Extra-cellular Lipid in the Matrix of Human Articular Cartilage

Abstract

Human articular cartilage and some other cartilages contain, in addition to intracellular lipid, lipid which is extracellular and lying in particulate form in the matrix. In human cartilage this is most prominent just below the surface, and the lipid particles are often concentrated near the chondrocytes of the superficial cell layers. The formation is seen best in intact cartilages, such as those covering the head of the humerus in adult patients. The nature of this lipid has not been identified further than by its acceptance of fat-soluble oil red-O and by its electron microscopic appearance. Occasional particles show membranous structure and presumably consist of lipoprotein of cellular origin. Though some free lipid undoubtedly originates from disintegrating cartilage cells, most of the extracellular lipid lies in the neighborhood of healthy intact cells, and the theory is advanced that it derives from their extruded cytoplasmic processes. No evidence was found to suggest an association between lipid loading of the matrix and the development of the cartilaginous lesion of osteo-arthritis.