A computational algorithm to simulate disorganization of collagen network in injured articular cartilage

Cartilage defects are a known risk factor for osteoarthritis. Estimation of structural changes in these defects could help us to identify high risk defects and thus to identify patients that are susceptible for the onset and progression of osteoarthritis. Here, we present an algorithm combined with computational modeling to simulate the disorganization of collagen fibril network in injured cartilage. Several potential triggers for collagen disorganization were tested in the algorithm following the assumption that disorganization is dependent on the mechanical stimulus of the tissue. We found that tensile tissue stimulus alone was unable to preserve collagen architecture in intact cartilage as collagen network reoriented throughout the cartilage thickness. However, when collagen reorientation was based on both tensile tissue stimulus and tensile collagen fibril strains or stresses, the collagen network architecture was preserved in intact cartilage. Using the same approach, substantial collagen reorientation was predicted locally near the cartilage defect and particularly at the cartilage–bone interface. The developed algorithm was able to predict similar structural findings reported in the literature that are associated with experimentally observed remodeling in articular cartilage. The proposed algorithm, if further validated, could help to predict structural changes in articular cartilage following post-traumatic injury potentially advancing to impaired cartilage function.     

Surface energetics to assess biomass attachment onto immobilized metal-ion chromatography adsorbents in expanded beds

Cell-to-support interaction and cell-to-cell agglomeration phenomena have been studied in a model system composed of intact yeast cells and Chelating-Streamline™ adsorbents. Biomass components and beaded adsorbents were mainly characterized by contact angle determinations with three diagnostic liquids. Complementarily, zeta potential measurements were performed. These experimental values were employed to calculate free energy of interaction versus distance profiles in aqueous media. The effect of immobilized metal-ion type and buffer pH on the interaction energy was evaluated. Calculations indicated that moderate interaction between cell particles and adsorbent beads can develop due to the presence of Cu²⁺ ions onto the solid phase. The strength of interaction increased with buffer pH, within the range 6.0 to 8.3 e.g. secondary energy pockets increased from |15| to |60| kT. Cell-to-cell secondary energy minimum was ≥ |14| kT showing low-to-moderate tendencies to aggregate, particularly at pH ≥ 8. Extended DLVO predictions were generally confirmed by biomass deposition experiments. However, an exception was found when working with immobilized Cu²⁺ at pH 8 since yeast cells were able to sequestrate such immobilized ions. Therefore, lower-than-expected values for the depositions coefficient (α) were observed. Understanding biomass attachment onto Chelating supports can help in better design and operate expanded bed adsorption of bioproducts.     

The serine protease Omi/HtrA2 is involved in XIAP cleavage and in neuronal cell death following focal cerebral ischemia/reperfusion

Omi/HtrA2 is a pro-apoptotic mitochondrial serine protease involved in both forms of apoptosis, caspase-dependent as well as caspase-independent cell death. However, the impact of Omi/HtrA2 in the apoptotic cell machinery that takes place in vivo under pathological conditions such as cerebral ischemia remains unknown. The present study was monitored in order to examine whether Omi/HtrA2 plays a decisive role in apoptosis observed after focal cerebral ischemia in rats. Male adult rats were subjected to 90min of focal cerebral ischemia followed by reperfusion and treated with vehicle or ucf-101, a novel and specific Omi/HtrA2 inhibitor, prior reperfusion. Focal cerebral ischemia/reperfusion induced a mitochondrial up-regulation of Omi/HtrA2 and significantly increased cytosolic accumulation of Omi/HtrA2. Furthermore, ischemia led to activation of caspase-3 and degradation X-linked inhibitor of apoptosis protein (XIAP). Treatment of animals prior ischemia with ucf-101, the specific inhibitor of Omi/HtrA2, was able to (1) reduce the number of TUNEL-positive cells, to (2) attenuate the XIAP-breakdown and to (3) reduce the infarct size. This study shows for the first time that focal cerebral ischemia in rats results in Omi/HtrA2 translocation from the mitochondria to the cytosol, where it participates in neuronal cell death. Blocking the proteolytic activity of Omi/HtrA2 with specific inhibitors, such as the ucf-101, could be a novel way to afford neuroprotection and minimize cellular damage in cerebral ischemia/reperfusion.     

Identification of a Novel Pathway of Transforming Growth Factor-β1 Regulation by Extracellular NAD+ in Mouse Macrophages: IN VITRO AND IN SILICO STUDIES

Extracellular β-nicotinamide adenine dinucleotide (NAD(+)) is anti-inflammatory. We hypothesized that NAD(+) would modulate the anti-inflammatory cytokine Transforming Growth Factor (TGF)-β1. Indeed, NAD(+) led to increases in both active and latent cell-associated TGF-β1 in RAW 264.7 mouse macrophages as well as in primary peritoneal macrophages isolated from both C3H/HeJ (TLR4-mutant) and C3H/HeOuJ (wild-type controls for C3H/HeJ) mice. NAD(+) acts partially via cyclic ADP-ribose (cADPR) and subsequent release of Ca(2+). Treatment of macrophages with the cADPR analog 3-deaza-cADPR or Ca(2+) ionophores recapitulated the effects of NAD(+) on TGF-β1, whereas the cADPR antagonist 8-Br-cADPR, Ca(2+) chelation, and antagonism of L-type Ca(2+) channels suppressed these effects. The time and dose effects of NAD(+) on TGF-β1 were complex and could be modeled both statistically and mathematically. Model-predicted levels of TGF-β1 protein and mRNA were largely confirmed experimentally but also suggested the presence of other mechanisms of regulation of TGF-β1 by NAD(+). Thus, in vitro and in silico evidence points to NAD(+) as a novel modulator of TGF-β1.     

Mechano-acoustic determination of Young's modulus of articular cartilage

The compressive stiffness of an elastic material is traditionally characterized by its Young's modulus. Young's modulus of articular cartilage can be directly measured using unconfined compression geometry by assuming the cartilage to be homogeneous and isotropic. In isotropic materials, Young's modulus can also be determined acoustically by the measurement of sound speed and density of the material. In the present study, acoustic and mechanical techniques, feasible for in vivo measurements, were investigated to quantify the static and dynamic compressive stiffness of bovine articular cartilage in situ. Ultrasound reflection from the cartilage surface, as well as the dynamic modulus were determined with the recently developed ultrasound indentation instrument and compared with the reference mechanical and ultrasound speed measurements in unconfined compression (n=72). In addition, the applicability of manual creep measurements with the ultrasound indentation instrument was evaluated both experimentally and numerically. Our experimental results indicated that the sound speed could predict 47% and 53% of the variation in the Young's modulus and dynamic modulus of cartilage, respectively. The dynamic modulus, as determined manually with the ultrasound indentation instrument, showed significant linear correlations with the reference Young's modulus (r(2)=0.445, p<0.01, n=70) and dynamic modulus (r(2)=0.779, p<0.01, n=70) of the cartilage. Numerical analyses indicated that the creep measurements, conducted manually with the ultrasound indentation instrument, were sensitive to changes in Young's modulus and permeability of the tissue, and were significantly influenced by the tissue thickness. We conclude that acoustic parameters, i.e. ultrasound speed and reflection, are indicative to the intrinsic mechanical properties of the articular cartilage. Ultrasound indentation instrument, when further developed, provides an applicable tool for the in vivo detection of cartilage mechano-acoustic properties. These techniques could promote the diagnostics of osteoarthrosis.     

Design of a Wide Ranging Highly Sensitive Pressure Sensor Based on Two-Dimensional Photonic Crystals

Plasmonics - A highly sensitive pressure sensor operating over a wide pressure range based on two-dimensional photonic crystals having a Mach-Zehnder interferometer structure has been developed....     

Paraoxonases are associated with intestinal inflammatory diseases and intracellularly localized to the endoplasmic reticulum

We demonstrated previously that the paraoxonase (PON1/2/3) genes and proteins are expressed in human intestinal biopsies and in Caco-2 cells. The current study aims were to explore whether PON1/2/3 expression is different in inflammatory bowel diseases (IBD) or celiac disease compared to healthy controls, and to explore the intracellular localization of PON1/2/3. Our results showed that significantly fewer biopsies expressed PON1 and PON3 in the duodenum of celiac patients (PON1, P<0.0001; PON3, P=0.03), in the terminal ileum of Crohn's patients (PON1, P=0.001; PON3, P=0.008), and in the colon of UC patients (PON1, P=0.02; PON3, P=0.06) compared to controls. Since all three disorders share markedly elevated inflammatory mediators we explored the PON1/2/3 mRNA expression on cytokine stimulation. No changes were observed in Caco-2 and HT29 cells. Immunofluorescence experiments localized PON1/2/3 exclusively to the endoplasmic reticulum (ER) in both CaCo-2 and HT29 cells. These results demonstrate for the first time a novel relationship between PON1 and PON3 expression and several inflammatory gastrointestinal disorders. Together with the localization of PON1/2/3 enzymes to the ER, it may be suggested that PON1/2/3 may have extracellular functions as part of the host response in IBD and celiac disease.