Prolonged Application of High Fluid Shear to Chondrocytes Recapitulates Gene Expression Profiles Associated with Osteoarthritis

BACKGROUND: Excessive mechanical loading of articular cartilage producing hydrostatic stress, tensile strain and fluid flow leads to irreversible cartilage erosion and osteoarthritic (OA) disease. Since application of high fluid shear to chondrocytes recapitulates some of the earmarks of OA, we aimed to screen the gene expression profiles of shear-activated chondrocytes and assess potential similarities with OA chondrocytes. METHODOLOGY/PRINCIPAL FINDINGS: Using a cDNA microarray technology, we screened the differentially-regulated genes in human T/C-28a2 chondrocytes subjected to high fluid shear (20 dyn/cm(2)) for 48 h and 72 h relative to static controls. Confirmation of the expression patterns of select genes was obtained by qRT-PCR. Using significance analysis of microarrays with a 5% false discovery rate, 71 and 60 non-redundant transcripts were identified to be ≥2-fold up-regulated and ≤0.6-fold down-regulated, respectively, in sheared chondrocytes. Published data sets indicate that 42 of these genes, which are related to extracellular matrix/degradation, cell proliferation/differentiation, inflammation and cell survival/death, are differentially-regulated in OA chondrocytes. In view of the pivotal role of cyclooxygenase-2 (COX-2) in the pathogenesis and/or progression of OA in vivo and regulation of shear-induced inflammation and apoptosis in vitro, we identified a collection of genes that are either up- or down-regulated by shear-induced COX-2. COX-2 and L-prostaglandin D synthase (L-PGDS) induce reactive oxygen species production, and negatively regulate genes of the histone and cell cycle families, which may play a critical role in chondrocyte death. CONCLUSIONS/SIGNIFICANCE: Prolonged application of high fluid shear stress to chondrocytes recapitulates gene expression profiles associated with osteoarthritis. Our data suggest a potential link between exposure of chondrocytes/cartilage to abnormal mechanical loading and the pathogenesis/progression of OA

The AMPA antagonist ZK 200775 in patients with acute ischaemic stroke: A double-blind, multicentre, placebo-controlled safety and tolerability study

Background and Purpose: ZK 200775 is a selective competitive AMPA receptor antagonist. It has demonstrated neuroprotective efficacy in experimental models of stroke and tolerability in healthy volunteers. We tested the safety and tolerability of ZK 200775 in patients with acute ischaemic stroke. Methods: In a multicentre double-blind, randomised, placebo-controlled phase II trial, 61 ischaemic stroke patients were treated with either placebo or active drug in a dose finding design. Twenty-five patients received placebo, 12 patients received a total dose of 262.5 mg in 48 h ( group 1) and 13 patients received a total dose of 525 mg in 48 h ( group 2), and 11 patients received a total dose of 105 mg over a period of 6 h ( group 3). We studied the pharmacokinetics of the compound and the effect of the infusion on the neurologic and haemodynamic parameters of the patients. The study was not powered to detect neuroprotective efficacy. Results: In group 2 there was a significant transient worsening in the mean NIH stroke scale score 14 - 18 h after the start of treatment. This was due to reduction of consciousness ( stupor and coma) in 8 out of 13 patients. Level of consciousness improved approximately 6 h after cessation of infusion. No significant haemodynamic responses were observed. Even after reduction of the administered dose and duration of infusion to 6 h ( group 3), 2 patients experienced a reduction in level of consciousness. The effect of ZK 200775 on level of consciousness gave cause for concern and the trial was stopped prematurely for safety reasons. Conclusions: The AMPA antagonist ZK 200775 reversibly worsened the neurological condition in patients with acute ischaemic stroke. Our results suggest that ZK 200775 exerts significant sedative effects in patients with acute stroke which preclude its further development as a neuroprotective agent in this indication. Copyright (C) 2005 S. Karger AG, Basel

Twenty-Four Centrifuge Tests to Quantify Sensitivity of Lateral Spreading to Dr and PGA

Twenty-four centrifuge model tests have been conducted at nine different geotechnical centrifuge facilities around the world as part of the international LEAP effort (liquefaction experiments and analysis projects). All of the centrifuge models represent a 4 m deep 5 degree sloping submerged sand deposit. The mean effective PGA of the input motion for all of the experiments was approximately 0.15 g and the mean relative density was approximately 65%, but the effective PGA's varied between about 0.07 g and 0.3 g, and the relative densities varied between about 40% and 75%. The test matrix was designed to enable experimental quantification of not only the median response but also the trend and sensitivity of the model response to density and shaking intensity. Quantification of the sensitivity of the response to initial conditions is a prerequisite for objective evaluation of the quality of the model test data. In other words, a discrepancy between two experiments should be evaluated after accounting for the uncertainty in the initial conditions and the sensitivity of the response to initial conditions. For the first time, a sufficient number of experiments has been performed on a similar problem to provide meaningful quantitative evaluation of the trend between PGA, density, and displacement. The sensitivity is quantified by the gradient of the trend and the uncertainty of the trend is quantified from the residuals between the fitting data and the trend