Cell-matrix traction

F. Chowdhury, Y. Li, Y.C. Poh, T. Yokohama-Tamaki, N. Wang, and T.S. Tanaka, Soft substrates promote homogeneous self-renewal of embryonic stem cells via downregulating cell-matrix tractions, PLoS One, 5 (12) el5655, Dec. 2010. 

Huebsch, N., Arany, P.R., Mao, A.S., Shvartsman, D., Ah, O.A., Bencherif, S.A., Rivera-Feliciano, J., Mooney, D.J. Harnessing traction-mediated manipulation of the cell/matrix interface to control stem-cell fate. Nature Materials 9, 518-526 (2010)... 

The concentration of the bound receptors was determined using standard reaction kinetic equations where the forward rate constant was lO pm /s [14] and the reverse rate constant was 1 s [8]. It has been shown that cells have polarity in which the anterior is more strongly attached to the matrix than the posterior. To model this, the reverse rate coefficient was increased hnearly from the anterior to the posterior of the cell, where it was 100 times as large [16], This caused the concentration of bound receptors to decrease towards the rear of the cell, which led to less cell-ECM traction at that location as well. Furthermore, it was assumed that diffusion of the cell receptors and ECM proteins were negligible. Both the initial concentrations of the receptors and ECM proteins werel0,000 molecules/pm in the simulations [14]. 

Where a melt-crystallized polymer has been processed by drawing, rolling or other means to produce an aligned structure in which lamellae as well as polymer chains have discernible order, a pseudocrystalline unit cell is present. Provided that this unit cell contains elements of the crystals as well as the boundaries between crystals and that it is entirely typical of the material as a whole then it could be considered as a RVE within the meaning defined above. The lamella crystal itself sometimes considered as embedded in an amorphous matrix would not seem to be an acceptable RVE for reasons similar to those advanced against the Takayanagi model, namely that its modulus is dependent upon the surface tractions. The boundaries between lamella crystals in the matrix must be included in an acceptable RVE. 

How are the mechanical properties of the ECM probed by cells In other words, what cellular machinery is used to sense and respond to the local substrate rigidity This active molecular rheometer is essentially composed of two modules a probe and a transducer The probe is required to generate traction forces and convey them to the substrate. The second module generates intracellular signals based on the mechanical response of the matrix. 

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