Proliferation in primary and restenotic coronary atherectomy tissue. Implications for antiproliferative therapy

Inhibition of apoptosis and caspase-3 in vascular smooth muscle cells by plasminogen activator inhibitor type-1

Increased expression of plasminogen activator inhibitor type 1 (PAI-1) is associated with decreased apoptosis of neoplastic cells. We sought to determine whether PAI-1 alters apoptosis in vascular smooth muscle cells (VSMC) and, if so, by what mechanisms. A twofold increase in the expression of PAI-1 was induced in VSMC from transgenic mice with the use of the SM-22alpha gene promoter (SM22-PAI+). Cultured VSMC from SM22-PAI+ mice were more resistant to apoptosis induced by tumor necrosis factor plus phorbol myristate acetate or palmitic acid compared with VSMC from negative control littermates. Both wild type (WT) and a stable active mutant form of PAI-1 (Active) inhibited caspase-3 amidolytic activity in cell lysates while a serpin-defective mutant (Mut) PAI-1 did not. Similarly, both WT and Active PAI-1 decreased amidolytic activity of purified caspase-3, whereas Mut PAI-1 did not. WT but not Mut PAI-1 decreased the cleavage of poly-[ADP-ribose]-polymerase (PARP), the physiological substrate of caspase-3. Noncovalent physical interaction between caspase-3 and PAI-1 was demonstrable with the use of both qualitative and quantitative in vitro binding assays. High affinity binding was eliminated by mutations that block PAI-1 serpin activity. Accordingly, attenuated apoptosis resulting from elevated expression of PAI-1 by VSMC may be attributable, at least in part, to reversible inhibition of caspase-3 by active PAI-1.

Pathogen burden, inflammation, proliferation and apoptosis in human in-stent restenosis. Tissue characteristics compared to primary atherosclerosis

Pathogenic events leading to in-stent restenosis (ISR) are still incompletely understood. Among others, inflammation, immune reactions, deregulated cell death and growth have been suggested. Therefore, atherectomy probes from 21 patients with symptomatic ISR were analyzed by immunohistochemistry for pathogen burden and compared to primary target lesions from 20 stable angina patients. While cytomegalovirus, herpes simplex virus, Epstein-Barr virus and Helicobacter pylori were not found in ISR, acute and/or persistent chlamydial infection were present in 6/21 of these lesions (29%). Expression of human heat shock protein 60 was found in 8/21 of probes (38%). Indicated by distinct signals of CD68, CD40 and CRP, inflammation was present in 5/21 (24%), 3/21 (14%) and 2/21 (10%) of ISR cases. Cell density of ISR was significantly higher than that of primary lesions (977 +/- 315 vs. 431 +/- 148 cells/mm(2); p < 0.001). There was no replicating cell as shown by Ki67 or PCNA. TUNEL(+) cells indicating apoptosis were seen in 6/21 of ISR specimens (29%). Quantitative analysis revealed lower expression levels for each intimal determinant in ISR compared to primary atheroma (all p < 0.05). In summary, human ISR at the time of clinical presentation is characterized by low frequency of pathogen burden and inflammation, but pronounced hypercellularity, low apoptosis and absence of proliferation.

Correlation between gene expression and morphological alterations in baboon carotid after balloon dilatation injury

Treatment for fibroproliferative restenosis after angioplasty and endovascular surgery is an unmet medical need. Rational therapy and drug design still lack the very basic knowledge about the underlying biological processes leading to pathological changes in the vessel wall. We have developed a primate model for vascular response to denudation-overstretch injury of baboon carotid artery. With this model, we have investigated the time course of vascular expression of 41,000 human cDNA clones and correlated these changes with carotid histology and function. Analysis revealed 20,788 differentially regulated cDNA clones. After high stringency data selection, the most prominently regulated 1629 cDNA clones representing 1510 genes of known function were clustered. Genes corresponding to functional and anatomical alterations in the injured carotid wall were further aligned into functional groups according to Gene Ontology classification. The observed expression patterns faithfully reflected the functional and anatomical alterations observed in the vascular wall in response to injury. The analysis presents a tentative model for genomic response to balloon catheter injury and a road map to identify time-related genomic alterations in human vascular specimens.

Implications of proprotein Convertase 5 (PC5) in the arterial restenotic process in a porcine model

INTRODUCTION

Convertases (PCs), especially PC5, have been detected in various layers of atherosclerotic and injured arteries. We postulate that PCs could be important enzymes in vascular disease thus studied PC5 expression in a porcine balloon and stent coronary arterial vascular injury model.

METHODS

Immunohistochemistry and in situ hybridization of slides of porcine arteries from paraffin blocks were studied 1, 7, 14 and 28 days post injury.

RESULTS

Immunohistochemistry studies show expression of PC5 in control artery endothelial cells, weak medial smooth muscle cell (SMC) staining and strong staining in the small nerves of the adventitia. At 7, 14 and 28 days postinjury, there is strong positive PC5 staining of the neointimal cells and the adventitial vasa vasora and myofibroblasts. Colocalization immunohistochemistry confirms the smooth muscle staining properties of the myofibroblast-like cells in both these locations. Single-label immunohistochemistry studies show the same cells to stain strongly positive with TGF-B, PDGF, matrix metalloproteinase-2 (MMP-2) and MMP-9.

CONCLUSION

PC5 may be involved in the process of arterial injury via its effect on growth factors (GFs) and mediators. These preliminary observations suggest that the convertases, especially PC5, represent a target for future study in the process of arterial injury.

Molecular regulation of vascular smooth muscle cell differentiation in development and disease

The focus of this review is to provide an overview of the current state of knowledge of molecular mechanisms/processes that control differentiation of vascular smooth muscle cells (SMC) during normal development and maturation of the vasculature, as well as how these mechanisms/processes are altered in vascular injury or disease. A major challenge in understanding differentiation of the vascular SMC is that this cell can exhibit a wide range of different phenotypes at different stages of development, and even in adult organisms the cell is not terminally differentiated. Indeed, the SMC is capable of major changes in its phenotype in response to changes in local environmental cues including growth factors/inhibitors, mechanical influences, cell-cell and cell-matrix interactions, and various inflammatory mediators. There has been much progress in recent years to identify mechanisms that control expression of the repertoire of genes that are specific or selective for the vascular SMC and required for its differentiated function. One of the most exciting recent discoveries was the identification of the serum response factor (SRF) coactivator gene myocardin that appears to be required for expression of many SMC differentiation marker genes, and for initial differentiation of SMC during development. However, it is critical to recognize that overall control of SMC differentiation/maturation, and regulation of its responses to changing environmental cues, is extremely complex and involves the cooperative interaction of many factors and signaling pathways that are just beginning to be understood. There is also relatively recent evidence that circulating stem cell populations can give rise to smooth muscle-like cells in association with vascular injury and atherosclerotic lesion development, although the exact role and properties of these cells remain to be clearly elucidated. The goal of this review is to summarize the current state of our knowledge in this area and to attempt to identify some of the key unresolved challenges and questions that require further study.

c-kit-Immunopositive vascular progenitor cells populate human coronary in-stent restenosis but not primary atherosclerotic lesions

Progress in the treatment of human in-stent restenosis (ISR) is hampered by an imprecise understanding of the nature of the cells that occlude vascular stents. Recent studies suggest that circulating vascular progenitor cells may mediate vascular repair and lesion formation. Moreover, functional endothelial progenitor cells appear to play a protective role in attenuating vascular lesion formation. Hence, we sought to answer two important questions: 1). Are primitive cells found in ISR lesions? 2). Is the abundance of cultured angiogenic cells (CACs) in patients with ISR different from that in patients with non-ISR lesions or normal controls? Human coronary atherectomy tissue from 13 ISR, 6 postangioplasty restenosis (RS), and 14 primary (PR) atherosclerotic lesions, as well as 15 postmortem coronary artery cross sections from young individuals without atherosclerosis, were studied. All 13 ISR and 4 of 6 RS tissue specimens contained cells that immunolabeled for the primitive cell marker c-kit and smooth muscle alpha-actin, whereas the intima and media of PR lesions and normal arteries were devoid of c-kit-immunopositive cells. The abundance of peripheral blood mononuclear cell-derived CACs was assessed in 10 patients with ISR, 6 patients with angiographically verified patent stents, and 6 individuals with no clinical evidence of coronary artery disease. CACs were less abundant in ISR patients than in non-ISR controls (13.9 +/- 3.1 vs. 22.3 +/- 6.7 cells/high-power field, P < 0.05), and both of these groups had fewer CACs than non-coronary artery disease patients (37.6 +/- 3.8, P < 0.05). These findings suggest a unique pathogenesis for ISR and RS lesions that involves c-kit-immunopositive smooth muscle cells. Moreover, the paucity of CACs in patients with ISR may contribute to the pathogenesis of ISR, perhaps because of attenuated reendothelialization.

Early adaptation of human lower extremity vein grafts: wall stiffness changes accompany geometric remodeling

OBJECTIVE

To quantitatively describe the temporal changes in elastic properties and wall dimensions in lower-extremity vein grafts after implantation.

DESIGN OF STUDY

This is a prospective study of patients (N = 38) undergoing lower extremity bypass grafts (N = 41) with autologous veins. Pulse wave velocity (PWV), luminal diameter, and wall thickness measurements were obtained by duplex ultrasound scan intraoperatively and at 1, 3, and 6 months postoperatively for assessment of graft dimensions and wall stiffness.

RESULTS

Lower extremity vein grafts showed an increase in PWV (from 16 +/- 1 to 21 +/- 3 cm/s; mean +/- SEM; P =.08), reflecting an increase in wall stiffness (from 1.2 +/- 0.2 to 2.5 +/- 0.7 x 10(6) dynes/cm; P =.02) and wall thickness (from 0.47 +/- 0.03 to 0.61 +/- 0.004 mm; P =.04) over the first 6 months after implantation. Changes in lumen diameter were positively correlated with changes in external graft diameter (P <.01) and negatively correlated with initial lumen diameter (P <.01) but not with changes in the wall thickness.

CONCLUSIONS

These results suggest complex remodeling of vein grafts during the first several months after implantation, with increased wall thickness occurring independent of variable changes in lumen diameter. Simultaneously, a marked increase in wall stiffness over this interval suggests a likely role for collagen deposition.

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.

Intravascular brachytherapy: a review of the current vascular biology

Restenosis is a major limitation of coronary angioplasty, requiring further intervention in the majority of cases. Intracoronary radiation has been employed in recent years to prevent restenosis lesions with effective results, principally in in-stent restenosis. Restenosis is generally considered as an excessive form of normal wound healing divided up in processes: elastic recoil, neointimal hyperplasia, and negative vascular remodeling. Restenosis has previously been regarded as a proliferative process in which neointimal thickening, mediated by a cascade of inflammatory mediators and other factors, is the key factor. Data from recent studies have pointed to negative vascular remodeling as a major contributing factor. Recent studies have also identified particular cell lines that might be critical regulators of restenosis, particularly monocyte-derived macrophages and myofibroblasts. This review summarizes the current theories of vascular biology pertaining to restenosis in coronary arteries and the potential mechanisms of why radiation may effectively inhibit restenosis.

Airway structural alterations selectively associated with severe asthma

To identify airway pathologic abnormalities selectively associated with severe asthma, we examined 10 control subjects, 10 patients with intermittent asthma, 15 patients with mild-to-moderate persistent asthma, 15 patients with severe persistent asthma, and 10 patients with chronic obstructive pulmonary disease. Bronchial biopsies were assessed for epithelial integrity; subepithelial basement membrane (SBM) thickness; collagen type III deposition; eosinophil, neutrophil, and fibroblast numbers; mucous gland and airway smooth muscle (ASM) areas; SBM-ASM distance; ASM hypertrophy (increased cell size); and the expression of the contractile proteins alpha-actin, smooth muscle myosin heavy-chain isoforms, myosin light-chain kinase, and the phosphorylated form of the regulatory light chain of myosin. Neither mucosal eosinophilia nor neutrophilia, epithelial damage, or SBM thickness reflected asthma severity. In contrast, higher numbers of fibroblasts (p < 0.001), an increase in collagen type III deposition (p < 0.020), larger mucous gland (p < 0.040) and ASM (p < 0.001) areas, augmented ASM cell size (p < 0.001), and myosin light-chain kinase expression (p < 0.005) distinguished patients with severe persistent asthma from patients with milder disease or with chronic obstructive pulmonary disease. Stepwise multivariate regression analysis established that fibroblast numbers and ASM cell size were negatively associated with prebronchodilator and postbronchodilator FEV1 values in patients with asthma. We conclude that fibroblast accumulation and ASM hypertrophy in proximal airways are selective determinants of severe persistent asthma.

Vascular failure: a hypothesis

Although cardiac failure has been studied extensively, vascular failure is not a recognizable term. We suggest that it is reasonable to argue that failure of the vessel to control its mass, contractile capacity, and lumen will involve pathways similar to cardiac failure. Vascular failure, or perhaps more accurately arterial failure, has very different consequences. Failure to control mass and external diameter will result in hypertension or loss of lumen in atherosclerosis. We review what is known about this normal remodeling response and its failure, and propose directions for research.

Quantification of the cell-cycle inhibitors p27(Kip1) and p21(Cip1) in human atherectomy specimens: primary stenosis versus restenosis

Proliferation, a key determinator of vascular proliferative diseases, is dependent on cyclin/cyclin-dependent kinase (CDK) complexes, which are controlled by cyclin-dependent kinase inhibitors (CKIs) such as p27(Kip1) and p21(Cip1). Both have prognostic significance in various human malignancies. We have determined the levels of p27(Kip1) and p21(Cip1) in human directional coronary atherectomy specimens of primary lesions (n = 15) and lesions of in-stent restenosis (n = 18) in comparison to those of other vascular regions and have correlated CKI levels with clinical data. Quantitative immunoblotting demonstrated low expression of p27(Kip1) in primary lesions (5.9 +/- 0.5 ng/mg protein) compared with that in aorta (14.9 +/- 0.9 ng/mg), internal mammary artery (16.7 +/- 1.1 ng/mg), and carotid artery thrombendarterectomy specimens (16.5 +/- 1.7 ng/mg). Similarly, p27(Kip1) levels in lesions of in-stent restenosis were found to be significantly reduced (6.3 +/- 1.1 ng/mg; mean time of restenosis development 367 +/- 61 days). p27(Kip1) levels did, however, not have prognostic significance for the development of restenosis, and expression levels of proliferating cell nuclear antigen and CDK2 were similar in all groups examined, indicating low proliferative activity. Clinically, p27(Kip1) was not of value in predicting the development of restenosis. Furthermore, p27(Kip1) tissue levels were not increased in statin-treated patients, implying that the favorable effect of these drugs is not a result of p27(Kip1) stabilization. However, the relative content of p21(Cip1) was found to be significantly up-regulated in restenosis compared with that in primary lesions (225%) and the other vascular regions. Our data imply that negative-feedback mechanisms are still intact in coronary proliferative disease, thereby contrasting the finding of deregulated proliferation in malignancies.

Biodegradable nanoparticles for drug and gene delivery to cells and tissue

Biodegradable nanoparticles formulated from poly (D,L-lactide-co-glycolide) (PLGA) have been extensively investigated for sustained and targeted/localized delivery of different agents including plasmid DNA, proteins and peptides and low molecular weight compounds. Research about the mechanism of intracellular uptake of nanoparticles, their trafficking and sorting into different intracellular compartments, and the mechanism of enhanced therapeutic efficacy of nanoparticle-encapsulated agent at cellular level is more recent and is the primary focus of the review. Recent studies in our laboratory demonstrated rapid escape of PLGA nanoparticles from the endo-lysosomal compartment into cytosol following their uptake. Based on the above mechanism, various potential applications of nanoparticles for delivery of therapeutic agents to the cells and tissue are discussed.

Drug eluting stents: are human and animal studies comparable?

Animal models of stenting probably predict human responses as the stages of healing are remarkably similar. What is characteristically different is the temporal response to healing, which is substantially prolonged in humans. The prevention of restenosis in recent clinical trials of drug eluting stents may represent a near absent or incomplete phase of intimal healing. Continued long term follow up of patients with drug eluting stents for major adverse cardiac events and angiographic restenosis is therefore imperative.

Dynamics of endocytosis and exocytosis of poly(D,L-lactide-co-glycolide) nanoparticles in vascular smooth muscle cells

PURPOSE

The purpose of this work was to characterize the process of endocytosis, exocytosis, and intracellular retention of poly (D,L-lactide-co-glycolide) nanoparticles in vitro using human arterial vascular smooth muscle cells (VSMCs).

METHODS

Nanoparticles containing bovine serum albumin (BSA) as a model protein and 6-coumarin as a fluorescent marker were formulated by a double emulsion-solvent evaporation technique. The endocytosis and exocytosis of nanoparticles in VSMCs were studied using confocal microscopy and their intracellular uptake and retention were determined quantitatively using high-performance liquid chromatography.

RESULTS

Cellular uptake of nanoparticles (mean particle size 97 +/- 3 nm) was a concentration-, time-, and energy-dependent endocytic process. Confocal microscopy demonstrated that nanoparticles were internalized rapidly, with nanoparticles seen inside the cells as early as within 1 min after incubation. The nanoparticle uptake increased with incubation time in the presence of nanoparticles in the medium; however, once the extracellular nanoparticle concentration gradient was removed, exocytosis of nanoparticles occurred with about 65% of the internalized fraction undergoing exocytosis in 30 min. Exocytosis of nanoparticles was slower than the exocytosis of a fluid phase marker, Lucifer yellow. Furthermore, the exocytosis of nanoparticles was reduced after the treatment of cells with the combination of sodium azide and deoxyglucose, suggesting that exocytosis of nanopartides is an energy-dependent process. The nanoparticle retention increased with increasing nanoparticle dose in the medium but the effect was relatively less significant with the increase in incubation time. Interestingly, the exocytosis of nanoparticles was almost completely inhibited when the medium was depleted of serum. Further studies suggest that the addition of BSA in the serum free medium with or without platelet derived growth factor (PDGF) induced exocytosis of nanoparticles. The above result suggests that the protein in the medium is either adsorbed onto nanoparticles and/or carried along with nanoparticles inside the cells, which probably interacts with the exocytic pathway and leads to greater exocytosis of nanoparticles.

CONCLUSIONS

The study demonstrated that endocytosis and exocytosis of nanoparticles are dynamic and energy-dependent processes. Better understanding of the mechanisms of endocytosis and exocytosis, studies determining the effect of nanoparticle formulation and composition that may affect both the processes, and characterization of intracellular distribution of nanoparticles with surface modifications would be useful in exploring nanoparticles for intracellular delivery of therapeutic agents.

Enhanced extracellular matrix accumulation in restenosis of coronary arteries after stent deployment

OBJECTIVES

The goal of this study was to evaluate the cellular and extracellular composition of human coronary arterial in-stent restenosis after various periods of time following stent deployment.

BACKGROUND

Neointimal in-growth rather than stent recoil is thought to be important for coronary arterial in-stent restenosis. There is only limited data on the cellular and extracellular composition changes with time after stent deployment.

METHODS

We analyzed 29 coronary arterial in-stent restenotic tissue samples (14 left anterior descending coronary artery, 10 right coronary artery, and 5 left circumflex artery) retrieved by using directional coronary atherectomy from 25 patients at 0.5 to 23 (mean, 5.7) months after deployment of Palmaz-Schatz stents employing histochemical and immunocytochemical techniques.

RESULTS

Cell proliferation was low (0% to 4%). Myxoid tissue containing extracellular matrix (ECM) enriched with proteoglycans was found in 69% of cases and decreased over time after stenting. Cell-depleted areas were found in 57% of cases and increased with time after stenting. Versican, biglycan, perlecan, and hyaluronan were present with varying individual distributions in all samples. Positive transforming growth factor-beta1 staining was found in 80% of cases. Immunostaining with alpha-smooth muscle actin identified the majority of cells as smooth muscle cells with occasional macrophages present (< or =12 cells per section).

CONCLUSIONS

These data suggest that enhanced ECM accumulation rather than cell proliferation contribute to later stages of in-stent restenosis. Balloon angioplasty of in-stent restenosis may, therefore, fail due to ECM changes during: 1) additional stent expansion, 2) tissue extrusion out of the stent, or 3) tissue compression.

Human in-stent restenosis tissue obtained by means of coronary atherectomy consists of an abundant proteoglycan matrix with a paucity of cell proliferation

BACKGROUND

In-stent restenosis (ISR) is a shortcoming of percutaneous coronary revascularization. Although neointimal cell proliferation is suspected to be the cause of this problem, little histological characterization of this tissue or data on cell replication exist. The purpose of this study was to examine the histologic features and proliferation profile of coronary ISR tissue derived from atherectomy procedures performed on patients with clinical evidence of ISR.

METHODS

ISR tissue retrieved by means of atherectomy from 20 coronary lesions was subjected to histomorphological analyses and immunocytochemistry as a means of examining proteoglycan expression. Cell proliferation was assessed with 2 sensitive markers of replication, in situ hybridization for histone 3 messenger RNA expression and immunocytochemistry for Ki-67 expression.

RESULTS

The ISR atherectomy specimens consisted primarily of smooth muscle cells, with occasional focal collections of inflammatory cells and organizing thrombus. All specimens had low levels of interstitial collagen and an abundant proteoglycan matrix, with biglycan being overexpressed more commonly than decorin. Cell proliferation was found in only 1 of 20 specimens (2 cells).

CONCLUSION

Established ISR lesions contained an abundant proteoglycan matrix and a paucity of proliferating cells. Future therapeutic strategies for ISR should include targeting extracellular matrix production.

Proliferative activity in stenotic human aortocoronary bypass grafts

BACKGROUND

Aortocoronary bypass graft disease is responsible for long-term failure of autologous vein grafts. The analyses of proliferation and cell type characterisation in human bypass grafts harvested during re-do surgery make it possible to investigate the cellular processes leading to bypass graft failure.

METHODS

30 stenotic vein grafts and 25 control veins were explantated during re-do heart surgery procedures. The total area and cell count of the neointima, media and adventitia were calculated computer-assisted. Actively proliferating cells were identified using antibody to Ki-67 and positive cells were determined by double-label immunocytochemistry with SMC alpha-actin, CD 31 (endothelial cells), CD 68 (macrophages) and CD 45 (T-lymphocytes).

RESULTS

Active proliferation was detected in different cell types with an average proliferation index of 0.15%, 0.18% and 0.086% for neointima, media and adventitia. Only 9% of proliferating cells in the neointima were SMC (not identified cells 40%); correspondingly, 14% SMC (not identified cells 33%) were detected in the media. Endothelial cells turned out to be the predominant proliferating cell type in all sections of the vessel wall.

CONCLUSION

Proliferation in our series of stenotic vein grafts occurred at a low level, but was significantly higher compared to native control veins. While proliferation may play an important role in early lesions, our data clearly show low proliferation activity in advanced graft lesions. The identification of proliferating macrophages and T-lymphocytes implicate an additional inflammatory component in the development of human bypass graft disease.

SUMMARY

To clarify the role of cellular proliferation in human aortocoronary bypass grafts, we characterized the cellular composition and proliferation index in 30 stenotic saphenous vein grafts in comparison to 25 native veins. Proliferation in our series of stenotic vein grafts occurred at a low level, but was significantly higher compared to native control veins.

High glucose inhibits apoptosis in human coronary artery smooth muscle cells by increasing bcl-xL and bfl-1/A1

Cardiovascular disease is a serious complication in diabetic patients. To elucidate the precise mechanisms of atherosclerosis in diabetic patients, the effects of high glucose concentration (25 mM) on apoptosis regulation and bcl-2 family protein expression in human coronary artery smooth muscle cells (CASMC) were examined. Treatment with a high level of glucose (25 mM) caused a significant decrease in apoptosis in CASMC compared with the same cells treated with a physiologically normal glucose concentration (5.5 mM) (23.9 +/- 2.4% vs. 16.5 +/- 1.8%; P < 0.01). With respect to apoptosis regulation, treatment of CASMC with high glucose concentration markedly increased mRNA expressions of bcl-xL and bfl-1/A1 compared with cells treated with normal glucose. High glucose induced phosphorylation of phosphatidylinositol 3-kinase (PI 3-K) and extracellular signal-regulated kinase (ERK)1/2 along with bcl-xL and bfl-1/A1 upregulation. These results suggest that high glucose suppresses apoptosis via upregulation of bcl-xL and bfl-1/A1 levels through PI 3-K and ERK1/2 pathways in CASMC. High glucose-induced increase in the expression of antiapoptotic proteins may be important in the development of atherosclerosis in diabetic patients.

Cell replication induces in-stent lesion growth in rabbit carotid artery with preexisting intimal hyperplasia

This study examined the responses of rabbit carotid artery with a preexisting intimal lesion, to stent implantation and balloon dilation. Rabbit carotid arteries were injured with a Fogarty catheter, and 28 days later the same arteries were subjected to implantation of a Palmaz-Schatz stent or balloon dilation angioplasty. Intimal size was significantly increased after stent implantation and balloon dilation, and no significant difference was detected between the two procedures. After stent implantation, replicating intimal cells were increased mainly in the inner intima, and the increase of cell replication was prolonged until day 28. In contrast, a significant increase of intimal cell replication was detected only at 2 days after balloon dilation. Intimal cell number after stent implantation was significantly higher than that after balloon dilation from day 7. Abundant leukocytes adhered to the luminal surface until 14 days after stent implantation, and significant infiltration of macrophages was observed in the mid-intima. Activation of proteases was prolonged, and obvious accumulation of proteoglycans was detected after stent implantation as compared with balloon dilation. These findings suggest that, an increase in cell replication is critical in the development of in-stent restenosis, and that inflammatory responses represent a unique property after stent implantation.

Time courses of apoptosis and cell proliferation and their relationship to arterial remodeling and restenosis after angioplasty in an atherosclerotic rabbit model

OBJECTIVES

We sought to evaluate whether cellular mass changes (including apoptosis and proliferation) after arterial injury could interact with restenosis and arterial remodeling.

BACKGROUND

The mechanisms controlling arterial remodeling after angioplasty remain poorly understood. Apoptosis and cell proliferation have been previously described after balloon angioplasty. However, their importance in the occurrence of arterial remodeling and restenosis is unknown.

METHODS

Atherosclerosis was induced in 48 femoral arteries of New Zealand White rabbits by air-desiccation and a high-cholesterol diet. One month later, angioplasty was performed in 40 arteries. Apoptosis, cell proliferation, residual stenosis and arterial remodeling were evaluated at 2 h and 3, 7, 14, 21 and 28 days after angioplasty.

RESULTS

Cell proliferation and apoptosis profiles were similar, but the peak in cell proliferation occurred approximately four days earlier than the peak in apoptosis in the neointima and media. Apoptosis density was positively correlated with arterial remodeling in the neointima and media (r = 0.69, p = 0.005 and r = 0.50, p = 0.05, respectively). Moreover, residual stenosis was inversely correlated with apoptosis density in the neointima and media (r = -0.62, p = 0.008 and r = -0.52, p = 0.04, respectively). In contrast, cell proliferation was independent of restenosis and arterial remodeling.

CONCLUSIONS

In this model, cell proliferation preceded apoptosis throughout the four weeks after angioplasty. Apoptosis was inversely correlated with restenosis. Interestingly, apoptosis was also related to enlargement remodeling after balloon angioplasty.

Apoptosis of vascular smooth muscle cells is induced by Fas ligand derived from monocytes/macrophage

Fas and its ligand (FasL), are a receptor-ligand pair identified as promoting cell death in several tissues. Apoptosis of vascular smooth muscle cells (VSMCs) in human atherosclerotic plaque may contribute to weakening of the fibrous cap, ultimately resulting in plaque rupture. We investigated the ability of monocytes to induce apoptosis of cultured VSMCs through Fas/FasL pathway. In addition, we examined the association of FasL with apoptosis in human coronary plaques. Both activated monocytes and the supernatant obtained from activated monocytes were able to kill cultured VSMCs. The apoptotic response of VSMCs was almost completely blocked by the caspase inhibitor z-VAD-fmk and was partially blocked by incubation with antagonistic anti-Fas IgG1 which suggests that Fas/FasL system was involved in the induction of cell death. An approximate 30 kDa protein, which represents a cleaved, soluble form of FasL, was identified in culture medium from activated monocytes, but not in culture medium from control, unactivated monocytes. Immunohistochemical analysis of human atherosclerotic coronary lesions showed that FasL is expressed by macrophages, and microvessels in the adventitia as well as in the plaque. Finally, double-staining with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and FasL antibody showed that FasL enriched lesions always included a number of TUNEL-positive cells. These data suggest that Fas/FasL pathway can be employed by monocytes/macrophages to induce VSMC apoptosis in the atherosclerotic lesions.

Propionyl-L-carnitine reduces intimal hyperplasia after injury in normocholesterolemic rabbit carotid artery by modulating proliferation and caspase 3-dependent apoptosis of vascular smooth muscle cells

Previously we documented that propionyl-L-carnitine (PLC) reduces the growth of atherosclerotic lesions in cholesterol-fed aged rabbits in association with a decrease of plaque smooth muscle cell (SMC) proliferation and plasma triglycerides. To clarify whether PLC might influence SMC growth through mechanisms other than triglyceride lowering, we investigated the effect of a daily treatment per os with PLC on carotid intimal hyperplasia after ballooning in normocholesterolemic rabbits. PLC did not induce variations of plasma triglyceride and cholesterol. One week later, the number of proliferating SMCs was reduced in PLC as compared with controls. After 3 weeks, morphometric analysis demonstrated a reduced neointimal relative volume and percentage of stenosis but not vessel area in PLC as compared with controls. This associated with an intimal reduced SMC number and an increased apoptotic rate as detected by nick-end labelling (TUNEL) and ligation-mediated polymerase chain reaction (PCR). Western blotting also demonstrated an increase of caspase-3 cleavage in PLC carotids. Antiproliferative and pro-apoptotic effects of PLC were confirmed in vitro on actively proliferating and serum deprived SMCs, respectively. Molecules with an additional cell-specific, pro-apoptotic action may represent a new therapeutic tool in reducing intimal SMC hyperplasia following angioplasty or stenting procedures.

Mechanisms of angioplasty and stent restenosis: implications for design of rational therapy

Restenosis after angioplasty or stenting remains the major limitation of both procedures. A vast array of drug therapies has been used to prevent restenosis, but they have proven to be predominantly unsuccessful. Recent trends in drug therapy have attempted to refine the molecular and biological targets of therapy, based on the assumption that a single biological process or molecule is critical to restenosis. In contrast, both stenting and brachytherapy, which are highly nonspecific, can successfully reduce restenosis after angioplasty or stenting, respectively. This review examines the biology of both angioplasty and stent stenosis, focussing on human studies. We also review the landmark human trials that have definitively proven successful therapies, such as stenting and brachytherapy. We suggest that the successful trials of stenting and brachytherapy and the failure of other treatments have highlighted the shortcomings of conventional animal models of arterial intervention, and gaps in our knowledge of human disease. In contrast to arguments advocating gene therapy, these studies suggest that the most likely successful drug therapy will have a wide therapeutic range, targeting as many of the components or biological processes contributing to restenosis as possible.

Therapeutic implications of inflammation in atherosclerotic cardiovascular disease

Atherosclerosis represents a spectrum of pathologic lesions with diverse clinical sequelae. In this review, we build upon the paradigm that arteriosclerosis represents an inflammatory disease. By examining mechanisms involved in the response to vascular injury, we can more effectively implement targeted therapy aimed at halting or regressing arteriosclerosis.

Expression of a novel RNA-splicing factor, RA301/Tra2beta, in vascular lesions and its role in smooth muscle cell proliferation

RA301/Tra2beta, a sequence-specific RNA-binding protein, was first cloned as a stress molecule in re-oxygenated astrocytes. In human vascular tissues, we have found enhanced RA301/Tra2beta expression in coronary artery with intimal thickening, and atherosclerotic aorta. Balloon injury to the rat carotid artery induced RA301/Tra2beta transcripts followed by expression of the antigen, which was detected in medial and neointimal vascular smooth muscle cells (VSMCs). In cultured VSMCs, hypoxia/re-oxygenation caused induction of RA301/Tra2beta and was accompanied by cell proliferation, both of which were blocked by the addition of either diphenyl iodonium, a NADPH oxidase inhibitor, PD98059, a mitogen-activated protein kinase kinase inhibitor, or antisense oligonucleotide for RA301/Tra2beta. Consistent with a link between RA301/Tra2beta and cell proliferation, platelet-derived growth factor also induced expression of RA301/Tra2beta in cultured VSMCS: These data suggest a possible role for RA301/Tra2beta in the regulation of VSMC proliferation, especially in the setting of hypoxia/re-oxygenation-induced cell stress.

Structure of carotid artery in baboon and rat and differences in their response to endothelial denudation angioplasty

BACKGROUND

Most studies dealing with vascular response to injury have been conducted using rodent and rabbit models, although it is expected that the response to injury in these species is dissimilar from man.

AIMS

Here we compare the structure of native carotid artery in rat and baboon and the response of these vessels to endothelial denudation angioplasty.

METHODS

In both species, the carotid is a musculoelastic artery. Only baboon carotid has a distinct intima, correlating in size with the weight of male baboons. Complete endothelial denudation of left carotid was performed on eight male baboons and 24 male rats by applying an equivalent pull force with a Fogarthy catheter. The animals were sacrificed prior to and 15 min and 2, 3, 4, 7, 14 and 28 days postinjury, one baboon and three rats per time point.

RESULTS

Re-endothelialization in the baboon was complete already on day 4, whereas in the rat it was still incomplete on day 28. The proliferative response to injury was far smaller in the baboon than in the rat, the intimal area increased only by 5-fold in baboon compared with 25-fold in rat, and the number of intimal nuclei by 4-fold in baboon compared with 12-fold in rat. Complete compensatory remodelling of the lumen size occurred in the baboon, whereas in the rat remodelling remained incomplete. The cell types participating in the response were, however, similar: deposition of thrombocytes on denuded luminal surface, expression of alpha-actin by intimal cells, and lack of any significant white cell infiltration in the denuded intima.

CONCLUSIONS

Baboon carotids are very different from rat carotids both in their native structure and in their response to injury. With the limited amount of information available from human vessels, baboon carotids closely resemble human carotids in both respects.

Replication in restenotic atherectomy tissue

Previously, we demonstrated that replication in restenotic coronary atherectomy specimens was an infrequent and modest event. In general, this data was interpreted with caution, as immunocytochemistry for the proliferating cell nuclear antigen (PCNA) was used to subjectively assess proliferation and most of the tissue specimens were resected more than 3 months after the initial interventional procedure. The purpose of the present study was to use a more sensitive method of detecting replication, in situ hybridization for histone 3 (H3) mRNA, to determine the replication profile of human directional atherectomy specimens. Restenotic directional coronary atherectomy specimens from lesions that had undergone an interventional procedure within the preceding 3 months were studied. In addition, larger atherectomy specimens from peripheral arterial lesions were assessed to ensure that pockets of replication were not being overlooked in the smaller coronary specimens. We found evidence for replication in tissue resected from 2/17 coronary and 9/12 peripheral artery restenotic lesions. In contrast, 3/11 specimens resected from primary lesions of peripheral arteries also expressed H3 mRNA. We estimated that the maximum percentage of cells that were replicating in restenotic coronary, restenotic peripheral and primary peripheral artery tissue slides to be <0.5, < or =1.2 and <0.01%, respectively. Replication was found in tissue specimens resected both early and late after a previous interventional procedure. For specimens with >15 replicating cells per slide we found high levels of focal replication. Therefore, cell replication, as assessed by the expression of H3 mRNA, was infrequent in restenotic coronary artery specimens, whereas peripheral restenotic lesions had more frequent and higher levels of replication regardless of the interval from the previous interventional procedure. For all specimens the percentage of cells that were replicating was low, however focal areas with relatively high replication indices were presented. Although replication was more abundant in restenotic lesions it does not appear to be a dominant event in the pathophysiology of restenosis.

The good smooth muscle cells in atherosclerosis

The formation of a fibrous cap made up of intimal smooth muscle cells and connective tissue is part of an attempt by the vessel wall to encapsulate the toxic products accumulating in the necrotic core of atherosclerotic lesions, and should be viewed as a beneficial healing response. In this review, we discuss the development of the intima and the potential origins of the intimal smooth muscle cell with a focus on the unique properties of these cells. We further discuss the role of intimal smooth muscle cells in plaque rupture and in wound healing, and the relationship of wound healing to the loss of lumen that occurs with development of advanced atherosclerotic lesions.

The effect of protein kinase C and its alpha subtype on human vascular smooth muscle cell proliferation, migration and fibronectin production

BACKGROUND

Vascular smooth muscle cell (SMC) migration, proliferation and extracellular matrix protein production are key steps in the formation of intimal hyperplasia, a process that leads to failure of vascular reconstructions. Protein kinase C (PKC) may be involved in all 3 cellular events. PKC consists of a family of 11 isotypes, 8 of which we have identified in human vascular SMCs. In this study we evaluate the role of PKCalpha as a second messenger for proliferation, migration and fibronectin production induced by human saphenous vein SMCs.

METHODS

DNA synthesis was evaluated by using (3)H-thymidine incorporation. Mitogen-activated protein kinase (MAP-K) activation was quantified by Western blotting with an antibody to its phosphorylated substrate, Elk-1. Chemotaxis was evaluated by using a microchemotaxis chamber. SMC fibronectin was measured by Western blotting. For all experiments, PKCalpha was blocked with a selective inhibitor, Gö6976.

RESULTS

Gö6976, at concentrations that allow selective inhibition of PKCalpha, inhibited platelet-derived growth factor-stimulated SMC proliferation and MAP-K activation by 30% to 40% and 30% to 60%, respectively. SMC chemotaxis was stimulated approximately 2-fold by the PKCalpha inhibitor. Neither basal nor transforming growth factor-betaI induced fibronectin production was affected by Gö6976.

CONCLUSIONS

Our data suggest that PKCalpha is a positive mediator of SMC proliferation and MAP-K activity, a negative regulator of migration and has no effect on SMC fibronectin production. These data suggest that modulating activities of specific PKC isotypes might be useful in both the study and control of intimal hyperplasia.

Neointimal formation at the sites of anastomosis of the internal thoracic artery grafts after coronary artery bypass grafting in human subjects: an immunohistochemical analysis

OBJECTIVES

The aim of this study was to evaluate the cellular composition and cell proliferative activity of neointimal tissue in human internal thoracic artery grafts and to characterize the differentiation state of neointimal smooth muscle cells at early stages after coronary artery bypass grafting.

METHODS

The anastomotic sites and body segments of 7 patent grafts were obtained at autopsy from 7 patients who died within 92 days after operation. Serial sections were examined by immunohistochemical techniques to identify macrophages, endothelial cells, smooth muscle cell phenotype, and proliferating cells. For the identification of the cell types that show cell proliferative activity, immunodouble staining was also performed.

RESULTS

In all body segments the luminal surface was completely covered by endothelial cells, and no areas showed thrombus formation or neointimal proliferation after grafting. In contrast, in the anastomotic segments endothelial denudation and focal disruption of the internal elastic lamina with adherence of fibrin-platelet thrombus and infiltration of macrophages were observed in the earliest stage after grafting. At these sites of injury, early neointimal tissue response had occurred, and cell proliferative activity was detected in macrophages and dedifferentiated smooth muscle cells. During the evolution of neointimal thickening, redifferentiation of neointimal smooth muscle cells occurred associated with the decline in proliferative activity.

CONCLUSIONS

These observations strongly support the concept that excessive neointimal proliferation, which may occur at the site of anastomosis because of extensive damage to the arterial wall, could be one of the possible causes of failure of the internal thoracic artery graft in human beings.

Restenosis: a challenge for pharmacology

The quest for an anti-restenotic drug continues to be a major challenge in the field of cardiovascular pharmacology because most therapies with proven efficacy in experimental neointima models have failed to limit restenosis. Some drug classes, including glycoprotein IIb/IIIa antagonists, nitric oxide donors and the antioxidant probucol, have recently demonstrated potential benefits in clinical trials. Progress in the development of local delivery systems for administration of drugs, antisense oligonucleotides or genes, in combination with an improved understanding of the pathogenesis of restenosis holds promise for ultimate pharmacotherapy of this condition.

Is MIB-1 proliferation index a predictor for response to neoadjuvant therapy in patients with esophageal cancer?

BACKGROUND

The overall survival rate for patients with an esophageal cancer remains poor. As a consequence, preoperative chemoradiation was introduced for patients with tumor stage T >1 M0 regardless of tumor histology or localization. However, factors predicting response to this therapy pretherapeutically are largely unknown.

METHODS

Clinical results of preoperative chemoradiation were investigated. The rates of proliferation and apoptosis were determined in pretherapeutic tumor samples and correlated with tumor response and long-term survival after surgery.

RESULTS

A complete tumor response due to chemoradiation (n = 42; cervically localized tumors excluded) was achieved in 11 patients (26%) after resection. Five-year survival rate was significantly improved in these patients compared with those who did not respond to chemoradiation (48% versus 5.5%; P = 0.003). Chemoradiation was performed without benefit in 43%. Perioperative hospital mortality rate was 14.3% in all patients. No correlation of apoptosis with response to chemoradiation or postoperative long-term survival was observed. However, there was a clear correlation between the proliferation rate as determined by MIB-1 immunohistology. Five-year survival rate of patients with a proliferation index (PI) >/=39% was 38% compared with 0% in tumors with a PI <39%. Tumors with a PI >/=39% responded to chemoradiation in 71.4%, but 100% of tumors with a PI <39% did not. Mean survival time of these patients was 33 months and 11 months, respectively (P = 0.015).

CONCLUSIONS

The results indicate that the PI may be used for stratification of patients treatment prior surgery. However, these results need further validation in larger patient numbers in the search for factors indicating response pretherapeutically to preoperative chemoradiation in esophageal cancer.

Molecular mechanisms in intimal hyperplasia

Intimal hyperplasia is the process by which the cell population increases within the innermost layer of the arterial wall, such as occurs physiologically during closure of the ductus arteriosus and during involution of the uterus. It also occurs pathologically in pulmonary hypertension, atherosclerosis, after angioplasty, in transplanted organs, and in vein grafts. The underlying causes of intimal hyperplasia are migration and proliferation of vascular smooth muscle cells provoked by injury, inflammation, and stretch. This review discusses, at a molecular level, both the final common pathways leading to smooth muscle migration and proliferation and their (patho)-physiological triggers. It emphasizes the key roles played by growth factors and extracellular matrix-degrading metalloproteinases, which act in concert to remodel the extracellular matrix and permit cell migration and proliferation.

Role of endothelial cell denudation and smooth muscle cell dedifferentiation in neointimal formation of human vein grafts after coronary artery bypass grafting: therapeutic implications

OBJECTIVE

To provide better insights into the genesis of neointimal thickening in human vein grafts early after surgery.

DESIGN

Retrospective study.

SETTING

Tertiary referral centre.

SUBJECTS

18 distal anastomotic sites of patent grafts, obtained at necropsy from eight patients who died over differing periods (ranging from two days to nine months) after the procedure.

MAIN OUTCOME MEASURES

Immunohistochemical evaluation of smooth muscle cell phenotype modulation in relation to proliferative activity.

RESULTS

The earliest changes are characterised by loss of surface lining endothelial cells and insudation of blood corpuscular elements admixed with fibrin-platelet thrombus. At sites of injury vimentin positive and actin negative spindle shaped cells appear in the intima, while the related pre-existent media shows focal absence of actin positive smooth muscle cells. Proliferative activity colocalises at these sites. With time distinct neointimal thickening occurs, associated with disappearance of proliferative activity and a phenotypic shift of the smooth muscle cells.

CONCLUSIONS

The observation that luminal endothelial cell denudation, with insudation of the intima with blood elements, occurs in the very early stages suggests that these phenomena are responsible for the observed dedifferentiation of pre-existent smooth muscle cells, known to be a prerequisite for cell proliferation and the evolution of intimal thickening. It is likely, therefore, that platelet released growth factors play a pivotal role, which thus may provide a target for preventive pharmacological intervention.

Genetic instability and atherosclerosis: can somatic mutations account for the development of cardiovascular diseases?

Several observations suggest that cancer and atherosclerosis may entail fundamentally common biological mechanisms. The accumulation of lipids and the proliferation of smooth muscle cells (SMCs) are the main histological features of sclerotic plaque formation. The most prominent theory concerning the pathophysiological mechanisms of atherosclerotic plaque formation is the "inflammatory response to injury" hypothesis, which states that SMC proliferation is an inflammation-fibroproliferative reaction to different insults to the artery wall. However, recent evidence suggests that alterations at the DNA level may contribute significantly to the development of the disease. In accordance with these findings, the "monoclonal" hypothesis of atherosclerosis has been suggested. This hypothesis proposes that atherosclerosis begins as a mutation or viral infection, transforming a single, isolated smooth muscle cell into the progenitor of a proliferative clone, as seen in carcinogenesis. Studies of DNA damage in atherosclerotic tissues are lacking. Biological evidence for the hypothesis that cancer and atherosclerosis may share pathological mechanisms is discussed, emphasizing the need to perform studies investigating the involvement of somatic mutations in heart diseases.

Pathology of in-stent restenosis

The process of in-stent restenosis parallels wound healing responses. Stent deployment results in early thrombus deposition and acute inflammation, granulation tissue development, and ultimately smooth muscle cell proliferation and extracellular matrix synthesis. The severity of arterial injury during stent placement correlates with increased inflammation and late neointimal growth. These pathological findings provide useful targets for therapies aimed at reducing the incidence of in-stent restenosis.

Histopathologic comparison of human coronary in-stent and post-balloon angioplasty restenotic tissue

Histomorphometric studies for smooth muscle cells, macrophages, tissue factor, collagen, and cell proliferation were performed on 20 atherectomy specimens from patients with in-stent restenosis and 20 specimens from patients with post-balloon PTCA restenosis. Smooth muscle cell content was larger and proliferation index was higher in in-stent restenotic tissue; macrophage, tissue factor, and collagen content were larger in post-balloon percutaneous transluminal coronary angioplasty restenotic tissue, suggesting a more cellular and proliferative response with less thrombogenic potential in human tissue from in-stent restenosis than tissue from post-balloon percutaneous transluminal coronary angioplasty restenosis.

14-3-3Gamma interacts with and is phosphorylated by multiple protein kinase C isoforms in PDGF-stimulated human vascular smooth muscle cells

It has recently been demonstrated that some members of the 14-3-3 protein family play an important role in signal transduction leading to cellular proliferation. We have previously shown that expression of 14-3-3gamma is induced by growth factors in human vascular smooth muscle cells (VSMC). In this study, we cloned the human homolog of 14-3-3gamma and observed many potential phosphorylation sites, suggesting the potential for post-translational modification. In VSMC treated with platelet-derived growth factor (PDGF), 14-3-3gamma protein was expressed and phosphorylated in an activation-dependent manner. Platelet-derived growth factor-induced phosphorylation could be inhibited by phosphokinase C (PKC) inhibitory compounds, and 14-3-3gamma could be phosphorylated in the absence of PDGF by compounds that activate PKC. We also demonstrated interaction between 14-3-3gamma and several PKC isoforms (alpha, beta, gamma, theta, and delta), implicating these PKC family isoforms as the kinases responsible for PDGF-induced 14-3-3gamma phosphorylation. We found that 14-3-3gamma interacted with the signal transduction protein Raf-1, suggesting that 14-3-3gamma provides a link between this protein and PKC. Thus, 14-3-3gamma may represent a signal transduction protein that is regulated transcriptionally and post-transcriptionally by growth factors.

Special communicationthe critical role of mechanical forces in blood vessel development, physiology and pathology

The following extended abstracts were presented at the Research Initiatives in Vascular Disease Conference, Movers and Shakers in the Vascular Tree-Hemodynamic and Biomechanical Factors in Blood Vessel Pathology, sponsored by The Lifeline Foundation and the Cardiovascular & Interventional Radiology Research and Educational Foundation; jointly sponsored by the International Society for Cardiovascular Surgery, North American Chapter, The Society for Vascular Surgery, and The Society of Cardiovascular and Interventional Radiology; in cooperation with the National Institutes of Health-National Heart, Lung &Blood Institute on Mar 11-12, 1999, in Bethesda, Md.

Coronary atherosclerosis and interventions: pathological sequences and restenosis

The primary cause of cardiac morbidity and mortality in developed countries is ischemic (coronary) heart disease. The incidence of this disease is virtually all due to atherosclerosis, and ischemic heart disease is also the most prevalent disease in the industrialized world, causing over 40% of all deaths in the United States and Western Europe. In Japan, the incidence of ischemic heart disease due to coronary atherosclerosis is gradually increasing as well. Compared with the classical nomenclature of atherosclerosis; that is, fatty streak, fibrous plaque and complicated lesions, the term Stary's classification has been universally accepted because it reflects the more recently acquired knowledge about the morphological and biochemical details of the processes in coronary atherosclerosis, which have been obtained by new strategies such as angioscopy, intravascular ultrasound and molecular biological methods. The term Stary's classification has been applied for the coronary atherosclerosis of patients with acute coronary syndrome at the National Cardiovascular Center, for the analysis of predisposing atherosclerosis of these patients. The recent findings regarding acute coronary syndrome resulting from a rupture of coronary atherosclerotic plaques indicate that this syndrome is probably the most important mechanism underlying the sudden onset. It has been found that the risk of plaque rupture may depend more on plaque composition than on plaque size. Plaques rich in soft extracellular lipids and macrophages are possibly more vulnerable to plaque rupture. Two of the goals of the present review are to clarify how plaque disruption occurs and to elucidate the relationship between plaque disruption and coronary risk factors in elderly Japanese patients with acute coronary syndrome. Coronary stents have been shown to be efficacious in the treatment of acute and threatened closure complicating percutaneous transluminal coronary angioplasty (PTCA) and have produced encouraging initial results in the prevention of restenosis. In the autopsy study of restenosis after PTCA, it was observed that dense caps of collagen fibers in the adventitia in the vicinity of the disrupted internal elastic laminae were present in all of the remodeling lesions. It is suggested that remodeling, which resulted in adventitial scarring, is one of the major causative factors of restenosis after PTCA. The long-term success of stenting, however, remains limited by the occurrence of late in-stent restenosis, with an incidence of 20-42% depending on the stent design and the patient population studied. Another aim of the present review is to describe the pathological mechanism of restenosis after PTCA and/or stent replacement and, consequently, the vascular remodeling that occurs around adventitial tissue after PTCA and intimal hyperplasia that is chronically irritated by a foreign body granulomatous reaction after stenting. Finally, the results of the investigation of the effect of a tissue factor pathway inhibitor on the prevention of interventional restenosis is described.

Pharmacological effects of HMG CoA reductase inhibitors other than lipoprotein modulation

The HMG CoA reductase inhibitors reduce levels of low-density lipoproteins, raise high-density lipoproteins, and lower triglycerides. However, there are other pharmacological effects derived from HMG CoA reductase inhibitor therapy. Certain HMG CoA reductase inhibitors affect atherosclerotic plaque composition, endothelial function, platelet and clotting factors, and immune functioning. The unique extrahepatic pharmacological profile of agents in this class has not been fully characterized. All of the HMG CoA reductase inhibitors studied have improved endothelium-dependent vasodilatation. Vascular smooth muscle proliferation is not significantly affected by pravastatin but is by the other agents. Of all the HMG CoA reductase inhibitors, cerivastatin is the most potent inhibitor of vascular smooth muscle proliferation. Pravastatin is the only agent proven to significantly reduce platelet-thrombus formation and fibrinogen levels. Simvastatin has no effect on platelet-thrombus formation or fibrinogen levels, while atorvastatin and lovastatin have been shown to increase fibrinogen in some studies. Plasminogen activator inhibitor-1 levels are decreased by pravastatin, are not affected by atorvastatin, and are significantly increased by lovastatin and simvastatin. Pravastatin also has clinical benefits in transplant medicine as a result of inhibiting natural killer cell function, an effect that has not been explored with other HMG CoA reductase inhibitors.

Endovascular irradiation prevents smooth muscle cell proliferation and neointimal hyperplasia in rabbits

The present study examined the temporal responses and the efficacy of 192Ir-HDR endovascular irradiation for preventing smooth muscle cell proliferation of rabbit iliac arteries after PTA with a cutting balloon catheter. Endovascular irradiation with 12 Gy was randomly performed on the one side of iliac arterial segment with the unirradiated side serving as a control. Animals were euthanatized 1, 2, 3, 4, 8 and 12 week(s) after angioplasty. Histopathological and immunohistochemical studies were carried out. Histopathology showed repair of the dissection by cellular accumulation and a striking reduction in the amount of neointimal hyperplasia in the irradiated arteries as compared with control vessels. A peak of PCNA-positive ratio was in neointima of the control arterial segments at a week. 2-4 weeks after irradiation, the neointimal PCNA-positive ratio was still significantly increased in the control arterial segments compared with the irradiated arterial segments. After 8 weeks, PCNA-positive ratio was below 1% in both irradiated arterial segments and the control. Our results showed that the 192Ir-HDR afterloading irradiation with a dose of 12 Gy can be considered sufficient for inhibiting neointimal hyperplasia in angioplastized rabbit iliac arteries with cutting balloon catheter.