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Extensive Remodeling (extensive + remodeling)
Selected AbstractsMonocilia on chicken embryonic endocardium in low shear stress areasDEVELOPMENTAL DYNAMICS, Issue 1 2006Kim Van der Heiden Abstract During cardiovascular development, fluid shear stress patterns change dramatically due to extensive remodeling. This biomechanical force has been shown to drive gene expression in endothelial cells and, consequently, is considered to play a role in cardiovascular development. The mechanism by which endothelial cells sense shear stress is still unidentified. In this study, we postulate that primary cilia function as fluid shear stress sensors of endothelial cells. Such a function already has been attributed to primary cilia on epithelial cells of the adult kidney and of Hensen's node in the embryo where they transduce mechanical signals into an intracellular Ca2+ signaling response. Recently, primary cilia were observed on human umbilical vein endothelial cells. These primary cilia disassembled when subjected to high shear stress levels. Whereas endocardial,endothelial cells have been reported to be more shear responsive than endothelial cells, cilia are not detected, thus far, on endocardial cells. In the present study, we use field emission scanning electron microscopy to show shear stress-related regional differences in cell protrusions within the cardiovasculature of the developing chicken. Furthermore, we identify one of these cell protrusions as a monocilium with monoclonal antibodies against acetylated and detyrosinated alpha-tubulin. The distribution pattern of the monocilia was compared to the chicken embryonic expression pattern of the high shear stress marker Krüppel-like factor-2. We demonstrate the presence of monocilia on endocardial,endothelial cells in areas of low shear stress and postulate that they are immotile primary cilia, which function as fluid shear stress sensors. Developmental Dynamics 235:19,28, 2006. © 2005 Wiley-Liss, Inc. [source] Morphologic changes associated with functional adaptation of the navicular bone of horsesJOURNAL OF ANATOMY, Issue 5 2007V. A. Bentley Abstract Failure of functional adaptation to protect the skeleton from damage is common and is often associated with targeted remodeling of bone microdamage. Horses provide a suitable model for studying loading-related skeletal disease because horses are physically active, their exercise is usually regulated, and adaptive failure of various skeletal sites is common. We performed a histologic study of the navicular bone of three groups of horses: (1) young racing Thoroughbreds (n = 10); (2) young unshod ponies (n = 10); and (3) older horses with navicular syndrome (n = 6). Navicular syndrome is a painful condition that is a common cause of lameness and is associated with extensive remodeling of the navicular bone; a sesamoid bone located within the hoof which articulates with the second and third phalanges dorsally. The following variables were quantified: volumetric bone mineral density; cortical thickness (Ct.Th); bone volume fraction, microcrack surface density; density of osteocytes and empty lacunae; and resorption space density. Birefringence of bone collagen was also determined using circularly polarized light microscopy and disruption of the lacunocanalicular network was examined using confocal microscopy. Remodeling of the navicular bone resulted in formation of transverse secondary osteons orientated in a lateral to medial direction; bone collagen was similarly orientated. In horses with navicular syndrome, remodeling often led to the formation of intracortical cysts and development of multiple tidemarks at the articular surface. These changes were associated with high microcrack surface density, low bone volume fraction, low density of osteocytes, and poor osteocyte connectivity. Empty lacunae were increased in Thoroughbreds. Resorption space density was not increased in horses with navicular syndrome. Taken together, these data suggest that the navicular bone may experience habitual bending across the sagittal plane. Consequences of cumulative cyclic loading in horses with navicular syndrome include arthritic degeneration of adjacent joints and adaptive failure of the navicular bone, with accumulation of microdamage and associated low bone mass, poor osteocyte connectivity, and low osteocyte density, but not formation of greater numbers of resorption spaces. [source] Repair of porcine articular cartilage defect with a biphasic osteochondral composite,JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2007Ching-Chuan Jiang Abstract Autologous chondrocyte implantation (ACI) has been recently used to treat cartilage defects. Partly because of the success of mosaicplasty, a procedure that involves the implantation of native osteochondral plugs, it is of potential significance to consider the application of ACI in the form of biphasic osteochondral composites. To test the clinical applicability of such composite construct, we repaired osteochondral defect with ACI at low cell-seeding density on a biphasic scaffold, and combined graft harvest and implantation in a single surgery. We fabricated a biphasic cylindrical porous plug of DL-poly-lactide-co-glycolide, with its lower body impregnated with ,-tricalcium phosphate as the osseous phase. Osteochondral defects were surgically created at the weight-bearing surface of femoral condyles of Lee-Sung mini-pigs. Autologous chondrocytes isolated from the cartilage were seeded into the upper, chondral phase of the plug, which was inserted by press-fitting to fill the defect. Defects treated with cell-free plugs served as control. Outcome of repair was examined 6 months after surgery. In the osseous phase, the biomaterial retained in the center and cancellous bone formed in the periphery, integrating well with native subchondral bone with extensive remodeling, as depicted on X-ray roentgenography by higher radiolucency. In the chondral phase, collagen type II immunohistochemistry and Safranin O histological staining showed hyaline cartilage regeneration in the experimental group, whereas only fibrous tissue formed in the control group. On the International Cartilage Repair Society Scale, the experimental group had higher mean scores in surface, matrix, cell distribution, and cell viability than control, but was comparable with the control group in subchondral bone and mineralization. Tensile stress,relaxation behavior determined by uni-axial indentation test revealed similar creep property between the surface of the experimental specimen and native cartilage, but not the control specimen. Implanted autologous chondrocytes could survive and could yield hyaline-like cartilage in vivo in the biphasic biomaterial construct. Pre-seeding of osteogenic cells did not appear to be necessary to regenerate subchondral bone. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1277,1290, 2007 [source] Ex vivo assessment of mouse cervical remodeling through pregnancy via 23Na MRSNMR IN BIOMEDICINE, Issue 8 2010Xiang Xu Abstract Preterm birth occurs in 12.5% of births in the United States and can lead to risk of infant death or to lifelong serious health complications. A greater understanding by which the two main processes, uterine contraction and cervical remodeling are regulated is required to reduce rates of preterm birth. The cervix must undergo extensive remodeling through pregnancy in preparation for parturition, the process of labor and delivery of young. One key aspect of this dynamic process is a change in the composition and abundance of glycosaminoglycans (GAGs) and proteoglycans within the extracellular matrix, which influences the loss of tensile strength or stiffness of the cervix during labor. 23Na NMR spectroscopy has previously been validated as a method to quantify GAGs in tissues. In the current study, the Na+ concentration was measured at several time points through pregnancy in mouse cervices using 23Na NMR spectroscopy. The Na+ concentration increased progressively during pregnancy and peaked one day before birth followed by a rapid decline after birth. The same trend was seen in GAGs as measured by a biochemical assay using independent cervix samples over the course of pregnancy. We suggest that monitoring the Na+ concentration via 23Na NMR spectroscopy can serve as an informative physiological marker in evaluating the stages of cervical remodeling ex vivo and warrants further investigation to determine its utility as a diagnostic tool for the identification of women at risk for impending preterm birth. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||