Vessel Formation Is Induced Prior to the Appearance of Cartilage in BMP-2-Mediated Heterotopic Ossification

Heterotopic ossification (HO), or endochondral bone formation at nonskeletal sites, often results from traumatic injury and can lead to devastating consequences. Alternatively, the ability to harness this phenomenon would greatly enhance current orthopedic tools for treating segmental bone defects. Thus, understanding the earliest events in this process potentially would allow us to design more targeted therapies to either block or enhance this process. Using a murine model of HO induced by delivery of adenovirus-transduced cells expressing bone morphogenetic protein 2 (BMP-2), we show here that one of the earliest stages in this process is the establishment of new vessels prior to the appearance of cartilage. As early as 48 hours after induction of HO, we observed the appearance of brown adipocytes expressing vascular endothelial growth factors (VEGFs) simultaneous with endothelial progenitor replication. This was determined by using a murine model that possesses the VEGF receptor 2 (Flk1) promoter containing an endothelial cell enhancer driving the expression of nuclear-localized yellow fluorescent protein (YFP). Expression of this marker has been shown previously to correlate with the establishment of new vasculature, and the nuclear localization of YFP expression allowed us to quantify changes in endothelial cell numbers. We found a significant increase in Flk1-H2B::YFP cells in BMP-2-treated animals compared with controls. The increase in endothelial progenitors occurred 3 days prior to the appearance of early cartilage. The data collectively suggest that vascular remodeling and growth may be essential to modify the microenvironment and enable engraftment of the necessary progenitors to form endochondral bone. © 2010 American Society for Bone and Mineral Research

Assessing mechanical integrity of spinal fusion by in situ endochondral osteoinduction in the murine model

<p>Abstract</p> <p>Background</p> <p>Historically, radiographs, micro-computed tomography (micro-CT) exams, palpation and histology have been used to assess fusions in a mouse spine. The objective of this study was to develop a faster, cheaper, reproducible test to directly quantify the mechanical integrity of spinal fusions in mice.</p> <p>Methods</p> <p>Fusions were induced in ten mice spine using a previously described technique of in situ endochondral ossification, harvested with soft tissue, and cast in radiolucent alginate material for handling. Using a validated software package and a customized mechanical apparatus that flexed and extended the spinal column, the amount of intervertebral motion between adjacent vertebral discs was determined with static flexed and extended lateral spine radiographs. Micro-CT images of the same were also blindly reviewed for fusion.</p> <p>Results</p> <p>Mean intervertebral motion between control, non-fused, spinal vertebral discs was 6.1 ± 0.2° during spine flexion/extension. In fusion samples, adjacent vertebrae with less than 3.5° intervertebral motion had fusions documented by micro-CT inspection.</p> <p>Conclusions</p> <p>Measuring the amount of intervertebral rotation between vertebrae during spine flexion/extension is a relatively simple, cheap (<$100), clinically relevant, and fast test for assessing the mechanical success of spinal fusion in mice that compared favorably to the standard, micro-CT.</p

Potentiometric sensors for high temperature liquids

The purpose of this chapter is to present a brief overview of the potentiometric sensors available for applications in high temperature liquids. The topics addressed include: the calculation rules of the e.m.f. of the electrochemical chain, with special emphasis on sources of errors, a discussion on the reference electrodes of the cells according to the temperature and the types of analyzed solutions. Finally, the state of the art of the potentiometric sensors available for monitoring of oxygen, hydrogen and carbon in molten metals and for studying oxoacidic properties of molten salts is presented

Electronic conductivity of non stoichiometric yttria-doped ceria

Une méthode d'étude fondée sur une utilisation quantitative de la coloration électrochimique a été appliquée à la cérine dopée à l'oxyde d'yttrium. La largeur du domaine de non-stoechiométrie de la cérine dépend de la teneur en yttrium. Sa conductivité électronique est simplement proportionnelle au nombre d'électrons injectés. Elle est due à un mécanisme de saut. Contrairement à l'hypothèse habituelle, la mobilité électronique varie de façon significative avec la teneur en yttrium.A method of investigation based on a quantitative utilisation of the electrochemical coloration was applied to yttria doped ceria. The width of its non-stoichiometry range depends upon the yttria content. Its electronic conductivity is simply proportional to the number of injected electrons. It is due to a hopping process. In contrast to the usual assumption the electronic mobility was found to vary significantly with the yttria content

HfO2-based electrolyte potentiometric oxygen sensors for liquid sodium

International audienc