Developing force measurement techniques for cell mechanics and adhesion

• Main Author: Jin, Tianrong
• Published: University of Warwick 2016
• Subjects: 571.6; QP Physiology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.714880

Cellular force is essential in maintaining the normal function of a biological cell. The primary goal of this study is to develop experimental methods to quantitatively determine forces generated from cell contraction and cell-to-cell adhesion. A novel method has been developed to measure the cell contraction forces exerted within a cell-embedded collagen matrix. The technique provides a 3D cell-matrix model which allows estimation of the cell contraction forces over a certain period of time. It was found that embedded fibroblast cells are able to cause a shrinkage of their surrounding matrix due to cell contractility. Tailored equipment which has ultimate force and displacement resolutions of 10 nN and 100 nm respectively has been constructed to accurately determinate the elasticity of cell-embedded collagen matrix. In combination with a mathematical model, the cell contraction force can be calculated based on the geometric parameters of the collagen matrix before and after the shrinkage. Reagents of agonist (histamine) or antagonist (ML-7) have been used to stimulate or block the fibroblast contraction force. They both show the effect of altering the stiffness of an extracellular matrix which is critical in the determination of cell contraction forces. More importantly, the analysis of the measured data based on a non-linear mechanical model have also confirmed that the elasticity of the extracellular matrix will influence the fibroblast contraction force. Cell-to-cell adhesion is an intricate interplay of mechanical, chemical and electrical signals between cells. A novel method based on Atomic Force Microscopy Single Cell Force Spectroscopy (AFM-SCFS) has been applied to examine cell-to-cell adhesion of human kidney proximal tubule HK2 cells. Ketamine was used to evoke early changes in expression of proteins (E-cadherin, N-cadherin and β-catenin) central to adherens junctions that lead to the loss of cell-to-cell adhesion force. The results provide strong evidence that the illicit substance Ketamine has major impacts on renal function and the loss of intracellular adherent energy. Overall, both cell contraction and cell-to-cell adhesion experiments demonstrated that the changes of biological states evoke protein interactions which would ultimately lead to the biomechanical alterations. Therefore, characterising the changes of mechanobiological properties can provide new insight into the investigation of physiological and pathological issues.