Noradrenaline has opposing effects on the hydraulic conductance of arterial intima and media.

The uptake of circulating macromolecules by the arterial intima is thought to be a key step in atherogenesis. Such transport is dominantly advective, so elucidating the mechanisms of water transport is important. The relation between vasoactive agents and water transport in the arterial wall is incompletely understood. Here we applied our recently-developed combination of computational and experimental methods to investigate the effects of noradrenaline (NA) on hydraulic conductance of the wall (Lp), medial extracellular matrix volume fraction (ϕ(ECM)) and medial permeability (K1(1)) in the rat abdominal aorta. Experimentally, we found that physiological NA concentrations were sufficient to induce SMC contraction and produced significant decreases in Lp and increases in ϕ(ECM). Simulation results based on 3D confocal images of the extracellular volume showed a corresponding increase in K1(1), attributed to the opening of the ECM. Conversion of permeabilities to layer-specific resistances revealed that although the total wall resistance increased, medial resistance decreased, suggesting an increase in intimal resistance upon application of NA

Targeted Molecular Iron Oxide Contrast Agents for Imaging Atherosclerotic Plaque.

Overview: Cardiovascular disease remains a leading cause of death worldwide, with vulnerable plaque rupture the underlying cause of many heart attacks and strokes. Much research is focused on identifying an imaging biomarker to differentiate stable and vulnerable plaque. Magnetic Resonance Imaging (MRI) is a non-ionising and non-invasive imaging modality with excellent soft tissue contrast. However, MRI has relatively low sensitivity (micromolar) for contrast agent detection compared to nuclear imaging techniques. There is also an increasing emphasis on developing MRI probes that are not based on gadolinium chelates because of increasing concerns over associated systemic toxicity and deposits1. To address the sensitivity and safety concerns of gadolinium this project focused on the development of a high relaxivity probe based on superparamagnetic iron oxide nanoparticles for the imaging of atherosclerotic plaque with MRI. With development, this may facilitate differentiating stable and vulnerable plaque in vivo. Aim: To develop a range of MRI contrast agents based on superparamagnetic iron oxide nanoparticles (SPIONs), and test them in a murine model of advanced atherosclerosis. Methods: Nanoparticles of four core sizes were synthesised by thermal decomposition and coated with poly(maleicanhydride-alt-1-octadecene) (PMAO), poly(ethyleneimine) (PEI) or alendronate, then characterised for core size, hydrodynamic size, surface potential and relaxivity. On the basis of these results, one candidate was selected for further studies. In vivo studies using 10 nm PMAO-coated SPIONs were performed in ApoE -/- mice fed a western diet and instrumented with a perivascular cuff on the left carotid artery. Control ApoE -/- mice were fed a normal chow diet and were not instrumented. Mice were scanned on a 3T MR scanner (Philips Achieva) with the novel SPION contrast agent, and an elastin-targeted gadolinium agent that was shown previously to enable visualisation of plaque burden. Histological analysis was undertaken to confirm imaging findings through staining for macrophages, CX3CL1, elastin, tropoelastin, and iron. Results: The lead SPION agent consisted of a 10 nm iron oxide core with poly(maleicanhydride-alt-1-octadecene), (-36.21 mV, r2 18.806 mmol-1/s-1). The irregular faceting of the iron oxide core resulted in high relaxivity and the PMAO provided a foundation for further functionalisation on surface -COOH groups. The properties of the contrast agent, including the negative surface charge and hydrodynamic size, were designed to maximise circulation time and evade rapid clearance through the renal system or phagocytosis. In vitro testing showed that the SPION agent was non-toxic. In vivo results show that the novel contrast agent accumulates in similar vascular regions to a gadolinium-based contrast agent (Gd-ESMA) targeted to elastin, which accumulates in plaque. There was a significant difference in SPION signal between the instrumented and the contralateral non-instrumented vessels in diseased mice (p = 0.0411, student's t-test), and between the instrumented diseased vessel and control vessels (p = 0.0043, 0.0022, student's t-test). There was no significant difference between the uptake of either contrast agent between stable and vulnerable plaques (p = 0.3225, student's t-test). Histological verification was used to identify plaques, and Berlin Blue staining confirmed the presence of nanoparticle deposits within vulnerable plaques and co-localisation with macrophages. Conclusion: This work presents a new MRI contrast agent for atherosclerosis which uses an under-explored surface ligand, demonstrating promising properties for in vivo behaviour, is still in circulation 24 hours post-injection with limited liver uptake, and shows good accumulation in a murine plaque model

New developments in mechanotransduction: Cross talk of the Wnt, TGF-β and Notch signalling pathways in reaction to shear stress

Mechanotransduction, the ability of cells to detect and react to mechanical forces, is increasingly playing a critical role in a variety of physiological and pathophysiological processes. While the focus has previously been on the MAPK, NF-8B and ROS generating pathways, ancient embryological pathways have reached little attention. Recently, a surge of new studies have been published on these pathways and their role in mechanotransduction and this review paper aims to provide a concise overview on the latest studies and brings them in to a larger perspective. Special emphasis is on the non-canonical aspects of the Wnt, TGF-b and Notch pathways and their role in flow

Engineering a Multicomponent Spinal Motion Segment-Like Construct from Mesenchymal Stem Cells

Conference theme: The Intervertebral Disc - from Degeneration to Therapeutic Motion PreservationThe abstract can be viewed at http://www.spineresearchforum.org/WFSR_2014_Thieme_AbstractBook_with_Cover.pdfOral PresentationIntroduction The task of engineering the intervertebral disc is challenging as the complex tissue needs to integrate with the host tissue and performits function after the implantation. The vertebrae connected to the endplates are essential to integrate with the host vertebrae tissue which had been shown by Luk et al in whole disc transplantation.1 Hence, engineering the complex tissue needs to integrate the different components of the vertebrae (VB), cartilaginous endplate (CEP), nucleus pulposus (NP), and annulus fibrosus (AF); both biologically and mechanically. In this study, the multiple component spinal motion segments were fabricated by integrating these components. The construct was then loaded in a bioreactor and supplied with mechanical and biological stimulation. The functional aspect of the fabricated endplate-like construct was evaluated by a permeability test. Materials and Methods Rabbit mesenchymal stem cells (rMSCs) were encapsulated in collagen and induced to differentiate toward osteogenic and chondrogenic lineages before fabricating trilayered osteochondral (OC) constructs as previously mentioned. To test the nutritional function of the OC construct which acts as the endplate, rabbit nucleus pulposus cells (rNPCs)-encapsulated collagen microspheres were trapped in a sealed chamber formed with the OC construct such that the nutrients have to diffuse through the OC construct to reach the inside of the chamber. Cell viability of the rNPCs was then evaluated. To fabricate the multiple component construct, a rMSCs encapsulated collagen-GAG precipitate was added in between two OC construct and placed in between the shaft of the bioreactor. Then a layer of rMSC encapsulated collagen was formed around the construct to form the AF-like lamella. Torsional loading was applied onto the construct to study its effect on cell alignment in the AF-like lamella. Finally, one to three layers of AF-like lamellae were added to the spinal motion segment construct and cultured in the bioreactor with complex loading for 14 days. Histological, ultrastructural, and mechanical evaluation was done on the construct. Results In the custom developed functionality test for nutrient transport, the rNPCs in the chamber were viable at the end of the culture showed that nutrientswere able to diffuse through the OC construct. For the effect of torsional loading on cell alignment in the AF-like lamella, alignment analysis showed that the cells were aligned along a preferred axis under torsional loading compared with control group without loading. However, no collagen fibers alignment was found in this study. The multiple component construct was fabricated with each component similar to the spinal motion segment. The different components of the construct were well integrated throughout the culture and were shown by histology. Mean torsional stiffness of the constructs significantly increased as the number of rMSC encapsulated AF-like layer increased. Conclusion This study demonstrated the feasibility to engineer a spinal motion segment-like tissue with collagen and MSC. The OC constructs demonstrated its nutritional function and can be used as a vertebra-endplate construct in this model. rMSC encapsulated in collagen gel can be induced to re-orientate and align in a certain direction by applying cyclic torsional force on the tubular structure. This can be a tissue engineered model to study the effects of various strategies in functional remodeling and maturation of the intervertebral disc. Disclosure of Interest None declared Reference 1. Luk KD, Ruan DK. Intervertebral disc transplantation: a biological approach to motion preservation. Eur Spine J 2008;17(Suppl 4):504–51

Polymeric Nanoparticles

Self-assembling polymers, which are either amphiphilic block copolymers with hydrophobic and hydrophilic blocks, hydrophilic polymer backbones substituted with hydrophobic units or polymers with a low aqueous solubility, may all be used to prepare aqueous dispersions of polymeric nanoparticles. The amphiphilic variants form polymeric micelles and polymeric bilayer vesicles. The hydrophobic polymers form dense amorphous polymeric particles. Polymeric particles, of whichever nature, may be loaded with hydrophobic and hydrophilic drugs, and the bioavailability of the drug compound is altered by this encapsulation within a polymeric nanoparticle. This simple concept has been exploited heavily to yield enhancements in oral, tumour and brain bioavailability and some of these polymeric nanoparticle formulations have undergone clinical testing and even been commercialised, e.g. the nanoparticle paclitaxel formulation AbraxaneNon peer reviewe