Abstract
To examine the changes in coronary artery morphology and the distribution of smooth muscle cells during the progression of coronary atherosclerosis after cardiac transplantation, intimal and medial tissues were evaluated and the density of smooth muscle cells in the media were measured 30 and 60 days after transplantation by microspectrophotometry from rats receiving both auto- and allo-transplantation. Transplanted animals were given cyclosporine A to prevent graft rejection. Signs of rejection were not seen in the animals receiving auto-transplants. Rejection gradually progressed after transplantation in animals receiving allografts. The intima of the coronary arteries in the allograft group was significantly thickened at both 30 and 60 days after transplantation. The total intimal area in the day 60 group was significantly increased relative to the day 30 group among animals receiving allo-transplantation. The medial area of the coronary arteries in the group receiving allotransplantation was significantly less than that of the auto-transplantation group at both 30 and 60 days after transplantation. Azocarmine G stain revealed that the principal component of the thickened intima was smooth muscle cells. Coronary arteries in the allotransplantation group had disruption of the internal elastic lamina. We therefore hypothesized that the smooth muscle cells (SMCs) in the intima are probably derived from the media. The density of SMCs in the media was measured by microspectrophotometry. The density of SMCs was significantly decreased in the allo-transplantation group relative to the autotransplantation group. We conclude that intimal thickening of the coronary arteries is due to SMC proliferation, the myocytes being from the media through disruption of the internal elastic lamina. This process is similar to the mechanism of the development of atherosclerosis.
Published Version
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