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Biomolecules and Tissue Properties
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Another small proteoglycan found in many collagenous tissues is decorin. It is a nonaggregating proteoglycan that is present in cartilage in molar amounts. It is the main proteoglycan in meniscus. It is also widely distributed in mesenchymal tissues, associated and bound to collagen. It interacts with fibrillar collagen using its core protein. Decorin binds at the d and e bands of collagen; this involves mainly the leucine-rich repeats of the core protein. Decorin binding influences collagen fibrillogenesis. The binding of decorin to fiber-forming collagens affects the collagen fibril diameter. A lack of decorin leads to thinner fibrils. Decorin knockout mice exhibit fragile skin, probably because of irregularly shaped collagen. Decorin folds on itself into a “U” shape and the arms of the “U” bind with two collagen molecules. This probably creates space between fibrils regulating fibril thickness.
Positional information in the extracellular matrix
Published in David M. Gardiner, Regenerative Engineering and Developmental Biology, 2017
Anne Q. Phan, Md. Ferdous Anower-E-Khuda
Extracellular PGs, the largest class of PGs, function as bridging molecules connecting various ECM molecules and as mediators of cell signaling. Aggrecan is dominant in cartilage and provides a mechano-sensitive feedback to the chondrocytes. Versican regulates cell adhesion, migration, and inflammation. Small leucine-rich PGs (SLRPs) interact with various collagens, bind with receptor tyrosine kinases and innate immune receptors, and modulate various cell signaling pathways. Decorin binds transforming growth factor beta (TGF-β), insulin-like growth factor receptor (IGFR), and vascular endothelial growth factor receptor 2 (VEGFR2). Circulating macrophages secret biglycan as a danger-signaling molecule for Toll-like receptor (TLR 2/4), an innate immunity receptor. Perlecan influences cell adhesion, growth, and survival. Agrin plays an important biological role in organizing basement membrane and clustering acetylcholine receptors. The cell surface PGs, syndecans, and glypicans interact with other ECM components and numerous growth factors mostly through their HS GAG chains. HS is involved in a wide variety of biological functions, too vast to be reviewed here, but briefly summarized in the next section.
Cell and Extracellular Matrix Interactions in a Dynamic Biomechanical Environment:
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
The proteoglycan biglycan, which has been found to bind elastin (Reinboth et al. 2002), is present in the ventricularis (Latif et al. 2005a, Stephens et al. 2008), where it may contribute to elastogenesis. Elastin retains its elastic properties only when hydrated and becomes brittle when dry (Lillie and Gosline 2002), so the presence of proteoglycans and GAGs in the elastin-rich ventricularis is likely important in maintaining the layer’s mechanical properties. Decorin, which plays a role in collagen fibrillogenesis (Danielson et al. 1997), has been found in the collagen-rich fibrosa (Latif et al. 2005a, Stephens et al. 2008).
Ex vivo study correlating the stiffness of the ovine patellar tendon to age and weight
Published in International Biomechanics, 2022
Françoise Kayser, Edoardo Bori, Sophie Fourny, Fanny Hontoir, Peter Clegg, Alexandra Dugdale, Bernardo Innocenti, Jean-Michel Vandeweerd
Proteoglycans also are involved in viscoelastic changes in aged tendons. Decorin is the most abundant proteoglycan in the small leucine-rich proteoglycan family (SLRP) in tendons. Decorin regulates the assembly of collagen I which is the primary structural unit and transmits mechanical force (Xu et al. 2018). The absence of decorin leads to an abnormal collagen fibrillogenesis, decreased tendon strength and stiffness (Danielson et al. 1997). Decorin and biglycan are essential regulators of collagen fibril and matrix assembly and provide overlapping functions rather than single deficiency-related abnormalities. A study in a both decorin and biglycan gene expression knockout mouse model showed changes in structural properties as a shift to larger diameter fibrils with increased heterogeneity, and altered mechanical properties as decreased stiffness (Robinson et al. 2017). A study carried out on old rats found decreased proteoglycan 4 and elastin mRNA expression in tendons was responsible for the increased tendon stiffness observed with ageing through reduced gliding properties of fascicular sheets (Kostrominova and Brooks 2013).