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Collagen Architecture (collagen + architecture)
Selected AbstractsCollagen architecture and failure processes in bovine patellar cartilageJOURNAL OF ANATOMY, Issue 4 2001JACK L. LEWIS Cartilage fails by fibrillation and wearing away. This study was designed to identify the microscopic failure processes in the collagen network of bovine cartilage using scanning electron microscopy. Cartilage samples from fibrillated cartilage from the bovine patella were removed from the bone, fixed, digested to remove proteoglycans, freeze-fractured, and processed for SEM. The architecture of the collagen network in the normal cartilage was first defined, and then the failure processes were identified by examining sites of fibrillation and at crack tips. The bovine patellar cartilage was organised with a superficial layer composed of 3,5 lamina, attached to a sub-superficial tissue by angled bridging fibrils. Collagen in the sub-superficial tissue was organised in lamina oriented in the radial direction up to the transition zone. Failure of the system occurred by cracks forming in superficial layer and lamina, creating flaps of lamina that rolled up into the larger ,fronds'. Larger cracks not following the laminar planes occurred in the transition, mid, and deep zones. Failure at the crack tips in the sub-superficial tissue appeared to be by peeling of collagen fibrils, as opposed to breaking of collagen fibrils, suggesting a ,glue' bonding the collagen fibrils in a parallel fashion. Cracks propagated by breaking these bonds. This bond could be a site of disease action, since weakening of the bond would accelerate crack propagation. [source] Effects of mechanical loading on collagen propeptides processing in cartilage repairJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 1 2010Rosmarie Hardmeier Abstract Injured articular cartilage has poor reparative capabilities and if left untreated may develop into osteoarthritis. Unsatisfactory results with conventional treatment methods have brought as an alternative treatment the development of matrix autologous chondrocyte transplants (MACTs). Recent evidence proposes that the maintenance of the original phenotype by isolated chondrocytes grown in a scaffold transplant is linked to mechanical compression, because macromolecules, particularly collagen, of the extracellular matrix have the ability to ,self-assemble'. In load-bearing tissues, collagen is abundantly present and mechanical properties depend on the collagen fibre architecture. Study of the active changes in collagen architecture is the focus of diverse fields of research, including developmental biology, biomechanics and tissue engineering. In this review, the structural model of collagen assembly is presented in order to understand how scaffold geometry plays a critical role in collagen propeptide processing and chondrocyte development. When physical forces are applied to different cell-based scaffolds, the resulting specific twist of the scaffolds might be accompanied by changes in the fibril pattern synthesis of the new collagen. The alteration in the scaffolds due to mechanical stress is associated with cellular signalling communication and the preservation of N-terminus procollagen moieties, which would regulate both the collagen synthesis and the diameter of the fibre. The structural difference would also affect actin stabilization, cytoskeleton remodelling and proteoglycan assembly. These effects seemed to be dependent on the magnitude and duration of the physical stress. This review will contribute to the understanding of mechanisms for collagen assembly in both a natural and an artificial environment. Copyright © 2009 John Wiley & Sons, Ltd. [source] T2 relaxation reveals spatial collagen architecture in articular cartilage: A comparative quantitative MRI and polarized light microscopic studyMAGNETIC RESONANCE IN MEDICINE, Issue 3 2001Miika T. Nieminen Abstract It has been suggested that orientational changes in the collagen network of articular cartilage account for the depthwise T2 anisotropy of MRI through the magic angle effect. To investigate the relationship between laminar T2 appearance and collagen organization (anisotropy), bovine osteochondral plugs (N = 9) were T2 mapped at 9.4T with cartilage surface normal to the static magnetic field. Collagen fibril arrangement of the same samples was studied with polarized light microscopy, a quantitative technique for probing collagen organization by analyzing its ability to rotate plane polarized light, i.e., birefringence (BF). Depthwise variation of safranin O-stained proteoglycans was monitored with digital densitometry. The spatially varying cartilage T2 followed the architectural arrangement of the collagen fibril network: a linear positive correlation between T2 and the reciprocal of BF was established in each sample, with r = 0.91 ± 0.02 (mean ± SEM, N = 9). The current results reveal the close connection between the laminar T2 structure and the collagen architecture in histologic zones. Magn Reson Med 46:487,493, 2001. © 2001 Wiley-Liss, Inc. [source] The Effects of Brain Natriuretic Peptide on Scar Formation in Incisional Rat WoundsACADEMIC EMERGENCY MEDICINE, Issue 10 2008Breena R. Taira MD Abstract Background:, Brain natriuretic peptide (BNP) is a peptide that reduces scar formation in the heart by blocking transforming growth factor-, (TGF-,). Although TGF-, is known to play a role in scar formation in the myocardium, little is known about the effects of BNP on cutaneous wound healing. Objectives:, The objective was to determine if the administration of BNP in healing cutaneous wounds reduces the amount of scarring. Methods:, This was a laboratory investigation using 40 wild-strain rats. Three full-thickness 1-cm incisional wounds were created on each animal and randomized to intradermal BNP, saline, or no treatment. Wounds were excised at 3, 7, 14, 31, and 60 days and examined histologically for scar surface area and collagen architecture. Those wounds excised at 30 days were subjected to a measure of tensile strength and those excised at 60 days were evaluated prior to excision for cosmesis using a scar evaluation scale. The proportion of wounds healing without visually apparent scar was the main outcome. Groups were compared with Fisher's exact and Kruskal-Wallis tests. Results:, Wounds treated with BNP were more likely to heal without an apparent scar when compared to those treated with saline or control (37.5% vs. 0%, p = 0.03). There were no between-group differences in the surface area of the scars or the collagen architecture. Incisional tensile strength was also similar across treatments. Conclusions:, Treatment of rat incisions with BNP reduced the number of visually apparent scars but did not affect the histologic appearance of the scars or the incisional tensile strength. [source] | ||||||||||