Endovascular Injury Research Articles

The Estrogen Effects on Endothelial Repair and Mitogen-Activated Protein Kinase Activation Are Abolished in Endothelial Nitric-Oxide (NO) Synthase Knockout Mice, but Not by NO Synthase Inhibition by N-Nitro- l-arginine Methyl Ester

We have previously shown that estrogen exerts a vasoprotective effect by accelerating reendothelialization after perivascular artery injury through activation of the estrogen receptor alpha. Because 17beta-estradiol (E2) is known to increase the bioavailability of nitric oxide, in this study, we used the same perivascular model to characterize the role of the endothelial nitric oxide synthase (eNOS) pathway in reendothelialization. Surprisingly, we found that the stimulatory effect of E2 on reendothelialization was not altered following pharmacological inhibition of nitric-oxide synthase enzymatic activity by N-nitro-L-arginine methyl ester, whereas it was abolished in eNOS-deficient (eNOS-/-) mice. This discrepancy between eNOS gene inactivation and the pharmacological inhibition of eNOS was confirmed in a classical model of endovascular injury. When assessing the involvement of eNOS in short-term membrane-associated signaling events induced by E2, we found that E2 stimulated phosphorylation of extracellular signal-regulated kinase 1/2 in isolated perfused carotid arteries from wild-type mice in the absence or presence of N-nitro-l-arginine methyl ester, whereas this stimulation was abolished in carotid arteries from eNOS-/- mice. Similar results were obtained in primary cultures of mouse aortic endothelial cells. These data reveal an original and unexpected role of eNOS, in which its presence but not its enzymatic activity appears to be a determinant for estrogen signaling in the endothelium. The consequences of this novel function of eNOS with respect to vascular diseases should be explored.

Abstract 397: Perivascular Fat Tissue Plays An Atheroprotective Role In Neointimal Formation After Angioplasty

Background: Obesity is associated with chronic inflammation and increases risk for cardiovascular disease and type 2 diabetes. Recently visceral, as opposed to subcutaneous, fat tissue confers the most cardio-metabolic risk. The aim of the present study is to determine whether perivascular fat tissue contributes to neointimal formation after angioplasty. Methods and Results: An endovascular injury was induced in the femoral arteries of wild-type mice without or with removal of perivascular adipose tissue. Neointimal area and Neointima/Media ratio were markedly enhanced by removal of perivascular adipose mice (P=0.05). Visceral fat tissue (VAT) or subcutaneous fat tissue (SAT) were harvested from GFP-transgenic mice and transplanted around the injured femoral without endogenous perivascular fat. Neointimal formation was markedly enhanced in the VAT-transplantation group compared with the SAT-transplantation group (P=0.05). Real-time PCR analysis showed that the transplanted VAT had significantly higher proinflammatory cytokines, TNF alpha, IL-6, MCP-1, and PAI-1, mRNA levels than the SAT (P=0.05). Next, the effects of VAT and SAT on smooth muscle cell proliferation were investigated in vitro. Conditioned medium was prepared from extracts of VAT and SAT. Cell proliferation was measured by MTS assay. VAT stimulated smooth muscle cell proliferation compared with SAT (P=0.05). Conclusions: The present study demonstrates that perivascular adipose tissue protects neointimal formation after angioplasty. VAT stimulates neointimal formation and smooth muscle cell proliferation, probably by secreting proinflammatory cytokines, at least in part. Adipocytokines, particularly secreted from perivascular fat tissue, may play a role in the pathogenesis of neointimal formation after angioplasty.

Abstract 1041: Endovascular Injury Affects Adipocytokine Profile Of The Periadventitial Adipose Tissue

Background: Adipose tissue secretes not only proinflammatory cytokines but also anti-inflammatory cytokines such as adiponectin. Arteries are surrounded by abundant periadventitial fat tissues, which have been suggested to play a role in maintenance of vascular homeostasis. Here, we investigated whether endovascular injury affects the profile of adipocytokines expressed by perivascular adipose tissue (PAT). Methods and Results: First, the femoral artery of C57BL/6 mice was overstretched by insertion of a large wire. Real-time PCR analysis revealed that wire injury markedly down-regulated adiponectin expression (0.64±0.09 fold, p<0.01) and up-regulated expression of proinflammatory cytokines, TNF alpha, IL-6, PAI-1, and MCP-1 (p<0.01) 1 day after overstretch within PAT. Neutrophils and macrophages accumulated in the adventitia surrounding the injury site at 1 day after the injury. Inflammation was associated temporally with the expression of mRNAs encoding inflammatory adipocytokines. Second, the iliac artery of Wistar rats was dilated percutaneously with a balloon for 1 minute. There were up-regulation of proinflammatory cytokines and down-regulation of adiponectin 1 and 3days after endovascular injury within PAT (p<0.05). Third, abdominal aortas removed from Wistar rat with PAT were dilated with a balloon PTCA catheter for 1 minute ex vivo. After stretching, aortas with PAT were cultured for 6 hours, and we observed increased synthesis of proinflammatory cytokines and decreased synthesis of adiponectin within PAT (p<0.05). Fourth, the stimulation of TNF alpha, which markedly increased in injured arteries, caused significant down-regulation of adiponectin expression and up-regulation of IL-6, PAI-1, and MCP-1 in 3T3L1-derived adipocytes (p<0.01). Conclusions: Angioplasty may induce the changes of perivascular cytokines expression. The accumulation of neutrophils and macrophages at PAT in injured arteries and/or increased proinflammatory expression of injured vascular arteries may reflect these proinflammatory activities of PAT. Increased proinflammatory cytokines and decreased anti-inflammatory cytokine adiponectin in PAT possibly may have a role in vascular remodeling following PTCA-mediated vascular injury.

Diverse Contribution of Bone Marrow–Derived Cells to Vascular Remodeling Associated With Pulmonary Arterial Hypertension and Arterial Neointimal Formation

Recent evidence suggests that bone marrow (BM)-derived cells may differentiate into vascular cells that participate in arterial repair and/or lesion formation. However, it remains uncertain whether BM-derived cells also can participate in vascular remodeling associated with pulmonary arterial hypertension. The BM of Sprague-Dawley rats was reconstituted with that of green fluorescent protein-transgenic rats. The BM-chimeric rats were injected intraperitoneally with 60 mg/kg monocrotaline after unilateral subpneumonectomy, and they concurrently underwent wire-mediated endovascular injury in femoral artery. After 28 days, they had elevated right ventricular systolic pressure (58.8+/-5.4 versus 20.4+/-2.4 mm Hg in sham-control; P<0.01). The pulmonary arterioles were markedly thickened, with an infiltration of green fluorescent protein-positive macrophages into the perivascular areas. The endothelium of pulmonary arterioles contained only a few green fluorescent protein-positive cells, and green fluorescent protein-positive cells were seldom detected as smooth muscle cells in the lesions of thickened pulmonary arterioles. In contrast, BM-derived smooth muscle-like cells could be readily detected in the thickened neointima and media of the wire-injured femoral artery. Moreover, intravenous injection of 1x10(8) BM cells from young rats had no beneficial effects on pulmonary hypertension, pulmonary arterial remodeling, or survival in the aged rats treated with monocrotaline plus unilateral subpneumonectomy. No injected BM cell was identified as an endothelial cell or a smooth muscle cell. These results suggest that BM-derived cells can participate in arterial neointimal formation after mechanical injury, whereas they do not contribute substantially to pulmonary arterial remodeling associated with monocrotaline-induced pulmonary arterial hypertension in the pneumonectomized rats.

Postinjury vascular intimal hyperplasia in mice is completely inhibited by CD34+ bone marrow-derived progenitor cells expressing membrane-tethered anticoagulant fusion proteins.

Coagulation proteins promote neointimal hyperplasia and vascular remodelling after vessel injury, but the precise mechanisms by which they act in vivo remain undetermined. This study, using an injury model in which the neointima is derived from bone marrow (BM)-derived cells, compared inhibition of tissue factor or thrombin on either BM-derived or existing vascular smooth muscle cells. Two transgenic (Tg) mouse strains expressing membrane-tethered tissue factor pathway inhibitor (TFPI) or hirudin (Hir) fusion proteins driven by an alpha smooth muscle actin (SMA) promoter were generated (alpha-TFPI-Tg and alpha-Hir-Tg) and the phenotype after wire-induced endovascular injury was compared with that in wild-type (WT) controls. WT mice developed progressive neointimal expansion, whereas injury in either Tg was followed by repair back to a preinjured state. This was also seen when WT mice were reconstituted with BM from Tg mice but not when Tgs were reconstituted with WT BM, in which injury was followed by slowly progressive neointimal expansion. Injection of CD34+ cells from Tg mice into injured WT mice resulted in the accumulation of fusion protein-expressing cells from day 3 onwards and an absence of neointimal hyperplasia in those areas. Neointimal development after wire-induced endovascular injury in mice was completely inhibited when BM-derived cells infiltrating the damaged artery expressed membrane tethered anticoagulant fusion proteins under an alpha-SMA promoter. These findings enhance our understanding of the pathological role that coagulation proteins play in vascular inflammation.

An Experimental Model for the Treatment of Lethal Bleeding Injury to the Juxtahepatic Vena Cava With Stent Graft

Juxtahepatic vein injuries present a high mortality rate. Our objectives were to develop an experimental model of endovascular lethal injury of the juxtahepatic inferior vena cava (JHIVC) and to evaluate its hemodynamic alterations; to treat the lesion with volume replacement, and a stent graft (SG); and to follow the animals after treatment. Twenty dogs were anesthetized and monitored [heart rate (HR), mean arterial pressure (MAP), vesical and peritoneal pressures], and submitted to a JHIVC endovascular injury. After volume replacement the dogs were divided into two groups: control (GI) and experimental (GII). GI was observed until death. GII was treated with SG and followed by Doppler ultrasound (DUS) and cavography for 4 (GIIA), and 8 weeks (GIIB), and then sacrificed and IVC and SG were analyzed. GI presented increased abdominal pressures, arterial hypotension, and death after 80 minutes. GII had a 100% survival rate till sacrifice, without clinical repercussions. At DUS and cavography all SG were patent, with monophasic pulsatile flow. On US, SG diameters after 2, 4, and 8 weeks did not show differences. On cavography IVC diameters presented no difference between groups GIIA and GIIB throughout the experiment. These data analyzed for the GII as a whole, showed statistically significant differences. Average lumen diameter reduction of SG was 27.43+/-20,00%. Pressure values in the IVC cranially, caudally to the SG, and inside the SG, did not show differences. In the IVC with the SG we observed a thicker neointima layer, and the injury in the media layer was covered with fibroconnective tissue. We developed an experimental dog model of endovascular lethal injury of the JHIVC with significant increase in abdominal pressures, and a mortality rate of 100%. The treatment of this lesion with SG resulted in a thickened neointima layer, and a 27% reduction in the JHIVC lumen diameter, without clinical repercussion, and with a 100% survival rate.

Assessment of Hemostatic Risk Factors in Predicting Arterial Thrombotic Events

Arterial thrombosis results from endovascular injury and, to a lesser extent, alterations in hemostatic equilibrium. Although multiple hereditary and acquired hemostatic risk factors have been described in the pathophysiology of venous thrombosis, the degree and type of abnormalities that contribute to arterial thrombosis are less well understood. Endothelial cell injury with the elaboration of proinflammatory mediators stimulates the process of arterial thrombosis. Although this is most often the result of endovascular injury attributable to atherosclerotic disease, other disease states can elicit a similar response as well. Similarly, once thrombosis has been initiated, variations in the activity of coagulation proteins and endogenous anticoagulants, as well as the kinetics of platelet aggregation, may alter the effectiveness of thrombus formation. Epidemiological studies have identified several acquired or inherited states that may result in endothelial damage or altered hemostatic equilibrium, thereby predisposing patients to arterial thrombosis. These include hyperhomocysteinemia, elevated C-reactive protein, antiphospholipid antibodies, elevated fibrinogen, Factor VII, plasminogen activator inhibitor-1 (PAI-1), hereditary thrombophilias, and platelet hyper-reactivity. This review explores our present understanding of these risk factors in the development of arterial thrombotic events. At present, the literature supports a role for hyperhomocysteinemia, elevated C-reactive protein, and elevated fibrinogen as risk factors for arterial thrombosis. Similarly, the literature suggests that lupus anticoagulants and, to a lesser extent, elevated titers of cardiolipin IgG antibodies predispose to arterial vascular events. In certain subsets of patients, including those with concomitant cardiac risk factors, <55 years of age, and women, hereditary thrombophilias such as carriership of the factor V Leiden and the prothrombin G20210A mutations may confer a higher risk of arterial thrombosis. However, the data on Factor VII, PAI-1, and platelet receptor polymorphisms are contradictory or lacking.

The neointimal response to endovascular injury is increased in obese Zucker rats.

Restenosis after revascularization procedures is accelerated in persons with type 2 diabetes. The current study tested the hypothesis that the neointimal response to endovascular injury is enhanced in female obese Zucker (OZ) rats, a model of type 2 diabetes. Animals were randomized to receive either a standard diet (SD) or a diabetogenic diet (DD) for 6 weeks. Four weeks later, balloon injury of the right common carotid artery was induced. All rats were euthanized 2 weeks after injury. Lean Zucker (LZ) rats served as controls. At the time of death, plasma glucose was elevated in OZ rats fed a SD (208 +/- 13 mg/dl) and a DD (288 +/- 21 mg/dl) compared to corresponding LZ rats (SD: 153 +/- 8; DD: 132 +/- 7 mg/dl). The ratio of high-density lipoprotein cholesterol (HDLc) to total cholesterol (Totc), an index of atherogenicity, was reduced in OZ rats on both diets (SD: 0.77 +/- 0.06; DD: 0.80 +/- 0.09) compared to LZ controls (SD: 1.11 +/- 0.02; DD: 1.20 +/- 0.05). Histomorphometric analysis of injured arteries showed that the intima to media (I : M) ratio was significantly increased in OZ (1.37 +/- 0.07) compared to LZ (0.79 +/- 0.08) rats. Elevations in plasma glucose and triglycerides (Tg) correlated positively and decreases in HDLc negatively with an increased I : M ratio. Administration of the DD did not further enhance the I : M ratio in LZ (0.87 +/- 0.06) or OZ (1.29 +/- 0.09) rats. These results suggest that neointima formation following endoluminal injury of the carotid artery is enhanced at an early stage in the development of diabetes mellitus.

Laser-light scattering, a new method for continuous monitoring of platelet activation in circulating fluid

We evaluated a novel technique of laser-light scattering (LLS) to detect platelet-volume changes continuously, reflecting platelet aggregation in circulating fluid. Carotid arteries from 20 dogs were mounted in a dual perfusion chamber. Balloon angioplasty (BA) was performed and arteries perfused with platelet-rich plasma (PRP). A He-Ne laser beam was passed through cuvettes connected to tubing draining the arteries. From the angle of incidence, the average volume of aggregates was measured by the ratio of scattering light at 1 to 5 degrees' spread on the diode array of a multichannel analyzer. Platelet volume varied linearly with the scattered light ratio at 1 to 5 degrees (y = −24.2 + 27.6 x [y = particle size, μm3; x = scattered light ratio at 1/5 degrees]). For comparison, we used an electronic particle counter (Coulter counter) to measure platelet volume. P-selectin expression was measured to confirm platelet activation. Comparing 10 uninjured and 10 BA-injured arteries, we found that platelet volume as measured with LLS increased from 21.6 ± 4.1 to 52.1 ± 12.5 μm3 (P <.003); as measured with the Coulter counter, it increased from 29.9 ± 2.4 to 62.3 ± 7.0 μm3 (P <.005). Six BA-injured arteries perfused with PRP and aspirin (0.2 mg/mL) were compared with six arteries treated with BA alone. The aspirin decreased platelet volume as measured with LLS from 56.2 ± 11.8 to 40.2 ± 12.7 μm3 (P <.01); the Coulter counter revealed a decrease from 51.9 ± 18.5 to 38.8 ± 14.2 μm3 (P <.001). Coulter counter and LLS results were correlated: r = 0.74, P <.05. The peak of P-selectin expression coincided with peak platelet volume. These data demonstrate that increases in circulating-platelet size stimulated by endovascular injury can be reliably and continuously monitored with the use of LLS. (J Lab Clin Med 2003;141:50-7)

Drotrecogin Alfa (Activated): The First Fda-Approved Treatment for Severe Sepsis

Drotrecogin alfa (activated) (Xigris, Eli Lilly and Company, Indianapolis, Ind) is a recombinant form of human activated protein C. It was approved by the Food and Drug Administration in the last quarter of 2001 for the reduction of mortality due to severe sepsis in adult patients who are at high risk of death (1). This is a unique indication. While many investigational drugs have been proposed as treatments for sepsis in the past, and several have even made it to clinical trials (2), only drotrecogin alfa (activated) has shown a survival benefit. The definition of sepsis given by the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference has 2 parts: infection and 2 of the 4 systemic inflammatory response syndrome (SIRS) criteria (temperature ≥38£C or s36£C, heart rate ≥90 beats/minute, respiratory rate ≥20 breaths/minute or PaCO2≤32 mm Hg, white blood cell count ≥12,000/μL or ≤4000/μL or >10% immature forms). The definition of severe sepsis includes the above plus organ dysfunction, hypoperfusion, or hypotension (3). This syndrome is a result of the body's systemic inflammatory and procoagulant responses to infection and is associated with significant morbidity and mortality (4, 5). While reports of the incidence of severe sepsis have varied, a recent study of the incidence and outcomes of severe sepsis in the USA yielded an estimate of 751,000 cases of severe sepsis per year (3 cases per 1000 population) (6, 7). Another study found confirmed severe sepsis in 6.3 per 100 intensive care unit patients, with an associated mortality of 56% (8). The average cost per case of severe sepsis was estimated at $22,100, representing an annual figure of $16.7 billion in the USA (7). During severe sepsis the proinflammatory mediators released, including tumor necrosis factor-alfa (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6), not only induce the systemic inflammatory symptoms that are seen in the SIRS response but are also capable of activating the coagulation cascade and inhibiting fi-brinolysis. The thrombin generated as coagulation occurs then acts to further stimulate multiple inflammatory pathways. This process leads to the sequelae of severe sepsis, including endo-vascular injury, multiorgan dysfunction, and death (9).

Adenovirus-mediated heme oxygenase-1 gene delivery inhibits injury-induced vascular neointima formation.

Recent studies have demonstrated that systemic pharmacological induction of heme oxygenase-1 (HO-1), the inducible isoform of the initial and rate-limiting enzyme for heme catabolism, attenuates neointima formation after experimental vascular injury. We have now investigated the ability of localized adenovirus-mediated HO-1 (Ad-HO-1) gene delivery to modify arterial remodeling after balloon angioplasty. Two weeks after balloon angioplasty in the rat carotid artery, elevated HO-1 protein was observed in the Ad-HO-1 arteries compared with those exposed to empty adenovirus (Ad-E) or to PBS. The arteries exposed to Ad-HO-1 exhibited significantly reduced neointimal area, medial wall area, neointimal area/medial wall area ratio, and neointimal thickness compared with arteries exposed to Ad-E. The Ad-E vessels showed subtle reductions in each morphometric parameter compared with PBS vessels. In a separate group of animals, concomitant treatment of Ad-HO-1 with the HO-1 inhibitor tin protoporphyrin completely restored each morphometric parameter to control levels. Arteries exposed to Ad-HO-1 demonstrated significantly increased TUNEL labeling of apoptotic nuclei and significantly decreased PCNA labeling of DNA synthesis in the medial wall 48 hours after injury. These results indicate that HO-1 represents an important in vivo vasoprotective mediator that is capable of attenuating the pathophysiological remodeling response to endovascular injury and suggest that HO-1 may be a novel target for the treatment of vascular disease.

The chemotactic and mitogenic effects of platelet-derived growth factor-BB on rat aorta smooth muscle cells are inhibited by basic fibroblast growth factor.

In response to endovascular injury, platelet-derived growth factor-BB (PDGF-BB) and basic fibroblast growth factor (bFGF) are released locally and modulate vascular smooth muscle cells (SMC) proliferation and migration within the vascular wall. The aim of the present in vitro study was to determine how rat aorta SMC respond to the simultaneous exposure to PDGF-BB and bFGF. In a modified Boyden chamber assay bFGF exhibited a dose-dependent effect to inhibit the chemotactic action of PDGF-BB. A comparable result was observed in proliferation assays. In contrast, MIP-1 beta, epidermal growth factor (EGF), fibronectin and acidic FGF (aFGF) did not inhibit the chemotactic effect of PDGF-BB. Denatured bFGF did not exert an inhibitory effect and neutralizing antibodies either to bFGF or to bFGF-receptor abolished the inhibition observed in the presence of bFGF. The role played by PDGF receptor alpha (PDGF-Ralpha) was investigated in PDGF-Ralpha-dominant negative-transfected SMC, by selectively blocking PDGF-BB-binding to PDGF-Ralpha with neomycin, by neutralizing PDGF-Ralpha with a monoclonal antibody and by selectively stimulating PDGF-Ralpha with PDGF-AA; in all cases the effect of bFGF to inhibit PDGF-BB-directed SMC migration was abolished. These in vitro studies show that bFGF significantly inhibits PDGF-BB-induced SMC migration and proliferation and that this effect is mediated by both PDGF-Ralpha and bFGF receptor.

Shear stress downregulation of platelet-derived growth factor receptor-beta and matrix metalloprotease-2 is associated with inhibition of smooth muscle cell invasion and migration.

After endovascular injury, smooth muscle cells (SMCs) may be exposed to hemodynamic shear stress (SS), and these forces modulate neointima accumulation. The effect of SS on SMC migration and invasion is unknown, and it was examined in the present study. Bovine aortic SMCs were exposed to laminar SS of 12 dyne/cm(2) for 3 (SS3) or 15 (SS15) hours; control (C3 and C15) SMCs were kept under static conditions. Platelet-derived growth factor (PDGF)-BB-directed SMC migration and invasion were evaluated by a modified Boyden chamber assay with filters coated with either gelatin or reconstituted basement membrane proteins (Matrigel), respectively. SS15 inhibited both SMC migration and invasion (P<0.0001). There was no significant difference between SS3 and C3 cells. Media conditioned with SS15 cells exhibited a reduction in matrix metalloprotease-2 (MMP-2) by zymography and Western analysis. Northern blot analysis revealed no effect of SS15 on MMP-2 mRNA. In contrast, SS15 decreased MMP-2 activator and membrane-type MMP (MT-MMP or MMP-14) mRNA and protein. Furthermore, SS15 decreased PDGF receptor-beta (PDGF-Rbeta) mRNA and protein (P<0.05), and the SS-dependent decrease in PDGF-BB-directed cell migration was rescued by overexpressing PDGF-Rbeta. SS inhibits SMC migration and invasion via diminished PDGF-Rbeta expression. This effect of SS is associated with decreased MMP-2 secretion and MT-MMP downregulation.

Adenovirus-mediated gene transfer of the human tissue inhibitor of metalloproteinase-2 blocks vascular smooth muscle cell invasiveness in vitro and modulates neointimal development in vivo.

Endovascular injury induced by balloon withdrawal leads to the increased activation of matrix metalloproteinases (MMPs) in the vascular wall, allowing smooth muscle cells (SMCs) to digest the surrounding extracellular matrix (ECM) and migrate from the media into the intima. The objective of this study was to examine the effects of a replication-deficient adenovirus carrying the cDNA for human tissue inhibitor of metalloproteinase-2 (AdCMV.hTIMP-2) on SMC function in vitro and neointimal development in the injured rat carotid artery. Infection of cultured rat aortic SMCs at a multiplicity of infection of 100 with AdCMV.hTIMP-2 resulted in high-level expression of hTIMP-2 mRNA and protein secretion into the medium. Conditioned media (CM) from AdCMV. hTIMP-2-infected but not control virus (AdCMV.null or AdCMV. betagal)-infected SMCs inhibited MMP-2 activity on gelatin zymograms as well as the chemoattractant-directed migration of SMCs across reconstituted basement membrane proteins in the Boyden chamber assay. In contrast, AdCMV.hTIMP-2 CM had no effect on chemoattractant-directed migration of SMCs occurring in the absence of an ECM barrier or on the proliferation of cultured neointimal SMCs. Delivery of AdCMV.hTIMP-2 (2.5x10(9) pfu) to the carotid artery wall at the time of balloon withdrawal injury inhibited SMC migration into the intima by 36% (P<0.05) at 4 days and neointimal area by 53% (P<0.01) at 8 days and by 12% (P=NS) at 21 days after injury. AdCMV.hTIMP-2 had no effect on medial area. Adenovirus-mediated hTIMP-2 gene transfer inhibits SMC invasiveness in vitro and in vivo and delays neointimal development after carotid injury.

Modulation by beta-aminopropionitrile of vessel luminal narrowing and structural abnormalities in arterial wall collagen in a rabbit model of conventional balloon angioplasty versus laser balloon angioplasty.

This study was designed to assess the potential relationship between the late loss of angiographic luminal diameter and biochemical abnormalities of arterial wall collagen in rabbits subjected to angioplasty, and to test the hypothesis that beta-aminopropionitrile (beta APN), an inhibitor of lysyl oxidase, would inhibit such changes when administered orally for 1 mo after angioplasty. Endovascular injury was induced in rabbit iliac arteries by ipsilateral balloon angioplasty (BA) and by contralateral balloon angioplasty accompanied by exposure to continuous wave neodymium: yttrium aluminum garnet laser radiation (LBA). Computer measurement of angiographic luminal diameter demonstrated significant vessel narrowing at 1 and 6 mo after both procedures. By quantitative histology, the majority of the 1-mo loss in angiographic diameter could not be attributed to neointimal thickening. Analysis of collagen cross-linking by HPLC in collagen obtained from the LBA-injured segments of the arteries 1 mo after angioplasty revealed a significant increase, relative to values from uninjured arteries (P < 0.05), in the difunctional cross-link dihydroxylysinonorleucine (DHLNL). 6 mo after angioplasty, the content of hydroxypyridinium, the trifunctional maturational product of DHLNL, was significantly elevated in both BA- and LBA-treated arteries compared with values from uninjured arteries (P < 0.05). In animals administered beta APN, luminal narrowing at 1 mo, compared with controls, was attenuated (P < 0.01) and DHLNL content was decreased (P < 0.05) in arteries subjected to LBA, but not in arteries subjected to BA. The results suggest that lathyrogenic agents may be efficacious in favorably modulating LBA-induced alterations in vessel diameter and mural connective tissue.

Clinical and pathogenetic implications of histopathology in childhood polydermatomyositis.

Childhood dermatomyositis is a distinct subset of dermatomyositis with highly variable outcome. We reviewed our experience with 29 patients observed over 22 years and attempted to correlate tissue manifestation with outcome. Distinctive vascular lesions included non-necrotizing vasculitis and a unique spectrum of endovascular injury producing temporary or permanent occlusion of small arteries and capillaries. Vessels with noninflammatory endovasculopathy were often reactive with fluorescein-conjugated antisera to IgM, C3d, and/or fibrin. Lesions linked to endovascular injury include infarction, zonal myopathy, and loss of capillary network. We were able to identify half of the children destined to have persistent morbidity on the basis of severity of vasculopathy in pretreatment muscle-biopsy specimens. Our observations support a central role for endothelial cell injury in the pathogenesis of childhood dermatomyositis, suggest a basis for assessing the efficacy of therapy, and provide a focus for investigation of basic mechanisms.