keratan-sulfate and Aortic-Valve-Stenosis

Proteoglycans consist of a protein core to which at least one glycosaminoglycan chain is attached. They play important roles in the physiology and biomechanical function of tendons, ligaments and cardiovascular system through their involvement in regulation of assembly and maintenance of extracellular matrix, and as they participate in cell proliferation through their interactions with growth factors. They can be divided into two main groups of small and large proteoglycans. The small proteoglycans are also known as small leucine-rich proteoglycans (or SLRPs) which are encoded by 17 genes and are further subclassified into Classes I-V. Several members of Class I and II, such as decorin and biglycan from Class I, and Class II fibromodulin and lumican, are known to regulate collagen fibrillogenesis. Decorin limits the diameter of collagen fibrils during fibrillogenesis. The function of biglycan in fibrillogenesis is similar to that of decorin. Though biomechanical function of tendon is compromised in decorin-deficient mice, decorin can substitute for lack of biglycan in biglycan-deficient mice. New data also indicate an important role for biglycan in disorders of the cardiovascular system, including aortic valve stenosis and aortic dissection. Two members of the Class II of SLRPs, fibromodulin and lumican bind to the same site within the collagen molecule and can substitute for each other in fibromodulin- or lumican-deficient mice.Aggrecan and versican are the major representatives of the large proteoglycans. Though they are mainly found in the cartilage where they provide resilience and toughness, they are also present in tensile portions of tendons and, in slightly different biochemical form in fibrocartilage. Degradation with aggrecanase is responsible for the appearance of different forms of aggrecan and versican in different parts of the tendon where these cleaved forms play different roles. In addition, they are important components of the ventricularis of cardiac valves. Mutations in the gene for versican or in the gene for elastin (which binds to versican) lead to severe disruptions of normal developmental of the heart at least in mice.

Topics: Aggrecans; Animals; Aortic Aneurysm, Thoracic; Aortic Valve Stenosis; Biglycan; Chondroitin Sulfate Proteoglycans; Collagen; Decorin; Extracellular Matrix; Extracellular Matrix Proteins; Fibromodulin; Humans; Keratan Sulfate; Ligaments; Lumican; Mice; Protein Binding; Proteoglycans; Tendons; Versicans

To identify proteins related to the pathophysiology of aortic valve stenosis (AS), we investigated the protein profiles of AS aortic valves. Specifically, proteins were extracted from a thickened and calcified area (AS-C) and an apparently non-thickened and non-calcified area (AS-N) in an identical aortic valve leaflet in each of 6 AS patients. The proteins were then separated by 2-dimensional gel electrophoresis (2DE). Protein spots detected by 2DE were compared between the AS-C and AS-N samples. Protein spots of interest were subjected to protein identification by mass spectrometry.In total, 670 protein spots were detected by 2DE, 28 of which showed more than 1.5-fold different intensity (P < 0.05) between the AS-C and AS-N samples. Proteins were identified in 17 out of the 28 spots. Fibrinogen and lumican were identified in 9 and 3 spots, respectively. Intensity of these 12 spots was lower in the AS-C samples than in the AS-N samples. In the 1D-Western blot analysis, 4 lumican bands (80 kDa, 75 kDa, 65 kDa, and 53 kDa) were detected, of which 2 bands with 80 kDa and 75 kDa showed lower intensity in the AS-C samples than in the AS-N samples. When de-glycosylated protein samples were used in the 1D-Western blot, only a single lumican band with ~40 kDa was detected, indicating that lumican was variously glycosylated and that highly glycosylated lumican molecules were decreased in AS-C.Collectively, insufficient glycosylation of lumican in the thickened and calcified areas of AS aortic valves may be involved in the pathophysiology of AS.

Topics: Adult; Aged; Aged, 80 and over; Aortic Valve Stenosis; Blotting, Western; Chondroitin Sulfate Proteoglycans; Electrophoresis, Gel, Two-Dimensional; Female; Glycosylation; Humans; Keratan Sulfate; Lumican; Male; Middle Aged; Proteomics

On the basis of the role of small, leucine-rich proteoglycans (SLRPs) in fibrogenesis and inflammation, we hypothesized that they could be involved in cardiac remodeling and reverse remodeling as occurs during aortic stenosis and after aortic valve replacement. Thus, in a well-characterized aortic banding-debanding mouse model, we examined the SLRPs decorin and lumican and enzymes responsible for synthesis of their glycosaminoglycan (GAG) chains. Four weeks after banding of the ascending aorta, mice were subjected to a debanding operation (DB) and were subsequently followed for 3 or 14 days. Sham-operated mice served as controls. Western blotting revealed a 2.5-fold increase in the protein levels of glycosylated decorin in mice with left ventricular pressure overload after aortic banding (AB) with a gradual decrease after DB. Interestingly, protein levels of three key enzymes responsible for decorin GAG chain synthesis were also increased after AB, two of them gradually declining after DB. The inflammatory chemokine (C-X-C motif) ligand 16 (CXCL16) was increased after AB but was not significantly altered following DB. In cardiac fibroblasts CXCL16 increased the expression of the GAG-synthesizing enzyme chondroitin polymerizing factor (CHPF). The protein levels of lumican core protein with N-linked oligosaccharides increased by sevenfold after AB and decreased again 14 days after DB. Lumican with keratan sulfate chains was not regulated. In conclusion, this study shows alterations in glycosylated decorin and lumican core protein that might be implicated in myocardial remodeling and reverse remodeling, with a potential important role for CS/DS GAG chain-synthesizing enzymes.

Topics: Animals; Aortic Valve Stenosis; Blotting, Western; Cells, Cultured; Chemokine CXCL16; Chemokine CXCL6; Chondroitin Sulfate Proteoglycans; Decorin; Disease Models, Animal; Fibroblasts; Gene Expression Regulation, Enzymologic; Glucuronosyltransferase; Glycosylation; Glycosyltransferases; Inflammation Mediators; Keratan Sulfate; Lumican; Male; Mice; Mice, Inbred C57BL; Multifunctional Enzymes; Myocardial Contraction; Myocardium; N-Acetylgalactosaminyltransferases; Time Factors; Ultrasonography; Ventricular Pressure; Ventricular Remodeling