Matrix elasticity directs stem cell lineage specification.
TL;DR: Naive mesenchymal stem cells are shown here to specify lineage and commit to phenotypes with extreme sensitivity to tissue-level elasticity, consistent with the elasticity-insensitive commitment of differentiated cell types.
About: This article is published in Cell.The article was published on 2006-08-25 and is currently open access. It has received 12204 citations till now. The article focuses on the topics: Mesenchymal stem cell differentiation & Stem cell fate determination.
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TL;DR: YAP/TAZ are identified as sensors and mediators of mechanical cues instructed by the cellular microenvironment and are functionally required for differentiation of mesenchymal stem cells induced by ECM stiffness and for survival of endothelial cells regulated by cell geometry.
Abstract: Cells perceive their microenvironment not only through soluble signals but also through physical and mechanical cues, such as extracellular matrix (ECM) stiffness or confined adhesiveness. By mechanotransduction systems, cells translate these stimuli into biochemical signals controlling multiple aspects of cell behaviour, including growth, differentiation and cancer malignant progression, but how rigidity mechanosensing is ultimately linked to activity of nuclear transcription factors remains poorly understood. Here we report the identification of the Yorkie-homologues YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif, also known as WWTR1) as nuclear relays of mechanical signals exerted by ECM rigidity and cell shape. This regulation requires Rho GTPase activity and tension of the actomyosin cytoskeleton, but is independent of the Hippo/LATS cascade. Crucially, YAP/TAZ are functionally required for differentiation of mesenchymal stem cells induced by ECM stiffness and for survival of endothelial cells regulated by cell geometry; conversely, expression of activated YAP overrules physical constraints in dictating cell behaviour. These findings identify YAP/TAZ as sensors and mediators of mechanical cues instructed by the cellular microenvironment.
4,120 citations
TL;DR: Reduction of lysyl oxidase-mediated collagen crosslinking prevented MMTV-Neu-induced fibrosis, decreased focal adhesions and PI3K activity, impeded malignancy, and lowered tumor incidence, and data show how collagenCrosslinking can modulate tissue fibrosis and stiffness to force focal adhesion, growth factor signaling and breast malignancies.
3,396 citations
TL;DR: The extracellular matrix and ECM proteins are important in phenomena as diverse as developmental patterning, stem cell niches, cancer, and genetic diseases and these properties need to be incorporated into considerations of the functions of the ECM.
Abstract: The extracellular matrix (ECM) and ECM proteins are important in phenomena as diverse as developmental patterning, stem cell niches, cancer, and genetic diseases. The ECM has many effects beyond providing structural support. ECM proteins typically include multiple, independently folded domains whose sequences and arrangement are highly conserved. Some of these domains bind adhesion receptors such as integrins that mediate cell-matrix adhesion and also transduce signals into cells. However, ECM proteins also bind soluble growth factors and regulate their distribution, activation, and presentation to cells. As organized, solid-phase ligands, ECM proteins can integrate complex, multivalent signals to cells in a spatially patterned and regulated fashion. These properties need to be incorporated into considerations of the functions of the ECM.
2,858 citations
TL;DR: The functional requirements, and types, of materials used in developing state of the art of scaffolds for tissue engineering applications are described and where future research and direction is required are described.
2,648 citations
TL;DR: This Review discusses how different mechanisms interact and can be integrated to exert fine control in time and space over the drug presentation, and collects experimental release data from the literature and presents quantitative comparisons between different systems to provide guidelines for the rational design of hydrogel delivery systems.
Abstract: Hydrogel delivery systems can leverage therapeutically beneficial outcomes of drug delivery and have found clinical use. Hydrogels can provide spatial and temporal control over the release of various therapeutic agents, including small-molecule drugs, macromolecular drugs and cells. Owing to their tunable physical properties, controllable degradability and capability to protect labile drugs from degradation, hydrogels serve as a platform in which various physiochemical interactions with the encapsulated drugs control their release. In this Review, we cover multiscale mechanisms underlying the design of hydrogel drug delivery systems, focusing on physical and chemical properties of the hydrogel network and the hydrogel-drug interactions across the network, mesh, and molecular (or atomistic) scales. We discuss how different mechanisms interact and can be integrated to exert fine control in time and space over the drug presentation. We also collect experimental release data from the literature, review clinical translation to date of these systems, and present quantitative comparisons between different systems to provide guidelines for the rational design of hydrogel delivery systems.
2,457 citations
References
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TL;DR: Results indicate that MSCs may be “primed” toward a neural fate by the constitutive expression of neuronal antigens and that they seem to respond with an appropriate neural pattern of differentiation when exposed to the environment of the developing brain.
Abstract: Reports of neural transdifferentiation of mesenchymal stem cells (MSCs) suggest the possibility that these cells may serve as a source for stem cell-based regenerative medicine to treat neurological disorders. However, some recent studies controvert previous reports of MSC neurogenecity. In the current study, we evaluate the neural differentiation potential of mouse bone marrow-derived MSCs. Surprisingly, we found that MSCs spontaneously express certain neuronal phenotype markers in culture, in the absence of specialized induction reagents. A previously published neural induction protocol that elevates cytoplasmic cyclic AMP does not upregulate neuron-specific protein expression significantly in MSCs but does significantly increase expression of the astrocyte-specific glial fibrillary acidic protein. Finally, when grafted into the lateral ventricles of neonatal mouse brain, MSCs migrate extensively and differentiate into olfactory bulb granule cells and periventricular astrocytes, without evidence of cell fusion. These results indicate that MSCs may be "primed" toward a neural fate by the constitutive expression of neuronal antigens and that they seem to respond with an appropriate neural pattern of differentiation when exposed to the environment of the developing brain.
321 citations
"Matrix elasticity directs stem cell..." refers result in this paper
...To reinforce this conclusion and to rule out a role for myosin VI in matrix sensing, we repeated the above experiments with the myosin light chain kinase (MLCK) inhibitor, ML7 (Dhawan and Helfman, 2004)....
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01 Mar 2003
TL;DR: The first measurements of the intrinsic strain fluctuations of living cells are reported using a recently developed tracer correlation technique along with a theoretical framework for interpreting such data in heterogeneous media with nonthermal driving, indicating that the cytoskeleton can be treated as a course-grained continuum with power-law rheology.
320 citations
TL;DR: Substantial developmental loss of motor axons was detected in mice lacking NF-L and in double knockout NF-M;NF-H mice, supporting the view of a role for IFs in axon stabilization and how certain types of perikaryal neurofilament aggregates might confer protection in motor neuron disease.
Abstract: Five major types of intermediate filament (IF) proteins are expressed in mature neurons: the three neurofilament proteins (NF-L, NF-M, and NF-H), alpha-internexin, and peripherin. While the differential expression of IF genes during embryonic development suggests potential functions of these proteins in axogenesis, none of the IF gene knockout experiments in mice caused gross developmental defects of the nervous system. Yet, deficiencies in neuronal IF proteins are not completely innocuous. Substantial developmental loss of motor axons was detected in mice lacking NF-L and in double knockout NF-M;NF-H mice, supporting the view of a role for IFs in axon stabilization. Moreover, the absence of peripherin resulted in approximately 30% loss of small sensory axons. Mice lacking NF-L had a scarcity of IF structures and exhibited a severe axonal hypotrophy, causing up to 50% reduction in conduction velocity, a feature that would be very detrimental for large animal species. Unexpectedly, the NF-M rather than NF-H protein turned out to be required for proper radial growth of large myelinated axons. Studies with transgenic mice suggest that some types of IF accumulations, reminiscent of those found in amyotrophic lateral sclerosis (ALS), can have deleterious effects and even cause neurodegeneration. Additional evidence for the involvement of IFs in pathogenesis came from the recent discovery of neurofilament gene mutations linked to ALS and Charcot-Marie-Tooth disease (CMT2E). Conversely, we discuss how certain types of perikaryal neurofilament aggregates might confer protection in motor neuron disease.
318 citations
"Matrix elasticity directs stem cell..." refers background in this paper
...The latter are widely recognized as late neuronal markers (Lariviere and Julien, 2004)....
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...…Sweeney,1 and Dennis E. Discher1,2,3,4,* 1Pennsylvania Muscle Institute 2School of Engineering and Applied Science 3Cell & Molecular Biology Graduate Group 4Physics Graduate Group University of Pennsylvania, Philadelphia, PA 19104, USA *Contact: discher@seas.upenn.edu DOI 10.1016/j.cell.2006.06.044...
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...Neuron-specific cytoskeletal markers such as nestin, an early commitment marker, and b3 tubulin, expressed in immature neurons, as well as the mature marker neurofilament light chain (NFL) (Lariviere and Julien, 2004) and the early/midadhesion protein NCAM (Rutishauser, 1984), are all upregulated....
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...Intensity analyses of 680 Cell 126, 677–689, August 25, 2006 ª2006 Elsevier Inc. immunofluorescent images (e.g., Figures 2A and 2C) as well as Western blots (Figure 2C; inset) confirm that only cells on the softest matrices express protein markers for neuronal commitment (nestin), immature neurons (b3 tubulin), mid/late neurons (microtubule associated protein 2; MAP2), and even mature neurons (NFL, NFH, and P-NFH)....
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...Cells also were stained with lineage-specific antibodies: myogenesis with Myogenesis Differentiation Protein 1 (MyoD1; Chemicon) and desmin (Sigma); osteogenesis with Core Binding Factor a1 (CBFA1; Alpha Diagnostic International) and osteocalcin (EMD Biosciences); and neurogenesis with phosphorylated and dephosphorylated Neurofilament Heavy chain (NFH; Sternberger Monoclonal), Neurofilament Light chain (NFL; Sigma), nestin (BD Pharmagen), Microtubule Associated Protein 2 (MAP2; Chemicon), and b3 tubulin (Sigma) along with paxillin (Chemicon), skeletal muscle myosin heavy chain (Zymed), nonmuscle myosin IIA and IIB (Sigma), IIC (courtesy of R. Adelstein, NIH), and rhodamine-labeled phalloidin....
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TL;DR: A FRET technique is described that can be used to evaluate the mechanics of cell-material interactions at the molecular level and simultaneously quantify the cell-based nanoscale rearrangement of the material itself, and suggests that regulation of phenotype with substrate stiffness is related to alterations in cellular traction forces.
Abstract: The mechanical properties of cell adhesion substrates regulate cell phenotype, but the mechanism of this relation is currently unclear. It may involve the magnitude of traction force applied by the cell, and/or the ability of the cells to rearrange the cell adhesion molecules presented from the material. In this study, we describe a FRET technique that can be used to evaluate the mechanics of cell–material interactions at the molecular level and simultaneously quantify the cell-based nanoscale rearrangement of the material itself. We found that these events depended on the mechanical rigidity of the adhesion substrate. Furthermore, both the proliferation and differentiation of preosteoblasts (MC3T3-E1) correlated to the magnitude of force that cells generate to cluster the cell adhesion ligands, but not the extent of ligand clustering. Together, these data demonstrate the utility of FRET in analyzing cell–material interactions, and suggest that regulation of phenotype with substrate stiffness is related to alterations in cellular traction forces.
316 citations
"Matrix elasticity directs stem cell..." refers background in this paper
...…Sweeney,1 and Dennis E. Discher1,2,3,4,* 1Pennsylvania Muscle Institute 2School of Engineering and Applied Science 3Cell & Molecular Biology Graduate Group 4Physics Graduate Group University of Pennsylvania, Philadelphia, PA 19104, USA *Contact: discher@seas.upenn.edu DOI 10.1016/j.cell.2006.06.044...
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...The results have significant implications for understanding physical effects of the in vivo microenvironment and also for therapeutic uses of stem cells....
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...Stiffer matrices (25–40 kPa) that we show below mimic the crosslinked collagen of osteoids (Garcia and Reyes, 2005; Kong et al., 2005) yield polygonal MSCs similar in morphology to osteoblasts....
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...…example, collagen-I production is very low in MSCs on soft matrices <11 kPa (see downregulated matrix transcripts; Figure 1C), whereas on 34 kPa matrices, MSCs appear somewhat more secretory (e.g., BMP1-5 and COL3A1), consistent with the secreting hFOB osteoblasts (Figure 2E) (Kong et al., 2005)....
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TL;DR: It is proposed that zig-zag assemblies of myosin II filaments induce the formation of actin bundles by pulling on an actin filament network and that co-alignment of act in and myosIn filaments proceeds via folding of myOSin II filament assemblies in an accordion-like fashion.
Abstract: The morphogenesis of myosin II structures in active lamella undergoing net protrusion was analyzed by correlative fluorescence and electron microscopy. In rat embryo fibroblasts (REF 52) microinjected with tetramethylrhodamine-myosin II, nascent myosin spots formed close to the active edge during periods of retraction and then elongated into wavy ribbons of uniform width. The spots and ribbons initially behaved as distinct structural entities but subsequently aligned with each other in a sarcomeric-like pattern. Electron microscopy established that the spots and ribbons consisted of bipolar minifilaments associated with each other at their head-containing ends and arranged in a single row in an "open" zig-zag conformation or as a "closed" parallel stack. Ribbons also contacted each other in a nonsarcomeric, network-like arrangement as described previously (Verkhovsky and Borisy, 1993. J. Cell Biol. 123:637-652). Myosin ribbons were particularly pronounced in REF 52 cells, but small ribbons and networks were found also in a range of other mammalian cells. At the edge of the cell, individual spots and open ribbons were associated with relatively disordered actin filaments. Further from the edge, myosin filament alignment increased in parallel with the development of actin bundles. In actin bundles, the actin cross-linking protein, alpha-actinin, was excluded from sites of myosin localization but concentrated in paired sites flanking each myosin ribbon, suggesting that myosin filament association may initiate a pathway for the formation of actin filament bundles. We propose that zig-zag assemblies of myosin II filaments induce the formation of actin bundles by pulling on an actin filament network and that co-alignment of actin and myosin filaments proceeds via folding of myosin II filament assemblies in an accordion-like fashion.
315 citations