Molecular biology of atherosclerosis

The traditional view of atherosclerosis as a pathological lipid deposition within the artery wall has been redefined by a more complex concept of an ongoing inflammatory disease.The atherosclerotic process is initiated when cardiovascular risk factors, through a chemical, mechanical or immunological insult, activate and/or injury the endothelium, thus contributing to endothelial dysfunction and fragmentation. This triggers a cascade of inflammatory reactions, in which monocytes, macrophages, T lymphocytes, vascular smooth muscle cells actively participate. Particularly, atherosclerotic lesions have been seen to have increased expression of T helper-1 cells together with increased levels of the T helper-1 related pro-inflammatory cytokines. Along with pro-inflammatory cytokines, other molecular factors involved in atherosclerosis appearance, progression and complication include chemokines, growth factors, vasoactive substances, enzymes, apoptosis signals and many others. Many of these molecular factors are both involved as possible markers of the atherosclerotic disease activity and burden, but may also play a crucial role in the pathogenesis of the disease. In recent years, the discovery of progenitor cells of myeloid origin has offered the prospect of merging the most recent theories on the pathogenesis of atherosclerosis with the evolving concept of a role of these progenitor cells in the repair of the injured vessel wall and the neovascularisation of ischemic tissues. This review summarizes current knowledge about the biology of atherosclerosis with emphasis on the mechanisms of endothelial damage and repair and on the concept that the turnover and replacement of endothelial cells is a major determinant in the maintenance of vascular integrity.