Effect of fluid dynamics on decellularization efficacy and mechanical properties of blood vessels.

Decellularization of blood vessels is a promising approach to generate native biomaterials for replacement of diseased vessels. The decellularization process affects the mechanical properties of the vascular graft and thus can have a negative impact for in vivo functionality. The aim of this study was to determine how detergents under different fluid dynamics affects decellularization efficacy and mechanical properties of the vascular graft. We applied a protocol utilizing 1% TritonX, 1% Tributyl phosphate (TnBP) and DNase on porcine vena cava. The detergents were applied to the vessels under different conditions; static, agitation and perfusion with 3 different perfusion rates (25, 100 and 400 mL/min). The decellularized grafts were analyzed with histological, immunohistochemical and mechanical tests. We found that decellularization efficacy was equal in all groups, however the luminal ultrastructure of the static group showed remnant cell debris and the 400 mL/min perfusion group showed local damage and tearing of the luminal surface. The mechanical stiffness and maximum tensile strength were not influenced by the detergent application method. In conclusion, our results indicate that agitation or low-velocity perfusion with detergents are preferable methods for blood vessel decellularization.

Prediction of the frictional behavior of mammalian tissues against biomaterials.

Frictional and adhesion properties are important characteristics to be assessed in the development of new materials for biological applications, particularly for medical devices such as catheters. In this work a new computational method that predicts frictional and adhesive forces is presented. A multi-asperities adhesion model, based on the JKR theory, coupled with a Monte Carlo method was employed, together with a three components friction model. This takes into account interfacial adhesion, asperities deformation and viscous lubricant film shearing action. We have estimated the frictional coefficients of silicone and polyurethane (common materials in catheters) against aorta and vena cava. In order to do this, we have measured the surface properties of the two blood vessels tissues, such as surface energy components, asperity height distribution and asperity radius of curvature. These data have not been previously reported. The predictions in both the dry and in lubricated (with blood) cases are in very good agreement with our published experimental data of the same materials/tissue combinations.

Postmortem blood cadmium, lead, and mercury concentrations: comparisons with regard to sampling location and reference ranges for living persons.

This study's goal was to determine cadmium (Cd), lead (Pb), total mercury (THg), and inorganic mercury (IHg) levels in human cadavers to compare measured levels with established reference ranges for living persons and to determine whether blood levels varied with time from death to sample collection or by body collection site. Subjects (n = 66) recruited from the Fulton County Medical Examiner's Office in Atlanta, GA, were 20 years of age or older, had no penetrating trauma, no obvious source of environmental contamination of the vasculature, and had whole blood accessible from the femoral (F) site, the cardiac (C) site, or both. Geometric mean results were as follows: 2.59 microg/L F-Cd; 11.81 microg/L C-Cd; 1.03 microg/L F-THg; 2.01 microg/L C-THg; 0.29 microg/L F-IHg; 0.49 microg/L C-IHg; 1.78 microg/dL F-Pb; and 1.87 microg/dL C-Pb. Both F- and C-Cd levels as well as C-THg levels were significantly higher than reference values among living persons (C- and F-Cd, p < 0.0001 and C-THg, p = 0.0001, respectively). Based on regression modeling, as the postmortem interval increased, blood Cd levels increased (p < 0.006). Postmortem blood Cd concentrations were elevated compared to population values and varied with respect to sampling location and postmortem interval.

Differential expression of pancreatitis-associated protein and thrombospondins in arterial versus venous tissues.

BACKGROUND/AIMS: Arteries and veins modulate cardiovascular homeostasis and contribute to hypertension pathogenesis. Functional differences between arteries and veins are based upon differences in gene expression. To better characterize these expression patterns, and to identify candidate genes that could be manipulated selectively in the venous system, we performed whole genome expression profiling of arteries and veins. METHODS: We used the CodeLink platform and the major artery (thoracic aorta) and vein (caudal vena cava) of the rat. RESULTS: The most prominent difference was pancreatitis-associated protein (PAP1), expressed 64-fold higher in vena cava versus aorta. Expression of mRNA for thrombospondins (TSP-1, TSP-4) was greater than 5-fold higher in veins versus arteries. Higher mRNA expression of TSP-1, TSP-2, TSP-4 and PAP1 in vena cava versus aorta was confirmed by PCR. Immunohistochemical analysis of tissue sections qualitatively confirmed a higher expression of these proteins in vena cava versus aorta. CONCLUSION: This is the first gene array study of adult rat arterial and venous tissues, and also the first study to report differences in inflammatory genes between arteries and veins. Data from these studies may provide novel insights into the genetic basis for functional differences between arteries and veins in health and disease.

Suprahepatic vena cava manipulative bleeding alleviates hepatic ischemia-reperfusion injury in rats.

BACKGROUND: Little is known about time course and peak level of reactive oxygen species in suprahepatic vena cava after liver ischemia-reperfusion. OBJECTIVE: To determine time course and peak level of reactive oxygen species in suprahepatic vena cava after liver ischemia-reperfusion. To focus on the effects of suprahepatic vena cava manipulative bleeding on the hepatic ischemia-reperfusion injury in rat model. METHODS: In experiment Part I, blood was taken from suprahepatic vena cava and infrahepatic vena cava for malondialdehyde detection at different time points after reperfusion. Furthermore, we treated the experimental rats in Part II by suprahepatic vena cava manipulative bleeding or infrahepatic vena cava manipulative bleeding at 10 min after reperfusion. RESULTS: In experiment Part I, malondialdehyde concentration in suprahepatic vena cava elevated obviously with time and peaked at 10 min after reperfusion. The numbers of accumulated polymorphonuclear neutrophils was significantly increased in ischemia-reperfusion group from 10 min after reperfusion, compared with sham-operated group. In Part II, 2% of body weight suprahepatic vena cava manipulative bleeding with blood transfusion at 10 min after reperfusion significantly decreased circulating malondialdehyde, tumour necrosis factor-alpha, endothelin-1, hyaluronic acid, alanine aminotransferase, aspartate aminotransferase levels and polymorphonuclear neutrophil infiltrations in the liver. The 7-day survival rate of this group was 68.75% (11/16) which was significantly higher than other groups. CONCLUSIONS: We provided the first evidence that 2% of body weight suprahepatic vena cava manipulative bleeding with blood transfusion at 10 min after reperfusion significantly prevented liver ischemia-reperfusion injury.

Expression profiling identifies 147 genes contributing to a unique primate neointimal smooth muscle cell phenotype.

OBJECTIVE: This study represents the first in an effort to systematically characterize different intimas by using expression array analysis. METHODS AND RESULTS: We compared smooth muscle cells (SMCs) of the neointima formed 4 weeks after aortic grafting with those from normal aorta and vena cava from cynomolgus monkeys. Hybridization to cDNA arrays identified subsets of 147 and 45 genes differentially expressed in the neointima versus the aorta and vena cava, respectively. The expression pattern differentiating neointima from aortic SMCs was characterized largely by suppression. Only 13 genes were induced in the neointima: 7 encoded matrix proteins (6 collagens and 1 versican) and 2 encoded inducers of matrix synthesis (osteoblast-specific factor-2/Cbfa1 and connective tissue growth factor). The genes suppressed most in the neointima included the regulator of G-protein signaling-5, SPARClike-1/hevin, and nonmuscle myosin heavy chain-B. A smaller gene set differentiated the neointima from the vena cava. Most were induced (39 of 45 genes), and overlap with the neointima-aorta set was significant (10 of 13 genes). Array results were validated with Northern analysis, in situ hybridization, or immunohistochemistry. CONCLUSIONS: These data underscore the importance of matrix synthesis in neointimal maturation, and novel genes, newly associated with neointimal SMCs (regulator of G-protein signaling-5 and osteoblast-specific factor-2/Cbfa1), have raised new hypotheses regarding the pathogenesis of intimal hyperplasia.

Cardiac musculature of the cranial vena cava in the common tree shrew (Tupaia glis).

Cardiac musculature of the cranial vena cava in the common tree shrew (Tupaia glis) was examined by light and transmission electron microscopy. The common tree shrew has well developed cardiac myocyte layers in the tunica media of the cranial vena cava, extending from the right atrium to the root of the subclavian vein. Because the common tree shrew belongs to a primitive group of mammals, the occurrence of cardiac musculature in the cranial vena cava may be a common feature in lower mammals. The development of this musculature indicates that active contraction of the cranial vena cava wall occurs in this species. Electron micrographs showed the typical ultrastructure of myocytes and nerve endings. These observations suggest that this musculature may serve as a regulatory pump for the return of venous blood to the right atrium and as a blood reservoir system under conditions of rapid heart rate. Additionally, the presence of atrial natriuretic polypeptide (ANP) was also demonstrated in the myocytes of the vena cava immunohistochemically. These findings show that the cardiac endocrine organ for ANP develops even in the principal veins including the cranial vena cava.

von Willebrand factor in plasma, platelets, and selected tissues of ferrets.

By standard laboratory methods the presence and activity of von Willebrand factor (vWF) was detected and characterized in the ferret (Mustela putorius furo); vWF in plasma, platelets, and selected tissues (thoracic aorta, cranial vena cava, thoracic portion of caudal vena cava, and lung) was documented. Activity, antigenic concentration, plasma multimeric distribution, and localization within tissues were similar to those features in other species. Two differences were apparent: multimeric distribution of platelet vWF was skewed toward the smaller molecular weight multimers, and mucous goblet, but not ciliated, cells of the bronchial epithelium stained positive for vWF. Larger molecular weight multimers were not released subsequent to administration of 1-deamino-8-D-arginine-vasopressin. The ferret may be a useful animal model in studying the role of vWF in hemostasis, thrombosis, and atherosclerosis. In particular, the role of small molecular weight multimers found in ferret platelets may provide further insight into the roles of platelet vWF multimeric distribution, platelet adhesion, and thrombosis.

Calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY) levels are elevated in plasma and decreased in vena cava during endotoxin shock in the rat.

Calcitonin gene-related peptide (CGRP), a potent vasodilator, and neuropeptide Y (NPY), a potent vasoconstrictor and potentiator of norepinephrine-induced vasoconstriction, were examined in an animal model of endotoxin shock. Gram-negative bacterial endotoxin (lipopolysaccharide B from Salmonella enteritidis) was administered as a bolus (16.7 mg/kg, i.v.) to conscious, unrestrained rats, previously cannulated for blood pressure measurements and blood withdrawal. At 30 min, endotoxin caused 35-40 mm Hg drop in mean arterial pressure and significant increases in heart rate and plasma levels of glucose and lactate. By 3 hr, blood pressure had returned to near normal levels and remained normal until cardiovascular collapse at 4-6 hr (approximately 70% of the rats). Endotoxin elevated plasma CGRP levels by fourfold at 30 min and 22-fold at 3 hr. Of the organs tested, only vena cava showed significant decreases in CGRP levels. Endotoxin also elevated plasma NPY levels by 67% and decreased NPY levels in adrenal gland and vena cava at 30 min and 3 hr. The data suggest that both CGRP and NPY are released into the circulation during development of endotoxin shock in the rat. NPY may contribute to the compensatory mechanism, tending to bring arterial pressure back to normal levels during intermediate stages of endotoxemia. CGRP, because of its extremely high potency as a hypotensive agent, may contribute to the hypotension at both early and late stages during pathogenesis of endotoxin shock.