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Abstract During differentiation, skeletal muscle develops mature multinucleated muscle fibers, which could contract to exert force on a substrate. Muscle dysfunction occurs progressively in patients with muscular dystrophy, leading to a loss of the ability to walk and eventually to death. The synthetic glucocorticoid dexamethasone (Dex) has been used therapeutically to treat muscular dystrophy by an inhibition of inflammation, followed by slowing muscle degeneration and stabilizing muscle strength. Here, in mice with muscle injury, we found that Dex significantly promotes muscle regeneration via promoting kinesin-1 motor activity. Nevertheless, how Dex promotes myogenesis through kinesin-1 motors remains unclear. We found that Dex directly increases kinesin-1 motor activity, which is required for the expression of a myogenic marker (muscle myosin heavy chain 1/2), and also for the process of myoblast fusion and the formation of polarized myotubes. Upon differentiation, kinesin-1 mediates the recruitment of integrin β1 onto microtubules allowing delivery of the protein into focal adhesions. Integrin β1-mediated focal adhesion signaling then guides myoblast fusion towards a polarized morphology. By imposing geometric constrains via micropatterns, we have proved that cell adhesion is able to rescue the defects caused by kinesin-1 inhibition during the process of myogenesis. These discoveries reveal a mechanism by which Dex is able to promote myogenesis, and lead us towards approaches that are more efficient in improving skeletal muscle regeneration.

Summary: Recently, many super-resolution technologies have been demonstrated, significantly affecting biological studies by observation of cellular structures down to nanometer precision. However, current super-resolution techniques mostly rely on wavefront engineering or wide-field imaging of signal blinking or fluctuation, and thus imaging depths are limited due to tissue scattering or aberration. Here we present a technique that is capable of imaging through an intact Drosophila brain with 20-nm lateral resolution at ∼200 μm depth. The spatial resolution is provided by molecular localization of a photoconvertible fluorescent protein Kaede, whose red form is found to exhibit blinking state. The deep-tissue observation is enabled by optical sectioning of spinning disk microscopy, as well as reduced scattering from optical clearing. Together these techniques are readily available for many biologists, providing three-dimensional resolution of densely entangled dendritic fibers in a complete Drosophila brain. The method paves the way toward whole-brain neural network studies and is applicable to other high-resolution bioimaging. : Optical Imaging; Neuroscience; Techniques in Neuroscience Subject Areas: Optical Imaging, Neuroscience, Techniques in Neuroscience

Human mesenchymal stem cells (hMSCs) possess potential of bone formation and were proposed as ideal material against osteoporosis. Although interrogation of directing effect on lineage specification by physical cues has been proposed, how mechanical stimulation impacts intracellular viscoelasticity during osteogenesis remained enigmatic. Cyto-friendly 3D matrix was prepared with polyacrylamide and conjugated fibronectin. The hMSCs were injected with fluorescent beads and chemically-induced toward osteogenesis. The mechanical properties were assessed using video particle tracking microrheology. Inverted epifluorescence microscope was exploited to capture the Brownian trajectory of hMSCs. Mean square displacement was calculated and transformed into intracellular viscoelasticity. Two different stiffness of microspheres (12 kPa, 1 kPa) were established. A total of 45 cells were assessed. hMSCs possessed equivalent mechanical traits initially in the first week, while cells cultured in rigid matrix displayed significant elevation over elastic (G′) and viscous moduli (G″) on day 7 (p < 0.01) and 14 (p < 0.01). However, after two weeks, soft niches no longer stiffened hMSCs, whereas the effect by rigid substrates was consistently during the entire differentiation course. Stiffness of matrix impacted the viscoelasticity of hMSCs. Detailed recognition of how microenvironment impacts mechanical properties and differentiation of hMSCs will facilitate the advancement of tissue engineering and regenerative medicine.

We developed a microfluidic device to culture cellular spheroids of controlled sizes and suitable for live cell imaging by selective plane illumination microscopy (SPIM). We cocultured human umbilical vein endothelial cells (HUVECs) within the spheroids formed by hepatocellular carcinoma cells, and studied the distributions of the HUVECs over time. We observed that the migration of HUVECs depended on the size of spheroids. In the spheroids of ~200μm diameters, HUVECs migrated outwards to the edges within 48 h; while in the spheroids of ~250 μm diameters, there was no outward migration of the HUVECs up to 72 h. In addition, we studied the effects of pro-angiogenic factors, namely, vascular endothelial growth factor (VEGF) and fibroblast growth factor (β-FGF), on the migration of HUVECs in the carcinoma cell spheroid. The outward migration of HUVECs in 200 im spheroids was hindered by the treatment with VEGF and b-FGF. Moreover, some of the HUVECs formed hollow lumen within 72 h under VEGF and β-FGF treatment. The combination of SPIM and microfluidic devices gives high resolution in both spatial and temporal domains. The observation of HUVECs in spheroids provides us insight on tumor vascularization, an ideal disease model for drug screening and fundamental studies. [ABSTRACT FROM AUTHOR]

We have developed an approach to prepare large array nanostructured thin films using polyethylene oxide assisted self-assembly of polystyrene nanospheres as a template. By tuning the antidot diameter in the cobalt thin films, we found a crossover behavior in the magnetization reversal process. In addition, the effective moment per cobalt atom turns out to drop with growing antidot diameter which effectively increases the surface to bulk volume fraction. Our results suggest a tendency of reduced saturation magnetization in a ferromagnet/normal metal interface, where the mixing of itinerant electrons with ferromagnetic d electrons can give rise to observable effect. [ABSTRACT FROM AUTHOR]

The article discusses Invasive fungal infections (IFI) being once of the fatal cause for the patients receiving chemotherapy for hematologic malignancies. It examines patients receiving antifungal prophylaxis while treated with chemotherapy had recovered from neutropenia. It elaborates patients receiving induction chemotherapy had an IFI incidence of 6.7 % and accordingly fluconazole and caspofungin as antifungal prophylactic agents could be considered.