The rolling of human neutrophils on the endothelium is only an initial step of their extravasation, but it is a complicated dynamic process mediated cooperatively by the adhesion molecules expressed on the surfaces of endothelial cells and neutrophils, the shear stresses due to the blood flow, and the mechanical properties of the neutrophil/endothelial cell membranes and neutrophil microvilli. Therefore, the overall goal of this proposal is to investigate the details of these mechanical properties and how they will impact on the rolling process.
The specific aims are to: 1) extract """"""""single tethers to test the hypotheses that single tether formation from endothelial cells is a local phenomenon (i.e., it does not depend upon whether the cell is suspended or attached to a substrate, nor the surface receptor type used to form the tether), single tether formation from endothelial cells is modulated by stimulation, and single tethers can be extracted simultaneously from passive neutrophils and stimulated endothelial cells, 2) extract double tethers to test the hypotheses that double tether formation from human neutrophils or endothelial cells is modulated by stimulation, and double tethers can be extracted simultaneously from passive neutrophils and stimulated endothelial cells, 3) quantify the mechanical properties of a single neutrophil microvillus to test the hypotheses that the microvillus has different static properties in bending and compression compared with extension, and its viscoelastic properties are not significant during extension or compression, and 4) develop a biomechanical model to test the hypotheses that simultaneous tether formation from neutrophils and endothelial cells, compared with tether formation from neutrophils alone, further facilitates the rolling of neutrophils on the endothelium, and stimulating both neutrophils and endothelial cells, compared with stimulating neutrophils alone, also further facilitates the rolling of neutrophils on the endothelium. Tether formation from neutrophils and suspended endothelial cells will be performed with the micropipette aspiration technique, while tether formation from attached endothelial cells will be performed with the atomic force microscope. The microvillus mechanics will be studied with the optical tweezers, combined with the micropipette manipulation system.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL069947-03
Application #
6622966
Study Section
Surgery and Bioengineering Study Section (SB)
Program Officer
Harvath, Liana
Project Start
2002-04-01
Project End
2007-03-31
Budget Start
2003-04-01
Budget End
2004-03-31
Support Year
3
Fiscal Year
2003
Total Cost
$350,700
Indirect Cost
Name
Washington University
Department
Biomedical Engineering
Type
Schools of Engineering
DUNS #
068552207
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Chen, Yong; Lu, Lan; Shao, Jin-Yu (2016) Endothelial Surface Protrusion by a Point Force. Biophys J 110:1150-7
Liu, Baoyu; Shao, Jin-Yu (2012) Tangential tether extraction and spontaneous tether retraction of human neutrophils. Biophys J 103:2257-64
Chen, Yong; Yao, Da-Kang; Shao, Jin-Yu (2010) The constitutive equation for membrane tether extraction. Ann Biomed Eng 38:3756-65
Chen, Yong; Liu, Baoyu; Xu, Gang et al. (2009) Validation, In-Depth Analysis, and Modification of the Micropipette Aspiration Technique. Cell Mol Bioeng 2:351-365
Liu, Baoyu; Yu, Yan; Yao, Da-Kang et al. (2009) A direct micropipette-based calibration method for atomic force microscope cantilevers. Rev Sci Instrum 80:065109
Xu, Gang; Shao, Jin-Yu (2008) Human neutrophil surface protrusion under a point load: location independence and viscoelasticity. Am J Physiol Cell Physiol 295:C1434-44
Yao, Da-Kang; Shao, Jin-Yu (2008) A Novel Technique of Quantifying Flexural Stiffness of Rod-Like Structures. Cell Mol Bioeng 1:75-83
Girdhar, Gaurav; Shao, Jin-Yu (2007) Simultaneous tether extraction from endothelial cells and leukocytes: observation, mechanics, and significance. Biophys J 93:4041-52
Liu, Baoyu; Goergen, Craig J; Shao, Jin-Yu (2007) Effect of temperature on tether extraction, surface protrusion, and cortical tension of human neutrophils. Biophys J 93:2923-33
Yao, Da-Kang; Shao, Jin-Yu (2007) Flexibility of single microvilli on live neutrophils and lymphocytes. Phys Rev E Stat Nonlin Soft Matter Phys 76:021907

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