Connective tissue extracellular matrix

The extracellular matrix is the extracellular part of animal tissues that provides structural support it is the defining feature of connective tissue. Extracellular matrix includes the interstitial matrix and the basement membrane. Interstitial matrix is present between the cells (that is, in the intercellular spaces) it consists of polysaccharides and fibrous proteins, which act as a compression buffer. Basement membranes are sheet-like depositions of extracellular matrix on which various epithelial cells rest. 

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

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)...

Fig. 49.1. An overview of connective tissue extracellular matrix. Supporting the epithelial cell layer is a basal lamina, beneath which are collagen, elastic fibers, and proteoglycans. The cell types present in connective tissue, such as fibroblasts and macrophages, have been removed from the diagram for clarity.

Kielty, C.M., Hopkinson, 1., Grant, M.E. Collagen structure, assembly and organization in the extracellular matrix. In Connective Tissue and its Heritable Disorders Wiley-Liss, Chichester, pp. 103-147, 1993. 

Hyaluronic acid is a linear polysaccharide found in the highest concentrations in soft connective tissues where it fills an important structural role in the organization of the extracellular matrix (23,24). It has been used in ophthalmic preparations to enhance ocular absorption of timolol, a beta blocker used for the treatment of glaucoma (25), and in a viscoelastic tear formulation for conjunctivitis (26). The covalent binding of adriamycin and daunomycin to sodium hy-aluronate to produce water-soluble conjugates was recently reported (27). 

Matrix metalloproteinases Zinc-dependent enzymes capable of degrading extracellular matrix proteins, including connective tissue. 

Proteoglycans Glycosaminoglycans (mucopolysaccharides) bound to protein chains in covalent complexes. Proteoglycans are present in the extracellular matrix of connective tissue. 

Bone is an extremely dense connective tissue that, in various shapes, constitutes the skeleton. Although it is one of the hardest structures in the body, bone maintains a degree of elasticity owing to its structure and composition. It possesses a hierarchical structure and, as most of the tissues, is nanostructured in fact, it is a nanoscaled composite of collagen (organic extracellular matrix) and hydroxycarbonate apatite, (HCA, bone mineral). This nanostructure is in intimate contact with the bone cells (several microns in size), which result (at the macroscopic level) in the bone tissue. Figure 12.2 shows the bone hierarchical ordering from the bone to the crystalline structure of HCA. 

In contrast, some cytokines (e.g. some CSFs and EPO) appear to be expressed constitutively. In yet other instances cytokines such as PDGF and TGF-P are stored in cytoplasmic granules and can be rapidly released in response to appropriate stimuli. Other cytokines (mainly ones with growth factor activity, e.g. TGF-P, FGF and IL-1) are found bound to the extracellular matrix in connective tissue, bone and skin. These are released, bringing about a biological response upon tissue injury. 

TGF-Ps are pleiotrophic cytokines. They are capable of inhibiting the cell cycle and, hence, cell growth of several cell types, most notably epithelial and haematopoietic cells. These factors, however, stimulate the growth of other cell types, most notably cells that give rise to connective tissue, cartilage and bone. They induce the synthesis of extracellular matrix proteins and modulate the expression of matrix proteases. They also serve as a powerful chemoattractant for monocytes... 

Connective Tissue Tissue that supports and binds other tissues. It consists of connective tissue cells embedded in a large amount of extracellular matrix. [NIH]... 

Extracellular matrix, often the major component of connective tissues. 

The family of connective-tissue cells includes fibroblasts, chondrocytes (cartilage cells), and osteoblasts (bone-forming cells). They are specialized to secrete extracellular proteins, particularly collagens, and mineral substances, which they use to build up the extracellular matrix (see p. 346). By contrast, osteoclasts dissolve bone matter again by secreting and collagenases (see p. 342). 

Collagens are quantitatively the most abundant of animal proteins, representing 25% of the total. They form insoluble tensile fibers that occur as structural elements of the extracellular matrix and connective tissue throughout the body. Their name (which literally means glue-producers ) is derived from the gelatins that appear as a decomposition product when collagen is boiled. 

Fibroblasts Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules, [nih]... 

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