Arteriosclerosis in rat aortic allografts: early changes in endothelial integrity and smooth muscle phenotype.

BACKGROUND: Transplant arteriosclerosis remains a limiting factor for the long-term survival of transplanted organs and effective treatment is lacking. A rat model of aortic allografts was used to analyze this process by electron microscopy and further characterize the phenotypic properties of the cells involved. METHODS: A segment of abdominal aorta was transplanted orthotopically from Fischer to Lewis rats. The animals were killed 1-12 weeks after the operation (four to six rats/group), and the grafts were removed and processed for microscopy. RESULTS: The first changes (1 week) included detachment of endothelial cells, adhesion of degranulating platelets to the subendothelial matrix, and modification of smooth muscle cells in the media. The latter process was distinguished by loss of myofilaments and formation of a prominent endoplasmic reticulum and Golgi complex (shift from contractile to synthetic phenotype). Subsequently, modified smooth muscle cells invaded the intima. In parallel, lymphocytes and monocytes/macrophages infiltrated the intima and adventitia. The neointima grew in size by cell proliferation and production of extracellular matrix (4-8 weeks). Smooth muscle cells and monocytes/macrophages in the neointima and media were also noted to accumulate cytoplasmic lipid droplets and eventually turn into foam cells and die. Within the lipid-rich cell remnants, calcification occurred. Finally (12 weeks), the growth in mass of the intimal lesions ceased and in some places reformation of an endothelial lining was detected. Few viable smooth muscle cells remained in the media and the inflammatory infiltrate in the adventitia was reduced. CONCLUSIONS: These observations highlight the importance of early changes in endothelial integrity and smooth muscle phenotype in the development of allograft vascular disease and form the basis for a partly modified model of the cellular mechanisms in this process.

Fucoidan improves the renal blood flow in the early stage of renal ischemia/reperfusion injury in the rat.

It has been shown that monoclonal anti-P-selectin antibody administration protects renal function in an ischemic model of acute renal failure. This study was designed to evaluate the effect of administration of fucoidan, P-selectin inhibitor, on reduction in renal blood flow induced by ischemia/reperfusion injury in the rat. Experiments were performed on male Wistar rats weighting 35-400 g. The systemic blood pressure (mm Hg) (BP) and renal blood flow (RBF) were monitored continuously and renal vascular resistance (RVR) was calculated. After 20 min period of stabilization animals (6 rats in each group) received one of the following agents administered by continuous i.v. infusion during 165 min: 1 mg/kg of body weight of fucoidan (F1), 10 mg/kg of fucoidan (F10), 100 mg/kg of fucoidan (F100), 10 mg/kg of heparin (H), or 0.9% NaCl solution (control). After 15 min of drug administration the renal vessels of the both kidney were occluded with vascular clamps for 60 min. There were no significant changes in the initial values of RBF, RVR and BP between groups. None procedure affected significantly BP during all experiments. In F10 RBF returned to the initial values in 70th min of reperfusion and did not change up to 90th min. This value was significantly higher than respective value in the control group. In F1 group RBF in 90th min was also higher than in the control group, but it was not statistically significant. The dose of heparine and fucoidan used in the H and F100 groups failed to preserve RBF during reperfusion. In the present study we found that administration of fucoidan--P-selectin inhibitor, increases significantly postischemic renal blood flow and may have renoprotective activity.

Kidney transplantation in recipients with atherosclerotic iliac vessels.

The influence of atherosclerotic lesions of hypogastric and iliac arteries of kidney recipients on intraoperative surgical technique and one-year graft and patient survival was investigated. Among 1553 transplanted kidneys atherosclerotic lesions which required surgical intervention were found in 201 (12.9%) recipients. Thrombendarterectomy (TEA) of hypogastric artery was performed in 142 cases with subsequent anastomosis with the renal artery. Occlusion of hypogastric artery was an indication for renal graft artery to external iliac artery anastomosis in 32 patients. Atherosclerotic changes in external and common iliac artery required TEA in 25 patients and anastomosis between renal artery and external artery was performed. Ilio-iliac bypass or Y-graft simultaneously with kidney transplantation were performed in two cases. One-year survival rate of allografts and patients was 88% and 93%, respectively. No grafts were removed due to kidney artery thrombosis. We conclude that hypogastric artery after TEA provides adequate blood supply to kidney graft.

Overexpression of CD39/nucleoside triphosphate diphosphohydrolase-1 decreases smooth muscle cell proliferation and prevents neointima formation after angioplasty.

BACKGROUND: Growing evidence implicates the involvement of extracellular nucleotides in the regulation of platelet, leukocyte, endothelial cell (EC) and vascular smooth muscle cell (VSMC) phenotype and function. Within the quiescent vasculature, extracellular nucleotides are rapidly hydrolyzed by CD39, the dominant endothelial nucleoside triphosphate diphosphohydrolase (NTPDase-1). However, vascular CD39/NTPDase-1 activity is lost in EC activated by oxidative stress or proinflammatory mediators, and upon denudation of the endothelium following balloon injury. The consequent increase in extracellular nucleotide concentrations triggers signaling events leading to prothrombotic responses and increased VSMC proliferation. OBJECTIVES: To investigate the effect of overexpressed CD39/NTPDase-1 in injured aorta. METHODS: Using adenoviral-mediated gene transfer we expressed CD39/NTPDase-1 in mechanically denudated rat aortas. We measured intima formation by morphometry and VSMC proliferation by the [(3)H]-thymidine incorporation assay. RESULTS: Targeted expression of CD39 in injured vessels increased NTPDase activity (from 2.91 +/- 0.31 to 22.07 +/- 6.7 nmols Pi mg(-1) protein, 4 days after exposure to the adenovirus) and prevented the formation of neointima. The thickness of the intimal layer in injured aortas exposed to Ad-CD39 was 26.2 +/- 3.9 microm vs. 51.8 +/- 6.1 microm and 64.4 +/- 22.2 microm (P < 0.001) in vessels treated with Ad-beta-gal and saline, respectively. Moreover, targeted expression of CD39/NTPDase-1 caused a 70% (P < 0.01) decrease in proliferation of VSMC isolated from transduced rat aortas as compared with VSMC derived from control vessels. CONCLUSIONS: The presented data suggest that increasing CD39/NTPDase-1 activity in VSMC could represent a novel therapeutic approach for the prevention of stenosis associated with angioplasty and other occlusive vascular diseases.