Mechanical loading of intraluminal pressure mediates wound angiogenesis by regulating the TOCA family of F-BAR proteins

Regulation and mechanistic insights into tensile strain in mesenchymal stem cell osteogenic differentiation

Bone marrow mesenchymal stem cells (BMSCs) are integral to bone remodeling and homeostasis, as they are capable of differentiating into osteogenic and adipogenic lineages. This differentiation is substantially influenced by mechanosensitivity, particularly to tensile strain, which is a prevalent mechanical stimulus known to enhance osteogenic differentiation. This review specifically examines the effects of various cyclic tensile stress (CTS) conditions on BMSC osteogenesis. It delves into the effects of different loading devices, magnitudes, frequencies, elongation levels, dimensionalities, and coculture conditions, providing a comparative analysis that aids identification of the most conducive parameters for the osteogenic differentiation of BMSCs. Subsequently, this review delineates the signaling pathways activated by CTS, such as Wnt/β-catenin, BMP, Notch, MAPK, PI3K/Akt, and Hedgehog, which are instrumental in mediating the osteogenic differentiation of BMSCs. Through a detailed examination of these pathways, this study elucidates the intricate mechanisms whereby tensile strain promotes osteogenic differentiation, offering valuable guidance for optimizing therapeutic strategies aimed at enhancing bone regeneration.

Dermal Dive: An Overview of Cutaneous Wounding Techniques in Zebrafish

Cutaneous wounds are common injuries that affect millions of people around the world. In vulnerable populations such as the elderly and those with diabetes, defects in wound healing can lead to the development of chronic open wounds. Although mammalian models are commonly used to study cutaneous wound healing, the challenges of in vivo imaging in mammals have hampered detailed observation of cell coordination and cell signaling during wound healing. The zebrafish is becoming increasingly popular for studying cutaneous wound healing owing to its genetic accessibility, suitability for experimental manipulation, and the ability to perform live, in vivo imaging with cellular or even subcellular resolution. In this paper, we review some of the techniques that have been developed for eliciting cutaneous wounds in the zebrafish, including an economical method we recently developed using a rotary tool that generates consistent and reproducible full-thickness wounds. Combined with the thousands of transgenic lines and experimental assays available in zebrafish, the ability to generate reproducible cutaneous wounds makes it possible to study key cellular and molecular events during wound healing using this powerful experimental model organism.

Exosomes Derived from Mouse Breast Carcinoma Cells Facilitate Diabetic Wound Healing

BACKGROUND

Exosomes derived from breast cancer have been reported to play a role in promoting cell proliferation, migration, and angiogenesis, which has the potential to accelerate the healing process of diabetic wounds. The aim of this investigation was to examine the function of exosomes originating from 4T1 mouse breast carcinoma cells (TEXs) in the process of diabetic wound healing.

METHODS

The assessment of primary mouse skin fibroblasts cell proliferation and migration was conducted through the utilization of CCK-8 and wound healing assays, while the tube formation of HUVECs was evaluated by tube formation assay. High-throughput sequencing, RT-qPCR and cell experiments were used to detect the roles of miR-126a-3p in HUVECs functions in vitro. The in vivo study employed a model of full-thickness excisional wounds in diabetic subjects to explore the potential therapeutic benefits of TEXs. Immunohistochemical and immunofluorescent techniques were utilized to evaluate histological changes in skin tissues.

RESULTS

The findings suggested that TEXs facilitate diabetic wound healing through the activation of cell migration, proliferation, and angiogenesis. An upregulation of miR-126a-3p has been observed in TEXs, and it has demonstrated efficient transferability from 4T1 cells to HUVEC cells. The activation of the PI3K/Akt pathway has been attributed to miR-126a-3p derived from TEXs.

CONCLUSIONS

The promotion of chronic wound healing can be facilitated by TEXs through the activation of cellular migration, proliferation, and angiogenesis. The activation of the PI3K/Akt pathway by miR-126a-3p originating from TEXs has been discovered, indicating a potential avenue for enhancing the regenerative capabilities of wounds treated with TEXs.

Research progress on the regulatory role of cell membrane surface tension in cell behavior

Cell membrane surface tension has emerged as a pivotal biophysical factor governing cell behavior and fate. This review systematically delineates recent advances in techniques for cell membrane surface tension quantification, mechanosensing mechanisms, and regulatory roles of cell membrane surface tension in modulating major cellular processes. Micropipette aspiration, tether pulling, and newly developed fluorescent probes enable the measurement of cell membrane surface tension with spatiotemporal precision. Cells perceive cell membrane surface tension via conduits including mechanosensitive ion channels, curvature-sensing proteins (e.g. BAR domain proteins), and cortex-membrane attachment proteins (e.g. ERM proteins). Through membrane receptors like integrins, cells convert mechanical cues into biochemical signals. This conversion triggers cytoskeletal remodeling and extracellular matrix interactions in response to environmental changes. Elevated cell membrane surface tension suppresses cell spreading, migration, and endocytosis while facilitating exocytosis. Moreover, reduced cell membrane surface tension promotes embryonic stem cell differentiation and cancer cell invasion, underscoring cell membrane surface tension as a regulator of cell plasticity. Outstanding questions remain regarding cell membrane surface tension regulatory mechanisms and roles in tissue development/disease in vivo. Emerging tools to manipulate cell membrane surface tension with high spatiotemporal control in combination with omics approaches will facilitate the elucidation of cell membrane surface tension-mediated effects on signaling networks across various cell types/states. This will accelerate the development of cell membrane surface tension-based biomarkers and therapeutics for regenerative medicine and cancer. Overall, this review provides critical insights into cell membrane surface tension as a potent orchestrator of cell function, with broader impacts across mechanobiology.

Live Imaging of Cutaneous Wound Healing after Rotary Tool Injury in Zebrafish

Cutaneous wounds are common afflictions that follow a stereotypical healing process involving hemostasis, inflammation, proliferation, and remodeling phases. In the elderly and those suffering from vascular or metabolic diseases, poor healing after cutaneous injuries can lead to open chronic wounds susceptible to infection. The discovery of new therapeutic strategies to improve this defective wound healing requires a better understanding of the cellular behaviors and molecular mechanisms that drive the different phases of wound healing and how these are altered with age or disease. The zebrafish provides an ideal model for visualization and experimental manipulation of the cellular and molecular events during wound healing in the context of an intact, living vertebrate. To facilitate studies of cutaneous wound healing in zebrafish, we have developed an inexpensive, simple, and effective method for generating reproducible cutaneous injuries in adult zebrafish using a rotary tool. We demonstrate that our injury system can be used in combination with high-resolution live imaging to monitor skin re-epithelialization, immune cell recruitment and activation, and vessel regrowth in the same animal over time. This injury system provides a valuable experimental platform to study key cellular and molecular events during wound healing in vivo with unprecedented resolution.

Understanding the pathophysiology of acute critical illness: translational lessons from zebrafish models

The models used to investigate the pathophysiological mechanisms of acute critical illness are not limited to mammalian species. The zebrafish (Danio rerio) is a popular model organism for studying diseases due to its transparency and rapid development. The genes and signaling pathways involved in acute critical illness appear highly conserved among zebrafish and humans. Forward genetics such as random mutagenesis by a chemical mutagen or reverse genetics methods represented by CRISPR/Cas9 allowed researchers to reveal multiple novel aspects of pathological processes in areas including infection, immunity, and regeneration. As a model of sepsis, transgenic zebrafish allowed the visualization of lipopolysaccharide (LPS)-induced vascular leakage in vivo and the demonstration of changes in the expression of cellular junction proteins. Other transgenic zebrafish visualizing the extravascular migration of neutrophils and macrophages have demonstrated a decrease in neutrophil numbers and an increased expression of an inflammatory gene, which replicates a phenomenon observed in humans in clinically encountered sepsis. The regenerative potential and the visibility of zebrafish organs also enabled clarification of important mechanisms in wound healing, angiogenesis, and neurogenesis. After spinal cord injury (SCI), a marker gene expressed in glial bridging was discovered. Furthermore, localized epithelial-to-mesenchymal transition (EMT) and molecular mechanisms leading to spinal cord repair were revealed. These translational studies using zebrafish show the potential of the model system for the treatment of acute critical illnesses such as sepsis, organ failure, and trauma.

Cell-based mechanisms and strategies of co-culture system both in vivo and vitro for bone tissue engineering

The lack of a functional vascular supply has been identified as a major challenge limiting the clinical introduction of stem cell-based bone tissue engineering (BTE) for the repair of large-volume bone defects (LVBD). Various approaches have been explored to improve the vascular supply in tissue-engineered constructs, and the development of strategies that could effectively induce the establishment of a functional vascular supply has become a major goal of BTE research. One of the state-of-the-art methods is to incorporate both angiogenic and osteogenic cells in co-culture systems. This review clarifies the key concepts involved, summarises the cell types and models used to date, and systematically evaluates their performance. We also discuss the cell-to-cell communication between these two cell types and the strategies explored in BTE constructs with angiogenic and osteogenic cells to optimise their functions. In addition, we outline unresolved issues and remaining obstacles that need to be overcome for further development in this field and eventual successful repair of LVBD.

Extracellular vesicles modulate key signalling pathways in refractory wound healing

Chronic wounds are wounds that cannot heal properly due to various factors, such as underlying diseases, infection or reinjury, and improper healing of skin wounds and ulcers can cause a serious economic burden. Numerous studies have shown that extracellular vesicles (EVs) derived from stem/progenitor cells promote wound healing, reduce scar formation and have significant advantages over traditional treatment methods. EVs are membranous particles that carry various bioactive molecules from their cellular origins, such as cytokines, nucleic acids, enzymes, lipids and proteins. EVs can mediate cell-to-cell communication and modulate various physiological processes, such as cell differentiation, angiogenesis, immune response and tissue remodelling. In this review, we summarize the recent advances in EV-based wound healing, focusing on the signalling pathways that are regulated by EVs and their cargos. We discuss how EVs derived from different types of stem/progenitor cells can promote wound healing and reduce scar formation by modulating the Wnt/β-catenin, phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin, vascular endothelial growth factor, transforming growth factor β and JAK-STAT pathways. Moreover, we also highlight the challenges and opportunities for engineering or modifying EVs to enhance their efficacy and specificity for wound healing.

The infrapatellar fat pad contributes to spontaneous healing after complete anterior cruciate ligament injury

Anterior cruciate ligament (ACL) injuries have a very low healing capacity but have recently been shown to heal spontaneously with conservative treatment. This study examined the mechanism of spontaneous ACL healing by focusing on the intra-articular tissues of the knee joint. Skeletally mature Wistar rats (n = 70) were randomly assigned to two groups: the controlled abnormal movement (CAM) and anterior cruciate ligament transection (ACLT) groups. The ACL was completely transected at the mid-portion in both groups. Only the CAM group underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice for histological, and molecular biology analyses. The results showed that the behavior of the stump after ACL injury differed between models 12 h after injury. The femoral stump in the ACLT group retreated posteriorly and upwardly. Macrophage polarity analysis revealed that the stump immune response in the CAM group was more activated than that in the ACLT group 6 h after injury. Microarray analysis of the ACL parenchyma and infrapatellar fat pads suggested the involvement of nuclear factor kappa B (NF-κB) signaling. Real-time polymerase chain reaction (PCR) analysis showed that NF-κB gene expression in the infrapatellar fat pad was significantly increased in the CAM group than in the ACLT group. However, there was no difference in the gene expression levels in the ACL parenchyma between models. In conclusion, the healing response of the ACL was activated within 12 h of injury, resulting in differences in the healing response between the models. It has been suggested that infrapatellar fat pads are involved in the healing process and that angiogenesis and antiapoptotic effects through NF-κB signaling may contribute to this mechanism.

Silver@Prussian Blue Core-Satellite Nanostructures as Multimetal Ions Switch for Potent Zero-Background SERS Bioimaging-Guided Chronic Wound Healing

Metal-organic framework-based metal ion therapy has attracted increasing attention to promote the cascade wound-healing process. However, multimetal ion synergistic administration and accurately controlled ion release are still the challenges. Herein, an aptamer-functionalized silver@cupriferous Prussian blue (ACPA) is established as a metal-based theranostic nanoagent for a chronic nonhealing diabetic wound treatment. Prussian blue offers a programmable nanoplatform to formulate metal ion prescriptions, achieving cooperative wound healing. Silver, copper, and iron ions are released from ACPA controlled by the near-infrared-triggered mild hyperthermia and then synergistically participate in antipathogen, cell migration, and revascularization. ACPA also demonstrates a unique core-satellite nanostructure which enables it with improved surface-enhanced Raman scattering (SERS) capability as potent bacteria-targeted Raman-silent nanoprobe to monitor the residual bacteria during wound healing with nearly zero background. The theranostic feature of ACPA allows high-performance SERS imaging-guided chronic wound healing in infectious diabetic skin and keratitis.

Cell protrusions and contractions generate long-range membrane tension propagation

Membrane tension is thought to be a long-range integrator of cell physiology. Membrane tension has been proposed to enable cell polarity during migration through front-back coordination and long-range protrusion competition. These roles necessitate effective tension transmission across the cell. However, conflicting observations have left the field divided as to whether cell membranes support or resist tension propagation. This discrepancy likely originates from the use of exogenous forces that may not accurately mimic endogenous forces. We overcome this complication by leveraging optogenetics to directly control localized actin-based protrusions or actomyosin contractions while simultaneously monitoring the propagation of membrane tension using dual-trap optical tweezers. Surprisingly, actin-driven protrusions and actomyosin contractions both elicit rapid global membrane tension propagation, whereas forces applied to cell membranes alone do not. We present a simple unifying mechanical model in which mechanical forces that engage the actin cortex drive rapid, robust membrane tension propagation through long-range membrane flows.

Cell-stretching devices: advances and challenges in biomedical research and live-cell imaging

Basic human functions such as breathing and digestion require mechanical stretching of cells and tissues. However, when it comes to laboratory experiments, the mechanical stretching that cells experience in the body is not often replicated, limiting the biomimetic nature of the studies and the relevance of results. Herein, we establish the importance of mechanical stretching during in vitro investigations by reviewing seminal works performed using cell-stretching platforms, highlighting important outcomes of these works as well as the engineering characteristics of the platforms used. Emphasis is placed on the compatibility of cell-stretching devices (CSDs) with live-cell imaging as well as their limitations and on the research advancements that could arise from live-cell imaging performed during cell stretching.

Exploring membrane mechanics: The role of membrane-cortex attachment in cell dynamics

The role of plasma membrane (PM) tension in cell dynamics has gained increasing interest in recent years to understand the mechanism by which individual cells regulate their dynamic behavior. Membrane-to-cortex attachment (MCA) is a component of apparent PM tension, and its assembly and disassembly determine the direction of cell motility, controlling the driving forces of migration. There is also evidence that membrane tension plays a role in malignant cancer cell metastasis and stem cell differentiation. Here, we review recent important discoveries that explore the role of membrane tension in the regulation of diverse cellular processes, and discuss the mechanisms of cell dynamics regulated by this physical parameter.

From lymphatic endothelial cell migration to formation of tubular lymphatic vascular network

During development, lymphatic endothelial cell (LEC) progenitors differentiate from venous endothelial cells only in limited regions of the body. Thus, LEC migration and subsequent tube formation are essential processes for the development of tubular lymphatic vascular network throughout the body. In this review, we discuss chemotactic factors, LEC-extracellular matrix interactions and planar cell polarity regulating LEC migration and formation of tubular lymphatic vessels. Insights into molecular mechanisms underlying these processes will help in understanding not only physiological lymphatic vascular development but lymphangiogenesis associated with pathological conditions such as tumors and inflammation.

Electrochemical sensing of oxygen metabolism for a three-dimensional cultured model with biomimetic vascular flow

Microphysiological systems (MPSs) with three-dimensional (3D) cultured models have attracted considerable interest because of their potential to mimic human health and disease conditions. Recent MPSs have shown significant advancements in engineering perfusable vascular networks integrated with 3D culture models, realizing a more physiological environment in vitro; however, a sensing system that can monitor their activity under biomimetic vascular flow is lacking. We designed an open-top microfluidic device with sensor capabilities and demonstrated its application in analyzing oxygen metabolism in vascularized 3D tissue models. We first validated the platform by using human lung fibroblast (hLF) spheroids. Then, we applied the platform to a patient-derived cancer organoid and evaluated the changes in oxygen metabolism during drug administration through the vascular network. We found that the platform could integrate a perfusable vascular network with 3D cultured cells, and the electrochemical sensor could detect the change in oxygen metabolism in a quantitative, non-invasive, and real-time manner. This platform would become a monitoring system for 3D cultured cells integrated with a perfusable vascular network.