serum glucose as compared to SH, which normalized by one month following surgery. Serum insulin levels and rate of beta cell proliferation were similar in both groups after one week and one month. CONCLUSION: The simplified sleeve gastrectomy is a technically straightforward, low-mortality technique for creating a bariatric mouse model which most faithfully replicates bariatric surgery performed in humans. This model can be a valuable tool to investigate the glucose tolerance and beta cell effects of bariatric surgery.

Specific induction of tie1 promoter by disturbed flow in atherosclerosis-prone vascular niches and flow-obstructing pathologies.

Nonlaminar flow is a major predisposing factor to atherosclerosis. Yet little is known regarding hemodynamic gene regulation in disease-prone areas of the vascular tree in vivo. We have determined spatial patterns of expression of endothelial cell receptors in the arterial tree and of reporter gene constructs in transgenic animals. In this study we show that the endothelial cell-specific receptor Tie1 is induced by disturbed flow in atherogenic vascular niches. Specifically, tie1 expression in the adult is upregulated in vascular bifurcations and branching points along the arterial tree. It is often confined to a single ring of endothelial cells functioning as sphincters and hence experiencing the steepest gradient in shear stress. In aortic valves, tie1 is asymmetrically induced only in endothelial cells encountering changes in flow direction. Disturbance of laminar flow by a surgical interposition of a vein into an artery led to induction of tie1, specifically in the region where the differently sized vessels adjoin. In pathological settings, tie1 expression is specifically induced in areas of disturbed flow because of the emergence of aneurysms and, importantly, in endothelial cells precisely overlying atherosclerotic plaques. Hemodynamic features of atherosclerotic lesion-prone regions, recreated in vitro with the aid of a flow chamber with a built-in step, corroborated an upregulated tie1 promoter activity only in cells residing where flow separation and recirculation take place. These defined promoter elements might be harnessed for targeting gene expression to atherosclerotic lesions.