Biological mechanisms of microvessel formation in advanced atherosclerosis: The big Five

Advanced atherosclerotic lesions prone to rupture are characterized by a distinct histomorphology and pathobiology that became in recent years, increasingly related to the process of intraplaque neovascularization. Molecular mechanisms that regulate angiogenesis and that are active in the plaque region may destabilize advanced lesions by promoting microvessel growth and thus providing an entry route for inflammatory cells secondary to the luminal endothelium. In addition, angiogenic factors can also define intraplaque microvessel integrity and endothelial barrier function, determining the prevalence of intraplaque hemorrhaging. Here, we aim to compose a hypothetical model for angiogenic regulation of vulnerable plaque development, based on the evidence of clinical correlation and experimental functional studies that are provided for five of the most well-described angiogenic pathways in the current literature.     

Apoptosis and angiogenesis are induced in the unstable coronary atherosclerotic plaque

OBJECTIVE: Apoptosis and angiogenesis may be involved in the pathogenesis of atherosclerosis and plaque destabilization. In this study, we investigated if apoptosis and angiogenesis were induced in the unstable human coronary atherosclerotic plaque compared to stable atherosclerotic plaque. METHODS: Atherosclerotic plaques from patients with stable (n = 9) and unstable angina (n = 13) were obtained by directional coronary atherectomy performed during percutaneous transluminal coronary angioplasty. Apoptosis was detected by terminal deoxynucleotidyl transferase end labelling (TUNEL), as well as by immunostaining for caspase 3, Bax and Bcl-2. Neovascularization was determined by immunostaining for the endothelial cell-specific CD31, vascular endothelial growth factor (VEGF-A), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), hypoxia inducible factor-1alpha (HIF-alpha), and the sections were quantified blindly. RESULTS: The apoptotic nuclei were more frequently found in the unstable coronary atherosclerotic plaques. When the number of apoptotic cells was quantified, an increased apoptotic index was found in the unstable plaques (P = 0.04). The positive staining for caspase-3 was increased in the unstable plaques (P = 0.0008), while no difference in either Bax or Bcl-2 was found between groups. Neovascularization, as evidenced by lumens surrounded by a CD31 positive endothelial layer, was more frequently present in the plaques from patients with unstable angina (P = 0.04). The number of cells with positive staining for VEGF-A was increased in unstable plaques (P = 0.005). No difference of Ang I, Ang II, HIF1-alpha was found between groups. CONCLUSIONS: In unstable human coronary plaques, apoptosis probably involving caspase 3 was found. The plaques had an increased neovascularization, probably induced by VEGF-A. These factors may contribute to explaining plaque destabilization and intraplaque haemorrhage.     

Fibrin fragment E stimulates the proliferation,migration and differentiation of human microvascular endothelial cells in vitro

Various factors involved in haemostasis also regulate the development of new blood vessels by a process called angiogenesis. Enzymatic cleavage of fibrin yields a variety of fibrin degradation products, particularly in areas of intense angiogenesis such as in healing wounds and active atherosclerotic plaques. One of these, fibrin fragment E (FnE), is a potent angiogenic factor in the chick chorioallantoic membrane assay of angiogenesis. Here, we extend these studies to show that FnE stimulates the proliferation, migration and differentiation of human dermal microvascular endothelial cells (HuDMECs) in vitro, both in the absence and presence of such additional endothelial growth factors as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF). We also show that these stimulatory effects occur at concentrations of the protein known to be present in angiogenic tissues in vivo. FnE enhanced the angiogenic effects of VEGF or bFGF, indicating a possible synergy between the signalling pathways used by these three angiogenic factors. This revised version was published online in June 2006 with corrections to the Cover Date.     

Atherosclerotic plaque characterization by 0.5-mm-slice multislice computed tomographic imaging.

BACKGROUND: It has been proposed that 0.5-mm-slice multislice computed tomography (MSCT) is a noninvasive tool for the detection of atherosclerotic plaque, but the validity of such an assessment has not been demonstrated by an invasive investigation. The present study was performed to compare the 0.5-mm-slice MSCT density of plaques with intravascular ultrasound (IVUS) findings. METHODS AND RESULTS: Atherosclerotic plaques were characterized in 37 consecutive patients undergoing percutaneous interventions. Based on the IVUS echogenecity, the plaques were classified as soft (n=18), fibrous (n=40) or calcified (n=40). In these 98 plaques, 0.5-mm-slice MSCT plaque density was calculated in 443 regions-of-interest, including 331 lesional foci and 112 luminal cross-sections, and represented as Hounsfield units (HU). MSCT density of the 3 types of plaque was 11+/-12 HU, 78+/-21 HU, and 516 +/-198 HU respectively. Computed tomography density of the (contrast-filled) lumen was 258+/-43 HU. There were statistically highly significant differences in the densitometric characteristics among the 4 groups (soft, fibrous, calcified plaque and lumen) by nonparametric Kruskal-Wallis test (p<0.0001). CONCLUSIONS: The IVUS-based coronary plaque configuration can be accurately identified by 0.5-mm slice MSCT. Noninvasive assessment of plaque characterization will ensure emphasis on the vessel wall beyond the vascular lumen.     

Tenascin-C is associated with coronary plaque instability in patients with acute coronary syndromes.

BACKGROUND: Tenascin-C (TNC) is an extracellular matrix glycoprotein that increases after inflammation and injury. In cultured cells TNC has been reported to markedly induce the expression of matrix metalloproteinase-9, which stimulates collagen degradation in the fibrous cap of human atherosclerotic plaque. METHODS AND RESULTS: Immunohistochemical techniques were used to analyze the expression of TNC protein in 51 coronary atherectomy specimens obtained from patients with stable angina pectoris (SAP, n=23) or acute coronary syndromes (ACS) (n=28; unstable angina pectoris, n=20, acute myocardial infarction, n=8). Immunostaining for alpha-smooth muscle actin, CD68, CD45, and CD31 was also performed in serial sections to identify the cell types that express TNC protein. The %TNC + area (percentage of the area of immunostaining for TNC protein in the total surface area of the plaque) was larger in coronary samples with the plaque characteristics of thrombus, angiogenesis, intraplaque hemorrhage, and macrophage (CD68(+)), and lymphocyte (CD45 (+)) clusters than in coronary samples without them (52+/-3.4 vs 39+/-4.8, p<0.05; 57+/-3.7 vs 36+/-3.7, p<0.01; 51+/-3.6 vs 39+/-4.8, p<0.05; 53+/-3.4 vs 33+/-4.5, p<0.01; 56+/-4.1 vs 37+/-3.6, p<0.01, respectively). The presence of other components, such as dense fibrous tissue, neointimal hyperplasia, atheromatous gruel and calcification, was not significantly correlated with the %TNC + area. The %TNC + area was larger in coronary samples from patients with ACS than in samples from patients with SAP (56+/-3.2% vs 34+/-4.3%, p<0.01). CONCLUSIONS: The results suggest that TNC may have specific functions in coronary plaque formation and may be involved in the pathogenesis of coronary lesions in ACS.     

Inhibition of plaque neovascularization reduces macrophage accumulation and progression of advanced atherosclerosis

Plaque angiogenesis promotes the growth of atheromas, but the functions of plaque capillaries are not fully determined. Neovascularization may act as a conduit for the entry of leukocytes into sites of chronic inflammation. We observe vasa vasorum density correlates highly with the extent of inflammatory cells, not the size of atheromas in apolipoprotein E-deficient mice. We show atherosclerotic aortas contain activities that promote angiogenesis. The angiogenesis inhibitor angiostatin reduces plaque angiogenesis and inhibits atherosclerosis. Macrophages in the plaque and around vasa vasorum are reduced, but we detect no direct effect of angiostatin on monocytes. After angiogenesis blockade in vivo, the angiogenic potential of atherosclerotic tissue is suppressed. Activated macrophages stimulate angiogenesis that can further recruit inflammatory cells and more angiogenesis. Our findings demonstrate that late-stage inhibition of angiogenesis can interrupt this positive feedback cycle. Inhibition of plaque angiogenesis and the secondary reduction of macrophages may have beneficial effects on plaque stability.     

Systemic infections cause exaggerated local inflammation in atherosclerotic coronary arteries: clues to the triggering effect of acute infections on acute coronary syndromes

Systemic infections can trigger heart attacks. We conducted an autopsy study to investigate the pathologic effect of systemic infections on coronary artery inflammation.We studied 14 atherosclerotic patients diagnosed with an acute systemic infection. Our control group (n=13) had atherosclerosis without infection. The groups were similar in luminal stenosis and age. Coronary artery sections were stained with H&E and markers for macrophages (CD68), T cells (CD3), and dendritic cells (S100).On pathologic examination, 5 infected patients had acute myocardial infarction with thrombosis. Macrophage density in plaques and in periadventitial fat was higher in the infected group (NS). The infected patients' adventitia had significantly more macrophages (1,577 +/- 1,872 vs 265 +/- 185 per mm(2); P=0.047). The macrophage density, similar in the control group's adventitia and plaque, was significantly greater in the infected group's adventitia than in the plaque. The adventitia and periadventitial fat of the infected group had more T cells than did samples from the control group (48.4 +/- 45.0 vs 14.1 +/- 6.3 per mm(2); P=0.002). The groups exhibited similar plaque T-cell density. The infected patients' plaques, but not the adventitia and periadventitial fat, had more dendritic cells than did the controls' (3.2 +/- 2.5 vs 0.3 +/- 0.5 per mm(2); P=0.022).To our knowledge, this is the 1st report to establish a connection between acute systemic infections and significant increases in inflammatory cells in the atherosclerotic coronary arteries of human beings. This offers a new therapeutic target for preventing heart attacks in high-risk patients.     

Atherosclerotic plaque progression and vulnerability to rupture: angiogenesis as a source of intraplaque hemorrhage

Observational studies of necrotic core progression identify intraplaque hemorrhage as a critical factor in atherosclerotic plaque growth and destabilization. The rapid accumulation of erythrocyte membranes causes an abrupt change in plaque substrate characterized by increased free cholesterol within the lipid core and excessive macrophage infiltration. Neoangiogenesis is associated closely with plaque progression, and microvascular incompetence is a likely source of intraplaque hemorrhage. Intimal neovascularization is predominantly thought to arise from the adventitia, where there are a plethora of pre-existing vasa vasorum. In lesions that have early necrotic cores, the majority of vessels invading from the adventitia occur at specific sites of medial wall disruption. A breech in the medial wall likely facilitates the rapid in-growth of microvessels from the adventitia, and exposure to an atherosclerotic environment stimulates abnormal vascular development characterized by disorganized branching and immature endothelial tubes with "leaky" imperfect linings. This network of immature blood vessels is a viable source of intraplaque hemorrhage providing erythrocyte-derived phospholipids and free cholesterol. The rapid change in plaque substrate caused by the excessive accumulation of erythrocytes may promote the transition from a stable to an unstable lesion. This review discusses the potential role of intraplaque vasa vasorum in lesion instability as it relates to plaque rupture.     

Angiogenesis in human normal and pathologic adrenal cortex

The angiogenic phenotype of 13 normal adrenal glands (N), 13 aldosterone-producing adenomas (APA), 12 cortisol-producing adenomas (CPA), 13 nonfunctioning adrenal cortical adenomas (NFA), and 13 adrenal cortical carcinomas (CA) was investigated. Intratumoral vascular density was explored by CD34, a marker of endothelial cells, and the angiogenic status was investigated by vascular endothelial growth factor (VEGF) expression, an important angiogenic factor expressed by tumoral cells. Vascular density, quantified as the number of vessels per square millimeter, was significantly lower (P < 0.0001) in CA (110.3 +/- 27.8) than in N (336.6 +/- 14.5), APA (322.8 +/- 19.1), CPA (288.5 +/- 14.3), and NFA (274.2 +/- 19.8). VEGF expression, calculated as the percentage of positive cells, was significantly greater (P < 0.0001) in CA (85.3 +/- 2.1) than in APA (56.5 +/- 7.5), CPA (38.5 +/- 7.0), N (33.1 +/- 6.1), and NFA (0.76 +/- 0.6). In APA, a negative relation between CD34 and plasma renin activity (P < 0.0002) and a positive association between CD34 and aldosterone levels (P < 0.05) was found. In conclusion, the angiogenic phenotype of CA is characterized by VEGF overexpression but low vascularization, a finding suggesting a dissociation between angiogenic potential and neoangiogenic capabilities of these tumors. The lack of VEGF expression in NFA and the close association between angiogenesis and functional status in APA also suggest a possible influence of the angiogenic phenotype on hormonal secretion of these endocrine tumors.     

Relation of atherothrombosis burden and volume detected by intravascular ultrasound to angiographic no-reflow phenomenon during stent implantation in patients with acute myocardial infarction

This study investigated the mechanism of occurrence of the no-reflow phenomenon during stent implantation in patients with acute myocardial infarction (AMI) using intravascular ultrasound (IVUS) with volumetric analysis. Of 70 patients with AMI who underwent IVUS-guided stent implantation within 24 hours of symptom onset, 12 developed decreased Thrombolysis In Myocardial Infarction flow grade during stent implantation and without subsequent restoration to Thrombolysis In Myocardial Infarction flow grade before stenting. External elastic membrane cross-sectional area and maximum diameter at the culprit lesion as measured by IVUS before stent implantation were significantly larger in the no-reflow group (n = 12) than in the normal reflow group (n = 58; 20.1 +/- 6.5 vs 16.4 +/- 4.3 mm2, p = 0.015 for cross-sectional area and 5.2 +/- 0.9 vs 4.8 +/- 0.6 mm, p = 0.049 for maximum diameter). Plaque volume, volumetric plaque burden (plaque volume/external elastic membrane volume), and change in plaque volume during stent implantation (plaque volume after vs before) were significantly greater in the no-reflow group than in the normal reflow group (239 +/- 142 vs 178 +/- 72 mm3, p = 0.030; 0.76 +/- 0.07 vs 0.71 +/- 0.06, p = 0.010; and -46 +/- 63 vs -11 +/- 37 mm3, p = 0.013, respectively). In conclusion, high atherothrombotic burden and decreased plaque volume as detected by IVUS may be risk factors for development of the no-reflow phenomenon during stent implantation in patients with AMI.     

Ultrasonic angioplasty in totally occluded peripheral arteries. Initial clinical, histological, and angiographic results

BACKGROUND. Ultrasonic angioplasty was recently shown to ablate thrombi and atherosclerotic plaques in vitro and to recanalize occluded arteries in experimental animal models. The goal of the present study was to examine the clinical feasibility of ultrasonic angioplasty. METHODS AND RESULTS. Intraoperative ultrasonic angioplasty was performed in vivo on totally occluded peripheral arteries (n = 7). The ultrasonic angioplasty device consists of a 1.6-mm diameter flexible wire attached to a piezoelectric crystal generating ultrasound at 20 kHz. The controls, totally occluded human atherosclerotic femoral arterial segments (n = 6), were crossed mechanically with the ultrasound wire ex vivo but without application of ultrasonic energy. Ultrasonic angioplasty achieved successful recanalization without perforation in all vessels. Angiograms of the treated arteries showed an average lumen patency of 82.5%. Histological examination of the recanalized arteries revealed that the recanalization had taken place through intima diffusely involved with complicated plaque. The treated arteries, compared with the controls, had greater area of recanalized lumen (5.9 +/- 1.8 versus 1.7 +/- 0.4 mm2, p less than 0.05) and more flow (49.3 +/- 16.0 versus 11.8 +/- 4.9 ml/min, p less than 0.03). The damage in treated and control arteries was similar. Size-distribution analysis of the plaque debris from the treated arteries showed that 41 +/- 5% of the debris was 0.2-8 microns, 48 +/- 8% was 8-30 microns, and the remainder was 30-100 microns. In the mechanically crossed arteries, there was a shift in the distribution to larger size debris with 47 +/- 1% greater than 100 microns (p less than 0.001). CONCLUSIONS. Ultrasonic angioplasty may be a useful clinical method for recanalization of total occlusions in patients with peripheral vascular disease. Ultrasonic energy appears to cause controlled injury to the atherosclerotic intima by selectively disrupting the ultrasound-sensitive occlusion.     

Accuracy of multidetector spiral computed tomography in identifying and differentiating the composition of coronary atherosclerotic plaques: a comparative study with intracoronary ultrasound

OBJECTIVES: We evaluated the accuracy of contrast-enhanced multidetector spiral computed tomography (MDCT) for the noninvasive detection and classification of coronary plaques and compared it with intracoronary ultrasound (ICUS). BACKGROUND: Noninvasive determination of plaque composition and plaque burden may be important to improve risk stratification and to monitor progression of coronary atherosclerosis. METHODS: We included 46 consecutive patients with a distinctive risk profile, who were investigated by ICUS (Goldvision, 20 MHz, Jomed Inc., Rancho Cordova, California). Due to the inability to slow the heart rate below 65 beats/min (n = 7) and due to renal insufficiency (n = 2), nine of 46 consecutive patients could not be studied by MDCT (Sensation 16, Siemens, Forchheim, Germany). RESULTS: In the remaining 37 patients, 68 vessels were investigated by ICUS, and 58 of these vessels were visualized by MDCT with image quality sufficient for analysis. In these vessels that were divided in 3-mm sections, MDCT correctly classified 62 of 80 (78%) sections containing hypoechoic plaque areas, 87 of 112 (78%) sections containing hyperechoic plaque areas, and 150 of 158 (95%) sections containing calcified plaque tissue. In 484 of 525 (92%) sections, atherosclerotic lesions were correctly excluded. The MDCT-derived density measurements within coronary lesions revealed significantly different values for hypoechoic (49 HU [Hounsfield Units] +/- 22), hyperechoic (91 HU +/- 22), and calcified plaques (391 HU +/- 156, p < 0.02). CONCLUSIONS: This study demonstrates that, in the case of diagnostic image quality, contrast-enhanced MDCT permits an accurate identification of coronary plaques and that computed tomography density values measured within plaques reflect echogenity and plaque composition.     

Overexpression of heme oxygenase-1 in coronary atherosclerosis of Japanese autopsies with diabetes mellitus: Hisayama study

Few studies regarding the topographical expression of heme oxygenase-1 (HO-1) and its pathophysiological role in human coronary atherosclerotic lesions, particularly in relation to type 2 diabetes mellitus (DM) and intimal angiogenesis, have been reported. HO-1 expression was immunohistochemically examined in 312 tissue blocks of coronary arteries obtained from 53 Japanese autopsy cases in Hisayama cohort study that included 19 diabetic subjects and 34 age- and sex-matched non-diabetic subjects (56-93 years old, mean+/-S.D.: 73+/-10). The HO-1 was ubiquitously distributed in atherosclerotic intima, and was mainly expressed by macrophages and endothelial cells, and partly by smooth muscle cells. The prevalence of HO-1 expression increased as the lesion type (as classified by the American Heart Association (AHA) Committee) and stenotic grade progressed (p<0.0001), and was significantly higher in diabetic than in non-diabetic subjects (p<0.01). This HO-1 overexpression was associated with greater CD-68-positive macrophage infiltration (p=0.005). Interestingly, the distribution of HO-1-positive cells was accentuated in coronary atherosclerotic lesions with intimal microvessels in diabetic subjects (p<0.05), particularly those with hypercholesterolemia (p<0.05), and was preferentially distributed in the shoulder region of atherosclerotic lesion type IV in the AHA classification (p<0.01). In conclusion, HO-1 expression was distributed in overall human coronary atherosclerotic lesions, particularly in diabetic subjects, indicating that HO-1 expression is intimately associated with atherogenesis and may play an important role as an adaptive molecule in the inflammatory-repair process. The association of HO-1 overexpression with a greater extent of intraplaque angiogenesis suggests a multi-faceted role for HO-1 in modulating the progression of atherosclerosis.     

Quantitative assessment of angiogenesis in murine antigen-induced arthritis by intravital fluorescence microscopy

Inhibition of angiogenesis might be a therapeutic approach to prevent joint destruction caused by the overgrowing synovial tissue during chronic joint inflammation. The aim of this study was to investigate angiogenesis in the knee joint of mice with antigen-induced arthritis (AIA) by means of intravital microscopy. In 14 mice (C57BL6/129Sv) intravital microscopic assessment was performed on day 8 after AIA induction in two groups (controls, AIA). Synovial tissue was investigated by intravital fluorescence microscopy using FITC-dextran (150 kD). Quantitative assessment of vessel density was performed according to the following categories: functional capillary density (FCD, vessels <10 microm in diameter), functional vessel density (FVD, vessels >10 microm) and FVD of vessels with angiogenic criteria (convoluted vessels, abrupt changes of diameter, vessels which are generated by sprouting and progressively pruned and remodelled). Microvessel count was performed using immunohistochemistry. There was no significant difference in FCD between the control group (337 +/- 9 cm/cm2; mean +/- SEM) and the AIA group (359 +/- 13 cm/cm2). The density of vessels larger than 10 microm diameter was significantly increased in animals with AIA (135 +/- 10 vs. 61 +/- 5 cm/cm2 in control). The density of blood vessels with angiogenic criteria was enhanced in arthritic animals (79 +/- 17 vs. 12 +/- 2 cm/cm2 in control). There was a significant increase in the microvessel count in arthritic animals (297 +/- 25 vs. 133 +/- 16 mm(-2) in control). These findings demonstrate that angiogenesis in murine AIA can be assessed quantitatively using intravital microscopy. Further studies will address antiangiogenic strategies in AIA.     

Angiogenesis as a novel component of inflammatory bowel disease pathogenesis

BACKGROUND & AIMS: Angiogenesis is a critical component of neoplastic and chronic inflammatory disorders, but whether angiogenesis also occurs in inflammatory bowel disease (IBD) has yet to be established. We assessed mucosal vascularization, expression of endothelial alphaVbeta3 integrin, angiogenic factors, and their bioactivity in Crohn's disease (CD) and ulcerative colitis (UC) mucosa. METHODS: Mucosal endothelium was immunostained for CD31 and factor VIII and quantified by digital morphometry. alphaVbeta3 expression was studied in vivo by confocal microscopy and in vitro by flow cytometric analysis of human intestinal microvascular endothelial cells (HIMECs). Vascular endothelial growth factor (VEGF), interleukin (IL)-8, and bFGF levels were measured in mucosal extracts and cells and angiogenic bioactivity shown by induction of HIMEC migration and the corneal and chorioallantoic membrane angiogenesis assays. RESULTS: Microvessel density was increased in IBD mucosa. Endothelial alphaVbeta3 was strongly expressed in IBD but only sporadically in normal mucosa and was up-regulated in HIMECs by VEGF, tumor necrosis factor alpha, and bFGF. IBD mucosal extracts induced a significantly higher degree of HIMEC migration than control mucosa, and this response was mostly dependent on IL-8 and less on basic fibroblast growth factor or vascular endothelial growth factor. Compared with normal mucosa, IBD mucosal extracts induced a potent angiogenic response in both the corneal and chorioallantoic membrane assays. CONCLUSIONS: These results provide morphological, phenotypic and functional evidence of potent angiogenic activity in both CD and UC mucosa, indicating that the local microvasculature undergoes an intense process of inflammation-dependent angiogenesis. Thus, angiogenesis appears to be an integral component of IBD pathogenesis, providing the practical and conceptual framework for anti-angiogenic therapies in IBD.     

The vascular architecture of the chick chorioallantoic membrane: sequential quantitative evaluation using corrosion casting

Microvascular corrosion casting was used for evaluating qualitatively and quantitatively angiogenesis in the chick chorioallantoic membrane (CAM). Series of CAMs from day 8 to 18 were examined. The density of plexus capillaries increases rapidly until day 10 and then remains constant. The vessels connected to the plexus (first order vessels) increase in number and length between days 10 and 12. The vessels initiating from first-order vessels (second order) also increase in number but remain nearly the same in lengths and diameters. Compared to previous studies using stereomicroscopy, significant differences in vessel numbers and lengths exist, which can be explained by the low resolution and magnification resulting in too low vascular densities of the pre- and post-capillaries. The third-order vessels increase in number until day 12 when they reach a plateau, whereas higher-order vessels increase in number. These results give an insight into the vascular development of this organ, and provide the basis for assessing the targets and effects of angiogenic or antiagiogenic agents. This revised version was published online in June 2006 with corrections to the Cover Date.     

Systemic sclerosis stimulates angiogenesis in the chick embryo chorioallantoic membrane

Skin biopsies from patients with systemic sclerosis (SSc) were investigated for their angiogenic activity by using the chick embryo chorioallantoic membrane (CAM) assay. Ten samples of SSc and 10 of normal skin from age- and sex-matched subjects were grafted onto the CAM, and the angiogenic response in pathological and control implants was assessed on histological sections by a planimetric point-count method 4 days after grafting. The vascular counts in the area underlying the SSc were significantly higher than those of normal skin and a dense mononuclear cell infiltrate was detectable around the blood vessels in pathological specimens. These results suggest that SSc may promote angiogenesis, perhaps leading to the release of several angiogenic factors. Moreover, the role played in the angiogenic response by the inflammatory cells forming the cellular infiltrate is suggested by this study.