Electron microscopic studies in human atherosclerosis: Extracellular elements in aortic dofs and streaks

Abstract

The extracellular components of small grayish-yellow atherosclerotic dots and streaks removed at necropsy from 17 human aortae not later than 3 hours postmortem, were examined with the electron microscope. The broadened intercellular spaces which separated widely the intimal cells contained in more superficial layers moderately to intensely electron dense, fibrillar and granular fibrin material and other blood proteins. Small osmiophilic bodies of different sizes and configuration were present in the deeper portions of earlier lesions and were more numerous in more advanced lesions. The latter contained less fibrin. In addition, myelin-like figures were often seen either “free” in the extracellular space or associated with degenerating elastic elements, remnants of fibrin, and with cellular membranes of intimal smooth muscle cells. These myelinated bodies possessed often a core of variable electron density and texture, but it was possible to identify the cores at times as shreds of elastic tissue, basement membrane-like substance, or remnants of fibrin. It is believed on the basis of the present studies that degeneration of elastica, insuded fibrin and detached basement membrane of smooth muschle cells as well as the many osmiophilic bodies interpreted as precipitated lipoproteins derived from blood, contribute to the presence of the extracellular fat.