Dynamic Force Generation by Neural Stem Cells

Article

Abstract

Mechanical cues may have important roles in tissue morphogenesis; progression through complex functions like differentiation may be associated with changes in cellular force generation and mechanosensing. To explore this concept, we use elastomer pillar arrays to map forces generated by neural stem cells in vitro, and identify two distinct dynamics of force generation. First, cell generated forces decrease as cells transition from a proliferative mode to differentiation, a process covering several days. This change in force generation correlates with a loss of sensitivity to substrate rigidity over a series of polydimethylsiloxane substrates. Second, neural stem cells exhibit a faster pattern of localized contractions at the cell body and outlying processes; each lasts on the order of minutes, and is not synchronized across the cell. This faster process is reminiscent of migratory behavior observed in vivo, and may be involved in controlling the motion of internal structures such as the cell nucleus. These results together provide new clues into the role of forces during development, and may lead to design principles for materials targeted for use in the central nervous system.

Keywords

Cellular traction force Stem cell Microenvironment Differentiation Proliferation 

Supplementary material

12195_2009_97_MOESM1_ESM.avi (4.8 mb)
Supplementary Figure 1Pulsatile nuclear migration by radial-glia-like NSCs in vitro. The position of the nucleus in each frame was determined by fitting a oval to the cell body; the centroid of this structure is indicated by the green dot in each frame. The bottom frame compares average force generation under the nucleus and nucleus position as a function of time (AVI 4905 kb)
Supplementary Figure 2

Application of blebbstatin to cells in expansion media induces rapid changes in morphology. Corresponding effects on nuclear migration are quantified in Fig. 5D, E (AVI 3787 kb)

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Supplementary Figure 3Cells differentiated from SVZ-NSCs were present as clusters migrating over each other in a pulsate mode, resembling “chain migration” of neuroblasts in the SVZ stem cell niche (AVI 8701 kb)
12195_2009_97_MOESM4_ESM.pdf (106 kb)
Supplementary Figure 4Detail of molecular architecture shown in Fig. 4a, 1 DIV. µPAs were coated with fluorescently-labeled laminin (blue). The µPA array is the standard dimensions of 1 µm diameter, 2 µm center-to-center spacing, 7 µm height; the field of view of this image measures 133 µm across. Actin cytoskeleton and cell nuclei were stained with phalloidin (green) and DAPI (red), respectively. Image stacks were collected in standard epifluorescence mode then deconvoluted and projected onto the indicated visualization planes using standard image processing software (PDF 106 kb)
12195_2009_97_MOESM5_ESM.avi (4.8 mb)
Supplementary Figure 5Transient, multisite force generation by NSCs in culture. Each time series was collected at 30 s intervals (showed at 1-min interval), covering a 10-min observation period (AVI 4935 kb)

Copyright information

© Biomedical Engineering Society 2009

Authors and Affiliations

  • P. Shi
    • 1
  • K. Shen
    • 1
  • S. Ghassemi
    • 2
  • J. Hone
    • 2
  • L. C. Kam
    • 1
  1. 1.Department of Biomedical EngineeringColumbia UniversityNew YorkUSA
  2. 2.Department of Mechanical EngineeringColumbia UniversityNew YorkUSA

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