Pathobiological Determinants of Atherosclerosis in Youth (PDAY)

BACKGROUND:

The International Atherosclerosis Project (IAP) quantified atherosclerosis of the aorta and coronary arteries in over 31,000 persons age 10 to 69 who died between 1960 and 1965 in fifteen cities and countries throughout the world. The IAP established that the average severity of atherosclerosis differed widely in many parts of the world and that the differences correlated with mortality from ischemic heart disease. It also demonstrated that the fatty streaks of childhood were prevalent and severe in both boys and girls. Fibrous plaques generally first appeared between the ages of 20 and 30 and in proportion to the prevalence of ischemic disease in the adult population. Since the results of the IAP were first published in 1968, research into atherosclerosis has changed greatly from gross and microscopic morphological methods to manipulation of experimental animals, in vitro culture of arterial wall cells, and the application of micro-chemical, physical chemical, and immunological techniques to tissues.

The use of these newer techniques made it possible to test the hypothesis that a series of changes in the fatty streak between the ages of fifteen and twenty-five lead to the typical fibrous plaque and to test the hypothesis that lesions other than fatty streaks precede and may progress to fibrous plaques. The study also tested associations of the established risk factors for atherosclerosis with early stages of lesion progression as seen in young persons.

The protocol for this study served as the basis of the protocol developed by the World Health Organization (WHO) Committee on Pathobiological Determinants of Atherosclerosis in Youth. It was planned to incorporate this study into the WHO study so that cross-cultural and geographic factors could be evaluated in populations with higher and lower incidence of atherosclerosis.

DESIGN NARRATIVE:

A common protocol was followed for collecting risk factor data and coronary arteries and aortas from approximately 1,000 autopsies per year for three years. Specimens were collected and preserved in a standardized way at each collection center. Data management and statistical analysis were conducted at the University of Texas in San Antonio. The unit at Louisiana State University was composed of three central laboratories: the lipid biochemistry center; the coronary heart disease risk factor center; and a gross morphology center. The morphometry central laboratory was located at Ohio State University. Administration and coordination were directed from the University of Chicago and the University of Illinois.

In addition to serving as collection centers, many of the centers carried out individual research projects. At the University of Alabama in Birmingham, two separate but related investigations were conducted: Dr. Miller analyzed the various collagens by solubilizing them as peptide fractions and isolating the peptides via chromatography; Dr. Gay used monoclonal antibodies to define the distribution of the various collagens in atheromatous lesions. At the West Virginia University under Dr. Jagannathan, there were studies on isomeric fatty acids and proteoglycans. Dr. Reichenbach at the University of Washington studied the distribution of immunocytochemical markers of smooth muscle cell differentiation and leukocyte subpopulations in the coronary arteries as well as searched for viral DNA in plaques. At Baylor, the three-dimensional distribution of lipid inclusions, macrophages, and smooth muscle cells in coronary arteries were determined by digital fluorescence. Dr. Mergner of the University of Maryland collected specimens in the immediate autopsy program which provided specimens free of autolysis. He also performed transmission and scanning electron microscopy, X-ray microanalysis, lipid analysis, and immunofluorescence and immunoperoxidase procedures to define calcium content and cytoskeletal components. Dr. Virmani at Vanderbilt determined the role of biogenic amines such as histamine, serotonin, and catecholamines in atherosclerosis and correlated the content of amines with the presence of mast cells in the adventitia.

In 1988, two regular research grants were awarded as part of this multicenter study. The grant at the Southwest Foundation for Biomedical Research determined the genotypes for each subject with respect to restriction fragment length polymorphisms in apolipoprotein and LDL receptor genes using Southern blot analyses of DNA from liver samples sent from each collection center. It also typed the subjects for apo E isoform genotypes using oligonucleotide probes. The grant at Ohio State University correlated 3-D coronary axial geometry and pathology.

Some of the major questions addressed by the study included: whether some or all fatty streaks progressed to fibrous plaques and the transitional lesions; the morphometric and biochemical lesion changes indicated by progression; the frequency and features of insudative and proliferative lesions which may portend progressive disease; sex differences in lesions; whether immune complexes or viral infections were implicated.

In FY 1991, six grants were awarded under the title "Risk Factors in Early Human Atherogenesis" (RFEHA). The purpose was to extend the ongoing PDAY and to : obtain an adequate number of female cases so that risk factor associations could be accurately detected and studied; to increase the power of the study in general to detect associations of risk factors with raised lesions, which began to appear in this age group; and to increase the power of the study to detect genetic influences on atherosclerosis. REFHA added 1,400 new specimens to the 1,800 cases already collected in PDAY to achieve approximately 3,000 total specimens. Emphasis was placed on female cases and those that provided the best opportunity to study transition lesions between fatty streaks and fibrous plaques.

In 1998, the NHLBI awarded R24HL60808 for five years to provide and maintain an archive of human cardiovascular and other tissues which can be used by other United States and international investigators to study human atherosclerosis. The investigators, as part of PDAY and RFEHA, have assembled autopsy material (mostly of aorta and coronary artery, but with other tissues including liver, serum, and adipose tissue) from over 3,000 Black and white males and females. These were from autopsies on individuals ages 15 to 34 and obtained within 48 hours of death. The grant for the cardiovascular specimen and data library was renewed through July 2007.