A time-lapse and quantitative modelling analysis of neural stem cell motion in the absence of directional cues and in electric fields

School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, United Kingdom.
Journal of Neuroscience Research (Impact Factor: 2.73). 11/2010; 88(15):3267-74. DOI: 10.1002/jnr.22502
Source: PubMed

ABSTRACT Neural stem cell (NSC) migration is an important component of their developmental function and therapeutic potential. Understanding their mode of migration and their response to guidance cues can contribute to improved therapies for CNS repair, in which appropriate homing to sites of injury is essential. Using time-lapse imaging, we have analyzed the NSC mode of migration in vitro, both in the absence of directional cues and in the presence of applied electric fields (EFs), previously shown to constitute a strong directional signal for these cells. Without EFs, NSCs displayed an amoeboid motion, characterized by small lamellipodial-like protrusions with changing orientations, leading to highly tortuous migration. In EFs, tortuosity diminished as electrotaxis toward the cathode occurred. EFs suppressed the formation of protrusions oriented toward the anode, suggesting that restriction of protrusions with opposing orientation could underlie the change from tortuous motion to directed migration. Treatment with LY294002, a phosphatidylinositol-3-OH kinase (Pi3K) inhibitor, reduced the cathodal bias of protrusions in EFs and the frequency of changes in direction. We generated a model of NSC migration with only two key parameters, which could accurately reproduce experimental migration patterns, and we used it to show that both effects of LY294002 contribute to impair electrotaxis, although decreased protrusion bias is the most important. Our results show that control of protrusion orientation by EFs is an important component of the electrotactic response. A simple modelling approach might be useful in understanding how diverse pharmacological treatments or genetic deletions affect different kinds of directional cell migration.

Download full-text


Available from: Bing Song, Mar 22, 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we present a novel framework for the modeling of cell-migration, and more specifically the migration of human keratinocytes. The model decouples the embodiment of an artificial cell into two elements. A cell-body is implemented by two sets of springs forming a membrane and a supporting cortical-cytoskeleton, which allows for cell-body rigidity and flexibility. The leading-edge, a structure spreading around the cell-body, is simulated with a stochastic cellular-automata. It defines the migratory forces that pull the cell-body according to its local spread around the cell. The overall movement of the leading-edge depends on stochastic interaction with the environment and guides the whole cell movement through spatiotemporal integration of local forces. We demonstrate that our cell migration model allows for spontaneous symmetry-breaking and directed cell movement and has in-built obstacle-avoidance, closely mimicking the migration of living cells. The model is extended to simulate chemotactic behavior, the artificial cell can sense and move along a gradient with its trajectory depending on the cell shape, stiffness and leading-edge dynamics. In summary, we have developed a novel cell migration model with emergent properties, wherein local forces create an integrated cell movement. The presented interplay of the distributed physical and an informational embodiment is not limited in reach to the example of cell migration, but can of interest for design of perception-action loops and sensor evolution in general.
    Artificial Life (ALIFE), 2013 IEEE Symposium on; 01/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Following injury such as stroke, adult mammalian subependymal neural precursor cells (NPCs) are induced to proliferate and migrate toward the lesion site where they differentiate into neural cells, albeit with limited efficacy. We are interested in enhancing this migratory ability of NPCs with the long-term goal of promoting neural repair. Herein we build on our previous studies demonstrating that direct current electric fields (DCEFs) promote rapid and cathode-directed migration of undifferentiated adult NPCs (but not differentiated phenotypes) - a phenomenon known as galvanotaxis. While galvanotaxis represents a promising strategy to promote NPC recruitment to lesion sites, stimulation of neural tissue with DCEFs is not a clinically-viable strategy due to the associated accumulation of charge and toxic byproducts. Balanced biphasic waveforms prevent the accumulation of charge and thus are outside of the limitations of DCEFs. In this study, we investigated the effects of balanced biphasic electrical stimulation on the migratory behaviour of undifferentiated subependymal NPCs and their differentiated progeny. NPCs were isolated from the subependymal zone of adult mouse brains and cultured in a NPC colony-forming assay to form neurospheres. Neurospheres were plated onto galvanotaxis chambers in conditions that either promoted maintenance in an undifferentiated state or promoted differentiation into mature phenotypes. Chambers containing cells were then time-lapse imaged in the presence of either biphasic monopolar, or biphasic bipolar electrical stimulation, or in the complete absence of electrical stimulation. Single cell migration was subsequently tracked and the cells' magnitude of velocity, directedness and tortuosity were quantified. We demonstrate, for the first time, the use of balanced biphasic electric fields to induce galvanotaxis of NPCs. Undifferentiated adult mouse subependymal NPCs exposed to biphasic monopolar stimulation undergo rapid and directed migration toward the cathode. In contrast, both biphasic bipolar stimulation and the lack of electrical stimulation produced non-directed migration of NPCs. Notably, NPCs induced to differentiate into mature phenotypes prior to exposure to electrical stimulation do not migrate in the presence or absence of biphasic stimulation. We purport that balanced biphasic stimulation represents a clinically-viable technique for mobilizing NPCs that may be integrated into strategies for promoting endogenous neurorepair.
    Stem Cell Research & Therapy 04/2015; 6(1):67. DOI:10.1186/s13287-015-0049-6 · 4.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pathotropic neural stem and/or progenitor cells (NSCs) can potentially deliver therapeutic agents to otherwise inaccessible cancers. In glioma, NSCs are found in close contact with tumor cells, raising the possibility that specificity of NSC contact with glioma targets originates in the tumor cells themselves. Alternatively, target preferences may originate, at least in part, in the tumor microenvironment. To better understand mechanisms underlying NSC interactions with glioma cells, we examined NSC-target cell contacts in a highly simplified 3-dimensional peptide hydrogel (Puramatrix) in which cell behaviors can be studied in the relative absence of external cues. HB1.F3 is an immortalized clonal human NSC line extensively characterized in preclinical investigations. To study contact formation between HB1.F3 NSCs and glioma cells, we first examined co-cultures of eGFP-expressing HB1.F3 (HB1.F3.eGFP) NSCs and dsRed-expressing U251 glioma (U251.dsRed) cells. Using confocal microscopy, HB1.F3.eGFP cells were observed contacting or encircling U251.dsRed glioma cells, but never the reverse. Next, examining specificity of these contacts, no significant quantitative differences in either percentages of HB1.F3 NSCs contacting targets, or in the extent of target cell encirclement, were observed when HB1.F3.eGFP cells were presented with various potential target cells (human glioma and breast cancer cell lines, patient-derived brain tumor lines, non-tumor fibroblasts, primary mouse and human astroglial cells, and primary adult and newborn human dermal fibroblasts) except that interactions between HB1.F3 cells did not progress beyond establishing contacts. Finally cytoskeletal mechanisms employed by HB1.F3.eGFP cells varied with the substrate. When migrating in Puramatrix, HB1.F3 NSCs exhibited intermittent process extension followed by soma translocation, while during encirclement their movements were more amoeboid. We conclude that formation of contacts and subsequent encirclement of target cells by HB1.F3 NSCs is an intrinsic property of these NSCs, and that preferential contact formation with tumor cells in vivo must therefore be highly dependent on microenvironmental cues.
    PLoS ONE 12/2012; 7(12):e51859. DOI:10.1371/journal.pone.0051859 · 3.53 Impact Factor