title: Neutrophil adhesion and chemotaxis depend on substrate mechanics.
abstract: Neutrophil adhesion to the vasculature and chemotaxis within tissues play critical roles in the inflammatory response to injury and pathogens. Unregulated neutrophil activity has been implicated in the progression of numerous chronic and acute diseases such as rheumatoid arthritis, asthma, and sepsis. Cell migration of anchorage-dependent cells is known to depend on both chemical and mechanical interactions. Although neutrophil responses to chemical cues have been well characterized, little is known about the effect of underlying tissue mechanics on neutrophil adhesion and migration. To address this question, we quantified neutrophil migration and traction stresses on compliant hydrogel substrates with varying elasticity in a micro-machined gradient chamber in which we could apply either a uniform concentration or a precise gradient of the bacterial chemoattractant fMLP. Neutrophils spread more extensively on substrates of greater stiffness. In addition, increasing the stiffness of the substrate leads to a significant increase in the chemotactic index for each fMLP gradient tested. As the substrate becomes stiffer, neutrophils generate higher traction forces without significant changes in cell speed. These forces are often displayed in pairs and focused in the uropod. Increases in the mean fMLP concentration beyond the K(D) of the receptor lead to a decrease in chemotactic index on all surfaces. Blocking with an antibody against beta(2)-integrins leads to a significant reduction but not an elimination of directed motility on stiff materials, but no change in motility on soft materials, suggesting neutrophils can display both integrin-dependent and integrin-independent motility. These findings are critical for understanding how neutrophil migration may change in different mechanical environments in vivo and can be used to guide the design of migration inhibitors that more efficiently target inflammation.
authors.affiliation: Department of Bioengineering University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Risat A
authors.initials: RA
authors.lastname: Jannat
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Robbins
authors.forename: Brendon G
authors.initials: BG
authors.lastname: Ricart
authors.forename: Micah
authors.initials: M
authors.lastname: Dembo
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Hammer
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology*; D002478:Cells, Cultured; D002633:Chemotaxis / Q000502:physiology*; D003198:Computer Simulation; D022001:Focal Adhesions / Q000502:physiology*; D006801:Humans; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008954:Models, Biological; D009504:Neutrophils / Q000502:physiology*; D033081:Shear Strength / Q000502:physiology*; D013314:Stress, Mechanical
references.citation: J Biol Chem. 1983 Feb 25;258(4):2340-9
references.pmid: 6822565
references.citation: Nat Cell Biol. 2001 May;3(5):466-72
references.pmid: 11331874
references.citation: Nat Immunol. 2007 Oct;8(10):1076-85
references.pmid: 17721537
references.citation: Curr Biol. 2006 Sep 5;16(17):1685-93
references.pmid: 16950104
references.citation: Annu Rev Biomed Eng. 2005;7:151-85
references.pmid: 16004569
references.citation: Cell. 2006 Jun 30;125(7):1361-74
references.pmid: 16814721
references.citation: Biophys J. 2008 Dec 15;95(12):6044-51
references.pmid: 18775964
references.citation: Cancer Cell. 2005 Sep;8(3):241-54
references.pmid: 16169468
references.citation: Biophys J. 1999 Apr;76(4):2307-16
references.pmid: 10096925
references.citation: J Cell Biol. 2001 May 14;153(4):881-8
references.pmid: 11352946
references.citation: Nat Cell Biol. 2008 Sep;10(9):1062-8
references.pmid: 19160486
references.citation: Adv Immunol. 2006;91:111-57
references.pmid: 16938539
references.citation: Science. 2006 May 5;312(5774):738-41
references.pmid: 16675699
references.citation: Biophys J. 2005 Jul;89(1):676-89
references.pmid: 15849250
references.citation: Proc Natl Acad Sci U S A. 2007 Aug 14;104(33):13349-54
references.pmid: 17684096
references.citation: Nat Biotechnol. 2002 Aug;20(8):826-30
references.pmid: 12091913
references.citation: Biophys J. 2001 Apr;80(4):1744-57
references.pmid: 11259288
references.citation: Nature. 2008 May 1;453(7191):51-5
references.pmid: 18451854
references.citation: J Cell Biol. 1988 Feb;106(2):303-9
references.pmid: 3339093
references.citation: Biophys J. 2007 Apr 1;92(7):L58-60
references.pmid: 17218464
references.citation: Trends Cell Biol. 2006 Apr;16(4):213-23
references.pmid: 16529933
references.citation: Biophys J. 2000 Jul;79(1):144-52
references.pmid: 10866943
references.citation: J Cell Physiol. 2005 Jul;204(1):198-209
references.pmid: 15669099
references.citation: J Cell Biol. 1977 Nov;75(2 Pt 1):606-16
references.pmid: 264125
references.citation: Curr Opin Cell Biol. 2008 Oct;20(5):525-32
references.pmid: 18499427
references.citation: Blood. 2009 Aug 13;114(7):1387-95
references.pmid: 19491394
references.citation: Cell. 1997 Jan 10;88(1):39-48
references.pmid: 9019403
references.citation: J Cell Biol. 2006 Oct 23;175(2):349-60
references.pmid: 17060501
references.citation: Cell. 2006 Aug 25;126(4):677-89
references.pmid: 16923388
references.citation: J Leukoc Biol. 2005 Feb;77(2):129-40
references.pmid: 15548573
references.citation: PLoS Comput Biol. 2009 Dec;5(12):e1000604
references.pmid: 20011123
references.citation: Cell. 2008 May 16;133(4):666-80
references.pmid: 18485874
references.citation: Immunity. 2006 Dec;25(6):867-9
references.pmid: 17174930
references.citation: Annu Rev Cell Biol. 1988;4:649-86
references.pmid: 2848555
references.citation: Nature. 1997 Feb 6;385(6616):537-40
references.pmid: 9020360
references.citation: Mol Biol Cell. 2001 Dec;12(12):3947-54
references.pmid: 11739792
references.citation: Anal Chem. 2001 Jul 1;73(13):3193-7
references.pmid: 11467573
references.citation: Proc Natl Acad Sci U S A. 1997 Dec 9;94(25):13661-5
references.pmid: 9391082
references.citation: Proc Natl Acad Sci U S A. 2006 Jul 18;103(29):10889-94
references.pmid: 16832052
references.citation: Science. 2008 Dec 12;322(5908):1687-91
references.pmid: 19074349