J. Jarmolych

Inhibition of atherosclerosis by cod-liver oil in a hyperlipidemic swine model

We studied the effect of cod-liver oil on the development and progression of coronary artery disease in swine subjected to coronary balloon abrasion and fed an atherogenic diet for eight months. Sections from serial 3-mm segments of the coronary arteries were analyzed morphometrically in 7 pigs given a cod-liver-oil supplement and 11 control animals not given the supplement. Significantly less disease was seen in the sections from the animals fed cod-liver oil. The mean lesion area per vessel, mean luminal encroachment per vessel, and mean maximal luminal encroachment per vessel were reduced in animals fed cod-liver oil, as compared with controls, (P = 0.05, P = 0.016, and P = 0.011, respectively). Both groups of animals had severe hyperlipidemia throughout the study. Differences in the extent of coronary atherosclerosis were not related to differences in plasma lipid levels. Platelet arachidonate was markedly reduced, platelet eicosapentaenoic acid was increased, and serum thromboxane was decreased in the oil-fed group as compared with the control group. We conclude that in our animal mode, dietary cod-liver oil retarded the development of coronary artery disease, possibly through changes in prostaglandin metabolism.

Aortic media explants cell proliferation and production of mucopolysaccharides, collagen, and elastic tissue☆

Abstract Segments of pig aortic medial tissue, cultured in a semisynthetic medium, develop a new growth starting about the fourth day. In the first week most cells in this new growth are primitive cells and fibroblast-like cells with only a few modified smooth muscle cells. At this period, only mucopolysaccharides can be identified in the extracellular substances. By the third week, the great majority of cells are modified smooth muscle cells. The extracellular substance is composed of collagen and elastic tissue in addition to mucopolysaccharides. Since the two phenomena, cell proliferation and the production of these specific extracellular substances, are among the most prominent features of early atherosclerosis, it would seem that this in vitro system could be used advantageously in experiments designed to study the role of individual factors implicated in atherogenesis.

Association of DNA synthesis and apparent dedifferentiation of aortic smooth muscle cells in vitro

Abstract Smooth muscle cells (SMC) of medial explants of swine thoracic aortas appear to undergo in the first few days of culture rapid dedifferentiation toward more primitive forms. The number of cells synthesizing DNA in the explants increases as the number of well differentiated SMC decreases. Electron microscopic autoradiography revealed that more of the cells incorporating 3 H-thymidine were poorly differentiated SMC. Thus it appears that in this in vitro situation dedifferentiation of SMC precedes rapid cell proliferation. In early cholesterol-induced atherosclerosis in swine many partially or completely undifferentiated cells are present. The results of the current in vitro study suggest that the undifferentiated cells in the atherosclerotic lesions could arise from mature SMC through dedifferentiation.

Regression of Advanced Atherosclerosis in Swine

Advanced complicated atherosclerosis was produced in the abdominal aorta of swine by a combination of mechanical injury and high-cholesterol, high-fat diet for four months. After removal of the high-cholesterol diet and placing the animal on swine mash for 14 months, there was a significant (P less than .005) decrease in size of lesions with remodeling of the intima toward a smooth surface. Sudanophilia had virtually disappeared and atheromas were almost absent in the regression group, as were thrombosis and hemorrhage in plaques. Cell proliferation, as judged by the number of labeled cells in autoradiography, was less pronounced in this group. There was no decrease in the numbers of segments showing calcification; however, the size of the calcified areas was smaller in the regression group than in the base line. The data suggest that advanced atherosclerosis is susceptible to regression on removal of the atherosclerotic stimulus.

Rapid production of advanced atherosclerosis in swine by a combination of endothelial injury and cholesterol feeding

Abstract The aim of the current study was to find out whether a combination of a balloon-endothelial-cell-denudation procedure and cholesterol feeding would result in more rapid growth of atherosclerotic lesions in the abdominal aorta of swine than if either were used alone. The results far exceeded our expectation. The two procedures appear to act synergistically. In the first 2 or 3 mo lesions are patchy and scattered but by 6 mo they become confluent so that practically the entire abdominal aorta is covered with thick lipid-rich atherosclerotic lesions. The lesions produced by 6 mo have many of the characteristics of advanced human lesions.

Experimental atherosclerosis in rhesus monkeys: I. Gross and light microscopy features and lipid values in serum and aorta☆

Abstract Forty-five rhesus monkeys were divided into five groups fed four different high-fat diets and a stock diet. The duration of feeding varied from 33 to 70 weeks. All monkeys fed the high-fat diets developed aortic proliferative lesions composed predominantly of spindle-shaped cells, most of them laden with lipid. The thickest of these proliferative lesions measured 0.85 mm, and most were thinner, suggesting that in the monkey receiving these high-fat diets some proliferative lesions can reach this range of thickness before undergoing necrosis. Atheromatous aortic lesions characterized by necrosis and the accumulation of lipid debris were found only in monkeys receiving high-fat diets for 70 weeks. In monkeys receiving a diet in which the lipid component was 30% peanut oil and 5% cholesterol, the fatty acid composition of the aorta was similar tothat in humans developing coronary artery atherosclerosis, in that the fatty acids showing the greatest accumulation were oleic and linoleic. The largest number of atheromatous lesions, however, was associated with a diet otherwise identical to the peanut oil-cholesterol diet but containing as its lipid component 30% butter and 5% cholesterol. This latter diet also resulted in higher serum lipid levels and higher aortic lipid levels per milligram of DNA than did peanut oil diet. High-fat diets fed to rhesus monkeys appear to produce both proliferative and atheromatous aortic lesions similar to those seen in the human as regards both light microscopy features and lipid composition. Work is now in progress assessing some of the metabolic features of these lesions.

“Preatheroma” phase of coronary atherosclerosis in man

Abstract “Preatheroma” is a term which we apply to the proliferative changes in the arterial wall which develop prior to the occurrence of atheroma. The changes are characterized chiefly by smooth muscle cell proliferation with extracellular fibrillar and nonfibrillar material. The preatheromatous lesion is similar to the atheroma in that it is a focal intimal lesion in the sense that some areas of the intima are involved to a greater degree than others. Preatheroma is more extensive in populations known to develop extensive atheromatous changes, such as North Americans, in contrast to certain Africans in whom atherosclerosis is seldom severe even in old age. Finally, atheroma is always preceded by an appreciable degree of preatheromatous changes. In our opinion, preatheroma is an integral part of the atherosclerotic process and a precursor of atheroma.

Comparison of pathologic and angiographic findings in a porcine preparation of coronary atherosclerosis.

Coronary atherosclerosis was induced in Yorkshire swine by diet-induced hyperlipidemia and balloon intimal abrasion of a coronary artery. Severe stenoses pathologically similar to the lesions of human atherosclerosis were seen after 8 months of the atherogenic regimen. To examine the relationship between the angiogram and pathology in the assessment of the extent and location of coronary atherosclerosis, antemortem angiographic results were compared with results of pathologic examination. Vernier caliper measurements of the coronary angiogram were compared with results of morphometric evaluation of perfusion-fixed coronary arteries. Isolated focal stenoses were correctly localized and quantified, as were focal lesions within vessels diffusely diseased. Both overestimation and underestimation of lesions occurred at bifurcation sites. Diffuse disease without focal stenoses was not well demonstrated angiographically. Vessels that were angiographically thought to be normal or only minimally diseased demonstrated significantly larger lumens angiographically than pathologically. This is believed to be due to fixation and paraffin-processing artifact, even though fixation was performed by perfusion at physiologic pressure. The demonstration of an excellent correlation between the luminal size as determined angiographically and morphometrically at sites of focal obstruction confirms the value of quantitation of coronary angiograms in vivo as a diagnostic tool in coronary atherosclerosis.

Increased DNA synthesis in aortic explants from swine fed a high-cholesterol diet☆

Abstract Medical explants from the thoracic aorta of swine fed a high-cholesterol (HC) diet, when cultured 4 or 9 days in semisynthetic medium containing serum at 20, 40, 60, or 80% concentration, show a higher rate of DNA synthesis, as measured by incorporation of 3 H-thymidine into DNA, than their paired controls from swine on a normal diet. This increased rate of DNA synthesis was independent of whether the serum supplement was normal or HC. Thus it appears that the HC diet has produced some changes in the medical cells which enhanced the growth potential of these cells. In general, HC serum in the medium resulted in a higher rate of DNA synthesis than normal serum in explants from swine on either a conventional or an HC diet.

The effect of ethane- l-hydroxy-1,1-diphosphonate (EHDP) on necrosis of atherosclerotic lesions

Administration of ethane-1-hydroxy-1,1-diphosphonate (EHDP) to swine with pre-established atherosclerosis resulted in lower lesion calcium concentration, smaller lesions and a decrease in the area of lesions involved in necrosis. Atherosclerosis was developed in Yorkshire swine by balloon catheter-injury to the abdominal aorta, followed by a high cholesterol-high lipid (HL) diet for 4 months. The administration of EHDP (20 mg/kg/day) was begun after these 4 months and continued for 5 additional months along with the atherogenic diet. Other swine were ballooned and fed HL diet for nine months. Morphometric analysis showed that the extent of lesions, expressed as ratio of intima to media was significantly less (P less than 0.05) in the EHDP-treated HL swine, compared to the HL diet-only group. The ratio of lesion areas showing lipid-rich necrotic debris to the area of media was also significantly smaller (P less than 0.05). Biochemical analysis showed that the lesion from the HL drug-treated group contained significantly less (P less than 0.05) calcium compared to that from the HL diet only. Finally, there was significant correlation between average lesion area and average lesion calcium concentration (P less than 0.02) for both groups. While the effect of EHDP on lesion size and calcium concentration has been previously reported for various species such as rabbit and monkey, this study is believed to be the first where a beneficial effect of EHDP on one of the most serious complications of atherogenesis - necrosis - has been documented. The mechanisms by which EHDP may affect necrosis are discussed.