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 m 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.

A thermodynamically motivated model for stress-fiber reorganization

“…For example, on stiff continuous substrates (Discher et al 2005) or on substrates comprising an array for stiff micro-posts (Tan et al 2003) cells form a strong network of actin/myosin stress-fibers while the same cells when placed on more compliant continuous or micro-post substrates form weak cytoskeletal networks. Similarly, cells seeded on substrates with ligand patterns develop specific actin and focal adhesion distributions that are a function of the ligand patterns shape and size (Parker et al 2002;Chen et al 2003).…”

Mechanotransduction and Growth Factor Signalling to Engineer Cellular Microenvironments

“…[67] In a following study, they developed a bed of microneedles to manipulate and measure cell traction forces as a function of the size of adhesion sites and cell spreading (Figure 5b). [68] It was shown that geometry-induced cytoskeletal tension and RhoA signalling could direct MSC fate, with osteogenic (adipogenic) differentiation associated [67] Copyright 1997, American Association for the Advancement of Science. b) Reproduced with permission.…”

Vers une cartographie des tensions mécaniques intracellulaires ?

“…Les cellules souches mésenchymateuses (MSC) peuvent par exemple se différencier en neurones, myoblastes ou ostéoblastes selon la rigidité de leur substrat de culture [4]. La mesure des déformations locales de substrats élastiques a permis d'évaluer à plusieurs dizaines de nN (nanonewtons) les forces exercées sur la matrice extracellulaire par des cellules lors de leur migration [5]. L'existence de points de signal en se déplaçant plus ou moins, sans direction.…”