Pushing myelination - developmental regulation of myosin expression drives oligodendrocyte morphological differentiation.

Oligodendrocytes are the central nervous system myelin-forming cells providing axonal electrical insulation and higher-order neuronal circuitry. The mechanical forces driving the differentiation of oligodendrocyte precursor cells into myelinating oligodendrocytes are largely unknown, but likely require the spatiotemporal regulation of the architecture and dynamics of the actin and actomyosin cytoskeletons. In this study, we analyzed the expression pattern of myosin motors during oligodendrocyte development. We report that oligodendrocyte differentiation is regulated by the synchronized expression and non-uniform distribution of several members of the myosin network, particularly non-muscle myosins 2B and 2C, which potentially operate as nanomechanical modulators of cell tension and myelin membrane expansion at different cell stages.This article has an associated First Person interview with the first author of the paper.

Protrusion membrane pearling emerges during 3D cell division.

Cell division is accompanied by dramatic changes in shape that ultimately lead to the physical separation of one cell into two. In 2D microenvironments, cells round up and remain adhered onto the substrate by thin retraction fibers during division. In contrast, in 3D environments, cells divide exhibiting long protrusions that guide the orientation of the division axis. However, the mechanism of cell division in three dimensions still remains poorly understood. Here we report the spontaneous formation of transient quasiperiodic membrane pearling on extended mitotic protrusions during 3D cell division. Protrusion membrane pearling may be initiated by the non-uniform distribution of focal adhesions and consequent stationary instability of the protrusive membrane. Overall, membrane pearling emergence may provide insights into a novel modality of 3D cell division with potential physiological relevance.

Mechanical plasticity during oligodendrocyte differentiation and myelination.

In the central nervous system, oligodendrocyte precursor cells are exclusive in their potential to differentiate into myelinating oligodendrocytes. Oligodendrocyte precursor cells migrate within the parenchyma and extend cell membrane protrusions that ultimately evolve into myelinating sheaths able to wrap neuronal axons and significantly increase their electrical conductivity. The subcellular force generating mechanisms driving morphological and functional transformations during oligodendrocyte differentiation and myelination remain elusive. In this review, we highlight the mechanical processes governing oligodendrocyte plasticity in a dynamic interaction with the extracellular matrix.

Analytical protocols for separation and electron microscopy of nanoparticles interacting with bacterial cells.

An important step toward understanding interactions between nanoparticles (NPs) and bacteria is the ability to directly observe NPs interacting with bacterial cells. NP-bacteria mixtures typical in nanomedicine, however, are not yet amendable for direct imaging in solution. Instead, evidence of NP-cell interactions must be preserved in derivative (usually dried) samples to be subsequently revealed in high-resolution images, for example, via scanning electron microscopy (SEM). Here, this concept is realized for a mixed suspension of model NPs and Staphylococcus aureus bacteria. First, protocols for analyzing the relative colloidal stabilities of NPs and bacteria are developed and validated based on systematic centrifugation and comparison of colony forming unit (CFU) counting and optical density (OD) measurements. Rate-dependence of centrifugation efficiency for each component suggests differential sedimentation at a specific predicted rate as an effective method for removing free NPs after co-incubation; the remaining fraction comprises bacteria with any associated NPs and can be examined, for example, by SEM, for evidence of NP-bacteria interactions. These analytical protocols, validated by systematic control experiments and high-resolution SEM imaging, should be generally applicable for investigating NP-bacteria interactions.

Modular coherence of protein dynamics in yeast cell polarity system.

In this study, we investigated on a systems level how complex protein interactions underlying cell polarity in yeast determine the dynamic association of proteins with the polar cortical domain (PCD) where they localize and perform morphogenetic functions. We constructed a network of physical interactions among >100 proteins localized to the PCD. This network was further divided into five robust modules correlating with distinct subprocesses associated with cell polarity. Based on this reconstructed network, we proposed a simple model that approximates a PCD protein's molecular residence time as the sum of the characteristic time constants of the functional modules with which it interacts, weighted by the number of edges forming these interactions. Regression analyses showed excellent fitting of the model with experimentally measured residence times for a large subset of the PCD proteins. The model is able to predict residence times using small training sets. Our analysis also revealed a scaffold protein that imposes a local constraint of dynamics for certain interacting proteins.

Microglial Rac1 is essential for experience-dependent brain plasticity and cognitive performance.

Microglia, the largest population of brain immune cells, continuously interact with synapses to maintain brain homeostasis. In this study, we use conditional cell-specific gene targeting in mice with multi-omics approaches and demonstrate that the RhoGTPase Rac1 is an essential requirement for microglia to sense and interpret the brain microenvironment. This is crucial for microglia-synapse crosstalk that drives experience-dependent plasticity, a fundamental brain property impaired in several neuropsychiatric disorders. Phosphoproteomics profiling detects a large modulation of RhoGTPase signaling, predominantly of Rac1, in microglia of mice exposed to an environmental enrichment protocol known to induce experience-dependent brain plasticity and cognitive performance. Ablation of microglial Rac1 affects pathways involved in microglia-synapse communication, disrupts experience-dependent synaptic remodeling, and blocks the gains in learning, memory, and sociability induced by environmental enrichment. Our results reveal microglial Rac1 as a central regulator of pathways involved in the microglia-synapse crosstalk required for experience-dependent synaptic plasticity and cognitive performance.

Timely and Blood-Based Multiplex Molecular Profiling of Acute Stroke.

Stroke is a leading cause of death and disability in the world. To address such a problem, early diagnosis and tailored acute treatment represent one of the major priorities in acute stroke care. Since the efficacy of reperfusion treatments is highly time-dependent, there is a critical need to optimize procedures for faster and more precise diagnosis. We provide a concise review of the most relevant and well-documented blood-protein biomarkers that exhibit greater potential for translational to clinical practice in stroke differential diagnosis and to differentiate ischemic stroke from hemorrhagic stroke, followed by an overview of the most recent point-of-care technological approaches to address this problem. The integration of fluid-based biomarker profiling, using point-of-care biosensors with demographic, clinical, and neuroimaging parameters in multi-dimensional clinical decision-making algorithms, will be the next step in personalized stroke care.

Reengineering Bone-Implant Interfaces for Improved Mechanotransduction and Clinical Outcomes.

The number of patients undergoing joint replacement surgery has progressively increased worldwide due to world population ageing. In the Unites States, for example, the prevalence of hip and knee replacements has increased more than 6 and 10 times, respectively, since 1980. Despite advances in orthopaedic implant research, including the development of novel implantable biomaterials, failures are still observed due to inadequate biomechanical compliance at the bone-implant interface. This comprises static and dynamic mechanical mismatch between the bone and the implant surface. The importance and robustness of biomechanical cues for controlling osteogenic differentiation of mesenchymal stem cells (MSC) have been highlighted in recent studies. However, in the context of bone regenerative medicine, it remains elusive how mechanobiological signals controlling MSC osteogenic differentiation dynamics are modulated in their interaction with the bone and with implants. In this review, we highlight recent technological advances aiming to improve host bone-implant interactions based on the osteogenic and mechanoresponsive potential of MSC, in the context of joint replacement surgery. First, we discuss the extracellular and intracellular mechanical forces underlying proper receptivity and stimulation of physiological MSC differentiation and linked osteogenic activity. Second, we provide a critical overview on how this knowledge can be integrated towards the development of biomaterials for improved bone-implant interfaces. Third, we discuss cross-disciplinarily which contributes to the next generation design of novel pro-active orthopaedic implants and their implantation success. Graphical Abstract.

Nanoparticles provide long-term stability of bevacizumab preserving its antiangiogenic activity.

Bevacizumab is one of the most common monoclonal antibodies used to treat cancer due to its antiangiogenic role. However, the frequent parenteral administrations are not attractive for the patient adhesion to the therapy. Nanoencapsulation of bevacizumab might be a useful alternative to increase administration intervals, due to controlled release properties. To achieve a long-term bevacizumab stability into PLGA nanoparticles, we developed an optimized and validated lyophilization protocol. The co-encapsulation of trehalose and bevacizumab into PLGA nanoparticles, associated to their lyophilization with external 10% (w/v) of trehalose, allowed maintenance of the physical-chemical characteristics of nanoparticles and bevacizumab secondary and tertiary structure. More relevant, the antiangiogenic activity of bevacizumab was kept over 6 months of storage while formulated with this protocol. No significant differences were found upon 6 months of storage at 4 °C and 25 °C/60% HR, and minor differences were observed for storage at 40 °C/75% HR, bringing to our knowledge, the first successfully report for monoclonal antibody storage at room temperature, without losing its structural and functional features. Our results served as starting point to understand the monoclonal antibody-based nanoparticle behavior over time, creating an innovative approach for a long-term monoclonal antibody stability. STATEMENT OF SIGNIFICANCE: Nanoencapsulation of monoclonal antibodies has boost the interest of researchers as an alternative to the current antibody-based therapy, changing the route of administrations through controlled release of monoclonal antibodies. Despite good results have been achieved with nanoencapsulation process, no strategy has still found concerning a long-term stability of nanoparticles and monoclonal antibodies. In this study, the aim was to find out a validated and optimized method that allows a long-term stability of nanoparticles and antibodies. Over 6 months of storage, an optimized nanosystem was considered stable for both nanoparticles and antibody structure, at 4 °C and 25 °C, resulting the first successfully report for monoclonal antibody storage at room temperature.

Polyester-Based Nanoparticles for the Encapsulation of Monoclonal Antibodies.

Aliphatic polyesters have been widely explored for biomedical applications (e.g., drug delivery systems, biomedical devices, and tissue engineering). Recently, polyesters have been used in nanoparticle formulations for the controlled release of monoclonal antibodies (mAbs) for the enhanced efficacy of antibody-based therapy. Polyester-based nanoparticles for mAb delivery provide decreased antibody dosage, increased antibody stability and protection and longer therapeutic action, ultimately translating to an increased therapeutic index. Additionally, nanoencapsulation holds the potential for the selective cellular recognition and internalization of mAbs, in the disease context when intracellular organelles and molecules (e.g., enzymes, transcription factors and oncogenic proteins) are the preferred target. We present here a detailed method to prepare mAb-loaded polyester-based nanoparticles and the various techniques to characterize the resulting nanoparticles and mAb structure. Finally, we highlight different biological approaches to assess the in vitro bioactivity of the antibody upon nanoparticle release.

A new paradigm for antiangiogenic therapy through controlled release of bevacizumab from PLGA nanoparticles.

Monoclonal antibodies have deserved a remarkable interest for more than 40 years as a vital tool for the treatment of various diseases. Still, there is a raising interest to develop advanced monoclonal antibody delivery systems able to tailor pharmacokinetics. Bevacizumab is a humanized immunoglobulin IgG1 used in antiangiogenic therapies due to its capacity to inhibit the interaction between vascular endothelial growth factor and its receptor. However, bevacizumab-based antiangiogenic therapy is not always effective due to poor treatment compliance associated to multiples administrations and drug resistance. In this work, we show a promising strategy of encapsulating bevacizumab to protect and deliver it, in a controlled manner, increasing the time between administrations and formulation shelf-life. Nanoencapsulation of bevacizumab represents a significant advance for selective antiangiogenic therapies since extracellular, cell surface and intracellular targets can be reached. The present study shows that bevacizumab-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles does not impair its native-like structure after encapsulation and fully retain the bioactivity, making this nanosystem a new paradigm for the improvement of angiogenic therapy.

Nano- and micro-based systems for immunotolerance induction in multiple sclerosis.

It is estimated that more than 2.5 million individuals worldwide have multiple sclerosis (MS). MS is an autoimmune neurodegenerative disease resulting from the destruction of the myelin sheath that enwraps axons driven by an immune cell attack to the central nervous system. Current therapeutic programs for MS focus in immunosuppression and more recently in the use of immunomodulatory molecules. These therapeutic approaches provide significant improvements in the management of the disease, but are frequently associated with an increased susceptibility of opportunistic infection. In this commentary, we highlight the application of nano and micro-technologies as emerging and innovative solutions for MS therapy with the potential to restore immune homeostasis via antigen-specific interactions. Furthermore, we propose and discuss the usage of a minimally invasive approach, namely microneedle patches, as a new therapeutic route. Microneedle patches for the delivery of specific antigens to restore immunotolerance in the context of multiple sclerosis.

Robust gap repair in the contractile ring ensures timely completion of cytokinesis.

Cytokinesis in animal cells requires the constriction of an actomyosin contractile ring, whose architecture and mechanism remain poorly understood. We use laser microsurgery to explore the biophysical properties of constricting rings in Caenorhabditis elegans embryos. Laser cutting causes rings to snap open. However, instead of disintegrating, ring topology recovers and constriction proceeds. In response to severing, a finite gap forms and is repaired by recruitment of new material in an actin polymerization-dependent manner. An open ring is able to constrict, and rings repair from successive cuts. After gap repair, an increase in constriction velocity allows cytokinesis to complete at the same time as controls. Our analysis demonstrates that tension in the ring increases while net cortical tension at the site of ingression decreases throughout constriction and suggests that cytokinesis is accomplished by contractile modules that assemble and contract autonomously, enabling local repair of the actomyosin network. Consequently, cytokinesis is a highly robust process impervious to discontinuities in contractile ring structure.

Epithelia migration: a spatiotemporal interplay between contraction and adhesion.

Epithelial tissues represent 60% of the cells that form the human body and where more than 90% of all cancers derived. Epithelia transformation and migration involve altered cell contractile mechanics powered by an actomyosin-based cytoskeleton and influenced by cell-cell and cell-extracellular matrix interactions. A balance between contractile and adhesive forces regulates a large number of cellular and tissue properties crucial for epithelia migration and tumorigenesis. In this review, the forces driving normal epithelia transformation into highly motile and invasive cells and tissues will be discussed.