@article {281, title = {Exploring the link between human embryonic stem cell organization and fate using tension-calibrated extracellular matrix functionalized polyacrylamide gels.}, journal = {Methods Mol Biol}, volume = {916}, year = {2012}, month = {2012}, pages = {317-50}, abstract = {

Human embryonic stem cell (hESc) lines are likely the in vitro equivalent of the pluripotent epiblast. hESc express high levels of the extracellular matrix (ECM) laminin integrin receptor α6β1 and consequently can adhere robustly and be propagated in an undifferentiated state on tissue culture plastic coated with the laminin rich basement membrane preparation, Matrigel, even in the absence of supporting fibroblasts. Such cultures represent a critical step in the development of more defined feeder free cultures of hESc; a goal deemed necessary for regenerative medical applications and have been used as the starting point in some differentiation protocols. However, on standard non-deformable tissue culture plastic hESc either fail or inadequately develop the structural/morphological organization of the epiblast in vivo. By contrast, growth of hESc on appropriately defined mechanically deformable polyacrylamide substrates permits recapitulation of many of these in vivo features. These likely herald differences in the precise nature of the integration of signal transduction pathways from soluble morphogens and represent an unexplored variable in hESc (fate) state space. In this chapter we describe how to establish viable hESc colonies on these functionalized polyacrylamide gels. We suggest this strategy as a prospective in vitro model of the genetics, biochemistry, and cell biology of pre- and early-gastrulation stage human embryos and the permissive and instructive roles that cellular and substrate mechanics might play in early embryonic cell fate decisions. Such knowledge should inform regenerative medical applications aimed at enabling or improving the differentiation of specific cell types from embryonic or induced embryonic stem cells.

}, keywords = {Acrylamides, Acrylic Resins, Calibration, Cell Culture Techniques, Cell Differentiation, Cell Polarity, Collagen, Crystallization, Drug Combinations, Elastic Modulus, Embryonic Stem Cells, Extracellular Matrix, Glutaral, Humans, Laminin, Ligands, Proteoglycans, Stress, Mechanical, Trypsin}, issn = {1940-6029}, doi = {10.1007/978-1-61779-980-8_24}, author = {Lakins, Johnathon N and Chin, Andrew R and Weaver, Valerie M} } @article {316, title = {Balancing forces: architectural control of mechanotransduction.}, journal = {Nat Rev Mol Cell Biol}, volume = {12}, year = {2011}, month = {2011 May}, pages = {308-19}, abstract = {

All cells exist within the context of a three-dimensional microenvironment in which they are exposed to mechanical and physical cues. These cues can be disrupted through perturbations to mechanotransduction, from the nanoscale-level to the tissue-level, which compromises tensional homeostasis to promote pathologies such as cardiovascular disease and cancer. The mechanisms of such perturbations suggest that a complex interplay exists between the extracellular microenvironment and cellular function. Furthermore, sustained disruptions in tensional homeostasis can be caused by alterations in the extracellular matrix, allowing it to serve as a mechanically based memory-storage device that can perpetuate a disease or restore normal tissue behaviour.

}, keywords = {Animals, Cell Adhesion, Extracellular Matrix, Homeostasis, Humans, Intercellular Junctions, Mechanotransduction, Cellular, Models, Biological, Stress, Mechanical}, issn = {1471-0080}, doi = {10.1038/nrm3112}, author = {DuFort, Christopher C and Paszek, Matthew J and Weaver, Valerie M} } @article {391, title = {Mechanics, malignancy, and metastasis: the force journey of a tumor cell.}, journal = {Cancer Metastasis Rev}, volume = {28}, year = {2009}, month = {2009 Jun}, pages = {113-27}, abstract = {

A cell undergoes many genetic and epigenetic changes as it transitions to malignancy. Malignant transformation is also accompanied by a progressive loss of tissue homeostasis and perturbations in tissue architecture that ultimately culminates in tumor cell invasion into the parenchyma and metastasis to distant organ sites. Increasingly, cancer biologists have begun to recognize that a critical component of this transformation journey involves marked alterations in the mechanical phenotype of the cell and its surrounding microenvironment. These mechanical differences include modifications in cell and tissue structure, adaptive force-induced changes in the environment, altered processing of micromechanical cues encoded in the extracellular matrix (ECM), and cell-directed remodeling of the extracellular stroma. Here, we review critical steps in this \"force journey,\" including mechanical contributions to tissue dysplasia, invasion of the ECM, and metastasis. We discuss the biophysical basis of this force journey and present recent advances in the measurement of cellular mechanical properties in vitro and in vivo. We end by describing examples of molecular mechanisms through which tumor cells sense, process and respond to mechanical forces in their environment. While our understanding of the mechanical components of tumor growth, survival and motility remains in its infancy, considerable work has already yielded valuable insight into the molecular basis of force-dependent tumor pathophysiology, which offers new directions in cancer chemotherapeutics.

}, keywords = {Animals, Biophysics, Cell Transformation, Neoplastic, Epigenesis, Genetic, Extracellular Matrix, Focal Adhesion Protein-Tyrosine Kinases, Humans, Lasers, Microscopy, Atomic Force, Models, Biological, Neoplasm Invasiveness, Neoplasm Metastasis, Neoplasms, rho-Associated Kinases, Stress, Mechanical}, issn = {1573-7233}, doi = {10.1007/s10555-008-9173-4}, author = {Kumar, Sanjay and Weaver, Valerie M} } @article {386, title = {A tense situation: forcing tumour progression.}, journal = {Nat Rev Cancer}, volume = {9}, year = {2009}, month = {2009 Feb}, pages = {108-22}, abstract = {

Cells within tissues are continuously exposed to physical forces including hydrostatic pressure, shear stress, and compression and tension forces. Cells dynamically adapt to force by modifying their behaviour and remodelling their microenvironment. They also sense these forces through mechanoreceptors and respond by exerting reciprocal actomyosin- and cytoskeletal-dependent cell-generated force by a process termed \&$\#$39;mechanoreciprocity\&$\#$39;. Loss of mechanoreciprocity has been shown to promote the progression of disease, including cancer. Moreover, the mechanical properties of a tissue contribute to disease progression, compromise treatment and might also alter cancer risk. Thus, the changing force that cells experience needs to be considered when trying to understand the complex nature of tumorigenesis.

}, keywords = {Animals, Cell Transformation, Neoplastic, Cytoskeleton, Disease Progression, Gene Expression, Humans, Mechanotransduction, Cellular, Neoplasms, Neoplastic Processes, Stress, Mechanical}, issn = {1474-1768}, doi = {10.1038/nrc2544}, author = {Butcher, Darci T and Alliston, Tamara and Weaver, Valerie M} } @article {421, title = {Tensional homeostasis and the malignant phenotype.}, journal = {Cancer Cell}, volume = {8}, year = {2005}, month = {2005 Sep}, pages = {241-54}, abstract = {

Tumors are stiffer than normal tissue, and tumors have altered integrins. Because integrins are mechanotransducers that regulate cell fate, we asked whether tissue stiffness could promote malignant behavior by modulating integrins. We found that tumors are rigid because they have a stiff stroma and elevated Rho-dependent cytoskeletal tension that drives focal adhesions, disrupts adherens junctions, perturbs tissue polarity, enhances growth, and hinders lumen formation. Matrix stiffness perturbs epithelial morphogenesis by clustering integrins to enhance ERK activation and increase ROCK-generated contractility and focal adhesions. Contractile, EGF-transformed epithelia with elevated ERK and Rho activity could be phenotypically reverted to tissues lacking focal adhesions if Rho-generated contractility or ERK activity was decreased. Thus, ERK and Rho constitute part of an integrated mechanoregulatory circuit linking matrix stiffness to cytoskeletal tension through integrins to regulate tissue phenotype.

}, keywords = {3T3 Cells, Animals, Cell Line, Tumor, Cell Shape, Cytoskeleton, Homeostasis, Mice, Neoplasms, Phenotype, Stress, Mechanical, Stromal Cells}, issn = {1535-6108}, doi = {10.1016/j.ccr.2005.08.010}, author = {Paszek, Matthew J and Zahir, Nastaran and Johnson, Kandice R and Lakins, Johnathon N and Rozenberg, Gabriela I and Gefen, Amit and Reinhart-King, Cynthia A and Margulies, Susan S and Dembo, Micah and Boettiger, David and Hammer, Daniel A and Weaver, Valerie M} }