Active Response Of Adherent Cells To Geometrical Signals

The microenvironment of cells plays a vital role in regulating cell morphological and physiological functions,and is composed of extracellular matrix and biochemical molecules that can promote and regulate cell functions.In the past several years,more and more experiments have shown that the mechanical and geometric signals of the cell microenvironment are as important as traditional biochemical factors in regulating cell behavior and fate.Many experiments have shown cell migration is guided by various micro / nano topologies in vivo and the invasion / metastasis of tumor cells.The process of embryonic development,tissue morphology,and even tumor cell invasion of living organisms,the curvature environment has played a very important role.In recent years,there have been many studies on the micro-surfaces such as micro-grooves,micro-pillars,etc.,to explore the influence of cell-scale topography on cell behavior preliminarily.Cells respond positively to biochemical,mechanical,and topological signals to affect cell morphology and activity.The changes in cell morphology are caused by internal forces related to the adhesion of actin fibers.The adhesion of actin fibers occurs according to the stimulation of the extracellular matrix(ECM)or adjacent cells.The physical mechanism of the transmission of cellular mechanical signals in the extracellular matrix and the activity / feedback of adherent cells under the stimulation of the geometric signals of the extracellular matrix is very useful for understanding many biological processes such as wound healing,tissue growth / regeneration and development.Cells have evolved multiple mechanisms to adapt well to their environment.Although there have been many studies that have explained the mechanism of cell migration on a two-dimensional topology,most of the real environment in vivo is not a two-dimensional plane,so studying the behavior of cells with different curvature signals under three-dimensional conditions and explaining the specific physical mechanism of cell migration under this topology becomes particularly important.Because the mechanical and geometric signals of the extracellular matrix are usually easier to be controlled,and the resulting efficacy to cells may be more permanent than biochemical factors or genetic materialmanipulation.Here we choose to study the migration response of adherent cells to different curvature signals.To study the influence of three-dimensional geometric structure on cell movement,the construction of topological substrate becomes particularly important.Due to the wide application of micro-fabrication technology in biological microfluidics,it provides the possibility of constructing different extracellular matrix structures.Here,we choose polydimethylsiloxane(PDMS)with good biocompatibility and great light transmittance to prepare substrates with different geometric signals.By designing a cylinder with a high length to provide sufficient space for cell migration,and with different radii of curvature.In the production of the silicon mold,we compared the two fabrication methods.According to the needs of the experiment,we chose a mold fabrication method that can prepare a flat and smooth surface,and hope to provide wide application in similar experiments in the future.In terms of cell selection,we first selected human breast tumor cells(epithelial cells,MCF-10A)with faster migration speed and human breast tumor cells with green fluorescent protein for better locating the cell.With the research processing and to prove the universality law of the cell migration,we also selected mouse embryonic fibroblasts(fibroblasts,NIH-3T3)with strong stress fibers to perform the same cell experiment.Through long-term cell trajectory tracking,we conducted a lot of data analysis.On this basis,calibration imaging of the intracellular cytoskeletal microstructure was also carried out to better explain the changes in cell movement under the curvature.Our results show that the cell migration behavior on curved surface is significantly different from it on a plane.Cells usually move randomly on a flat surface,but they show an obvious preferred direction on cylindrical surface.On cylinders with different curvatures,the cells will obviously show a bias in the direction of movement,which is called the "curvotaxis",which enables the cell to respond to curvature signals.In this project,we found that the curvature signal can not only accelerate cell movement and affect the choice of cell movement direction,but also reduce the correlation of cell movement direction.In summary,this study developed a method about three-dimensional curvature model for cell movement,summarized the laws of different cell movements on different curvature substrates,and tried to explain the internal mechanism withphysical models and the microstructure of the cell itself.This will also provide new applied theories in areas including biological science and medical research,especially regenerative medicine and tissue engineering field.