Differential endothelial gap junction expression in venous vessels exposed to different hemodynamics.

After being anastomosed with the artery, vein graft is exposed to abruptly increased hemodynamic stresses. These hemodynamic stresses may change the profile of endothelial gap junction expression as demonstrated in the artery, which may subsequently play active roles in physiological adaptation or pathophysiological changes of the vein grafts. We investigated the endothelial expression of gap junction in the venous vessels exposed to different hemodynamic stresses. Immunocytochemical analysis of the endothelial Cx expression was performed by observing the whole mounts of inferior vena cava (IVC) of aortocaval fistula (ACF) rats or IVC-banded ACF rats using confocal microscope. Immunocytochemical analysis demonstrated that in the endothelium of the native vein, the gap-junctional spot numbers (GJSNs) and the total gap-junctional areas (TGJAs) of Cx40 and Cx43 were lower than those of the thoracic aorta and that Cx37 was hardly detectable. In the IVCs of ACF rats, which were demonstrated to be exposed to a hemodynamic condition of high flow velocity and low pressure, the GJSNs and the TGJAs of all three Cxs were increased. In the IVCs of IVC-banded ACF rats, which were exposed to a hemodynamic condition of high pressure and low flow velocity, the GJSNs and the TGJAs of Cx37 increased markedly and those of Cx40 and Cx43 remained without significant changes. In conclusion, the endothelial expressions of gap junctions in the native veins were lower than those of the arteries. When exposed to different hemodynamic stresses, the gap junctions were expressed in specific patterns.

Degradation of the internal elastic laminae in vein grafts of rats with aortocaval fistulae: potential impact on graft vasculopathy.

The internal elastic lamina (IEL) of vein grafts may be modified when exposed to arterialized hemodynamics. We investigated changes of the IEL in the inferior vena cava (IVC) of rats with aortocaval fistulae (ACF). In the IVC of ACF rats, both a markedly increased flow velocity and a mildly increased pressure were demonstrated. In the lower segment where hemodynamic changes were prominent, neointimal hyperplasia was prominently found. The IEL of the IVC in sham-operated rats, observed by confocal microscopy, was composed of parallel elastic fibers. In ACF rats, the IEL degenerated progressively after surgery. The elastic fibers were stretched and gradually became sparse, a change that was more prominent in the lower segment. Eight weeks after surgery, the IEL hardly existed in some areas of the lower segment. Electron microscopy revealed decreased densities and diameters of elastic fibers. Reverse transcriptase-polymerase chain reaction analysis revealed an up-regulation of potent elastases, cathepsins K and S, and matrix metalloproteinase-2 in the IVC of ACF rats. Results of immunohistochemical studies localized cathepsin expression predominantly to the luminal endothelium lining the IEL, suggesting involvement of elastinolysis in the degradation of the IEL. We demonstrated the degradation of the IEL in the vein graft of ACF rats, especially in the segment exposed to prominent hemodynamic changes. IEL degradation may contribute to the development of neointimal hyperplasia in vein grafts.

Thrombosed arteriovenous fistula for hemodialysis access is characterized by a marked inflammatory activity.

BACKGROUND: Thrombosis is the dominant cause of failure of arteriovenous fistulas for hemodialysis access. Vascular inflammation, an important pathologic change in various human vascular diseases, may be involved in the thrombotic process of arteriovenous fistulas. METHODS: The inflammatory activities of 23 thrombosed and 13 non-thrombosed stenotic arteriovenous fistulas were compared by investigating the contents of macrophages and lymphocytes, and the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) using immunohistochemistry method. The expression of matrix metalloproteinase (MMP)-2 and MMP-9, which play important roles in thrombosis of human coronary artery, was also investigated. The immunoreaction results were characterized using a semiquantitative scoring system. RESULTS: The macrophage and lymphocyte contents of the thrombosed group were abundant, and markedly greater than those of the non-thrombosed group (P < 0.001 and P = 0.001, respectively). The infiltration of macrophages and neovasculature were spatially closely correlated. The expressions of VCAM-1, IL-6, and TNF-alpha, but not ICAM-1, were significantly higher in the thrombosed group (P = 0.031, P = 0.010, P < 0.001, and P= 1.000, respectively). The expression of MMP-2 was not different in either groups (P = 0. 344). Differential expression of MMP-9 by macrophages near the vascular lumen, but not those distant from the lumen, was observed in most thrombosed specimens. CONCLUSION: This study demonstrated that the thrombosed arteriovenous fistula was characterized by marked inflammation. We hypothesize that the preferential expression of MMP-9 at luminal edge may cause disruption of the anticoagulant endothelial barrier and contribute to luminal thrombosis of arteriovenous fistulas.

Three-dimensional reconstruction of the rabbit atrioventricular conduction axis by combining histological, desmin, and connexin mapping data.

BACKGROUND: The 3D structure of the atrioventricular conduction axis incorporating detailed cellular and molecular composition, especially that relating to gap-junctional proteins, is still unclear, impeding mechanistic understanding of cardiac rhythmic disorders. METHODS AND RESULTS: A 3D model of the rabbit atrioventricular conduction axis was reconstructed by combining histological and immunofluorescence staining on serial sections. The exact cellular boundaries, especially those between transitional cells and atrial myocardium, were demarcated by a dense and irregular desmin-labeling pattern in conductive myocardium. The model demonstrates that the atrioventricular conduction axis is segregated into 2 connecting compartments, 1 predominantly expressing connexin45 (compact node and transitional cells) and the other predominantly coexpressing connexin43 and connexin45 (His bundle, lower nodal cells, and posterior nodal extension). The transitional zone shows unique features of spatial complexity, including a bridging bilayer structure (a deep transitional zone connecting with a superficial atrial-transitional overlay) and asymmetrical continuity (wider atrial-transitional interfaces and shorter atrial-axial distances in the hisian portion than in the ostial portion). In the latter compartment, the His bundle, lower nodal cells, and posterior nodal extension form a continual axis and longitudinal transitional-axial interface. CONCLUSIONS: Key findings of the present study are the demonstration of a distinct anatomical border between transitional and atrial cells, connection between transitional cells and both lower nodal cells and posterior nodal extension, and distinctive connexin expression patterns in different compartments of the rabbit atrioventricular conduction axis. These features, synthesized in a novel 3D model, provide a structural framework for the interpretation of nodal function.

Highly increased cell proliferation activity in the restenotic hemodialysis vascular access after percutaneous transluminal angioplasty: implication in prevention of restenosis.

BACKGROUND: The effect of percutaneous transluminal angioplasty (PTA) in the treatment of hemodialysis vascular access stenosis is attenuated by a high restenosis rate, which results mainly from neointimal hyperplasia. Cellular proliferation is one of the most important biological mechanisms involved in neointimal hyperplasia and may be a potential target of intervention to prevent restenosis. METHODS: We investigated the activity of cellular proliferation of restenotic lesions by means of immunohistochemistry, using an antibody to the proliferating cell nuclear antigen. Specimens from 10 primary stenotic and 20 restenotic lesions of 30 Brescia-Cimino fistulae were obtained during revision. RESULTS: The proliferation index of the restenotic group was strikingly significantly greater than that of the primary stenotic group (intima, P < 0.001; media, P = 0.001). Proliferation indices of patients with diabetes in the restenotic group were significantly higher than those of patients without diabetes (intima, P = 0.028; media, P = 0.002). In the restenotic group, proliferation indices correlated negatively with the interval from PTA to restenosis (intima, r = -0.741; P < 0.001; media, r = -0.589; P = 0.006) and positively with the number of PTAs per lesion (intima, r = 0.754; P < 0.001; media, r = 0.506; P = 0.004). CONCLUSION: We show markedly high cellular proliferation activity in early restenotic lesions of arteriovenous fistulae. These findings indicate that adjunctive antiproliferative therapy is mandatory in preventing restenosis after PTA, especially in patients with diabetes.

Association between a novel 11-base pair deletion mutation in the promoter region of the scavenger receptor class B type I gene and plasma HDL cholesterol levels in Taiwanese Chinese.

OBJECTIVE: Scavenger receptor class B type I (SR-BI) is a multiligand cell-surface receptor that mediates the selective uptake of lipid from HDL cholesterol (HDL-C) into cells. This study hypothesized an association between functional variants in the promoter region of SR-BI gene and HDL-C levels. METHODS AND RESULTS: We identified 2 novel mutations in the SR-BI gene promoter region by using single-strand conformation polymorphism. One mutation was an 11-bp CCCCGCCCCGT deletion mutation from positions -140 to -150 relative to the transcription start site, corresponding to an Sp1 binding site; the other was a C-->T substitution at position -142. Twenty-six of 690 unrelated subjects were heterozygous for the -140 to -150 deletion mutation, and the allele frequency in this population was 0.02. This study showed that the deletion variant prevented binding of Sp1 to this region of the SR-BI promoter and effectively reduced transcriptional activities in HepG2 cells. Notably, the -140 to -150 deletion mutation was significantly associated with increased HDL-C levels and explained approximately 0.5% of the variation in HDL-C levels in this population. CONCLUSIONS: A genetic variant at the SR-BI gene promoter region might explain a significant proportion of individual differences in HDL-C levels among Taiwanese Chinese. Our results require further replication in an independent population.