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Collagen Crosslinks (collagen + crosslink)
Selected AbstractsTreatment of cartilage with ,-aminopropionitrile accelerates subsequent collagen maturation and modulates integrative repairJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2005Kevin B. McGowan Abstract Integrative repair of cartilage was previously found to depend on collagen synthesis and maturation. ,-aminopropionitrile (BAPN) treatment, which irreversibly blocks lysyl oxidase, inhibited the formation of collagen crosslinks, prevented development of adhesive strength, and caused a buildup of GuHCl-extractable collagen crosslink precursors. This buildup of crosslink precursor in the tissue may be useful for enhancing integrative repair. We tested in vitro the hypothesis that pre-treatment of cartilage with BAPN, followed by washout before implantation, could be a useful therapeutic strategy to accelerate subsequent collagen maturation. In individual cartilage disks, collagen processing was reversibly blocked by BAPN treatment (0.1 mM) as indicated by a BAPN-induced increase in the total and proportion of incorporated radiolabel that was extractable by 4 M guanidine-HCl, followed by a decrease, within 3,4 days of BAPN washout, in the proportion of extractable radiolabel to control levels. With a similar pattern, integration between pairs of apposed cartilage blocks was reversibly blocked by BAPN treatment, and followed by an enhancement of integration after BAPN washout. The low and high levels of integration were associated with enrichment in [3H]proline in a form that was susceptible and resistant, respectively, to extraction. With increasing duration up to 7 days after BAPN pre-treatment, the levels of [3H]proline extraction decreased, and the development of adhesive strength increased. Thus, BAPN can be used to modulate integrative cartilage repair. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] The role of intramuscular connective tissue in meat textureANIMAL SCIENCE JOURNAL, Issue 1 2010Takanori NISHIMURA ABSTRACT The structure, composition and amount of intramuscular connective tissue (IMCT) vary tremendously between muscles, species and breeds, and certainly contribute to meat texture. With animal growth, collagen crosslinks become more stable, and the structural integrity of IMCT increases. These changes increase the mechanical properties of IMCT, contributing to the toughening of meat. Intramuscular fat deposits, mainly in the perimysium between muscle fiber bundles, result in marbling. This causes the remodeling of IMCT structures and reduces the mechanical strength of IMCT, contributing to the tenderization of beef. The IMCT has been thought to be rather immutable compared to myofibrils during postmortem ageing of meat. However, recent studies have shown the disintegration of IMCT during postmortem ageing of meat and its relationship to tenderization of raw meat, although its contribution to cooked meat is still controversial. Given the large influence of IMCT on meat texture, further elucidations of molecular mechanisms which change the structural integrity of IMCT during chronological ageing of animals and postmortem ageing of meat are needed. [source] Fox-2 protein regulates the alternative splicing of scleroderma-associated lysyl hydroxylase 2 messenger RNA,ARTHRITIS & RHEUMATISM, Issue 4 2010Puneet Seth Objective Scleroderma (systemic sclerosis [SSc]) is a complex connective tissue disorder characterized by hardening and thickening of the skin. One hallmark of scleroderma is excessive accumulation of collagen accompanied by increased levels of pyridinoline collagen crosslinks derived from hydroxylysine residues in the collagen telopeptide domains. Lysyl hydroxylase 2 (LH2), an important alternatively spliced enzyme in collagen biosynthesis, acts as a collagen telopeptide hydroxylase. Changes in the pattern of LH2 alternative splicing, favoring increased inclusion of the alternatively spliced LH2 exon 13A, thereby increasing the levels of the long transcript of LH2 (LH2[long]), are linked to scleroderma disease. This study was undertaken to examine the role played by RNA binding protein Fox-2 in regulating exon 13A inclusion, which leads to the generation of scleroderma-associated LH2(long) messenger RNA (mRNA). Methods Phylogenetic sequence analysis of introns flanking exon 13A was performed. A tetracycline-inducible system in T-Rex 293 cells was used to induce Fox-2 protein, and endogenous LH2(long) mRNA was determined by reverse transcriptase,polymerase chain reaction. An LH2 minigene was designed, validated, and used in Fox-2 overexpression and mutagenesis experiments. Knockdown of Fox-2 was performed in mouse embryonic fibroblasts and in fibroblasts from SSc patients. Results Overexpression of Fox-2 enhanced the inclusion of exon 13A and increased the generation of LH2(long) mRNA, whereas knockdown of Fox-2 decreased LH2(long) transcripts. Mutational analysis of an LH2 minigene demonstrated that 2 of the 4 Fox binding motifs flanking LH2 exon 13A are required for inclusion of exon 13A. In early passage fibroblasts derived from patients with scleroderma, the knockdown of Fox-2 protein significantly decreased the endogenous levels of LH2(long) mRNA. Conclusion Our findings indicate that Fox-2 plays an integral role in the regulation of LH2 splicing. Knockdown of Fox-2 and other methods to decrease the levels of fibrosis-associated LH2(long) mRNA in primary scleroderma cells may suggest a novel approach to strategies directed against scleroderma. [source] Combined role of type IX collagen and cartilage oligomeric matrix protein in cartilage matrix assembly: Cartilage oligomeric matrix protein counteracts type IX collagen,induced limitation of cartilage collagen fibril growth in mouse chondrocyte culturesARTHRITIS & RHEUMATISM, Issue 12 2009K. Blumbach Objective Defects in the assembly and composition of cartilage extracellular matrix are likely to result in impaired matrix integrity and increased susceptibility to cartilage degeneration. The aim of this study was to determine the functional interaction of the collagen fibril,associated proteins type IX collagen and cartilage oligomeric matrix protein (COMP) during cartilage matrix formation. Methods Primary chondrocytes from mice deficient in type IX collagen and COMP (double-deficient) were cultured in monolayer or alginate beads. Anchorage of matrix proteins, proteoglycan and collagen content, collagen crosslinks, matrix metalloproteinase activity, and mechanical properties of the matrix were measured. Electron microscopy was used to study the formation of fibrillar structures. Results In cartilage lacking both type IX collagen and COMP, matrilin 3 showed decreased matrix anchorage. Less matrilin 3 was deposited in the matrix of double-deficient chondrocytes, while larger amounts were secreted into the medium. Proteoglycans were less well retained in the matrix formed in alginate cultures, while collagen deposition was not significantly affected. Electron microscopy revealed similar cartilage collagen fibril diameters in the cultures of double-deficient and wild-type chondrocytes. In contrast, a larger fibril diameter was observed in the matrix of chondrocytes deficient in only type IX collagen. Conclusion Our results show that type IX collagen and COMP are involved in matrix assembly by mediating the anchorage and regulating the distribution of other matrix macromolecules such as proteoglycans and matrilins and have counteracting effects on collagen fibril growth. Loss of type IX collagen and COMP leads to matrix aberrations that may make cartilage more susceptible to degeneration. [source] | ||||||||||