Mechanism Of Substrate Mechanical Properties On Cell Volume Regulation And Directional Migration

The extracellular microenvironment contains various parameters,such as topogra-phy,surface chemical functional groups,matrix elastic modulus,and surface adhesion energy.Those parameters play an important role in cell physiological activities and functions.In the research of biophysics,researchers have developed artificial extracel-lular matrix to simulate the environment in vivo.In this way,they can explore the effects of single parameter,such as regulating matrix stiffness or the density of matrix network anchoring points,in the extracellular microenvironment on cell function and behavior with low-cost and simple method.In recent years,cellular volume became a very im-portant parameter.A large number of studies have found that cellular volume regulation plays an important role in physiological processes,such as cell mitosis,tissue develop-ment,and gene expression.In this paper,experiments and numerical simulations were used to study the mechanism of various mechanical parameters of cell substrate on cell behaviors,such as volume regulation,and directional migration.This study provides theoretical support and experiment basis for bioengineering and biophysics research.The main research contents of this paper are as follows:1.Study cellular volume regulation mechanism by substrate elastic modulus,avail-able spread area,and effective adhesion energy.Here it shows that increasing substrate elastic modulus,available spread area,and effective adhesion energy decrease cellular volume significantly(up to 50%).In the dynamic cell spreading process,cellular vol-ume also decreases dramatically with increasing spread area.Studies of ion transport inhibition and osmotic shock experiments show that the decrease in cellular volume is due to the efflux of water and ions.When disrupting cortex contractility with cytoskele-ton inhibitor,cellular volume increases.Therefore,these results reveal the'“mechanism of adhesion-induced compression of cells".In particular,stronger interaction between cell and substrate leads to higher cortex contractility,which expels water and ions,and thus decrease cellular volume.2.Study mechanism of cell durotaxis on stiffness gradient gels.3T3 cells exhib-ite a typical durotaxis on PAAm gels with stiffness gradient of 40 kPa/mm.Compare with cells cultured on 40 kPa uniform PAAm gels,3T3 cells show faster migration speed.Ion pumps and cytoskeleton inhibition experiments showed that disruption of Na+,K+,Ca2+ transportation and cortex contractility result in the decrease of migra-tion speed and the lost of durotaxis.The measurement of the cortex tension on the pseudopods at both ends of the cells using AFM reveals that cells migrated to the higher cortex tension side,and when the ratio of cellular front side of cortex tension to cellu-lar rear side of cortex tension increase,the cell migrates faster.It also shows that the harder substrate is,the higher cortex tension in pseudopod.Combine with other re-searches,this work proposes that cell durotaxis is caused by the polar distribution of traction from substrate and the difference of local cortex tension between two sides of cells.