Varying regional topology within knee articular chondrocytes under simulated in vivo conditions
ABSTRACT Topographical cartilage variation across the knee joint has been previously reported, but there is only limited information on such gene expression profiles. Articular chondrocytes from eight different topographical regions of bovine knee joints were seeded within three-dimensional scaffolds and further cultured under static conditions (unloaded control group) or subjected to an artificial joint environment within a bioreactor (loaded group). Constructs were analyzed for glycosaminoglycan (GAG), DNA, and expression of Collagen-1,-2,-10, Aggrecan, COMP, Sox9, PRG-4, PTHrp, and MMP-1,-3,-13 mRNA after 2 weeks of in vitro culture. Exclusively among loaded constructs the overall GAG production was significantly different between regions. Patella chondrocytes had overall highest, and cells from the femoral notch had overall lowest GAG/DNA under loaded conditions. Gene expression was significantly different between regions for all targets except for Sox9, PRG-4, and PTHrp among controls and with the exception of Aggrecan, Sox9, and PTHrp among loaded samples. Under mechanical stimulation Collagen-1,-2 and Aggrecan was highest at the patello-femoral joint, whereas it was lowest at typical cartilage biopsy regions. There is a clear topographical variation among distinct regions across the knee joint for gene and matrix expression profiles under static and foremost under dynamic conditions.
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- "After 0.2 mm (5% of the scaffold height) of preload, the ceramic ball sinusoidally oscillated between 0.2 and 0.6 mm (5–15% of the scaffold height) at a frequency of 1 Hz. Simultaneously , the ball oscillated around an axis perpendicular to the scaffold axis over the scaffold surface at AE258 and 1 Hz to generate shear-like surface motion, as described in previous studies [Grad et al., 2005, 2006a,b; Wernike et al., 2008; Salzmann et al., 2010a]. Groups E2, E6, E7, and E8 were loaded every second day for 1 h twice a day with 8 h rest in between, for a total of 16 h loading after 21 days. "
ABSTRACT: Articular cartilage, once damaged, has very low regenerative potential. Various experimental approaches have been conducted to enhance chondrogenesis and cartilage maturation. Among those, non-invasive electromagnetic fields have shown their beneficial influence for cartilage regeneration and are widely used for the treatment of non-unions, fractures, avascular necrosis and osteoarthritis. One very well accepted way to promote cartilage maturation is physical stimulation through bioreactors. The aim of this study was the investigation of combined mechanical and electromagnetic stress affecting cartilage cells in vitro. Primary articular chondrocytes from bovine fetlock joints were seeded into three-dimensional (3-D) polyurethane scaffolds and distributed into seven stimulated experimental groups. They either underwent mechanical or electromagnetic stimulation (sinusoidal electromagnetic field of 1 mT, 2 mT, or 3 mT; 60 Hz) or both within a joint-specific bioreactor and a coil system. The scaffold-cell constructs were analyzed for glycosaminoglycan (GAG) and DNA content, histology, and gene expression of collagen-1, collagen-2, aggrecan, cartilage oligomeric matrix protein (COMP), Sox9, proteoglycan-4 (PRG-4), and matrix metalloproteinases (MMP-3 and -13). There were statistically significant differences in GAG/DNA content between the stimulated versus the control group with highest levels in the combined stimulation group. Gene expression was significantly higher for combined stimulation groups versus static control for collagen 2/collagen 1 ratio and lower for MMP-13. Amongst other genes, a more chondrogenic phenotype was noticed in expression patterns for the stimulated groups. To conclude, there is an effect of electromagnetic and mechanical stimulation on chondrocytes seeded in a 3-D scaffold, resulting in improved extracellular matrix production. Bioelectromagnetics. 9999:1-13. © 2013 Wiley Periodicals, Inc.Bioelectromagnetics 02/2014; 35(2). DOI:10.1002/bem.21822 · 1.86 Impact Factor
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ABSTRACT: Irrespective of the specifics of a given application, multisensor data fusion problem is mainly composed of three sub-problems: selection, fusion and estimation. Sensor measurements inherently incorporate varying degrees of uncertainty and are, occasionally, spurious and incorrect This, coupled with the practical reality of occasional sensor failure greatly compromises reliability and reduces confidence in sensor measurements. In order to avoid any false inferences, we need data pre-processing methods to make sure that the data to be merged is consistent. Selection of noisy sensor data is a preprocessing of data before merging and is referred to as choosing a representative subset of the sensors that are consistent. In this paper, we use genetic search and optimization approach to develop a genetic algorithm for qualifying the dataAmerican Control Conference, 1997. Proceedings of the 1997; 07/1997
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ABSTRACT: This study has been based on the assumption that articular motion is an important aspect of mechanotransduction in synovial joints. For this reason a new bioreactor concept, able to reproduce joint kinematics more closely, has been designed. The prototype consists of a rotating scaffold and/or cartilage pin, which is pressed onto an orthogonally rotating ball. By oscillating pin and ball in phase difference, elliptical displacement trajectories are generated that are similar to the motion paths occurring in vivo. Simultaneously, dynamic compression may be applied with a linear actuator, while two-step-motors generate the rotation of pin and ball. The whole apparatus is placed in an incubator. The control station is located outside. Preliminary investigations at the gene expression level demonstrated promising results. Compared with free-swelling control and/or simply compression-loaded samples, chondrocyte-seeded scaffolds as well as nasal cartilage explants exposed to interface motion both showed elevated levels of cartilage oligomeric matrix protein mRNA. The final design of the bioreactor will include four individual stations in line, which will facilitate the investigation of motion-initiated effects at the contacting surfaces in more detail.Tissue Engineering 09/2004; 10(9-10):1436-45. DOI:10.1089/ten.2004.10.1436 · 4.25 Impact Factor