Biphasic Dependence of Glioma Survival and Cell Migration on CD44 Expression Level

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Rectified Cell Migration on Saw-Like Micro-Elastically Patterned Hydrogels with Asymmetric Gradient Ratchet Teeth

To control cell motility is one of the essential technologies for biomedical engineering. To establish a methodology of the surface design of elastic substrate to control the long-range cell movements, here we report a sophisticated cell culture hydrogel with a micro-elastically patterned surface that allows long-range durotaxis. This hydrogel has a saw-like pattern with asymmetric gradient ratchet teeth, and rectifies random cell movements. Durotaxis only occurs at boundaries in which the gradient strength of elasticity is above a threshold level. Consequently, in gels with unit teeth patterns, durotaxis should only occur at the sides of the teeth in which the gradient strength of elasticity is above this threshold level. Therefore, such gels are expected to support the long-range biased movement of cells via a mechanism similar to the Feynman-Smoluchowski ratchet, i.e., rectified cell migration. The present study verifies this working hypothesis by using photolithographic microelasticity patterning of photocurable gelatin gels. Gels in which each teeth unit was 100–120 µm wide with a ratio of ascending:descending elasticity gradient of 1:2 and a peak elasticity of ca. 100 kPa supported the efficient rectified migration of 3T3 fibroblast cells. In addition, long-range cell migration was most efficient when soft lanes were introduced perpendicular to the saw-like patterns. This study demonstrates that asymmetric elasticity gradient patterning of cell culture gels is a versatile means of manipulating cell motility.     

Trafficking and Cell Migration

The migration of single cells and epithelial sheets is of great importance for gastrulation and organ formation in developing embryos and, if misregulated, can have dire consequences e.g. during cancer metastasis. A keystone of cell migration is the regulation of adhesive contacts, which are dynamically assembled and disassembled via endocytosis. Here, we discuss some of the basic concepts about the function of endocytic trafficking during cell migration: transport of integrins from the cell rear to the leading edge in fibroblasts; confinement of signalling to the front of single cells by endocytic transport of growth factors; regulation of movement coherence in multicellular sheets by cadherin turnover; and shaping of extracellular chemokine gradients. Taken together, endocytosis enables migrating cells and tissues to dynamically modulate their adhesion and signalling, allowing them to efficiently migrate through their extracellular environment.     

Transmembrane Lipid Migration in Planar Asymmetric Bilayer Membranes

Planar asymmetric bilayer membranes, formed by apposing a monolayer of the neutral lipid glyceroldioleate (GDO) with one of the negatively charged lipid oleyl acid phosphate (OAP), were used to measure the rate of transmembrane OAP migration. The assay for this lipid flip-flop was the interaction of Ca²⁺ ions with negatively charged lipids which causes membranes to break: when Ca²⁺ is added to the compartment limited initially by the neutral lipid, flip-flop of the charged lipid eventually results in membrane breakdown. At 22 ± 2°C, in the absence of an externally applied electric field, an upper limit to the half time of OAP flip-flop was measured as 18.7 h, with a tentative lower limit of 14.4 h.     

Flow and Diffusion in Channel-Guided Cell Migration

Collective migration of mechanically coupled cell layers is a notable feature of wound healing, embryonic development, and cancer progression. In confluent epithelial sheets, the dynamics have been found to be highly heterogeneous, exhibiting spontaneous formation of swirls, long-range correlations, and glass-like dynamic arrest as a function of cell density. In contrast, the flow-like properties of one-sided cell-sheet expansion in confining geometries are not well understood. Here, we studied the short- and long-term flow of Madin-Darby canine kidney (MDCK) cells as they moved through microchannels. Using single-cell tracking and particle image velocimetry (PIV), we found that a defined averaged stationary cell current emerged that exhibited a velocity gradient in the direction of migration and a plug-flow-like profile across the advancing sheet. The observed flow velocity can be decomposed into a constant term of directed cell migration and a diffusion-like contribution that increases with density gradient. The diffusive component is consistent with the cell-density profile and front propagation speed predicted by the Fisher-Kolmogorov equation. To connect diffusion-mediated transport to underlying cellular motility, we studied single-cell trajectories and occurrence of vorticity. We discovered that the directed large-scale cell flow altered fluctuations in cellular motion at short length scales: vorticity maps showed a reduced frequency of swirl formation in channel flow compared with resting sheets of equal cell density. Furthermore, under flow, single-cell trajectories showed persistent long-range, random-walk behavior superimposed on drift, whereas cells in resting tissue did not show significant displacements with respect to neighboring cells. Our work thus suggests that active cell migration manifests itself in an underlying, spatially uniform drift as well as in randomized bursts of short-range correlated motion that lead to a diffusion-mediated transport.     

Flow and Diffusion in Channel-Guided Cell Migration

Collective migration of mechanically coupled cell layers is a notable feature of wound healing, embryonic development, and cancer progression. In confluent epithelial sheets, the dynamics have been found to be highly heterogeneous, exhibiting spontaneous formation of swirls, long-range correlations, and glass-like dynamic arrest as a function of cell density. In contrast, the flow-like properties of one-sided cell-sheet expansion in confining geometries are not well understood. Here, we studied the short- and long-term flow of Madin-Darby canine kidney (MDCK) cells as they moved through microchannels. Using single-cell tracking and particle image velocimetry (PIV), we found that a defined averaged stationary cell current emerged that exhibited a velocity gradient in the direction of migration and a plug-flow-like profile across the advancing sheet. The observed flow velocity can be decomposed into a constant term of directed cell migration and a diffusion-like contribution that increases with density gradient. The diffusive component is consistent with the cell-density profile and front propagation speed predicted by the Fisher-Kolmogorov equation. To connect diffusion-mediated transport to underlying cellular motility, we studied single-cell trajectories and occurrence of vorticity. We discovered that the directed large-scale cell flow altered fluctuations in cellular motion at short length scales: vorticity maps showed a reduced frequency of swirl formation in channel flow compared with resting sheets of equal cell density. Furthermore, under flow, single-cell trajectories showed persistent long-range, random-walk behavior superimposed on drift, whereas cells in resting tissue did not show significant displacements with respect to neighboring cells. Our work thus suggests that active cell migration manifests itself in an underlying, spatially uniform drift as well as in randomized bursts of short-range correlated motion that lead to a diffusion-mediated transport.     

Protein Complex Assemblies in Epithelial Cell Polarity and Asymmetric Cell Division

Asymmetric local concentration of protein complexes on distinct membrane regions is a fundamental property in numerous biological processes and is a hallmark of cell polarity. Evolutionarily conserved core polarity proteins form specific and dynamic networks to regulate the establishment and maintenance of cell polarity, as well as distinct polarity-driven cellular events. This review focuses on the molecular and structural basis governing regulated formation of several sets of core cell polarity regulatory complexes, as well as their functions in epithelial cell polarization and asymmetric cell division.     

Acyl Migration in 1,2-Dibutyrin Dependence on Solvent and Water Activity

The rate of isomerization of 1,2-dibutyrin has been examined as a function of solvent, water activity, enzyme and the presence of hexanoic acid. The rate of acyl migration was found to be solvent dependent. Decreasing solvent polarity gave increasing rate. Addition of water to the most nonpolar solvent used, hexane, led to a decrease which followed the water activity. When solid salt hydrates were included in the reaction mixture, some led to no migration. When yeast alcohol dehydrogenase, lysozyme, lipase from Geotrichum candidum or hexanoic acid were present, the migration rate increased with increasing water activity.     

黏着斑激酶与细胞迁移

细胞迁移过程始于细胞前端板状伪足的形成、外周黏附的建立、细胞体的收缩和尾部的解离.黏着斑激酶是一种非受体酪氨酸蛋白激酶,通过其激酶活性和"脚手架"的功能在细胞迁移的各个过程中发挥关键作用.现重点介绍黏着斑激酶介导的信号转导通路及其在调控细胞迁移方面的研究进展.     

Study of Cell Migration in Microfabricated Channels

The method described here allows the study of cell migration under confinement in one dimension. It is based on the use of microfabricated channels, which impose a polarized phenotype to cells by physical constraints. Once inside channels, cells have only two possibilities: move forward or backward. This simplified migration in which directionality is restricted facilitates the automatic tracking of cells and the extraction of quantitative parameters to describe cell movement. These parameters include cell velocity, changes in direction, and pauses during motion. Microchannels are also compatible with the use of fluorescent markers and are therefore suitable to study localization of intracellular organelles and structures during cell migration at high resolution. Finally, the surface of the channels can be functionalized with different substrates, allowing the control of the adhesive properties of the channels or the study of haptotaxis. In summary, the system here described is intended to analyze the migration of large cell numbers in conditions in which both the geometry and the biochemical nature of the environment are controlled, facilitating the normalization and reproducibility of independent experiments.     

Membrane Nanowaves in Single and Collective Cell Migration

We report the characterization of three-dimensional membrane waves for migrating single and collective cells and describe their propagation using wide-field optical profiling technique with nanometer resolution. We reveal the existence of small and large membrane waves the amplitudes of which are in the range of ∼3–7 nm to ∼16–25 nm respectively, through the cell. For migrating single-cells, the amplitude of these waves is about 30 nm near the cell edge. Two or more different directions of propagation of the membrane nanowaves inside the same cell can be observed. After increasing the migration velocity by BMP-2 treatment, only one wave direction of propagation exists with an increase in the average amplitude (more than 80 nm near the cell edge). Furthermore for collective-cell migration, these membrane nanowaves are attenuated on the leader cells and poor transmission of these nanowaves to follower cells was observed. After BMP-2 treatment, the membrane nanowaves are transmitted from the leader cell to several rows of follower cells. Surprisingly, the vast majority of the observed membrane nanowaves is shared between the adjacent cells. These results give a new view on how single and collective-cells modulate their motility. This work has significant implications for the therapeutic use of BMPs for the regeneration of skin tissue.     

Annexins II and V Inhibit Cell Migration

Cell motility is a crucial component involved in wound healing, development, and tumor metastasis. This study investigated whether extracellular annexins, members of a calcium- and phospholipid-binding family of proteins, play a role in the migration of Lewis lung carcinoma cells. Using assays for wound closure and migration through 8-μm pores, it was found that annexins II and V significantly (>40%) inhibited migration of these highly metastatic cells. Additionally, anti-annexin II antibodies enhanced migration of these same cells in the wound closure assay, while an irrelevant antibody (anti-calmodulin) showed no effect. These effects may be due to annexin–membrane binding and inhibition of phospholipid movement that is necessary for the formation of membrane protrusions.     

Cyclin D1 Functions in Cell Migration

Cell migration is essential for developmental morphogenesis, tissue repair, and tumor metastasis. A recent study reveals that cyclin D1 acts to promote cell migration by inhibiting Rho/ROCK signaling and expression of thrombospondin-1 (TSP-1), an extracellular matrix protein that regulates cell migration in many settings including cancer. Given the frequent overexpression of cyclin D1 in cancer cells, due to its upregulation by Ras, Rho, Src, and other genes that drive malignant development, the new findings suggest that cyclin D1 may have a central role in mediating invasion and metastasis of cancer cells by controlling Rho/ROCK signaling and matrix deposition of TSP-1.     

In vitro Cell Migration and Invasion Assays

Migration is a key property of live cells and critical for normal development, immune response, and disease processes such as cancer metastasis and inflammation. Methods to examine cell migration are very useful and important for a wide range of biomedical research such as cancer biology, immunology, vascular biology, cell biology and developmental biology. Here we use tumor cell migration and invasion as an example and describe two related assays to illustrate the commonly used, easily accessible methods to measure these processes. The first method is the cell culture wound closure assay in which a scratch is generated on a confluent cell monolayer. The speed of wound closure and cell migration can be quantified by taking snapshot pictures with a regular inverted microscope at several time intervals. More detailed cell migratory behavior can be documented using the time-lapse microscopy system. The second method described in this paper is the transwell cell migration and invasion assay that measures the capacity of cell motility and invasiveness toward a chemo-attractant gradient. It is our goal to describe these methods in a highly accessible manner so that the procedures can be successfully performed in research laboratories even just with basic cell biology setup.     

Modelling Cell Migration and Adhesion During Development

Cell?Ccell adhesion is essential for biological development: cells migrate to their target sites, where cell?Ccell adhesion enables them to aggregate and form tissues. Here, we extend analysis of the model of cell migration proposed by Anguige and Schmeiser (J. Math. Biol. 58(3):395?C427, 2009) that incorporates both cell?Ccell adhesion and volume filling. The stochastic space-jump model is compared to two deterministic counterparts (a system of stochastic mean equations and a non-linear partial differential equation), and it is shown that the results of the deterministic systems are, in general, qualitatively similar to the mean behaviour of multiple stochastic simulations. However, individual stochastic simulations can give rise to behaviour that varies significantly from that of the mean. In particular, individual simulations might admit cell clustering when the mean behaviour does not. We also investigate the potential of this model to display behaviour predicted by the differential adhesion hypothesis by incorporating a second cell species, and present a novel approach for implementing models of cell migration on a growing domain.     

Good Time for Cell Adhesion and Migration

Our understanding of the molecular and cellular mechanisms controlling cell adhesion and migration has never been so high. The era of “molecular interactions” requires an appropriate tool for exchanging views, presenting outstanding results and discussing new concepts in the field. This is why we decided to launch Cell Adhesion and Migration (CAM), a multi-disciplinary journal publishing original research articles and reviews covering the latest aspects of cellular and molecular mechanisms and their regulation both during physiological and pathological processes.     

Contribution of Corneal Neovascularization to Dendritic Cell Migration into the Central Area during Human Corneal Infection

Compared with the peripheral corneal limbus, the human central cornea lacks blood vessels, which is responsible for its immunologically privileged status and high transparency. Dendritic cells (DCs) are present in the central avascular area of inflamed corneas, but the mechanisms of their migration to this location are poorly understood. Here, we investigated the contribution of vessel formation to DC migration into the central cornea, and analyzed the DC chemotactic factors produced by human corneal epithelial (HCE) cells. Using human eyes obtained from surgical procedures, we then assessed vessel formation, DC distribution, and activin A expression immunohistochemically. The results demonstrated increased numbers of vessels and DCs in the central area of inflamed corneas, and a positive correlation between the number of vessels and DCs. Activin A was expressed in the subepithelial space and the endothelium of newly formed blood vessels in the inflamed cornea. In infected corneas, DCs were present in the central area but no vascularization was observed, suggesting the presence of chemotactic factors that induced DC migration from the limbal vessels. To test this hypothesis, we assessed the migration of monocyte-derived DCs toward HCE cell supernatants with or without lipopolysaccharide (LPS) stimulation of HCE cells and inflammatory cytokines (released by HCE cells). DCs migrated toward tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, and activin A, as well as LPS-stimulated HCE cell supernatants. The supernatant contained elevated TNF-α, IL-6, and activin A levels, suggesting that they were produced by HCE cells after LPS stimulation. Therefore, vessels in the central cornea might constitute a DC migration route, and activin A expressed in the endothelium of newly formed vessels might contribute to corneal vascularization. Activin A also functions as a chemotactic factor, similar to HCE-produced TNF-α and IL-6. These findings enhance our understanding of the pathophysiology of corneal inflammation during infection.