@article{KarakayaBiderFranketal.2022,
  author    = {Karakaya, Emine and Bider, Faina and Frank, Andreas and Teßmar, J{\"o}rg and Sch{\"o}bel, Lisa and Forster, Leonard and Schr{\"u}fer, Stefan and Schmidt, Hans-Werner and Schubert, Dirk Wolfram and Blaeser, Andreas and Boccaccini, Aldo R. and Detsch, Rainer},
  title     = {Targeted printing of cells: evaluation of ADA-PEG bioinks for drop on demand approaches},
  series = {Gels},
  volume    = {8},
  journal   = {Gels},
  number    = {4},
  issn      = {2310-2861},
  doi       = {10.3390/gels8040206},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-267317},
  year      = {2022},
  abstract  = {A novel approach, in the context of bioprinting, is the targeted printing of a defined number of cells at desired positions in predefined locations, which thereby opens up new perspectives for life science engineering. One major challenge in this application is to realize the targeted printing of cells onto a gel substrate with high cell survival rates in advanced bioinks. For this purpose, different alginate-dialdehyde—polyethylene glycol (ADA-PEG) inks with different PEG modifications and chain lengths (1-8 kDa) were characterized to evaluate their application as bioinks for drop on demand (DoD) printing. The biochemical properties of the inks, printing process, NIH/3T3 fibroblast cell distribution within a droplet and shear forces during printing were analyzed. Finally, different hydrogels were evaluated as a printing substrate. By analysing different PEG chain lengths with covalently crosslinked and non-crosslinked ADA-PEG inks, it was shown that the influence of Schiff's bases on the viscosity of the corresponding materials is very low. Furthermore, it was shown that longer polymer chains resulted in less stable hydrogels, leading to fast degradation rates. Several bioinks highly exhibit biocompatibility, while the calculated nozzle shear stress increased from approx. 1.3 and 2.3 kPa. Moreover, we determined the number of cells for printed droplets depending on the initial cell concentration, which is crucially needed for targeted cell printing approaches.},
  language  = {en}
}
@article{JarauschNeuenrothAndagetal.2022,
  author    = {Jarausch, Johannes and Neuenroth, Lisa and Andag, Reiner and Leha, Andreas and Fischer, Andreas and Asif, Abdul R. and Lenz, Christof and Eidizadeh, Abass},
  title     = {Influence of shear stress, inflammation and BRD4 inhibition on human endothelial cells: a holistic proteomic approach},
  series = {Cells},
  volume    = {11},
  journal   = {Cells},
  number    = {19},
  issn      = {2073-4409},
  doi       = {10.3390/cells11193086},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-289872},
  year      = {2022},
  abstract  = {Atherosclerosis is an important risk factor in the development of cardiovascular diseases. In addition to increased plasma lipid concentrations, irregular/oscillatory shear stress and inflammatory processes trigger atherosclerosis. Inhibitors of the transcription modulatory bromo- and extra-terminal domain (BET) protein family (BETi) could offer a possible therapeutic approach due to their epigenetic mechanism and anti-inflammatory properties. In this study, the influence of laminar shear stress, inflammation and BETi treatment on human endothelial cells was investigated using global protein expression profiling by ion mobility separation-enhanced data independent acquisition mass spectrometry (IMS-DIA-MS). For this purpose, primary human umbilical cord derived vascular endothelial cells were treated with TNFα to mimic inflammation and exposed to laminar shear stress in the presence or absence of the BRD4 inhibitor JQ1. IMS-DIA-MS detected over 4037 proteins expressed in endothelial cells. Inflammation, shear stress and BETi led to pronounced changes in protein expression patterns with JQ1 having the greatest effect. To our knowledge, this is the first proteomics study on primary endothelial cells, which provides an extensive database for the effects of shear stress, inflammation and BETi on the endothelial proteome.},
  language  = {en}
}
@article{PereiraLipphausErginetal.2021,
  author    = {Pereira, Ana Rita and Lipphaus, Andreas and Ergin, Mert and Salehi, Sahar and Gehweiler, Dominic and Rudert, Maximilian and Hansmann, Jan and Herrmann, Marietta},
  title     = {Modeling of the Human Bone Environment: Mechanical Stimuli Guide Mesenchymal Stem Cell-Extracellular Matrix Interactions},
  series = {Materials},
  volume    = {14},
  journal   = {Materials},
  number    = {16},
  issn      = {1996-1944},
  doi       = {10.3390/ma14164431},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-245012},
  year      = {2021},
  abstract  = {In bone tissue engineering, the design of in vitro models able to recreate both the chemical composition, the structural architecture, and the overall mechanical environment of the native tissue is still often neglected. In this study, we apply a bioreactor system where human bone-marrow hMSCs are seeded in human femoral head-derived decellularized bone scaffolds and subjected to dynamic culture, i.e., shear stress induced by continuous cell culture medium perfusion at 1.7 mL/min flow rate and compressive stress by 10\% uniaxial load at 1 Hz for 1 h per day. In silico modeling revealed that continuous medium flow generates a mean shear stress of 8.5 mPa sensed by hMSCs seeded on 3D bone scaffolds. Experimentally, both dynamic conditions improved cell repopulation within the scaffold and boosted ECM production compared with static controls. Early response of hMSCs to mechanical stimuli comprises evident cell shape changes and stronger integrin-mediated adhesion to the matrix. Stress-induced Col6 and SPP1 gene expression suggests an early hMSC commitment towards osteogenic lineage independent of Runx2 signaling. This study provides a foundation for exploring the early effects of external mechanical stimuli on hMSC behavior in a biologically meaningful in vitro environment, opening new opportunities to study bone development, remodeling, and pathologies.},
  language  = {en}
}
@article{ScholzGehringGuanetal.2015,
  author    = {Scholz, Nicole and Gehring, Jennifer and Guan, Chonglin and Ljaschenko, Dmitrij and Fischer, Robin and Lakshmanan, Vetrivel and Kittel, Robert J. and Langenhan, Tobias},
  title     = {The adhesion GPCR Latrophilin/CIRL shapes mechanosensation},
  series = {Cell Reports},
  volume    = {11},
  journal   = {Cell Reports},
  doi       = {10.1016/j.celrep.2015.04.008},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148626},
  pages     = {866-874},
  year      = {2015},
  abstract  = {G-protein-coupled receptors (GPCRs) are typically regarded as chemosensors that control cellular states in response to soluble extracellular cues. However, the modality of stimuli recognized through adhesion GPCR (aGPCR), the second largest class of the GPCR superfamily, is unresolved. Our study characterizes the Drosophila aGPCR Latrophilin/dCirl, a prototype member of this enigmatic receptor class. We show that dCirl shapes the perception of tactile, proprioceptive, and auditory stimuli through chordotonal neurons, the principal mechanosensors of Drosophila. dCirl sensitizes these neurons for the detection of mechanical stimulation by amplifying their input-output function. Our results indicate that aGPCR may generally process and modulate the perception of mechanical signals, linking these important stimuli to the sensory canon of the GPCR superfamily.},
  language  = {en}
}
@phdthesis{Drechsler2008,
  author    = {Drechsler, Patrick Hans},
  title     = {Mechanics of adhesion and friction in stick insects and tree frogs},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-26836},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {Many arthropods and vertebrates can cling to surfaces using adhesive pads on their legs. These pads are either smooth and characterised by a specialised, soft cuticle or they are hairy, i.e. densely covered with flexible adhesive setae. Animals climbing with adhesive organs are able to control attachment and detachment dynamically while running. The detailed mechanisms of how tarsal pads generate adhesive and frictional forces and how forces are controlled during locomotion are still largely unclear. The aim of this study was to clarify the attachment mechanism of smooth adhesive pads as present in many insects and tree frogs. To understand the function of these fluid-based adhesive systems, I characterized their performance under standardized conditions. To this end, experiments were conducted by simultaneously measuring adhesion, friction, and contact area in single adhesive pads. The first result of this study showed that friction in stick insect attachment pads is anisotropic: Attachment pads regularly detached when slid away from the body. Further analyses of "immobilized" arolia revealed that this anisotropy is not caused by an increased shear stress in the proximal direction, but by the instability of the tarsus when pushed distally. In the second part of this study, I analysed the role of the pad secretion present in insects and tree frogs. In stick insects, shear stress was largely independent of normal force and increased with velocity, seemingly consistent with the viscosity effect of a continuous fluid film. However, measurements of the remaining force two minutes after a sliding movement showed that adhesive pads could sustain considerable static friction in insects and tree frogs. Repeated sliding movements and multiple consecutive pull-offs of stick insect single legs to deplete adhesive secretion showed that on a smooth surface, friction and adhesion strongly increased with decreasing amount of fluid in insects. In contrast, stick insect pull-off forces significantly decreased on a rough substrate. Thus, the secretion does not generally increase attachment but does so only on rough substrates, where it helps to maximize contact area. When slides with stick insect arolia were repeated at one position so that secretion could accumulate, sliding shear stress decreased but static friction remained clearly present. This suggests that static friction in stick insects, which is biologically important to prevent sliding, is based on non-Newtonian properties of the adhesive emulsion rather than on a direct contact between the cuticle and the substrate. \% Analogous measurements in toe pads of tree frogs showed that they are also able to generate static friction, even though their pads are wetted by mucus. In contrast to the mechanism proposed for insects, static friction in tree frogs apparently results from the very close contact of toe pads to the substrate and boundary lubrication. In the last section of this study, I investigated adhesive forces and the mode of detachment by performing pull-off measurements at different velocities and preloads. These experiments showed that preload has only an increasing effect on adhesion for faster pull-offs. This can be explained by the viscoelastic material properties of the stick insect arolium, which introduce a strong rate-dependence of detachment. During fast pull-offs, forces can spread over the complete area of contact, leading to forces scaling with area. In contrast, the pad material has sufficient time to withdraw elastically and peel during slow detachments. Under these conditions the adhesive force will concentrate on the circumference of the contact area, therefore scaling with a length, supporting models such as the peeling theory. The scaling of single-pad forces supported these conclusions, but large variation between pads of different stick insects did not allow statistically significant conclusions. In contrast, when detachment forces were quantified for whole insects using a centrifuge, forces scaled with pad contact area and not with length.},
  subject      = {Biomechanik},
  language  = {en}
}