Cell migration on material-driven fibronectin microenvironments

Cell migration is a fundamental process involved in a wide range of biological phenomena. However, how the underlying mechanisms that control migration are orchestrated is not fully understood. In this work, we explore the migratory characteristics of human fibroblasts using different organisations of fibronectin (FN) triggered by two chemically similar surfaces, poly(ethyl acrylate) (PEA) and poly(methyl acrylate) (PMA); cell migration is mediated via an intermediate layer of fibronectin (FN). FN is organised into nanonetworks upon simple adsorption on PEA whereas a globular conformation is observed on PMA. We studied cell speed over the course of 24 h and the morphology of focal adhesions in terms of area and length. Additionally, we analysed the amount of cell-secreted FN as well as FN remodelling. Velocity of human fibroblasts was found to exhibit a biphasic behaviour on PEA, whereas it remained fairly constant on PMA. FA analysis revealed more mature focal adhesions on PEA over time contrary to smaller FAs found on PMA. Finally, human fibroblasts seemed to remodel adsorbed FN more on PMA than on PEA. Overall, these results indicate that the cell–protein–material interface affects cell migratory behaviour. Analysis of FAs together with FN secretion and remodelling were associated with differences in cell velocity providing insights into the factors that can modulate cell motility

Electrospun fibrinogen-PLA nanofibres for vascular tissue engineering

Here we report on the development of a new type of hybrid fibrinogen–polylactic acid (FBG–PLA) nanofibres (NFs) with improved stiffness, combining the good mechanical properties of PLA with the excellent cell recognition properties of native FBG. We were particularly interested in the dorsal and ventral cell response to the nanofibres' organization (random or aligned), using human umbilical endothelial cells (HUVECs) as a model system. Upon ventral contact with random NFs, the cells developed a stellate-like morphology with multiple projections. The well-developed focal adhesion complexes suggested a successful cellular interaction. However, time-lapse analysis shows significantly lowered cell movements, resulting in the cells traversing a relatively short distance in multiple directions. Conversely, an elongated cell shape and significantly increased cell mobility were observed in aligned NFs. To follow the dorsal cell response, artificial wounds were created on confluent cell layers previously grown on glass slides and covered with either random or aligned NFs. Time-lapse analysis showed significantly faster wound coverage (within 12 h) of HUVECs on aligned samples vs. almost absent directional migration on random ones. However, nitric oxide (NO) release shows that endothelial cells possess lowered functionality on aligned NFs compared to random ones, where significantly higher NO production was found. Collectively, our studies show that randomly organized NFs could support the endothelization of implants while aligned NFs would rather direct cell locomotion for guided neovascularization

Development of a tool to optimize the performance of a Maui Cluster Scheduler

The use of Linux cluster computing in a scientific and heterogeneous environment has been growing very fast in the past years. The often conflicting user’s requests of shared resources are quite difficult to satisfy for the administrators, and, usually, lower the overall system efficiency. In this scenario a new tool to study and optimize the Maui Cluster Scheduler has been developed together with a new set of metrics to evaluate any given configuration. The main idea is to use the Maui internal simulator, fed by workloads produced either by a real cluster than by an ad hoc one, to test several scheduler configurations and then, using a genetic algorithm, to choose the best solution. In this work the architecture of the proposed tool is described together with the first results

Digital Recording of Historical Defensive Structures in Mountainous Areas Using Drones: Considerations and Comparisons

Digital recording of historic buildings and sites in mountainous areas could be challenging. The paper considers and discusses the case of historical defensive structures in the Italian Alps, designed and built to be not accessible. Drone images and photogrammetric techniques for 3D modeling play a fundamental role in the digital documentation of fortified constructions with non-contact techniques. This manuscript describes the use of drones for reconstructing the external surfaces of some fortified structures using traditional photogrammetric/SfM solutions and novel methods based on NeRFs. The case of direct orientation based on PPK and traditional GCPs placed on the ground is also discussed, considering the difficulties in placing and measuring control points in such environments

Hamiltonian solutions of the 3-body problem in (2+1)-gravity

We present a full study of the 3-body problem in gravity in flat (2+1)-dimensional space-time, and in the nonrelativistic limit of small velocities. We provide an explicit form of the ADM Hamiltonian in a regular coordinate system and we set up all the ingredients for canonical quantization. We emphasize the role of a U(2) symmetry under which the Hamiltonian is invariant and which should generalize to a U(N-1) symmetry for N bodies. This symmetry seems to stem from a braid group structure in the operations of looping of particles around each other, and guarantees the single-valuedness of the Hamiltonian. Its role for the construction of single-valued energy eigenfunctions is also discussed.Comment: 25 pages, no figure. v2: some calculation details removed to make the paper more concise (see v1 for the longer version), minor correction in a formula in the section on quantization, references added; results and conclusions unchange

Molecular clutch drives cell response to surface viscosity

Cell response to matrix rigidity has been explained by the mechanical properties of the actin-talin-integrin-fibronectin clutch. Here the molecular clutch model is extended to account for cell interactions with purely viscous surfaces (i.e., without an elastic component). Supported lipid bilayers present an idealized and controllable system through which to study this concept. Using lipids of different diffusion coefficients, the mobility (i.e., surface viscosity) of the presented ligands (in this case RGD) was altered by an order of magnitude. Cell size and cytoskeletal organization were proportional to viscosity. Furthermore, there was a higher number of focal adhesions and a higher phosphorylation of FAK on less-mobile (more-viscous) surfaces. Actin retrograde flow, an indicator of the force exerted on surfaces, was also seen to be faster on more mobile surfaces. This has consequential effects on downstream molecules; the mechanosensitive YAP protein localized to the nucleus more on less-mobile (more-viscous) surfaces and differentiation of myoblast cells was enhanced on higher viscosity. This behavior was explained within the framework of the molecular clutch model, with lower viscosity leading to a low force loading rate, preventing the exposure of mechanosensitive proteins, and with a higher viscosity causing a higher force loading rate exposing these sites, activating downstream pathways. Consequently, the understanding of how viscosity (regardless of matrix stiffness) influences cell response adds a further tool to engineer materials that control cell behavior

Material-driven fibronectin assembly for high-efficiency presentation of growth factors

Growth factors (GFs) are powerful signaling molecules with the potential to drive regenerative strategies, including bone repair and vascularization. However, GFs are typically delivered in soluble format at supraphysiological doses because of rapid clearance and limited therapeutic impact. These high doses have serious side effects and are expensive. Although it is well established that GF interactions with extracellular matrix proteins such as fibronectin control GF presentation and activity, a translation-ready approach to unlocking GF potential has not been realized. We demonstrate a simple, robust, and controlled material-based approach to enhance the activity of GFs during tissue healing. The underlying mechanism is based on spontaneous fibrillar organization of fibronectin driven by adsorption onto the polymer poly(ethyl acrylate). Fibrillar fibronectin on this polymer, but not a globular conformation obtained on control polymers, promotes synergistic presentation of integrin-binding sites and bound bone morphogenetic protein 2 (BMP-2), which enhances mesenchymal stem cell osteogenesis in vitro and drives full regeneration of a nonhealing bone defect in vivo at low GF concentrations. This simple and translatable technology could unlock the full regenerative potential of GF therapies while improving safety and cost-effectiveness

SARS-CoV-2 Mproinhibition by a zinc ion: structural features and hints for drug design

The first structure of the SARS-CoV-2 main protease in complex with an isolated zinc ion provides solid ground for the design of potent and selective metal-conjugated inhibitors