Integration of extracellular and intracellular forces in cell migration
Zusammenfassung der Projektergebnisse
This research project focused on the development and application of novel computational methods for reconstructing forces exerted by biological cells. Furthermore, imageprocessing tools have been developed for resolving the cell velocity field of collectively migrating cells. The research was performed in the group of Prof. Gaudenz Danuser (Harvard Medical School, Boston MA, USA) and relied on collaborations with experimental labs. In collaboration with the lab of Joan Brugge (Harvard Medical School, Boston MA, USA), we developed an assay for measuring the forces that MCF10A (normal mammary epithelial) cells exert on each other. The method is based on the measurement of forces that the cells exert on the underlying substrate (Traction Force Microscopy, TFM). The forces exerted between the cells are calculated from the measured traction forces using a computational model. With our approach we showed that cell-cell forces are significantly correlated with the intensity signals of fluorescently labeled E-cadherin, a transmembrane receptor that mediates cell-cell adhesion. We also showed that the cell-cell forces exerted by the cells depend on the number of their neighbors and that the cell-cell forces are modulated by the stiffness of the underlying substrate. During cell division we resolved the redistribution of cell-cell forces within a cluster. Similar processes may play a role in maintaining the mechanical integrity of proliferating cell collectives. By correlating cellcell and cell-matrix forces that are exerted by a cell, we answered the question of whether cell-cell forces are transmitted through a cell from one neighboring cell to another or if they are rather balanced locally by traction forces. We found that forces are transmitted through cells with downregulated cell-matrix adhesion or myosin contractility, but only weakly transmitted through control cells. Also in collaboration with the Brugge lab we studied the influence of substrate stiffness on collective cell migration using a wound healing assay. By tracking all MCF10A cells in the sheet individually, we resolved the cell velocity field in space and time. We showed that the cell speed and coordination of the collective movement depend on the stiffness of the underlying substrate. Perturbation of cell-cell adhesion strength and/or cell contractility showed that a subtle interplay between the two determines to which extent substrate stiffness influences collective migration. In the last two collaborative studies, we performed traction force measurements on single cells. Our collaborative study with the Brugge lab suggests that ovarian cancer spheroids apply forces through α5 β1 integrins on mesothelial cells in an in vitro model of cancer metastasis. In collaboration with the Groisman and Ginsberg labs (University of California San Diego, La Jolla, CA, USA), we demonstrated the feasibility of TFM in combination with Total Internal Reflection Microscopy (TIRF). The study was performed on human umbilical venous endothelial cells (HUVECs) on high refractive index polydimethylsyloxane (PDMS) substrates.
Projektbezogene Publikationen (Auswahl)
- High refractive index silicone gels for simultaneous total internal reflection fluorescence and traction force microscopy of adherent cells. PloS One 6(9):e23807, 2011
Gutierrez E., Tkachenko E., Besser A., Sundd P., Ley K., Danuser G., Ginsberg M.H., Groisman A.
- Ovarian cancer spheroids use myosin-generated force to clear the mesothelium. Cancer Discovery, 1(2):144–157, 2011
Iwanicki M.P., Davidowitz R.A., Ng M.R., Besser A., Muranen T., Merritt M., Danuser G., Ince T., Brugge J.S.
- Substrate stiffness regulates cadherin-dependent collective migration through myosin-II contractility. The Journal of Cell Biology 199(3):545–563, 2012
Ng M.R., Besser A., Danuser G., Brugge J.S.
