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Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury. Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction. However, the mechanisms involved remain unclear. In this study, we found that after spinal cord injury, resting microglia (M0) were polarized into pro-inflammatory phenotypes (MG1 and MG3), while resting astrocytes were polarized into reactive and scar-forming phenotypes. The expression of growth arrest-specific 6 (Gas6) and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury. In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia, and even inhibited the cross-regulation between them. We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway. This, in turn, inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways. In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord, thereby promoting tissue repair and motor function recovery. Overall, Gas6 may play a role in the treatment of spinal cord injury. It can inhibit the inflammatory pathway of microglia and polarization of astrocytes, attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment, and thereby alleviate local inflammation and reduce scar formation in the spinal cord.

As a natural immune cell and antigen presenting cell, macrophages have been studied and engineered to treat human diseases. Macrophages are well-suited for use as drug carriers because of their biological characteristics, such as excellent biocompatibility, long circulation, intrinsic inflammatory homing and phagocytosis. Meanwhile, macrophages’ uniquely high plasticity and easy re-education polarization facilitates their use as part of efficacious therapeutics for the treatment of inflammatory diseases or tumors. Although recent studies have demonstrated promising advances in macrophage-based drug delivery, several challenges currently hinder further improvement of therapeutic effect and clinical application. This article focuses on the main challenges of utilizing macrophage-based drug delivery, from the selection of macrophage sources, drug loading, and maintenance of macrophage phenotypes, to drug migration and release at target sites. In addition, corresponding strategies and insights related to these challenges are described. Finally, we also provide perspective on shortcomings on the road to clinical translation and production.

Abstract Acute respiratory infections (ARIs) are associated with high mortality and morbidity. Acute lung injury (ALI) is caused by the activation of immune cells during ARIs caused by viruses such as SARS-CoV-2. Aquaporin 1 (AQP1) is distributed in a variety of immune cells and is related to the occurrence of ALI, but the mechanism is not clear. A reference map of human single cells was used to identify macrophages in COVID-19 patients at the single-cell level. “FindMarkers” was used to analyze differentially expressed genes (DEGs), and “clusterProfiler” was used to analyze the functions of the DEGs. An M1 macrophage polarization model was established with lipopolysaccharide (LPS) in vitro, and the relationships among AQP1, pyroptosis and M1 polarization were examined by using an AQP1 inhibitor. Transcriptome sequencing and RT-qPCR were used to examine the molecular mechanism by which AQP1 regulates macrophage polarization and pyroptosis. Antigen presentation, M1 polarization, migration and phagocytosis are abnormal in SARS-CoV-2-infected macrophages, which is related to the high expression of AQP1. An M1 polarization model of macrophages was constructed in vitro, and an AQP1 inhibitor was used to examine whether AQP1 could promote M1 polarization and pyroptosis in response to LPS. Transcriptome and cell experiments showed that this effect was related to a decrease in chemokines caused by AQP1 deficiency. AQP1 participates in M1 polarization and pyroptosis in macrophages by increasing the levels of chemokines induced by LPS, which provides new insights for the diagnosis and treatment of ALI.

BACKGROUND: Microglia cells play a major role in maintaining the balance as well as the development and function reconstruction of the central nervous system. As a histone deacetylase inhibitor, Scriptaid can inhibit neuroinflammation and enhance neuroprotection. OBJECTIVE: To investigate the effect of silk fibroin methacryloyl hydrogel loaded with Scriptaid on the behaviors of microglia cells. METHODS: Microglia (BV2 cells) were cultured in medium containing different concentrations of Scriptaid (0, 0.1, 0.5, 1, 2, 5, 10 μmol/L). The optimal concentration of Scriptaid was screened by the CCK-8 assay and live/dead cell staining. Silk fibroin methacryloyl hydrogels loaded with or without Scriptaid were prepared using photocuring. The micromorphology, swelling properties, mechanical properties, slow release properties, and hydrophilicity of the hydrogels were characterized. Microglia (BV2 cells) were inoculated in the subventricular region of 24-well Transwell and cultured in five groups. In the control group, the cell culture medium was added to the lower chamber. In the lipopolysaccharide group, Scriptaid group, hydrogel group, and drug-loaded hydrogel group, cell culture media containing lipopolysaccharide were added into the lower chamber. After 24 hours of lipopolysaccharide intervention, in the Scriptaid group, hydrogel group and drug-loaded hydrogel group, Scriptaid, silk fibroin methacryloyl hydrogel, and silk fibroin methacryloyl hydrogel loaded with Scriptaid were added to the upper chamber, respectively. The culture medium was replaced with ordinary culture medium and continued to culture for 24 hours. The cell viability was detected by CCK-8 assay, and the cell phenotype was detected by immunofluorescence staining of induced nitric oxide synthase and arginase 1. RESULTS AND CONCLUSION: (1) Compared with the group without Scriptaid, the viability and number of BV2 cells were decreased after Scriptaid added. When Scriptaid 2 μmol/L or above was added, the cell viability was lower than the standardized cell viability (70%), and the number of BV2 cells was significantly reduced. Therefore, 1 μmol/L Scriptaid was selected to be loaded into the hydrogel. (2) Characterization experiments showed that the addition of Scriptaid did not affect the microscopic morphology, swelling rate of water absorption, compression modulus and hydrophilicity of silk fibroin methacryloyl hydrogel, and silk fibroin methacryloyl hydrogel had slow release performance. (3) The result of CCK-8 assay showed that compared with the control group, silk fibroin methacryloyl hydrogel significantly increased the viability of BV2 cells (P < 0.001). (4) Immunofluorescence staining showed that compared with the control group, the expression of inducible nitric oxide synthase was increased in the lipopolysaccharide group (P < 0.01); the expression of inducible nitric oxide synthase was decreased (P < 0.01) and the expression of arginase 1 was increased (P < 0.001) in the drug-loaded hydrogel group; the expression of arginase 1 was increased in the Scriptaid group (P < 0.01). (5) The results indicate that Scriptaid-loaded silk fibroin methacryloyl hydrogel is able to promote polarization of microglia to the M2 type after lipopolysaccharide induction. [ABSTRACT FROM AUTHOR]

Natural killer cells (NKCs) are non-specific immune lymphocytes with diverse morphologies. Their broad killing effect on cancer cells has led to increased attention towards activating NKCs for anticancer immunotherapy. Consequently, understanding the motion characteristics of NKCs under different morphologies and modeling their collective dynamics under cancer cells has become crucial. However, tracking small NKCs in complex backgrounds poses significant challenges, and conventional industrial tracking algorithms often perform poorly on NKC tracking datasets. There remains a scarcity of research on NKC dynamics. In this paper, we utilize deep learning techniques to analyze the morphology of NKCs and their key points. After analyzing the shortcomings of common industrial multi-object tracking algorithms like DeepSORT in tracking natural killer cells, we propose Distance Cascade Matching and the Re-Search method to improve upon existing algorithms, yielding promising results. Through processing and tracking over 5000 frames of images, encompassing approximately 300,000 cells, we preliminarily explore the impact of NKCs' cell morphology, temperature, and cancer cell environment on NKCs' motion, along with conducting basic modeling. The main conclusions of this study are as follows: polarized cells are more likely to move along their polarization direction and exhibit stronger activity, and the maintenance of polarization makes them more likely to approach cancer cells; under equilibrium, NK cells display a Boltzmann distribution on the cancer cell surface. [ABSTRACT FROM AUTHOR]

Background The incidence of multiple myeloma has long been high, however, there are fewer studies on phosphatidylinositol 3-kinase (PI3K) /serine-threonine kinase (AKT) signaling pathway and M2 macrophage polarization promoting the progression of multiple myeloma. Objective To investigate the expression of M2 macrophages in patients with multiple myeloma and the mechanism of PI3K/AKT signaling pathway promoting M2 macrophage polarization. Methods Forty-eight multiple myeloma patients diagnosed in the Department of Hematology of the Affiliated Hospital of Guilin Medical University from October 2021 to April 2022 were selected as the test group, and thirty healthy volunteers (healthy donors of blood marrow transplantation) in the same period were selected as the control group. Peripheral blood was taken from the 2 group and mononuclear cells were isolated, the proportion of M2 macrophages was determined by flow cytometry. RPMI8226 cells were subcultured by cell passage, and mononuclear macrophages THP-1 cells were cultured as macrophages by phorbol ester differentiation. According to the experimental requirements, tumor cells were cultured and transfected with siRNA to silence phosphatase and tensin homolog (PTEN) and divided into three groups, including blank group, siRNA-PTEN experimental group, and siRNA control group; the supernatants of the above three groups were collected and added to the macrophage co-culture system and then divided into four groups including M0 macrophage group, tumor cell supernatant group, siRNA-PTEN supernatant group, and siRNA supernatant group. The protein expression levels of AKT, p-AKT, PI3K-p85, and p-PI3K-p85 in the blank group, siRNA-PTEN experimental group, and siRNA control group of multiple myeloma cell culture were determined by Western blot assay. The mRNA expression levels of MMP2 and MMP9 in the blank group, siRNA-PTEN experimental group and siRNA control group were determined by fluorescence quantitative polymerase chain reaction (PCR) . The expression levels of specific antibodies CD163, CD206, and F4/80 in M2 macrophages in M0 macrophage group, tumor cell supernatant group, siRNA-PTEN supernatant group, and siRNA supernatant group were determined by flow cytometry. The mRNA expression levels of arginase 1 (ARG-1) and interleukin 10 (IL-10) in M0 macrophage group, tumor cell supernatant group, siRNA-PTEN supernatant group, and siRNA supernatant group were determined by fluorescence quantitative PCR. Results The expression level of M2 macrophages was higher in the test group than that in the control group (t=0.855, P

Liver fibrosis is the healing reaction of chronic liver injury caused by various factors such as viral infection, alcohol, and chemical substances and is a key link in the progression of chronic liver diseases to liver cirrhosis and liver cancer. Liver macrophages are considered important mediators of liver injury and repair, and the polarization trend of macrophages has a bidirectional regulatory effect on liver fibrosis. This article reviews the role of different phenotypes of liver macrophages in the development and progression of liver fibrosis, in order to provide new ideas for the prevention and treatment of fibrosis. [ABSTRACT FROM AUTHOR]

Finger-like structures emerging from groups of cells at the forefront of cell layer take crucial roles in the migration of collective cell assemblies. However, the mechanics of the finger-like structure has not been fully understood. Here, we constructed a two-dimensional collective cell migration model and quantitatively analyzed the cellular mechanics of finger-like structures during the collective cell migration through experimental study and numerical simulation. We found that substrate stiffness, cell density, cell prestress, and mechanical loading significantly influence the generation and behaviors of the finger-like structures by regulating the lamellipodia spreading area, cellular traction force, and collectivity of cell motion. We showed that the regions with higher maximum principal stress tend to produce larger finger-like structures. Increasing the spreading area of lamellipodia and the velocity of leader cells could promote the generation of higher finger-like structures. For a quantitative understanding of the mechanisms of the effects of these mechanical factors, we adopted a coarse-grained cell model based on the traction-distance law. Our numerical simulation recapitulated the cell velocity distribution, cell motility integrity, cell polarization, and stress distribution in the cell layer observed in the experiment. These analyses revealed the cellular mechanics of the finger-like structure and its roles in collective cell migration. This study provides valuable insights into the collective cell behaviors in tissue engineering and regenerative medicine for biomedical applications. [ABSTRACT FROM AUTHOR]

Glioblastoma is one of the deadliest malignancies facing modern oncology today. The ability of glioblastoma cells to diffusely spread into neighboring healthy brain makes complete surgical resection nearly impossible and contributes to the recurrent disease faced by most patients. Although research into the impact of iron on glioblastoma has addressed proliferation, there has been little investigation into how cellular iron impacts the ability of glioblastoma cells to migrate—a key question, especially in the context of the diffuse spread observed in these tumors. Herein, we show that increasing cellular iron content results in decreased migratory capacity of human glioblastoma cells. The decrease in migratory capacity was accompanied by a decrease in cellular polarization in the direction of movement. Expression of CDC42, a Rho GTPase that is essential for both cellular migration and establishment of polarity in the direction of cell movement, was reduced upon iron treatment. We then analyzed a single‐cell RNA‐seq dataset of human glioblastoma samples and found that cells at the tumor periphery had a gene signature that is consistent with having lower levels of cellular iron. Altogether, our results suggest that cellular iron content is impacting glioblastoma cell migratory capacity and that cells with higher iron levels exhibit reduced motility.Glioblastoma represents a deadly cancer that is particularly lethal owing to its ability to diffusely migrate and invade healthy brain tissue, making surgical resection unfeasible. Here, we describe the role iron plays in impacting glioblastoma cell migration. We discover that iron has an inhibitory role in glioblastoma migratory capacity as assessed by in vitro migration assays. Furthermore, we find that the reduction in migration is accompanied by reduced cellular polarization. [ABSTRACT FROM AUTHOR]

Liver fibrosis is a dynamic pathological process in which the structure and function of the liver abnormally change due to long-term complex inflammatory reactions and chronic liver injury caused by multiple internal and external factors. Previous studies believed that the activation of hepatic stellate cells is a critical part of the occurrence and development of liver fibrosis. However, an increasing number of studies have indicated that the macrophage plays an important role as a central regulator in liver fibrosis, and it directly affects the development and recovery of liver fibrosis. Studies of macrophages and liver fibrosis in the recent 10 years will be reviewed in this paper. This review will not only clarify the molecular mechanism of liver fibrosis regulated by macrophages but also provide new strategies and methods for ameliorating and treating liver fibrosis. [ABSTRACT FROM AUTHOR]

Objective: To study the protective effect of sargassum polysaccharides （SP） on macrophage polarization and iron death induced by lipopolysaccharide （LPS） in order to determine whether SP has a regulatory effect on immune function. Methods: Isolating, purificating and identificating SP, a mouse macrophage RAW264.7 cell line inflammation model induced by LPS was established. The CCK-8 method was used to detect the effect of SP on macrophage proliferation. The levels of CD80, CD163, IL-6, IL-10, Arginine-1 （Arg-1）, inducible nitric oxide synthase （iNOS）, IL-6 and TNF-α in macrophages were measured by real-time fluorescence quantitative PCR （RT-qPCR） and Western blot. In order to understand the iron death of macrophages, ROS content was detected with ROS assay kit, and glutathione peroxid 4（ GPX4） expression was detected by Western blot. Results: SP were isolated successfully and identified not as furanose. High concentration of SP promote the proliferation of macrophages and had a significant protective effect on the inhibition of cell proliferation induced by LPS. SP could polarize RAW264.7 cells to M2 and antagonize M1 polarization induced by LPS. LPS could significantly increase ROS in macrophages, while SP could significantly decrease the level of ROS. The expression of GPX4 protein in macrophages induced by LPS was significantly decreased, and the expression was significantly up-regulated by high concentration of SP （P<0.05）. Conclusion: SP induces macrophages M2 polarization and antagonizes LPS induced M1 polarization and ferroptosis of macrophages. [ABSTRACT FROM AUTHOR]

Each cell in a multicellular organism permanently adjusts the concentration of its cell surface proteins. In particular, epithelial cells tightly control the number of carriers, transporters and cell adhesion proteins at their plasma membrane. However, sensitively measuring the cell surface concentration of a particular protein of interest in live cells and in real time represents a considerable challenge. Here, we introduce a novel approach based on split luciferases, which uses one luciferase fragment as a tag on the protein of interest and the second fragment as a supplement to the extracellular medium. Once the protein of interest arrives at the cell surface, the luciferase fragments complement and generate luminescence. We compared the performance of split Gaussia luciferase and split Nanoluciferase by using a system to synchronize biosynthetic trafficking with conditional aggregation domains. The best results were achieved with split Nanoluciferase, for which luminescence increased more than 6000‐fold upon recombination. Furthermore, we showed that our approach can separately detect and quantify the arrival of membrane proteins at the apical and basolateral plasma membrane in single polarized epithelial cells by detecting the luminescence signals with a microscope, thus opening novel avenues for characterizing the variations in trafficking in individual epithelial cells. [ABSTRACT FROM AUTHOR]

Neutrophil recruitment to sites of infection and inflammation is an essential process in the early innate immune response. Upon activation, a subset of neutrophils rapidly assembles the multiprotein complex known as the NLRP3 inflammasome. The NLRP3 inflammasome forms at the microtubule organizing center, which promotes the formation of interleukin (IL)-1β and IL-18, essential cytokines in the immune response. We recently showed that mice deficient in NLRP3 (NLRP3-/-) have reduced neutrophil recruitment to the peritoneum in a model of thioglycolate- induced peritonitis. Here, we tested the hypothesis that this diminished recruitment could be, in part, the result of defects in neutrophil chemotaxis. We find that NLRP3-/- neutrophils show loss of cell polarization, as well as reduced directionality and velocity of migration toward increasing concentrations of leukotriene B4 (LTB4) in a chemotaxis assay in vitro, which was confirmed through intravital microscopy of neutrophil migration toward a laser-induced burn injury of the liver. Furthermore, pharmacologically blocking NLRP3 inflammasome assembly with MCC950 in vitro reduced directionality but preserved nondirectional movement, indicating that inflammasome assembly is specifically required for polarization and directional chemotaxis, but not cell motility per se. In support of this, pharmacological breakdown of the microtubule cytoskeleton via nocodazole treatment induced cell polarization and restored nondirectional cell migration in NLRP3- deficient neutrophils in the LTB4 gradient. Therefore, NLRP3 inflammasome assembly is required for establishment of cell polarity to guide the directional chemotactic migration of neutrophils. [ABSTRACT FROM AUTHOR]

During immune responses against invading pathogenic bacteria, the cytoskeleton network enables macrophages to implement multiple essential functions. To protect the host from infection, macrophages initially polarize to adopt different phenotypes in response to distinct signals from the microenvironment. The extracellular stimulus regulates the rearrangement of the cytoskeleton, thereby altering the morphology and migratory properties of macrophages. Subsequently, macrophages degrade the extracellular matrix (ECM) and migrate toward the sites of infection to directly contact invading pathogens, during which the involvement of cytoskeleton‐based structures such as podosomes and lamellipodia is indispensable. Ultimately, macrophages execute the function of phagocytosis to engulf and eliminate the invading pathogens. Phagocytosis is a complex process that requires the cooperation of cytoskeleton‐enriched super‐structures, such as filopodia, lamellipodia, and phagocytic cup. This review presents an overview of cytoskeletal regulations in macrophage polarization, ECM degradation, migration, and phagocytosis, highlighting the pivotal role of the cytoskeleton in host defense against infection. [ABSTRACT FROM AUTHOR]

Objectives: The mechanism of Brucella infection regulating macrophage phenotype has not been completely elucidated until now. This study aimed to determine the mechanism of Brucella abortus in the modulation of macrophage phenotype using RAW264.7 cells as a model. Materials and methods: RT-qPCR, ELISA and flow cytometry were used to detect the inflammatory factor production and phenotype conversion associated with M1/M2 polarization of macrophages by Brucella abortus infection. Western blot and immunofluorescence were used to analyze the role of nuclear factor kappa B (NF-κB) signaling pathway in regulation of Brucella abortus-induced macrophage polarization. Chromatin immunoprecipitation sequencing (Chip-seq), bioinformatics analysis and luciferase reporter assay were used to screen and validate NF-κB target genes associated with macrophage polarization and further verify its function. Results: The results demonstrate that B. abortus induces a macrophage phenotypic switch and inflammatory response in a time-dependent manner. With the increase of infection time, B. abortus infection-induced M1-type increased first, peaked at 12 h, and then decreased, whereas the M2-type decreased first, trough at 12 h, and then increased. The trend of intracellular survival of B. abortus was consistent with that of M2 type. When NF-κB was inhibited, M1-type polarization was inhibited and M2-type was promoted, and the intracellular survival of B. abortus increased significantly. Chip-seq and luciferase reporter assay results showed that NF-κB binds to the glutaminase gene (Gls). Gls expression was down-regulated when NF-κB was inhibited. Furthermore, when Gls was inhibited, M1-type polarization was inhibited and M2-type was promoted, the intracellular survival of B. abortus increasedsignificantly. Our data further suggest that NF-κB and its key target gene Gls play an important role in controlling macrophage phenotypic transformation. Conclusions: Taken together, our study demonstrates that B. abortus infection can induce dynamic transformation of M1/M2 phenotype in macrophages. Highlighting NF-κB as a central pathway that regulates M1/M2 phenotypic transition. This is the first to elucidate the molecular mechanism of B. abortus regulation of macrophage phenotype switch and inflammatory response by regulating the key gene Gls, which is regulated by the transcription factor NF-κB. [ABSTRACT FROM AUTHOR]

Cholesterol plays an important role in cancer progression, as it is utilized in membrane biogenesis and cell signaling. Cholesterol-lowering drugs have exhibited tumor-suppressive effects in oral squamous cell carcinoma (OSCC), suggesting that cholesterol is also essential in OSCC pathogenesis. However, the direct effects of cholesterol on OSCC cells remain unclear. Here, we investigated the role of cholesterol in OSCC with respect to caveolin-1 (CAV1), a cholesterol-binding protein involved in intracellular cholesterol transport. Cholesterol levels in OSCC cell lines were depleted using methyl-β-cyclodextrin and increased using the methyl-β-cyclodextrin-cholesterol complex. Functional analysis was performed using timelapse imaging, and CAV1 expression in cholesterol-manipulated cells was investigated using immunofluorescence and immunoblotting assays. CAV1 immunohistochemistry was performed on surgical OSCC samples. We observed that cholesterol addition induced polarized cell morphology, along with CAV1 localization at the trailing edge, and promoted cell migration. Moreover, CAV1 was upregulated in the lipid rafts and formed aggregates in the plasma membrane in cholesterol-added cells. High membranous CAV1 expression in tissue specimens was associated with OSCC recurrence. Therefore, cholesterol promotes the migration of OSCC cells by regulating cell polarity and CAV1 localization to the lipid raft. Furthermore, membranous CAV1 expression is a potential prognostic marker for OSCC patients. [ABSTRACT FROM AUTHOR]

Ion transport in composite electrodes plays a key role in the electrochemical performance of lithium‐metal batteries (LMBs), particularly at high current densities, and hence, some works have suggested the use of ionic conducting polymers as binders. Herein, in order to assess the importance of the type of ion conduction in binders, two poly(ionic liquid) polymers were analyzed as binders in LiFePO4 (LFP) cathodes: poly(lithium 1‐[3‐(methacryloyloxy)propylsulfonyl]‐1‐(trifluoromethane sulfonyl) imide) (PMTFSI−Li), and poly(diallyldimethylammonium bis(trifluoromethane sulfonyl)imide) (PDADMA−TFSI). Their functionalities allow modulating the individual transport of their counter‐ions, Li+ and TFSI−, respectively; in comparison with conventional PVDF binder. Thus, LFP−C‐Binder cathodes, namely C−PVDF, C−PDADMA−TFSI and C−PMTFSI−Li, were evaluated in LMBs. C−PMTFSI−Li exhibited the best performance reaching the theoretical specific capacity (170.3±0.8 mAh g−1) at C/10, an outstanding capacity at 10 C (100.6±0.5 mAh g−1), and long lifespan (>500 cycles at 1 C). C−PDADMA−TFSI showed good long‐term cycling and high performance at high C‐rate, while C−PVDF ended up fading before reaching 500 cycles. Surprisingly, it was observed that the presence of ionic binders into the cathode formulation influenced on Li0 metal deposition morphology, leading to a more homogeneous plating (specially PMTFSI−Li) in comparison with PVDF; and therefore, exhibiting a mitigation of mossy lithium growth. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Myoblast migration is crucial for myogenesis and muscular tissue homeostasis. However, its spatiotemporal control remains elusive. Here, we explored the involvement of plasma membrane cholesterol and sphingolipids in this process. In resting C2C12 mouse myoblasts, those lipids clustered in sphingomyelin/cholesterol/GM1 ganglioside (SM/chol/GM1)- and cholesterol (chol)-enriched domains, which presented a lower stiffness than the bulk membrane. Upon migration, cholesterol and sphingomyelin polarized at the front, forming cholesterol (chol)- and sphingomyelin/cholesterol (SM/chol)-enriched domains, while GM1-enriched domains polarized at the rear. A comparison of domain proportion suggested that SM/chol- and GM1-enriched domains originated from the SM/chol/GM1-coenriched domains found at resting state. Modulation of domain proportion (through cholesterol depletion, combined or not with actin polymerization inhibition, or sphingolipid synthesis inhibition) revealed that the higher the chol- and SM/chol-enriched domains, the higher the myoblast migration. At the front, chol- and SM/chol-enriched domains were found in proximity with F-actin fibers and the lateral mobility of sphingomyelin in domains was specifically restricted in a cholesterol- and cytoskeleton-dependent manner while domain abrogation impaired F-actin and focal adhesion polarization. Altogether, we showed the polarization of cholesterol and sphingomyelin and their clustering in chol- and SM/chol-enriched domains with differential properties and roles, providing a mechanism for the spatial and functional control of myoblast migration. [ABSTRACT FROM AUTHOR]

A tremendous commitment of resources is needed to acquire, understand and apply battery data in terms of performance and aging behavior. There are many state of performance (SOP) and state of health (SOH) metrics that are useful to guide alignment of batteries to end-use, yet how these metrics are measured or extracted can make the difference between usable, valuable datasets versus data that lacks the necessary integrity to meet baseline confidence levels for SOP/SOH quantification. This work will speak to 1) types of data that support SOP and SOH evaluations on mechanistic terms, 2) measurement conditions needed to assure high data integrity, 3) equipment limitations that can compromise data high fidelity, and 4) the impact of cell polarization on data quality. A common goal in battery research and field use is to work from a data platform that supports economical paths of data capture while minimizing down-time for battery diagnostics. An ideal situation would be to utilize data obtained during normal daily use (“pulses or cycles of convenience”) without stopping the daily duty cycles to perform dedicated SOP/SOH diagnostic routines. However, difficulties arise in trying to make use of daily duty cycle data (denoted as cycle-by-cycle, CBC) that underscores the need for standardization of conditions: temperature and duty cycles can vary over the course of a day and throughout a week, month and year; polarization can develop within an immediate cycle and throughout successive cycles as a hysteresis. If CBC data is envisioned as a data source to determine performance and aging trends, it should be recognized that polarization is a frequent consequence of CBC and thus makes it difficult to separate reversible and irreversible components to metrics such as capacity loss and resistance increase over aging. Since CBC conditions can have a major impact on data usability, we will devote part of this paper to CBC data conditioning and management. Differential analyses will also be discussed as a means to detect changing trends in data quality. Our target cell chemistries will be lithium-ion types NMC/graphite and LMO/LTO.

Stationary symmetrical fish keratocyte cells break symmetry and become motile spontaneously but slowly. We found that applying electric field (EF) accelerates the polarization by an order of magnitude. While spontaneously polarized cells move persistently for hours, the EF-induced polarity is lost in a majority of cells when the EF is switched off. However, if the EF is applied for a long time and then switched off, the majority of cell move stably. Myosin inhibition abolishes spontaneous polarization, but does not slow down EF-induced polarization, and after the EF is turned off, motility does not stop; however, the cell movements are erratic. Our results suggest that the EF rapidly polarizes the cells, but that resulting polarization becomes stable slowly, and that the EF bypasses the requirement for myosin action in motility initiation.

Brown algae are a group of multicellular, heterokont algae that have convergently evolved developmental complexity that rivals that of embryophytes, animals or fungi. Early in development, brown algal zygotes establish a basal and an apical pole, which will become respectively the basal system (holdfast) and the apical system (thallus) of the adult alga. Brown algae are interesting models for understanding the establishment of cell polarity in a broad evolutionary context, because they exhibit a large diversity of life cycles, reproductive strategies and, importantly, their zygotes are produced in large quantities free of parental tissue, with symmetry breaking and asymmetric division taking place in a highly synchronous manner. This review describes the current knowledge about the establishment of the apical-basal axis in the model brown seaweeds Ectocarpus , Dictyota , Fucus and Saccharina , highlighting the advantages and specific interests of each system. Ectocarpus is a genetic model system that allows access to the molecular basis of early development and life-cycle control over apical-basal polarity. The oogamous brown alga Fucus , together with emerging comparative models Dictyota and Saccharina, emphasize the diversity of strategies of symmetry breaking in determining a cell polarity vector in brown algae. A comparison with symmetry-breaking mechanisms in land plants, animals and fungi, reveals that the one-step zygote polarisation of Fucus compares well to Saccharomyces budding and Arabidopsis stomata development, while the two-phased symmetry breaking in the Dictyota zygote compares to Schizosaccharomyces fission, the Caenorhabditis anterior-posterior zygote polarisation and Arabidopsis prolate pollen polarisation. The apical-basal patterning in Saccharina zygotes on the other hand, may be seen as analogous to that of land plants. Overall, brown algae have the potential to bring exciting new information on how a single cell gives rise to an entire complex body plan. [ABSTRACT FROM AUTHOR]

Ischemic stroke accounts for 70-80% of all stroke cases. Immunity plays an important role in the pathophysiology of ischemic stroke. Microglia are the first line of defense in the central nervous system. Microglial functions are largely dependent on their pro-inflammatory (M1-like) or anti-inflammatory (M2-like) phenotype. Modulating neuroinflammation via targeting microglia polarization toward anti-inflammatory phenotype might be a novel treatment for ischemic stroke. Mesenchymal stem cells (MSC) and MSC-derived extracellular vesicles (MSC-EVs) have been demonstrated to modulate microglia activation and phenotype polarization. In this review, we summarize the physiological characteristics and functions of microglia in the healthy brain, the activation and polarization of microglia in stroke brain, the effects of MSC/MSC-EVs on the activation of MSC in vitro and in vivo, and possible underlying mechanisms, providing evidence for a possible novel therapeutics for the treatment of ischemic stroke. [ABSTRACT FROM AUTHOR]

Morphogenesis, wound healing, and some cancer metastases rely on the collective migration of groups of cells. In these processes, guidance and coordination between cells and tissues are critical. While strongly adherent epithelial cells have tomove collectively, loosely organized mesenchymal cells can migrate as individual cells. Nevertheless, many of them migrate collectively. This article summarizes how migratory reactions to cell-cell contacts, also called "contact regulation of locomotion" behaviors, organize mesenchymal collective cell migration. It focuses on one recently discovered mechanism called "guidance by followers", through which a cell is oriented by its immediate followers. In the gastrulating zebrafish embryo, during embryonic axis elongation, this phenomenon is responsible for the collective migration of the leading tissue, the polster, and its guidance by the following posterior axial mesoderm. Such guidance of migrating cells by followers ensures long-range coordination of movements and developmental robustness. Along with other "contact regulation of locomotion" behaviors, this mechanism contributes to organizing collective migration of loose populations of cells. [ABSTRACT FROM AUTHOR]

Cell migration is a cytoskeleton-driven cellular process involved in physiological and pathological events such as embryonic development and cancer metastasis. Fibroblasts have often been used to elucidate the mechanism of cell migration due to their high morphological polarity and migratory activity. We recently reported that human lung fibroblasts migrate straight for a long duration without external stimuli, which phenomenon we named intrinsic and directed migration (IDM) of fibroblasts. In this study, we explored proteins involved in IDM in order to elucidate the molecular mechanism. First, we focused on the differences in morphology and migratory behaviors between normal and immortalized fibroblasts—the former exhibit obvious polarity and IDM; the latter exhibit poorly polarized morphology and random migration. We compared the abundance of proteins functioning as the cytoskeletal components between them through proteomic analysis and found that LIM domain only protein 7 (LMO7) is overwhelmingly incorporated into the cytoskeletons of normal fibroblasts. Depletion of LMO7 inhibited the directed migration of normal fibroblast on the fibronectin (FN)-rich surface, suggesting that LMO7 is important for IDM. Moreover, on the FN-free surface, LMO7-depleted fibroblasts often failed to establish morphological polarity and hardly migrated. Thus, the present study identified LMO7 as a positive regulator of fibroblast polarization and IDM, especially in an environment where integrin-mediated substrate attachment is insufficient. • LMO7 is abundant in the cytoskeletal fraction of normal fibroblasts. • LMO7 is critical for the proper polarization and migration of fibroblasts. • The significance of LMO7 on fibroblast migration depends on the ECM condition. [ABSTRACT FROM AUTHOR]

The nematode (roundworm) Caenorhabditis elegans is one of the most popular animal models for the study of developmental biology, as its invariant development and transparent body enable in toto cellular-resolution fluorescence microscopy imaging of developmental processes at 1-min intervals. This has led to the development of various computational tools for the systematic and automated analysis of imaging data to delineate the molecular and cellular processes throughout the embryogenesis of C. elegans, such as those associated with cell lineage, cell migration, cell morphology, and gene activity. In this review, we first introduce C. elegans embryogenesis and the development of techniques for tracking cell lineage and reconstructing cell morphology during this process. We then contrast the developmental modes of C. elegans and the customized technologies used for studying them with the ones of other animal models, highlighting its advantage for studying embryogenesis with exceptional spatial and temporal resolution. This is followed by an examination of the physical models that have been devised—based on accurate determinations of developmental processes afforded by analyses of imaging data—to interpret the early embryonic development of C. elegans from subcellular to intercellular levels of multiple cells, which focus on two key processes: cell polarization and morphogenesis. We subsequently discuss how quantitative data-based theoretical modeling has improved our understanding of the mechanisms of C. elegans embryogenesis. We conclude by summarizing the challenges associated with the acquisition of C. elegans embryogenesis data, the construction of algorithms to analyze them, and the theoretical interpretation.

Saccharomyces cerevisiae has been widely used as a microbial cell factory to produce recombinant proteins. Therefore, enhancing the protein production efficiency of yeast cell factories to expand the market demand for protein products is necessary. Recombinant proteins are often retained in the secretory pathway because of the limited protein transport performed by vesicle trafficking. Cell polarization describes the asymmetric organization of the plasma membrane cytoskeleton and organelles and tightly regulates vesicle trafficking for protein transport. Engineering vesicle trafficking has broadly been studied by the overexpression or deletion of key genes involved but not by modifying cell polarization. Here, we used α-amylase as a reporter protein, and its secretion and surface-display were first improved by promoter optimization. To study the effect of engineering cell polarization on protein production, fourteen genes related to cell polarization were overexpressed. BUD1, CDC42, AXL1, and BUD10 overexpression increased the activity of surface-displayed α-amylase, and BUD1, BUD3, BUD4, BUD7, and BUD10 overexpression enhanced secreted α-amylase activity. Furthermore, BUD1 overexpression increased the surface-displayed and secreted α-amylase expression by 56% and 49%, respectively. We also observed that the combinatorial modification and regulation of gene expression improved α-amylase production in a dose-dependent manner. BUD1 and CDC42 co-overexpression increased the α-amylase surface display by 100%, and two genomic copies of BUD1 improved α-amylase secretion by 92%. Furthermore, these modifications were used to improve the surface display and secretion of the recombinant β-glucosidase protein. Our study affords a novel insight for improving the surface display and secretion of recombinant proteins. [ABSTRACT FROM AUTHOR]

The dynamics of single-cell migration on flat surfaces are usually modeled by a Langevin-like problem for particle velocity, consisting of a ballistic motion for short time intervals and a diffusive regime for long time intervals. However, experiments and simulations have revealed an additional diffusive motion at very short time intervals, which rules out the definition of cells' instantaneous velocities. The experimental consequence is that one cannot estimate velocity by decreasing time intervals in a sequence of measurements. While for ballistic motion, the ratio of displacement over time intervals converges to a constant value (the limit value is taken as the velocity estimate), for diffusive motion this ratio diverges. Here, instead of cell velocity, we consider cell polarization as the dynamical variable and assume evolution equations for polarization modulus (a biased Langevin equation) and direction (a Wiener process). This circumvents the measurement problems for cell velocity when the system presents short-time diffusion. That means we take cell speed and displacement as consequences of cell polarization. For displacements, we also considered an additional noise term to account for membrane fluctuations that, in fact, cause the short-time-interval diffusive behavior. As novel results, we obtain memory preservation in polarization modulus for short time intervals and a displacement distribution function that may present a maximum at finite values of polarization modulus, for adequate time intervals. We also obtain a bi-exponential displacement autocorrelation function, improving the agreement between theoretical fits and experiments or simulations. Overall, this model contributes to the robustness of experimental measurements in cell migration experiments, besides providing a sound basis for theoretical models. For wet laboratory procedures, our findings provide a warning in what regards velocity and speed estimates and we propose experimental protocols to obtain these estimates at different levels of precision. [ABSTRACT FROM AUTHOR]

Collective cell motion is crucial for various physiological and pathological processes, and it highly relies on physical factors in cell microenvironment. However, a quantitative understanding of the effect of the physical factors remains lacking. Here, we studied the collective motion of cells on patterned matrixes with experimental study and numerical simulation by quantitatively analyzing the features of cell collective motion. We found that the collectivity of cell motion is size-dependent. The cells have high collectivity on a small pattern, while they lose the collectivity on the large one. The geometry of the pattern also influences the collective motion by regulating the velocity distribution in the cell layer. Interestingly, the cell density can significantly influence the collective motion by changing the active stress of the cells. For a quantitative understanding of the mechanisms of the effect of these physical factors, we adopted a coarse-grained cell model that considers the active contraction of cells by introducing cell active stress in the model based on the traction-distance law. Our numerical simulation predicted not only the cell velocity, cell collectivity, and cell polarization, but also the stress distribution in the cell layer. The consistency between the numerical predictions and experimental results reveals the relationship between the pattern of collective cell motion and the stress distribution in the cell layer, which sheds light on the studies of tissue engineering for biomedical applications. [ABSTRACT FROM AUTHOR]

This article contains data related to the research article in this issue titled ameloblastin promotes polarization of ameloblast cell lines in a 3D cell culture system (Visakan et al., 2022). In the process of amelogenesis, the organic matrix components are pivotal to the establishment of ameloblast-matrix adhesion. Here we employ immortalized ameloblast cell lines and analyse their morphological changes in 3D cell culture when cultured in the presence of recombinant enamel matrix proteins- ameloblastin and amelogenin compared with controls. The recombinant proteins that were purified using high-performance liquid chromatography (HPLC) were characterized using SDS-gel electrophoresis. A 3D-on-top culture technique was employed, and the cells were analysed 24 and 72 h post inoculation using fluorescent and confocal microscopy for qualitative and quantitative changes. Aspect ratio of cells was measured and used as the parameter to compare between test proteins and controls. Repeated measurements of aspect ratio were recorded to analyse for statistical significance. Additionally, three distinct gel substrates were studied to examine the effect of composition and stiffness of the substrate on cell behaviour. The cells in the 3D culture were fixed and labelled using antibodies to junctional complex, polarity and tight junctional proteins following protocols for whole culture fixation. Co-localization between membrane and specific antibody labels were examined under confocal microscopy.

In the quest for better medicines, attention is increasingly turning to cell-based therapies. The rationale is that infused cells can provide a targeted therapy to precisely correct a complex disease phenotype. Between 1987 and 2010, autologous macrophages (MΦs) were used in clinical trials to treat a variety of human tumors; this approach provided a modest therapeutic benefit in some patients but no lasting remissions. These trials were initiated prior to an understanding of: the complexity of MΦ phenotypes, their ability to alter their phenotype in response to various cytokines and/or the environment, and the extent of survival of the re-infused MΦs. It is now known that while inflammatory MΦs can kill tumor cells, the tumor environment is able to reprogram MΦs into a tumorigenic phenotype; inducing blood vessel formation and contributing to a cancer cell growth-promoting milieu. We review how new information enables the development of large numbers of ex vivo generated MΦs, and how conditioning and gene engineering strategies are used to restrict the MΦ to an appropriate phenotype or to enable production of therapeutic proteins. We survey applications in which the MΦ is loaded with nanomedicines, such as liposomes ex vivo, so when the drug-loaded MΦs are infused into an animal, the drug is released at the disease site. Finally, we also review the current status of MΦ biodistribution and survival after transplantation into an animal. The combination of these recent advances opens the way for improved MΦ cell therapies.

Objective To investigate the inhibitory effect of salidroside (SAL) on osteoclast differentiation and polarization. Methods RAW264.7 cells were cultured in vitro and induced into osteoclasts by adding solvable receptor activator of nuclear factor kappa B ligand (sRANKL) for 5 days. The control group (culture medium without SAL) and the experimental group (culture medium with SAL in dosage of 15, 30, 60 mg/L respectively) were set. The results of inducing differentiation were compared by TRAP staining. F-Actin ring formation and osteoclast calcification were compared by phalloidin staining and alizarin red staining. Real time fluorescent quantitative reverse transcription polymerase chain reaction (qPCR) was used to detect expression levels of MMP-9, c-Src, CK and Integrin β3. The expression levels of MMP-9 and c-Src proteins were detected by Western blot assay. Results Compared with the control group, the number of TRAP positive cells, and F-Actin ring formation were significantly reduced in each experimental group. The calcification of osteoclasts and the alizarin red staining of osteoclasts were significantly deepened, indicating the the increased calcification (P＜0.05). Compared with the control group, the expression levels of MMP-9, CK and c-Src mRNA decreased in the 30 and 60 mg/L SAL groups, and the expression levels of MMP-9 and c-Src protein decreased significantly in each group. Conclusion Salidroside can inhibit the differentiation, polarization and bone resorption of osteoclasts, and its mechanism may be related to the down-regulation of MMP-9 and c-Src expression. [ABSTRACT FROM AUTHOR]

The process of polarization determines the head and tail of single cells. A mechanism of this kind frequently precedes the subsequent cell locomotion and it determines the direction of motion. The process of polarization has frequently been described as a reaction-diffusion mechanism combined with a source of stochastic perturbations. We selected a particular model of amoeboid cell crawling for the motion of Dictyostelium discoideum and studied the interplay between pattern formation and locomotion. Next, we integrated the model in a two-dimensional domain considering the shape deformations of the cells in order to characterize the dynamics. We observed that the condition of pattern formation is finely tuned and we propose a modification based on the use of a mass-conservation constraint to substantially increase the robustness of the mathematical model.

Mechanical guidance of tissue morphogenesis is an emerging method of regenerative medicine that can be employed to steer functional kidney architecture for the purpose of bioartificial kidney design or renal tissue engineering strategies. In kidney morphogenesis, apical-basal polarization of renal epithelial cells is paramount for tubule formation and subsequent tissue functions like excretion and resorption. In kidney epithelium, polarization is initiated by integrin-mediated cell-matrix adhesion at the cell membrane. Cellular mechanobiology research has indicated that this integrin-mediated adhesion is responsive to matrix stiffness, raising the possibility to use matrix stiffness as a handle to steer cell polarization. Herein, we evaluate apical-basal polarization in response to 2D substates of different stiffness (1, 10, 50 kPa and glass) in Madin Darby Canine Kidney cells (MDCKs), a classic canine-derived cell model of epithelial polarization, and in tubuloid-derived cells, established from human primary cells derived from adult kidney tissue. Our results show that sub-physiological (1 kPa) substrate stiffness with low integrin-based adhesion induces polarization in MDCKs, while MDCKs on supraphysiological (>10 kPa) stiffness remain unpolarized. Inhibition of integrin, indeed, allows for polarization on the supraphysiological substrates, suggesting that increased cellular adhesion on stiff substrates opposes polarization. In contrast, tubuloid-derived cells do not establish apical-basal polarization on 2D substrates, irrespective of substrate stiffness, despite their ability to polarize in 3D environments. Further analysis implies that the 2D cultured tubuloid-derived cells have a diminished mechanosensitive capacity when presented with different substrate stiffnesses due to immature focal adhesions and the absence of a connection between focal adhesions and the cytoskeleton. Overall, this study demonstrates that apical-basal polarization is a complex process, where cell type, the extracellular environment, and both the mechanical and chemical aspects in cell-matrix interactions performed by integrins play a role.

The isotropic metaphase actin cortex progressively polarizes as the anaphase spindle elongates during mitotic exit. This involves the loss of actomyosin cortex from opposing cell poles and the accumulation of an actomyosin belt at the cell centre. Although these spatially distinct cortical remodelling events are coordinated in time, here we show that they are independent of each other. Thus, actomyosin is lost from opposing poles in anaphase cells that lack an actomyosin ring owing to centralspindlin depletion. In examining potential regulators of this process, we identify a role for Aurora B kinase in actin clearance at cell poles. Upon combining Aurora B inhibition with centralspindlin depletion, cells exiting mitosis fail to change shape and remain completely spherical. Additionally, we demonstrate a requirement for Aurora B in the clearance of cortical actin close to anaphase chromatin in cells exiting mitosis with a bipolar spindle and in monopolar cells forced to divide while flat. Altogether, these data suggest a novel role for Aurora B activity in facilitating DNA‐mediated polar relaxation at anaphase, polarization of the actomyosin cortex, and cell division. Synopsis: Aurora B facilitates DNA‐mediated polar relaxation at anaphase and polarization of the actomyosin cortex to ensure a robust coupling of anaphase spindle elongation and cytokinesis. The clearance of actin from cell poles at anaphase does not depend on actomyosin ring assembly or on the centralspindlin complex.Aurora B activity is required for clearance of cortical actin network during anaphase and for actin clearance in the vicinity of chromosomes in artificially flattened cells.The role of Aurora B in cortical relaxation is independent of its role in regulating centralspindlin activity. [ABSTRACT FROM AUTHOR]

How cells sense and respond to mechanical stimuli remains an open question. Recent advances have identified the translocation of Yes-associated protein (YAP) between nucleus and cytoplasm as a central mechanism for sensing mechanical forces and regulating mechanotransduction. We formulate a spatiotemporal model of the mechanotransduction signalling pathway that includes coupling of YAP with the cell force-generation machinery through the Rho family of GTPases. Considering the active and inactive forms of a single Rho protein (GTP/GDP-bound) and of YAP (non-phosphorylated/phosphorylated), we study the cross-talk between cell polarization due to active Rho and YAP activation through its nuclear localization. For fixed mechanical stimuli, our model predicts stationary nuclear-to-cytoplasmic YAP ratios consistent with experimental data at varying adhesive cell area. We further predict damped and even sustained oscillations in the YAP nuclear-to-cytoplasmic ratio by accounting for recently reported positive and negative YAP-Rho feedback. Extending the framework to time-varying mechanical stimuli that simulate cyclic stretching and compression, we show that the YAP nuclear-to-cytoplasmic ratio's time dependence follows that of the cyclic mechanical stimulus. The model presents one of the first frameworks for understanding spatiotemporal YAP mechanotransduction, providing several predictions of possible YAP localization dynamics, and suggesting new directions for experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

A plasmonic metasurface composed of a self-assembled monolayer of gold nanoparticles allows for fluorescence imaging with high spatial resolution, owing to the collective excitation of localized surface plasmon resonance. Taking advantage of fluorescence imaging confined to the nano-interface, we examined actin organization in breast cancer cell lines with different metastatic potentials during cell adhesion. Live-cell fluorescence imaging confined within tens of nanometers from the substrate shows a high actin density spanning < 1 μm from the cell edge. Live-cell imaging revealed that the breast cancer cell lines exhibited different actin patterns during the initial phase of cell adhesion (∼ 1 h). Non-tumorous MCF10A cells exhibited symmetric actin localization at the cell edge, whereas highly metastatic MDA-MB-231 cells showed asymmetric actin localization, demonstrating rapid polarization of MDA-MB-231 cells upon adhesion. The rapid actin organization observed by our plasmonic metasurface-based fluorescence imaging provides information on how quickly cancer cells sense the underlying substrate. [Display omitted] • Live-cell imaging with high lateral and axial resolution was performed. • A plasmonic metasurface confines fluorescence within ∼ 20 nm from substrate. • Actin at cell edge similar to super-resolution microscopy of fixed cells was observed. • Breast cancer cells showed different actin organization within 1 h after attachment. [ABSTRACT FROM AUTHOR]

The apicobasal polarity of enterocytes determines where the brush border membrane (apical membrane) will form, but how this apical membrane faces the lumen is not well understood. The electrical signal across the epithelium could serve as a coordinating cue, orienting and polarizing enterocytes. Here, we show that applying a physiological electric field to intestinal epithelial cells, to mimic the natural electric field created by the transepithelial potential difference, polarized phosphorylation of the actin-binding protein ezrin, increased expression of intestinal alkaline phosphatase (ALPI, a differentiation marker) and remodeled the actin cytoskeleton selectively on the cathode side. In addition, an applied electric field also activated ERK1/2 and LKB1 (also known as STK11), key molecules in apical membrane formation. Disruption of the tyrosine protein kinase transmembrane receptor Ror2 suppressed activation of ERK1/2 and LKB1 significantly, and subsequently inhibited apical membrane formation in enterocytes. Our findings indicate that the endogenous electric field created by the transepithelial potential difference might act as an essential coordinating signal for apical membrane formation at a tissue level, through activation of LKB1 mediated by Ror2-ERK signaling.

Cell polarity refers to spatial di erences in the shape and structure of cells, which leads to the generation of diverse cell types playing di erent roles in biological processes. Cell polarization usually involves the localization of some specific signaling molecules to a proper location of the cell membrane. Recent studies proposed that delayed negative feedback may be important for maintaining the robustness of cell polarization and the observed oscillating behavior of signaling cluster. However, the fundamental mechanisms for achieving cell polarization under negative feedback remain controversial. In this paper, we formulate the cell polarization system as a non-local reaction di usion equation with positive and delayed negative feedback loops. Through the Turing stability analysis, we identify the parameter conditions, including the range of the time delay constant, for achieving cell polarization without any inhomogeneous spatial cues. Also, our numerical results support that by controlling the length of the time delay in negative feedback and the magnitude of positive feedback, the oscillating behavior of signaling cluster can be observed in our simulations.

Saccharomyces cerevisiae has been widely used as a microbial cell factory to produce recombinant proteins. Therefore, enhancing the protein production efficiency of yeast cell factories to expand the market demand for protein products is necessary. Recombinant proteins are often retained in the secretory pathway because of the limited protein transport performed by vesicle trafficking. Cell polarization describes the asymmetric organization of the plasma membrane cytoskeleton and organelles and tightly regulates vesicle trafficking for protein transport. Engineering vesicle trafficking has broadly been studied by the overexpression or deletion of key genes involved but not by modifying cell polarization. Here, we used α-amylase as a reporter protein, and its secretion and surface-display were first improved by promoter optimization. To study the effect of engineering cell polarization on protein production, fourteen genes related to cell polarization were overexpressed. BUD1, CDC42, AXL1, and BUD10 overexpression increased the activity of surface-displayed α-amylase, and BUD1, BUD3, BUD4, BUD7, and BUD10 overexpression enhanced secreted α-amylase activity. Furthermore, BUD1 overexpression increased the surface-displayed and secreted α-amylase expression by 56% and 49%, respectively. We also observed that the combinatorial modification and regulation of gene expression improved α-amylase production in a dose-dependent manner. BUD1 and CDC42 co-overexpression increased the α-amylase surface display by 100%, and two genomic copies of BUD1 improved α-amylase secretion by 92%. Furthermore, these modifications were used to improve the surface display and secretion of the recombinant β-glucosidase protein. Our study affords a novel insight for improving the surface display and secretion of recombinant proteins.

Blebs are cell protrusions generated by local membrane–cortex detachments followed by expansion of the plasma membrane. Blebs are formed by some migrating cells, e.g. primordial germ cells of the zebrafish. While blebs occur randomly at each part of the membrane in unpolarized cells, a polarization process guarantees the occurrence of blebs at a preferential site and thereby facilitates migration toward a specified direction. Little is known about the factors involved in the controlled and directed bleb generation, yet recent studies revealed the influence of an intracellular flow and the stabilizing role of the membrane–cortex linker molecule Ezrin. Based on this information, we develop and analyse a coupled bulk-surface model describing a potential cellular mechanism by which a bleb could be induced at a controlled site. The model rests upon intracellular Darcy flow and a diffusion–advection–reaction system, describing the temporal evolution from a homogeneous to a strongly anisotropic Ezrin distribution. We prove the well-posedness of the mathematical model and show that simulations qualitatively correspond to experimental observations, suggesting that indeed the interaction of an intracellular flow with membrane proteins can be the cause of the Ezrin redistribution accompanying bleb formation. [ABSTRACT FROM AUTHOR]

Prostate cancer is a life‐threatening condition worldwide. As the tumor progresses, smooth muscle cells (SMCs) become atrophic/dedifferentiated, within a series of stromal changes named stromal reaction. Here, we tested whether a laminin 111‐rich extracellular matrix (Lr‐ECM) could affect SMCs phenotype and differentiation status. Using time‐lapse microscopy, image analyses, quantitative real‐time reverse transcription polymerase chain reaction, immunohistochemistry and immunoblotting, and transmission electron microscopy, we showed that SMCs acquires a migratory behavior with a decreased expression of differentiation markers and relocation of focal adhesion kinase. SMCs set homotypic cell junctions and were active in autophagy/phagocytosis. Analysis of the migratory behavior showed that SMCs polarized and migrated toward each other, recognizing long‐distance signals such as matrix tensioning. However, half of the cell population were immotile, irrespective of the nearest neighbor distance, suggesting they do not engage in productive interactions, possibly as a result of back‐to‐back positioning. In conclusion, the Lr‐ECM, mimics the effects of the proliferating and infiltrating tumor epithelium, causing SMCs phenotypical change similar to that observed in the stromal reaction, in addition to a hitherto undescribed, stereotyped pattern of cell motility resulting from cell polarization. [ABSTRACT FROM AUTHOR]

Ischemic stroke, which is the second highest cause of death and the leading cause of disability, represents ~71% of all strokes globally. Some studies have found that the key elements of the pathobiology of stroke is immunity and inflammation. Microglia are the first line of defense in the nervous system. After stroke, the activated microglia become a double-edged sword, with distinct phenotypic changes to the deleterious M1 types and neuroprotective M2 types. Therefore, ways to promote microglial polarization toward M2 phenotype after stroke have become the focus of attention in recent years. In this review, we discuss the process of microglial polarization, summarize the alternation of signaling pathways and epigenetic regulation that control microglial polarization in ischemic stroke, aiming to find the potential mechanisms by which microglia can be transformed into the M2 polarized phenotype. [ABSTRACT FROM AUTHOR]

Stroke is a lethal cerebral disease with severe sequelae and high mortality. Microglia, the main immune cell in the cerebrum, possess therapeutic potential for strokes as its specific anti‐inflammatory phenotype can reduce inflammation and promote neuron regeneration. However, the on‐demand anti‐inflammatory polarization of microglia at the stroke site is uncontrollable for therapeutic application. Here, we develop a platelet hybrid microglia platform which can specifically polarize to the anti‐inflammatory phenotype by ultrasound irradiation for targeted cerebrum repair after stroke. The engineered microglia have strong adherence to the injured cerebral vessels with platelet membrane fusion and realize on‐demand anti‐inflammatory polarization with ultrasound‐responsive IL‐4 liposome decoration. The intravenously injected microglia platform showed anti‐inflammatory polarization at the stroke site with insonation, and accelerated the M2‐type polarization of endogenous microglia for long‐term stroke recovery. Satisfied prognoses were achieved with reduced apoptosis, promoted neurogenesis, and functional recovery, indicating the implications of the microglia platform for stroke therapy. [ABSTRACT FROM AUTHOR]

Cell migration plays vital roles in many biologically relevant processes such as tissue morphogenesis and cancer metastasis, and it has fascinated biophysicists over the past several decades. However, despite an increasing number of studies highlighting the orchestration of proteins involved in different signaling pathways, the functional roles of lipid membranes have been essentially overlooked. Lipid membranes are generally considered to be a functionless two-dimensional matrix of proteins, although many proteins regulating cell migration gain functions only after they are recruited to the membrane surface and self-organize their functional domains. In this review, we summarize how the logistical recruitment and release of proteins to and from lipid membranes coordinates complex spatiotemporal molecular processes. As predicted from the classical framework of the Smoluchowski equation of diffusion, lipid/protein membranes serve as a 2D reaction hub that contributes to the effective and robust regulation of polarization and migration of cells involving several competing pathways. [ABSTRACT FROM AUTHOR]

Directional auxin transport and formation of auxin maxima are critical for embryogenesis, organogenesis, pattern formation, and growth coordination in plants, but the mechanisms underpinning the initiation and establishment of these auxin dynamics are not fully understood. Here we show that a self-initiating and -terminating transient auxin flow along the marginal cells (MCs) contributes to the formation of an auxin maximum at the tip of Arabidopsis cotyledon that globally coordinates the interdigitation of puzzle-shaped pavement cells in the cotyledon epidermis. Prior to the interdigitation, indole butyric acid (IBA) is converted to indole acetic acid (IAA) to induce PIN2 accumulation and polarization in the marginal cells, leading to auxin flow toward and accumulation at the cotyledon tip. When IAA levels at the cotyledon tip reaches a maximum, it activates pavement cell interdigitation as well as the accumulation of the IBA transporter TOB1 in MCs, which sequesters IBA to the vacuole and reduces IBA availability and IAA levels. The reduction of IAA levels results in PIN2 down-regulation and cessation of the auxin flow. Hence, our results elucidate a self-activating and self-terminating transient polar auxin transport system in cotyledons, contributing to the formation of localized auxin maxima that spatiotemporally coordinate pavement cell interdigitation.

Cell polarity is important for controlling cell shape, motility and cell division processes. Vimentin intermediate filaments are important for cell migration and cell polarization in mesenchymal cells and assembly of vimentin and microtubule networks is dynamically coordinated, but the precise details of how vimentin mediates cell polarity remain unclear. Here, we characterize the effects of vimentin on the structure and function of the centrosome and the stability of microtubule filaments in wild-type and vimentin-null mouse embryonic fibroblasts. We find that vimentin mediates the structure of the pericentriolar material, promotes centrosome-mediated microtubule regrowth and increases the level of stable acetylated microtubules in the cell. Loss of vimentin also impairs centrosome repositioning during cell polarization and migration processes that occur during wound closure. Our results suggest that vimentin modulates centrosome structure and function as well as microtubule network stability, which has important implications for how cells establish proper cell polarization and persistent migration.

Endogenous electrical fields (EFs) at corneal and skin wounds send a powerful signal that directs cell migration during wound healing. This signal therefore may serve as a fundamental regulator directing cell polarization and migration. Very little is known of the intracellular and molecular mechanisms that mediate EF-induced cell polarization and migration. Here, we report that Chinese hamster ovary (CHO) cells show robust directional polarization and migration in a physiological EF (0.3-1 V/cm) in both dissociated cell culture and monolayer culture. An EF of 0.6 V/cm completely abolished cell migration into wounds in monolayer culture. An EF of higher strength (≥1 V/cm) is an overriding guidance cue for cell migration. Application of EF induced quick phosphorylation of glycogen synthase kinase 3β (GSK-3β) which reached a peak as early as 3 min in an EF. Inhibition of protein kinase C (PKC) significantly reduced EF-induced directedness of cell migration initially (in 1-2 h). Inhibition of GSK-3β completely abolished EF-induced GA polarization and significantly inhibited the directional cell migration, but at a later time (2-3 h in an EF). Those results suggest that GSK-3β is essential for physiological EF-induced Golgi apparatus (GA) polarization and optimal electrotactic cell migration.

The ability of epithelial tissues to heal after injury is essential for animal life, yet the mechanisms by which epithelial cells sense tissue damage are incompletely understood. In aquatic organisms such as zebrafish, osmotic shock following injury is believed to be an early and potent activator of a wound response. We find that, in addition to sensing osmolarity, basal skin cells in zebrafish larvae are also sensitive to changes in the particular ionic composition of their surroundings after wounding, specifically the concentration of sodium chloride in the immediate vicinity of the wound. This sodium chloride-specific wound detection mechanism is independent of cell swelling, and instead is suggestive of a mechanism by which cells sense changes in the transepithelial electrical potential generated by the transport of sodium and chloride ions across the skin. Consistent with this hypothesis, we show that electric fields directly applied within the skin are sufficient to initiate actin polarization and migration of basal cells in their native epithelial context in vivo, even overriding endogenous wound signaling. This suggests that, in order to mount a robust wound response, skin cells respond to both osmotic and electrical perturbations arising from tissue injury.