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Articular Cartilage
Published in Manoj Ramachandran, Tom Nunn, Basic Orthopaedic Sciences, 2018
Tim S. Waters, Nima Heidari, George Bentley
Proteoglycans are responsible for most of the water content of cartilage and also provide compressive strength to cartilage. They are large hydrophilic molecules containing chains of glycosaminoglycans (GAG) (chondroitin sulphate, keratan sulphate) bound by covalent bonds to a linear core of protein. GAGs have high negative charges from attached carboxyl and sulphate groups, which attract cations and water, thus increasing the osmotic pressure in the tissue. Aggrecan is the predominant proteoglycan in articular cartilage. Lesser proteoglycans present include decorin, byglycan, fibromodulin, syndecan, lumican and superficial zone protein.
Immunohistochemical Characterization of Extracellular Matrix in Tumor Tissues
Published in Róza Ádány, Tumor Matrix Biology, 2017
Proteoglycans are complex macromolecules that consist of a core protein to which one or more glycosaminoglycan side chains are covalently linked. The glycosaminoglycans are large molecules that are composed of repeating disaccharide units, and exist in four main forms: chondroitin sulfate and dermatan sulfate, heparan sulfate and heparin, keratan sulfate, and hyaluronic acid. The first three are protein-bound glycosaminoglycans in their natural forms, containing sulfate. Hyaluronic acid is a free glycosaminoglycan without a protein core and it lacks sulfate. During the past decade, diverse species of proteoglycans have been identified. They include aggrecan, versican, decorin, biglycan, proteoglycan-Lb, fibromodulin, lumican, perlecan, syndecan, and serglycinf.7,8 Characteristics of each proteoglycan are summarized in Table 1.
Structure and Function of Cartilage
Published in Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi, Articular Cartilage, 2017
Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi
Decorin and biglycan belong to the Class I SLRPs. Decorin, the most abundant SLRP in cartilage, is localized to the interterritorial matrix, with concentrations of decorin increasing with age (Roughley et al. 1994). The structure of decorin is semicircular with one dermatan or chondroitin sulfate attached. This concave structure supports its proposed function in associating with the collagen triple helix during fibril formation and regulating fibril spacing, as decorin has been observed “decorating” type II collagen fibrils. Interestingly, although decorin knockout mice have reduced tendon and skin tensile properties, resulting in skin fragility, the articular cartilage in adult mice appears normal (Reed and Iozzo 2002). Biglycan is localized to the pericellular matrix, with two dermatan or chondroitin sulfates attached. It is a regulator of bone formation, as biglycan knockout mice experience retarded skeletal growth (Young et al. 2002). Interestingly, both decorin and biglycan bind TGF-β. Fibromodulin, lumican, and prolargin belong to the Class II SLRPs, with both fibromodulin and lumican increasing in concentration with age. All three SLRPs bind to collagens. Fibromodulin has been linked to regulation of collagen fibril diameter (Hedbom and Heinegard 1989; Hedlund et al. 1994). The Class III SLRP epiphycan is found in the growth plate (Johnson et al. 1997).
Macular Corneal Dystrophy: An Updated Review
Published in Current Eye Research, 2021
Shalini Singh, Sujata Das, Chitra Kannabiran, Saumya Jakati, Sunita Chaurasia
MCD appears to be the result of a metabolic abnormality in keratan sulfate.20 Keratan sulfate is found in the corneal epithelium, Bowman’s membrane, keratocytes, Descemet membrane and endothelium. Carbohydrate sulfotransferase (CHST6) gene on chromosome 16(16q22) gene is explained to be important in producing sulfated keratan sulfate which is important glycosoaminoglycan in the adult cornea. CHST6 gene encodes N-acetylglucosamine 6-0-sulfotransferase, an enzyme which transfers sulfate to the unsulfated keratin chains on lumican.21,22 Lumican preserves the crucial size, ordered structure, impacts corneal hydration and hence the corneal transparency. This explains the stromal haze and the loss of corneal transparency due to mutation in CHST6 gene in MCD.
Differential expression of Lumican, Mimecan, Annexin A5 and Serotransferrin in ectopic and matched eutopic endometrium in ovarian endometriosis: a case-control study
Published in Gynecological Endocrinology, 2021
Tahreem Sahar, Aruna Nigam, Shadab Anjum, Farheen Waziri, S. K. Jain, Saima Wajid
Expression of Lumican has been reported exclusively to ectopic endometrium in a similar study [10]. High levels of Lumican expression have been reported to be associated with pathological grade tumor and low levels of estrogen receptors in cancer tissue [11]. Immunohistochemical and several microarray analyses have highlighted the role of Lumican in breast, pancreatic, colorectal, cervical, and several other cancers [12]. Mimecan, another SLRP family protein is involved in cell growth, migration, ECM assembly, and collagen fibrillogenesis [13]. Mimecan has also been identified as a differentially expressed gene in the leiomyomas of African Americans [14]. Mimecan along with other ECM proteins was found to be highly expressed in ectopic tissues of females suffering from endometriosis [9]. In the present study, we validated enhanced expression of Lumican and Mimecan (ECM proteins) in ectopic endometrium as compared to the eutopic endometrium. Thus, it can be suggested that they play an important role as a modulator of ECM in endometriosis by maintaining the structural composition, migration, and texture of ectopic endometrium.
Skin proteomics – analysis of the extracellular matrix in health and disease
Published in Expert Review of Proteomics, 2020
Jörn Dengjel, Leena Bruckner-Tuderman, Alexander Nyström
MS-based proteomics have been used since the early 2000s as an analytic tool for studying wound healing [159]. Despite the obvious necessity for wound healing of a timely and well-coordinated deposition and arrangement of the ECM, few studies have directly by means of proteomics interrogated the ECM in physiological and pathophysiological wounds. The insights toward specific changes in the ECM that have come from general proteomic analyses of diseased skin are scarce and often limited to the description of altered abundance in individual proteins. Collagen VI was shown to be increased in human scleroderma skin [160] and the SLRP asporin in human keloids. In one of the few studies with a more direct focus on the ECM in normal and pathologically healing skin Eming et al. compared wound exudates from healing leg wounds and chronic venous leg ulcers [161]. Healing wounds showed an increased abundance of collagen I, collagen III, perlecan, COMP, lumican, and fibulin. Contrastingly, exudates from chronic wounds contained more transitional ECM proteins, fibronectin, and vitronectin. Chronic ulcers also contained a unique abundance of olfactomedin-4, an ECM protein with reported immunosuppressive activities [161,162]. In addition, chronic wounds showed an imbalance in proteolytic activities due to the dysregulated balance of proteases and protease inhibitors [161].