Document Detail

Viscoelastic cell mechanics and actin remodelling are dependent on the rate of applied pressure.
MedLine Citation:
PMID:  22984454     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Living cells are subjected to external and internal mechanical stresses. The effects of these stresses on the deformation and subsequent biological response of the cells remains unclear. This study tested the hypothesis that the rate at which pressure (or stress) is applied influence the viscoelastic properties of the cell associated with differences in the dynamics of the actin cytoskeleton.
PRINCIPAL FINDING: Micropipette aspiration was used to determine the instantaneous and equilibrium moduli and the viscosity of isolated chondrocytes based on the standard linear solid (SLS) model and a variation of this incorporating Boltzmann superposition. Cells were visualised for 180 seconds following aspiration to 7 cmH(2)O at 0.35, 0.70 and 5.48 cmH(2)O/sec. Cell recovery was then examined for a further 180 seconds once the pressure had been removed. Reducing the rate of application of pressure reduced the levels of cell deformation and recovery associated with a significant increase in modulus and viscosity. Using GFP transfection and confocal microscopy, we show that chondrocyte deformation involves distortion, disassembly and subsequent reassembly of the cortical actin cytoskeleton. At faster pressure rates, cell deformation produced an increase in cell volume associated with membrane bleb formation. GFP-actin transfection inhibited the pressure rate dependent variation in cell mechanics indicating that this behaviour is regulated by GFP-sensitive actin dynamics.
CONCLUSION: We suggest that slower rates of aspiration pressure enable greater levels of cortical actin distortion. This is partially inhibited by GFP or faster aspiration rates leading to membrane bleb formation and an increase in cell volume. Thus the rate of application of pressure regulates the viscoelastic mechanical properties of living cells through pressure rate sensitive differences in actin dynamics. Therefore cells appear softer when aspirated at a faster rate in contrast to what is expected of a normal viscoelastic material.
Priyanka Pravincumar; Dan L Bader; Martin M Knight
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-09-11
Journal Detail:
Title:  PloS one     Volume:  7     ISSN:  1932-6203     ISO Abbreviation:  PLoS ONE     Publication Date:  2012  
Date Detail:
Created Date:  2012-09-17     Completed Date:  2013-03-12     Revised Date:  2013-07-11    
Medline Journal Info:
Nlm Unique ID:  101285081     Medline TA:  PLoS One     Country:  United States    
Other Details:
Languages:  eng     Pagination:  e43938     Citation Subset:  IM    
Institute of Bioengineering, School of Engineering and Material Science, Queen Mary University of London, London, United Kingdom.
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MeSH Terms
Actins / metabolism*
Cell Count
Cell Separation
Chondrocytes / cytology*,  physiology*
Green Fluorescent Proteins / metabolism
Models, Biological
Stress, Mechanical*
Reg. No./Substance:
0/Actins; 147336-22-9/Green Fluorescent Proteins

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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