A comparison of the quantitation of macrophage foam cell populations and the extent of apolipoprotein E deposition in developing atherosclerotic lesions in young people: high and low serum thiocyanate groups as an indication of smoking. PDAY Research Group. Pathobiological Determinants of Atherosclerosis in Youth.

Smoking is considered a major risk factor for the development and progression of atherosclerosis. The effects of apolipoprotein E (apo E) and macrophages in the pathogenesis and progression of human atherosclerosis have not been adequately elucidated even though they are frequent components of the diseased arterial intima. Anatomically standardized samples of arteries from young people whose risk factor indices indicated them as "smokers" or "non-smokers" have been studied micromorphometrically. It was found that smokers have a greater area in which apo E is deposited in the early stages of the disease than do non-smokers. Smokers also demonstrated greater "macrophage foam cell populations" than did non-smokers. The study also demonstrates a positive correlation between the number of macrophage foam cells and the extent of apo E deposition in the developing lesions of the thoracic and abdominal aortas of white men aged 30-34 years who have evidence of recent cigarette smoking as determined by their postmortem blood thiocyanate levels.

Evidence for more extensive deposits of epitopes of oxidized low density lipoprotein in aortas of young people with elevated serum thiocyanate levels. PDAY Research Group.

Elevated levels of low density lipoprotein (LDL) and smoking have long been recognized as risk factors for atherosclerosis and coronary heart disease (CHD). However, the mechanisms by which these factors contribute to the disease have not been fully elucidated. It has been postulated from in vitro studies using serum and LDL from smokers that smoking increases the oxidation of LDL, which in turn contributes to atherogenesis. We know of no direct evidence linking oxidized LDL (oxLDL) in human arteries to increased atherosclerosis in individuals who show elevated serum thiocyanate levels (HST) as an indicator of recent smoking. We have studied arterial samples from smokers micromorphometrically and found that 'smokers' have a greater area in which oxLDL can be identified in the early stages of the disease than do "nonsmokers', i.e., individuals with low serum thiocyanate levels (LST). This study demonstrates a positive correlation between the extent of oxLDL in the fatty streaks as well as the fatty plaques of standardized core sample areas of the thoracic and abdominal aortas of a sample group of young people, aged 15-34, who have evidence of recent smoking based on their postmortem serum thiocyanate levels.

Microscopic findings associated with blood pressure indices in postmortem human aorta samples from young people (ages 15-34).

Standardized postmortem samples of thoracic and abdominal aortas from traumatic death victims (aged 15-34 inclusive) were selected according to renal indices of estimated blood pressure. Half of the males had renal small-artery evidence of elevated blood pressure, and half did not. The group consisted of an approximately equal number of black and white males. All of the individuals were nonsmokers and had similar age, cholesterol, and HDL distribution. Lipid deposition in the thoracic and abdominal aorta sections was determined quantitatively by means of computer micromorphometry in sections stained with Oil Red O. Results showed that there is a marked increase in extracellular lipid deposition in the intima for those arteries studied with elevated renal indices of hypertension. In addition, there is significantly more extracellular lipid in the abdominal aortas in black males than in white males. Also notable was the finding that the thoracic aorta samples exhibited significantly thicker intimas and larger intimal areas in the high blood pressure index groups than in the low blood pressure index groups. These results suggest that the development of atherosclerotic lesions may be due to an increased deposition of extracellular lipid in the matrix of the arterial intima.

Atheroarteritis: a combined immunological and lipid imbalance.

This report traces the development of our knowledge about immune-complex arteritis from the early 20th Century to the present time. The emphasis is on the work which began with the seminal observations of serum sickness by Longcope, MacKenzie, and Rich, to the pathogenetic studies of serum sickness arteritis in rabbits by several groups including the outstanding contributions by Dixon and coworkers concerning the role of circulating immune complexes. This work was followed by investigations of the relationship to atherosclerosis revealed by the sustained studies by Minick et al. on serum sickness arteritis in hypercholesterolemic rabbits. This pioneering research work has more recently been of pivotal value in understanding the arteritis observed in certain primate species such as the cynomolgus and the nemestrina, in human lupus erythematosus, and in organ transplantation arteritis. More recently it has become apparent that one of the microscopic hallmarks of this type of immune complex injury is the concentic micro-architecture of the inflammatory arterial lesions, for which, when they are also lipid containing, we have coined the term artheroarteritis. The contributions of the neoantigens from glycosylated LDL and oxidized LDL to the development of this type of atheroarteritis are considered. New frontiers in this area of research are being opened by the PDAY study which offers new opportunities to link circulating immune complexes and new antigens to arheroarteritis with its accelerated stenotic arterial lesion development.

An overview of the quantitative influence of several risk factors on progression of atherosclerosis in young people in the United States. Pathobiological Determinants of Atherosclerosis in Youth (PDAY) Research Group.

This overview of the National Institutes of Health-supported, multicenter, investigator-initiated study of the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) is designed to summarize the plan, approaches, and the expanding contribution of this unique research program, which is now in its tenth year. It traces for the first time the development, the organization, and the function of the many new features and facets that are being used to yield needed information on the relationships between the classic risk factors and the topography, severity, and the cellular and chemical reactions that influence the development of the early raised plaques. It has also helped establish the factors that influence the progression of the four major types of intermediate raised lesions that grossly are all similar, well delineated fatty plaques. Most of the observations are quantitative. A few glimpses into the unique findings that have been published are presented.

A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association.

This report is the continuation of two earlier reports that defined human arterial intima and precursors of advanced atherosclerotic lesions in humans. This report describes the characteristic components and pathogenic mechanisms of the various advanced atherosclerotic lesions. These, with the earlier definitions of precursor lesions, led to the histological classification of human atherosclerotic lesions found in the second part of this report. The Committee on Vascular Lesions also attempted to correlate the appearance of lesions noted in clinical imaging studies with histological lesion types and corresponding clinical syndromes. In the histological classification, lesions are designated by Roman numerals, which indicate the usual sequence of lesion progression. The initial (type 1) lesion contains enough atherogenic lipoprotein to elicit an increase in macrophages and formation of scattered macrophage foam cells. As in subsequent lesion types, the changes are more marked in locations of arteries with adaptive intimal thickening. (Adaptive thickenings, which are present at constant locations in everyone from birth, do not obstruct the lumen and represent adaptations to local mechanical forces). Type II lesions consist primarily of layers of macrophage foam cells and lipid-laden smooth muscle cells and include lesions grossly designated as fatty streaks. Type III is the intermediate stage between type II and type IV (atheroma, a lesion that is potentially symptom-producing). In addition to the lipid-laden cells of type II, type III lesions contain scattered collections of extracellular lipid droplets and particles that disrupt the coherence of some intimal smooth muscle cells. This extracellular lipid is the immediate precursor of the larger, confluent, and more disruptive core of extracellular lipid that characterizes type IV lesions. Beginning around the fourth decade of life, lesions that usually have a lipid core may also contain thick layers of fibrous connective tissue (type V lesion) and/or fissure, hematoma, and thrombus (type VI lesion). Some type V lesions are largely calcified (type Vb), and some consist mainly of fibrous connective tissue and little or no accumulated lipid or calcium (type Vc).

A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association.

This report is the continuation of two earlier reports that defined human arterial intima and precursors of advanced atherosclerotic lesions in humans. This report describes the characteristic components and pathogenic mechanisms of the various advanced atherosclerotic lesions. These, with the earlier definitions of precursor lesions, led to the histological classification of human atherosclerotic lesions found in the second part of this report. The Committee on Vascular Lesions also attempted to correlate the appearance of lesions noted in clinical imaging studies with histological lesion types and corresponding clinical syndromes. In the histological classification, lesions are designated by Roman numerals, which indicate the usual sequence of lesions progression. The initial (type I) lesion contains enough atherogenic lipoprotein to elicit an increase in macrophages and formation of scattered macrophage foam cells. As in subsequent lesion types, the changes are more marked in locations of arteries with adaptive intimal thickening. (Adaptive thickenings, which are present at constant locations in everyone from birth, do not obstruct the lumen and represent adaptations to local mechanical forces). Type II lesions consist primarily of layers of macrophage foam cells and lipid-laden smooth muscle cells and include lesions grossly designated as fatty streaks. Type III is the intermediate stage between type II and type IV (atheroma, a lesion that is potentially symptom-producing). In addition to the lipid-laden cells of type II, type III lesions contain scattered collections of extracellular lipid droplets and particles that disrupt the coherence of some intimal smooth muscle cells. This extracellular lipid is the immediate precursor of the larger, confluent, and more disruptive core of extracellular lipid that characterizes type IV lesions. Beginning around the fourth decade of life, lesions that usually have a lipid core may also contain thick layers of fibrous connective tissue (type V lesion) and/or fissure, hematoma, and thrombus (type VI lesion). Some type V lesions are largely calcified (type Vb), and some consist mainly of fibrous connective tissue and little or no accumulated lipid or calcium (type Vc).

Chlamydia pneumoniae (TWAR) in coronary arteries of young adults (15-34 years old).

An association of Chlamydia pneumoniae with atherosclerosis of coronary and carotid arteries and aorta has been found by seroepidemiology and by demonstration of the organism in atheromata. Age-matched control tissue from persons without atherosclerosis was usually not available. We studied autopsy tissue from young persons, many with no atherosclerosis, to determine whether C. pneumoniae is present in atheroma in young persons with early atherosclerosis and to compare the findings in age- and sex-matched persons without atherosclerosis. A left anterior descending coronary artery sample, formalin-fixed, from 49 subjects, 15-34 years of age, from the multicenter study called Pathobiological Determinants of Atherosclerosis in Youth (PDAY), was examined by immunocytochemistry and the polymerase chain reaction (PCR) for the presence of C. pneumoniae and by PCR for cytomegalovirus. A hematoxylin/eosin-stained section was used to determine disease present in the studied sample. Seven of the artery samples were found to have atheromatous plaque, 11 had intimal thickening, and 31 had no lesions. Eight of the samples were positive for C. pneumoniae by immunocytochemistry (n = 7) and/or PCR (n = 3). Six of the 7 (86%) atheroma, 2 of the 11 (18%) with intimal thickening, and none of the 31 normal-appearing coronary samples were positive. Four were positive by PCR for cytomegalovirus, 2 from diseased arteries and 2 from normal arteries. Examination of the adjacent left coronary artery sample with a fat stain found abnormalities in 25 of the patients, but 19 still showed no evidence of atherosclerosis as a result of either examination. Thus, C. pneumoniae is found in coronary lesions in young adults with atherosclerosis but is not found in normal-appearing coronary arteries of both persons with and without other evidence of atherosclerosis.

New insights into the pathogenesis of atherosclerosis as revealed by PDAY. Pathobiological Determinants of Atherosclerosis in Youth.

In this progress report the major pathological results gained from the research program called The Pathological Determinants of Atherosclerosis in Youth (PDAY) are summarized. These results are made possible because of the many unique features of this multicenter study, which are also summarized. The following main accomplishments utilize special quantitative techniques to study cellular, chemical and molecular (genetic) features of the developing plaques in young people. These include for the first time: The greater incidence of early progressive lesions in selective apo E phenotypes. The greater incidence of progressive lesions in black youth with an apo B deletion genotype. The much higher concentration of epitopes of oxidized LDL in smokers than non-smokers. More prevalent macrophages and lymphocytes in the standardized thoracic aortic samples, where lesions progress slowly, than in the abdominal aortic core samples, where lesions are much more likely to become severe. A strong correlation between the mast cell population and the concentration of biogenic amines in the lesions. The location of Lp(a) specific antigens in these developing lesions as compared to apo B. The accumulation of extracellular lipid where progression of lesions is most rapid, with special emphasis on the effects of smoking. The correlation of modulation of the intimal smooth muscle cells with the sites where progression of the plaque is most frequent. Preliminary ultrastructural evidence of intimal platelet and leukocyte adherence and entrance into the intima of the thoracic aorta, where there is likely to be lack of progression of lesions. A review of the recently published biochemical evidence of the correlation of increased lesion cholesterol and collagen content in the abdominal aorta. The continuing studies and their implications are also summarized.

A definition of initial, fatty streak, and intermediate lesions of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association.

The compositions of lesion types that precede and that may initiate the development of advanced atherosclerotic lesions are described and the possible mechanisms of their development are reviewed. While advanced lesions involve disorganization of the intima and deformity of the artery, such changes are absent or minimal in their precursors. Advanced lesions are either overtly clinical or they predispose to the complications that cause ischemic episodes; precursors are silent and do not lead directly to complications. The precursors are arranged in a temporal sequence of three characteristic lesion types. Types I and II are generally the only lesion types found in children, although they may also occur in adults. Type I lesions represent the very initial changes and are recognized as an increase in the number of intimal macrophages and the appearance of macrophages filled with lipid droplets (foam cells). Type II lesions include the fatty streak lesion, the first grossly visible lesion, and are characterized by layers of macrophage foam cells and lipid droplets within intimal smooth muscle cells and minimal coarse-grained particles and heterogeneous droplets of extracellular lipid. Type III (intermediate) lesions are the morphological and chemical bridge between type II and advanced lesions. Type III lesions appear in some adaptive intimal thickenings (progression-prone locations) in young adults and are characterized by pools of extracellular lipid in addition to all the components of type II lesions.

A definition of initial, fatty streak, and intermediate lesions of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association.

The compositions of lesion types that precede and that may initiate the development of advanced atherosclerotic lesions are described and the possible mechanisms of their development are reviewed. While advanced lesions involve disorganization of the intima and deformity of the artery, such changes are absent or minimal in their precursors. Advanced lesions are either overtly clinical or they predispose to the complications that cause ischemic episodes; precursors are silent and do not lead directly to complications. The precursors are arranged in a temporal sequence of three characteristic lesion types. Types I and II are generally the only lesion types found in children, although they may also occur in adults. Type I lesions represent the very initial changes and are recognized as an increase in the number of intimal macrophages and the appearance of macrophages filled with lipid droplets (foam cells). Type II lesions include the fatty streak lesion, the first grossly visible lesion, and are characterized by layers of macrophage foam cells and lipid droplets within intimal smooth muscle cells and minimal coarse-grained particles and heterogeneous droplets of extracellular lipid. Type III (intermediate) lesions are the morphological and chemical bridge between type II and advanced lesions. Type III lesions appear in some adaptive intimal thickenings (progression-prone locations) in young adults and are characterized by pools of extracellular lipid in addition to all the components of type II lesions.

Atherosclerosis in a rhesus monkey with genetic hypercholesterolemia and elevated plasma Lp(a).

A female rhesus monkey with a marked elevation of total plasma cholesterol LDL and Lp(a) while on a low-fat, low-cholesterol diet, died at 22 years of age. Her spontaneous hypercholesterolemia was related to a genetically determined LDL receptor deficiency (Scanu, A.M. et al., J. Lipid Res., 29 (1988) 1671). Autopsy revealed grossly visible multifocal to diffuse raised yellow plaques predominantly in the aorta and, to a lesser extent, in the coronary arteries. Microscopically, the plaques in the aorta and in the coronary arteries showed heavy lipid deposition. Some had features seen in advanced human atherosclerotic plaques, including a fibrous cap and a necrotic core. Immunohistochemical staining showed a co-localization of apo(a) with apo B in lesion sites, a pattern seen frequently in advanced human atherosclerotic plaques. Evidence of fibrinogen/fibrin in the plaque areas was also seen, but was not co-localised with either Lp(a) or apo B. This monkey developed progressive atherosclerosis which was not induced by diet, but rather was dependent on the LDL receptor deficiency with a possible contribution by the elevated plasma levels of Lp(a).

Theories and new horizons in the pathogenesis of atherosclerosis and the mechanisms of clinical effects.

In this report, I relate some of the major new concepts of the cellular and humoral pathological changes of atherosclerosis to the many observations that have been made recently in the clinicopathological study of the Pathobiological Determinants of Atherosclerosis in Youth, in some of the more human lesion-related animal models, and in epidemiological studies. An effort is made to explain the transition from the many important gross findings to the microscopical, immunohistochemical, and micromorphometric observations that have been made in a number of recent large-scale autopsy studies that are still under way in a number of countries.