Light-Regulated Angiogenesis via a Phototriggerable VEGF Peptidomimetic

The application of growth factor based therapies in regenerative medicine is limited by the high cost, fast degradation kinetics, and the multiple functions of these molecules in the cell, which requires regulated delivery to minimize side effects. Here a photoactivatable peptidomimetic of the vascular endothelial growth factor (VEGF) that allows the light-controlled presentation of angiogenic signals to endothelial cells embedded in hydrogel matrices is presented. A photoresponsive analog of the 15-mer peptidomimetic Ac-KLTWQELYQLKYKGI-NH2 (abbreviated PQK) is prepared by introducing a 3-(4,5-dimethoxy-2-nitrophenyl)-2-butyl (DMNPB) photoremovable protecting group at the Trp4 residue. This modification inhibits the angiogenic potential of the peptide temporally. Light exposure of PQK modified hydrogels provide instructive cues to embedded endothelial cells and promote angiogenesis at the illuminated sites of the 3D culture, with the possibility of spatial control. PQK modified photoresponsive biomaterials offer an attractive approach for the dosed delivery and spatial control of pro-angiogenic factors to support regulated vascular growth by just using light as an external trigger

Membrane Tension Orchestrates Rear Retraction in Matrix-Directed Cell Migration.

In development, wound healing, and cancer metastasis, vertebrate cells move through 3D interstitial matrix, responding to chemical and physical guidance cues. Protrusion at the cell front has been extensively studied, but the retraction phase of the migration cycle is not well understood. Here, we show that fast-moving cells guided by matrix cues establish positive feedback control of rear retraction by sensing membrane tension. We reveal a mechanism of rear retraction in 3D matrix and durotaxis controlled by caveolae, which form in response to low membrane tension at the cell rear. Caveolae activate RhoA-ROCK1/PKN2 signaling via the RhoA guanidine nucleotide exchange factor (GEF) Ect2 to control local F-actin organization and contractility in this subcellular region and promote translocation of the cell rear. A positive feedback loop between cytoskeletal signaling and membrane tension leads to rapid retraction to complete the migration cycle in fast-moving cells, providing directional memory to drive persistent cell migration in complex matrices

Possibilities and Limitations of Photoactivatable Cytochalasin D for the Spatiotemporal Regulation of Actin Dynamics

The study of the actin cytoskeleton and related cellular processes requires tools to specifically interfere with actin dynamics in living cell cultures, ideally with spatiotemporal control and compatible with real time imaging. A phototriggerable derivative of the actin disruptor Cytochalasin D (CytoD) is described and tested here. It includes a nitroveratryloxycarbonyl (Nvoc) photoremovable protecting group (PPG) at the hydroxyl group at C7 of CytoD. The attachment of the PPG renders Nvoc-CytoD temporarily inactive, and enables light-dosed delivery of the active drug CytoD to living cells. This article presents the full structural and physicochemical characterization, the toxicity analysis. It is complemented with biological tests to show the time scales (seconds) and spatial resolution (cellular level) achievable with a UV source in a regular microscopy setu

Possibilities and Limitations of Photoactivatable Cytochalasin D for the Spatiotemporal Regulation of Actin Dynamics

The study of the actin cytoskeleton and related cellular processes requires tools to specifically interfere with actin dynamics in living cell cultures, ideally with spatiotemporal control and compatible with real time imaging. A phototriggerable derivative of the actin disruptor Cytochalasin D (CytoD) is described and tested here. It includes a nitroveratryloxycarbonyl (Nvoc) photoremovable protecting group (PPG) at the hydroxyl group at C7 of CytoD. The attachment of the PPG renders Nvoc-CytoD temporarily inactive, and enables light-dosed delivery of the active drug CytoD to living cells. This article presents the full structural and physicochemical characterization, the toxicity analysis. It is complemented with biological tests to show the time scales (seconds) and spatial resolution (cellular level) achievable with a UV source in a regular microscopy setup</div

Active superelasticity in three-dimensional epithelia of controlled shape

Fundamental biological processes are carried out by curved epithelial sheets that enclose a pressurized lumen. How these sheets develop and withstand three-dimensional deformations has remained unclear. Here we combine measurements of epithelial tension and shape with theoretical modelling to show that epithelial sheets are active superelastic materials. We produce arrays of epithelial domes with controlled geometry. Quantification of luminal pressure and epithelial tension reveals a tensional plateau over several-fold areal strains. These extreme strains in the tissue are accommodated by highly heterogeneous strains at a cellular level, in seeming contradiction to the measured tensional uniformity. This phenomenon is reminiscent of superelasticity, a behaviour that is generally attributed to microscopic material instabilities in metal alloys. We show that in epithelial cells this instability is triggered by a stretch-induced dilution of the actin cortex, and is rescued by the intermediate filament network. Our study reveals a type of mechanical behaviour—which we term active superelasticity—that enables epithelial sheets to sustain extreme stretching under constant tension

A Synthetic Zipper Peptide Motif Orchestrated via Co-operative Interplay of Hydrogen Bonding, Aromatic Stacking, and Backbone Chirality

Here, we report on a new class of synthetic zipper peptide which assumes its three-dimensional zipper-like structure via a co-operative interplay of hydrogen bonding, aromatic stacking, and backbone chirality. Structural studies carried out in both solid- and solution-state confirmed the zipper-like structural architecture assumed by the synthetic peptide which makes use of unusually remote inter-residual hydrogen-bonding and aromatic stacking interactions to attain its shape. The effect of chirality modulation and the extent of noncovalent forces in the structure stabilization have also been comprehensively explored via single-crystal X-ray diffraction and solution-state NMR studies. The results highlight the utility of noncovalent forces in engineering complex synthetic molecules with intriguing structural architectures

A Synthetic Zipper Peptide Motif Orchestrated via Co-operative Interplay of Hydrogen Bonding, Aromatic Stacking, and Backbone Chirality

Here, we report on a new class of synthetic zipper peptide which assumes its three-dimensional zipper-like structure via a co-operative interplay of hydrogen bonding, aromatic stacking, and backbone chirality. Structural studies carried out in both solid- and solution-state confirmed the zipper-like structural architecture assumed by the synthetic peptide which makes use of unusually remote inter-residual hydrogen-bonding and aromatic stacking interactions to attain its shape. The effect of chirality modulation and the extent of noncovalent forces in the structure stabilization have also been comprehensively explored via single-crystal X-ray diffraction and solution-state NMR studies. The results highlight the utility of noncovalent forces in engineering complex synthetic molecules with intriguing structural architectures

Active superelasticity in three-dimensional epithelia of controlled shape

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