Magnetic ion channel activation of TREK1 in human mesenchymal stem cells using nanoparticles promotes osteogenesis in surrounding cells

Magnetic ion channel activation technology uses superparamagnetic nanoparticles conjugated with targeting antibodies to apply mechanical force directly to stretch-activated ion channels on the cell surface, stimulating mechanotransduction and downstream processes. This technique has been reported to promote differentiation towards musculoskeletal cell types and enhance mineralisation. Previous studies have shown how mesenchymal stem cells injected into a pre-mineralised environment such as a foetal chick epiphysis, results in large-scale osteogenesis at the target site. However, the relative contributions of stem cells and surrounding host tissue has not been resolved, that is, are the mesenchymal stem cells solely responsible for the observed mineralisation or do mechanically stimulated mesenchymal stem cells also promote a host-tissue mineralisation response? To address this, we established a novel two-dimensional co-culture assay, which indicated that magnetic ion channel activation stimulation of human mesenchymal stem cells does not significantly promote migration but does enhance collagen deposition and mineralisation in the surrounding cells. We conclude that one of the important functions of injected human mesenchymal stem cells is to release biological factors (e.g., cytokines and microvesicles) which guide the surrounding tissue response, and that remote control of this signalling process using magnetic ion channel activation technology may be a useful way to both drive and regulate tissue regeneration and healing

Creating an Antibacterial with in Vivo Efficacy: Synthesis and Characterization of Potent Inhibitors of the Bacterial Cell Division Protein FtsZ with Improved Pharmaceutical Properties

3-Methoxybenzamide (1) is a weak inhibitor of the essential bacterial cell division protein FtsZ. Alkyl derivatives of 1 are potent antistaphylococcal compounds with suboptimal drug-like properties. Exploration of the structure-activity relationships of analogues of these inhibitors led to the identification of potent antistaphylococcal compounds with improved pharmaceutical properties

A 4D printed self-assembling PEGDA microscaffold fabricated by digital light processing for arthroscopic articular cartilage tissue engineering

AbstractArticular cartilage in synovial joints such as the knee has limited capability to regenerate independently, and most clinical options for focal cartilage repair merely delay total joint replacement. Tissue engineering presents a repair strategy in which an injectable cell-laden scaffold material is used to reconstruct the joint in situ through mechanical stabilisation and cell-mediated regeneration. In this study, we designed and 3D-printed millimetre-scale micro-patterned PEGDA biomaterial microscaffolds which self-assemble through tessellation at a scale relevant for applications in osteochondral cartilage reconstruction. Using simulated chondral lesions in an in vitro model, a series of scaffold designs and viscous delivery solutions were assessed. Hexagonal microscaffolds (750 μm x 300 μm) demonstrated the best coverage of a model cartilage lesion (at 73.3%) when injected with a 1% methyl cellulose solution. When chondrocytes were introduced to the biomaterial via a collagen hydrogel, they successfully engrafted with the printed microscaffolds and survived for at least 14 days in vitro, showing the feasibility of reconstructing stratified cartilaginous tissue using this strategy. Our study demonstrates a promising application of this 4D-printed injectable technique for future clinical applications in osteochondral tissue engineering.</jats:p

Remotely activated Mechanotransduction via magnetic nanoparticles promotes mineralization synergistically with bone morphogenetic protein 2:Applications for Injectable cell therapy

Bone requires dynamic mechanical stimulation to form and maintain functional tissue, yet mechanical stimuli are often lacking in many therapeutic approaches for bone regeneration. Magnetic nanoparticles provide a method for delivering these stimuli by directly targeting cell-surface mechanosensors and transducing forces from an external magnetic field, resulting in remotely controllable mechanotransduction. In this investigation, functionalized magnetic nanoparticles were attached to either the mechanically gated TREK1 K(+) channel or the (integrin) RGD-binding domains of human mesenchymal stem cells. These cells were microinjected into an ex vivo chick fetal femur (embryonic day 11) that was cultured organotypically in vitro as a model for endochondral bone formation. An oscillating 25-mT magnetic field delivering a force of 4 pN per nanoparticle directly against the mechanoreceptor induced mechanotransduction in the injected mesenchymal stem cells. It was found that cells that received mechanical stimuli via the nanoparticles mineralized the epiphyseal injection site more extensively than unlabeled control cells. The nanoparticle-tagged cells were also seeded into collagen hydrogels to evaluate osteogenesis in tissue-engineered constructs: in this case, inducing mechanotransduction by targeting TREK1 resulted in a 2.4-fold increase in mineralization and significant increases in matrix density. In both models, the combination of mechanical stimulation and sustained release of bone morphogenetic protein 2 (BMP2) from polymer microspheres showed a significant additive effect on mineralization, increasing the effectiveness of BMP2 delivery and demonstrating that nanoparticle-mediated mechanotransduction can be used synergistically with pharmacological approaches for orthopedic tissue engineering to maximize bone formation

Multimodal analysis of the differential effects of cyclic strain on collagen isoform composition, fibril architecture and biomechanics of tissue engineered tendon

Tendon is predominantly composed of aligned type I collagen, but additional isoforms are known to influence fibril architecture and maturation, which contribute to the tendon’s overall biomechanical performance. The role of the less well-studied collagen isoforms on fibrillogenesis in tissue engineered tendons is currently unknown, and correlating their relative abundance with biomechanical changes in response to cyclic strain is a promising method for characterising optimised bioengineered tendon grafts. In this study, human mesenchymal stem cells (MSCs) were cultured in a fibrin scaffold with 3%, 5% or 10% cyclic strain at 0.5 Hz for 3 weeks, and a comprehensive multimodal analysis comprising qPCR, western blotting, histology, mechanical testing, fluorescent probe CLSM, TEM and label-free second-harmonic imaging was performed. Molecular data indicated complex transcriptional and translational regulation of collagen isoforms I, II, III, V XI, XII and XIV in response to cyclic strain. Isoforms (XII and XIV) associated with embryonic tenogenesis were deposited in the formation of neo-tendons from hMSCs, suggesting that these engineered tendons form through some recapitulation of a developmental pathway. Tendons cultured with 3% strain had the smallest median fibril diameter but highest resistance to stress, whilst at 10% strain tendons had the highest median fibril diameter and the highest rate of stress relaxation. Second harmonic generation exposed distinct structural arrangements of collagen fibres in each strain group. Fluorescent probe images correlated increasing cyclic strain with increased fibril alignment from 40% (static strain) to 61.5% alignment (10% cyclic strain). These results indicate that cyclic strain rates stimulate differential cell responses via complex regulation of collagen isoforms which influence the structural organisation of developing fibril architectures. </jats:p

Evaluation of the growth environment of a hydrostatic force bioreactor for preconditioning of tissue-engineered constructs

Bioreactors have been widely acknowledged as valuable tools to provide a growth environment for engineering tissues and to investigate the effect of physical forces on cells and cell-scaffold constructs. However, evaluation of the bioreactor environment during culture is critical to defining outcomes. In this study, the performance of a hydrostatic force bioreactor was examined by experimental measurements of changes in dissolved oxygen (O2), carbon dioxide (CO2), and pH after mechanical stimulation and the determination of physical forces (pressure and stress) in the bioreactor through mathematical modeling and numerical simulation. To determine the effect of hydrostatic pressure on bone formation, chick femur skeletal cell-seeded hydrogels were subjected to cyclic hydrostatic pressure at 0?270?kPa and 1?Hz for 1?h daily (5 days per week) over a period of 14 days. At the start of mechanical stimulation, dissolved O2 and CO2 in the medium increased and the pH of the medium decreased, but remained within human physiological ranges. Changes in physiological parameters (O2, CO2, and pH) were reversible when medium samples were placed in a standard cell culture incubator. In addition, computational modeling showed that the distribution and magnitude of physical forces depends on the shape and position of the cell-hydrogel constructs in the tissue culture format. Finally, hydrostatic pressure was seen to enhance mineralization of chick femur skeletal cell-seeded hydrogels

Impact of lower plate structure on upper plate deformation at the NW Sumatran convergent margin from seafloor morphology

We present results from multibeam bathymetric data acquired during 2005 and 2006, in the region of maximum slip of the 26 Dec. 2004 earthquake (Mw 9.2). These data provide high-resolution images of seafloor morphology of the entire NW Sumatra forearc from the Sunda trench to the submarine volcanic arc just north of Sumatra. A slope gradient analysis of the combined dataset accurately highlights those portions of the seafloor shaped by active tectonic, depositional and/or erosional processes. The greatest slope gradients are located in the frontal 30 km of the forearc, at the toe of the accretionary wedge. This suggests that long-term deformation rates are highest here and that probably only minor amounts of slip are accommodated by other thrust faults further landward. Obvious N–S oriented lineaments observed on the incoming oceanic plate are aligned sub-parallel to the fracture zones associated with the Wharton fossil spreading center. Active strike-slip motion is suggested by recent deformation with up to 20–30 m of vertical offset. The intersection of these N–S elongated bathymetric scarps with the accretionary wedge partly controls the geometry of thrust anticlines and the location of erosional features (e.g. slide scars, canyons) at the wedge toe. Our interpretation suggests that these N–S lineaments have a significant impact on the oceanic plate, the toe of the wedge and further landward in the wedge. Finally, the bathymetric data indicate that folding at the front of the accretionary wedge occurs primarily along landward-vergent (seaward-dipping) thrusts, an unusual style in accretionary wedges worldwide. The N–S elongated lineaments locally act as boundaries between zones with predominant seaward versus landward vergence.<br/