title: Cells lying on a bed of microneedles: an approach to isolate mechanical force.
abstract: We describe an approach to manipulate and measure mechanical interactions between cells and their underlying substrates by using microfabricated arrays of elastomeric, microneedle-like posts. By controlling the geometry of the posts, we varied the compliance of the substrate while holding other surface properties constant. Cells attached to, spread across, and deflected multiple posts. The deflections of the posts occurred independently of neighboring posts and, therefore, directly reported the subcellular distribution of traction forces. We report two classes of force-supporting adhesions that exhibit distinct force-size relationships. Force increased with size of adhesions for adhesions larger than 1 microm(2), whereas no such correlation existed for smaller adhesions. By controlling cell adhesion on these micromechanical sensors, we showed that cell morphology regulates the magnitude of traction force generated by cells. Cells that were prevented from spreading and flattening against the substrate did not contract in response to stimulation by serum or lysophosphatidic acid, whereas spread cells did. Contractility in the unspread cells was rescued by expression of constitutively active RhoA. Together, these findings demonstrate a coordination of biochemical and mechanical signals to regulate cell adhesion and mechanics, and they introduce the use of arrays of mechanically isolated sensors to manipulate and measure the mechanical interactions of cells.
authors.affiliation: Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21205, USA.
authors.forename: John L
authors.initials: JL
authors.lastname: Tan
authors.forename: Joe
authors.initials: J
authors.lastname: Tien
authors.forename: Dana M
authors.initials: DM
authors.lastname: Pirone
authors.forename: Darren S
authors.initials: DS
authors.lastname: Gray
authors.forename: Kiran
authors.initials: K
authors.lastname: Bhadriraju
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Chen
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002138:Calibration; D002417:Cattle; D002478:Cells, Cultured; D051379:Mice; D008856:Microscopy, Fluorescence; D009339:Needles; D013314:Stress, Mechanical