Hyaluronan connective tissue extracellular matrix

Fig. 3.1 Composition of the connective tissue extracellular matrix. Collagen fibers, maroon Elastic fibers, green Hyaluronan-proteoglycan matrix, gray. Fibroblasts, a macrophage, a mast cell, and a capillary containing a red blood cell are also shown (Modified from Fig. 19-34 in The Molecular Biology of the Cell. B. Alberts et al., 4th Ed. 2002. Garland Science, Taylor Francis Group, NY)...

Hyaluronan in the Extracellular Matrix of Different Connective Tissues... 

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. 

Hyaluronan (also called hyaluronic acid or hyaluronate or HA) is an anionic water-soluble polysaccharide that is distributed widely throughout connective, epithelial and neural tissues. It is one of the main components of the extracellular matrix and widely contributes to cell proliferation and migration. HA is approved for injections by FDA for its... 

Oxidation stress is unbalanced between prooxidants and natural antioxidants in body that lead to several diseases such as rheumatoid. Hyaluronic acid (HA), is a high molecular weight biopolysacharide, is found in the extracellular matrix of soft connective tissues and is particularly concentrated in synovial fluid (SF). Half-live time of Hyaluronan in SF is approximately 12 hrs in normal conditions. This process is accelerated under normal oxidation stress that generates troubles in human joints. 

The major component of the synovial fluid, that is, hyaluronan, has two main functions namely lubricant and shock impulse damping [25]. Furthermore, hyaluronic acid is a major component of the extracellular matrix of the connective tissue. This kind of polymer should exhibit viscoelastic properties that directly depend on its microstructure and external parameters such as shear rate, stress and temperature. Knowledge of dependence of model synovial fluid viscosity on the shear rate, stress and temperature is very useful for biomedical applications, for example, in treatment of joint diseases. 

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