Biology

Evidence of a large-scale mechanosensing mechanism for cellular adaptation to substrate stiffness

Abstract

Cell migration plays a major role in many fundamental biological processes, such as morphogenesis, tumor metastasis, and wound healing. As they anchor and pull on their surroundings, adhering cells actively probe the stiffness of their environment. Current understanding is that traction forces exerted by cells arise mainly at mechanotransduction sites, called focal adhesions, whose size seems to be correlated to the force exerted by cells on their underlying substrate, at least during their initial stages. In fact, our data show by direct measurements that the buildup of traction forces is faster for larger substrate stiffness, and that the stress measured at adhesion sites depends on substrate rigidity. Our results, backed by a phenomenological model based on active gel theory, suggest that rigidity-sensing is mediated by a large-scale mechanism originating in the cytoskeleton instead of a local one. We show that large-scale mechanosensing leads to an adaptative response of cell migration to stiffness gradients. In response to a step boundary in rigidity, we observe not only that cells migrate preferentially toward stiffer substrates, but also that this response is optimal in a narrow range of rigidities. Taken together, these findings lead to unique insights into the regulation of cell response to external mechanical cues and provide evidence for a cytoskeleton-based rigidity-sensing mechanism.

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Evidence of a large-scale mechanosensing mechanism for cellular adaptation to substrate stiffness

Patterned domains of supported phospholipid bilayer using microcontactprinting of Pll-g-PEG molecules

Abstract

In this work, we propose a reliable microcontactprinting (μCP) process for generating Patterned SupportedPhospholipidsBilayer (P-SPB) confined by Poly-l-(lysine)-grafted-polyethylene(glycol) (Pll-g-PEG) molecular barriers. The efficiency of Pll-g-PEG for inhibiting the fusion process of incubated liposome was first analyzed by Quartz Micro Balance (QCM) measurements. The quality and stability of Pll-g-PEG patterns were then both verified by fluorescence microscopy and Atomic Force Microscopy (AFM) in liquid media. The micro domains of P-SPB produced were stable in liquid environment during several weeks and also during AFM imaging. This exceptional stability is a clear improvement compared to previous studies involving proteins as confinement barriers.

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Patterned domains of supported phospholipid bilayer using microcontactprinting of Pll-g-PEG molecules

Patterned surfaces and methods of use for stem cell culture

Abstract

Nanopatterned surfaces which provide for improved cell growth including improved stem cell differentiation. The patterned surfaces can comprise an array of fields of biologically active moieties and can be controlled by parameters which include the pitch between the fields and the size of the fields. Nanopatterning can be carried out with use of dip pen nanolithographic printing, microcontact printing, and nanoimprint lithography. Patterning can be carried out on surfaces over large areas, with good homogeneity, and/or using edge-to-edge methods.

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Patterned surfaces and methods of use for stem cell culture

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