Structural and adhesive proteins of the extracellular matrix
THE CONTEXT
Extracellular matrix (ECM) components provide tensile strength, recoil, resistance to compression, and attachment sites that support wound repair.
Collagen and vitamin C
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Collagens consist of three polypeptide chains braided into a triple helix. Fibrillar collagens, types I, II, III, and V, are the main types found in scar tissue, tendons, bones, and skin.
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Fibrillar collagen gains tensile strength through lateral covalent crosslinking of triple helices. This enzymatic process requires vitamin C, or ascorbic acid, as a cofactor.
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Vitamin C deficiency, or scurvy, therefore causes poor wound healing and easy bleeding.
Elastin and proteoglycans
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Elastin enables tissues to recoil and recover their shape after deformation. Elasticity is especially important in cardiac valves, large blood vessels, the uterus, skin, and ligaments.
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Proteoglycans form highly hydrated gels that resist compression. In joint cartilage, they also provide lubrication between adjacent bony surfaces.
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Proteoglycans act as reservoirs for secreted growth factors, including FGF and HGF.
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Some proteoglycans are integral cell membrane proteins involved in proliferation, migration, and adhesion, including through binding and concentrating growth factors and chemokines.
Adhesive glycoproteins
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Adhesive glycoproteins and adhesion receptors participate in cell–cell, cell–ECM, and ECM–ECM interactions.
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Fibronectin is a major component of interstitial ECM. It occurs in tissue and plasma and is synthesized by several cell types, including fibroblasts, monocytes, and endothelial cells.
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In healing wounds, fibronectin provides a scaffold for subsequent ECM deposition, angiogenesis, and reepithelialization.
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Laminin is the most abundant glycoprotein in basement membrane. It mediates attachment to the basement membrane and can modulate cell proliferation, differentiation, and motility.