Connective tissue extracellular matrix components

The Connective Tissue Extracellular Matrix and Its Major Components... 

Cell culture studies have shown that aldehydic products derived from ethanol metabolism and lipid peroxidation can increase collagen mRNA levels and enhance the expression of connective tissue proteins. Acetaldehyde is able to increase the production of several extracellular matrix components. Studies also show that hepatic stellate cells, which are the primary source of extracellular matrix, become readily activated under conditions involving enhanced oxidative stress and lipid peroxidation. 

Extracellular matrix, often the major component of connective tissues. 

Fibrillin microfibrils are widely distributed extracellular matrix assemblies that endow elastic and non elastic connective tissues with long-range elasticity. They direct tropoelastin deposition during elastic fibrillogenesis and form an outer mantle for mature elastic fibers. Microfibril arrays are also abundant in dynamic tissues that do not express elastin, such as the ciliary zonules of the eye. Mutations in fibrillin-1—the principal structural component of microfibrils—cause Marfan syndrome, a heritable disease with severe aortic, ocular, and skeletal defects. Isolated fibrillin-rich microfibrils have a complex 56 nm beads-on-a-string appearance the molecular basis of their assembly and... 

Cleary, E. G. (1987). The microfibrillar component of the elastic fibers. In Connective Tissue Disease. Molecular Pathology of the Extracellular Matrix (J. Uitto and A. J. Perejda, Eds.), pp. 55-81. Dekker, New York. 

Proteoglycans resemble polysaccharides more than proteins in as much as the carbohydrate makes up as much as 95% of the hiomolecule hy weight. Proteoglycans function as lubricants and structural components in connective tissue, mediate adhesion of cells to the extracellular matrix, and bind factors that stimulate cell proliferation. 

The normal artery wall is composed of three layers intima, media, and adventita (Figure 20-10). On the luminal side, the intima contains a single layer of endothelial cells. These cells permit passage of water and other substances from blood into tissue cells. On the peripheral side, the intimal layer is surrounded by a fenestrated sheet of elastic fibers (the internal elastic lamina). The middle portion of the intimal layer contains various extracellular components of connective tissue matrix and fibers and occasional smooth cells, depending on the type of artery, and the age and sex of the subject. 

Hyaluronan is continuously synthesized and secreted by fibroblasts, keratino-cytes, chondrocytes and other specialized cells in the extracellular matrix (ECMs) throughout the body. It is synthesized by HA synthase (see also Chapter 9) at the inner face of the plasma membrane [98]. The level of HA synthesis is very high in skin and cartilage [99]. Hyaluronic acid is not one of the major components of the ECMs of the connective tissues, but it is found in various locations such as synovial fluid, vitreous humor, and umbilical cords [100]. Its biological functions include the maintenance of mechanical properties such as swelling in connective tissues and control of tissue hydration, providing lubricating properties in synovial fluid and heart valves. 

Connective tissue, such as tendon and cartilage, differs from other solid tissues In that most of Its volume Is made up of extracellular matrix rather than cells. This matrix Is packed with Insoluble protein fibers and contains proteoglycans, various multladhesive proteins, and hyaluronan, a very large, nonsulfated GAG. The most abundant fibrous protein In connective tissue Is collagen. Rubberlike elastin fibers, which can be stretched and relaxed, also are present In deformable sites (e.g., skin, tendons, heart). As discussed later, the fibronectins, a family of multladhesive matrix proteins, form their own distinct fibrils In the matrix of some connective tissues. Although several types of cells are found In connective tissues, the various ECM components are produced largely by cells called fibroblasts. 

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