--- res: bibo_abstract: - "Directed cell migration is a hallmark feature, present in almost all multi-cellular\r\norganisms. Despite its importance, basic questions regarding force transduction\r\nor directional sensing are still heavily investigated. Directed migration of cells\r\nguided by immobilized guidance cues - haptotaxis - occurs in key-processes,\r\nsuch as embryonic development and immunity (Middleton et al., 1997; Nguyen\r\net al., 2000; Thiery, 1984; Weber et al., 2013). Immobilized guidance cues\r\ncomprise adhesive ligands, such as collagen and fibronectin (Barczyk et al.,\r\n2009), or chemokines - the main guidance cues for migratory leukocytes\r\n(Middleton et al., 1997; Weber et al., 2013). While adhesive ligands serve as\r\nattachment sites guiding cell migration (Carter, 1965), chemokines instruct\r\nhaptotactic migration by inducing adhesion to adhesive ligands and directional\r\nguidance (Rot and Andrian, 2004; Schumann et al., 2010). Quantitative analysis\r\nof the cellular response to immobilized guidance cues requires in vitro assays\r\nthat foster cell migration, offer accurate control of the immobilized cues on a\r\nsubcellular scale and in the ideal case closely reproduce in vivo conditions. The\r\nexploration of haptotactic cell migration through design and employment of such\r\nassays represents the main focus of this work.\r\nDendritic cells (DCs) are leukocytes, which after encountering danger\r\nsignals such as pathogens in peripheral organs instruct naïve T-cells and\r\nconsequently the adaptive immune response in the lymph node (Mellman and\r\nSteinman, 2001). To reach the lymph node from the periphery, DCs follow\r\nhaptotactic gradients of the chemokine CCL21 towards lymphatic vessels\r\n(Weber et al., 2013). Questions about how DCs interpret haptotactic CCL21\r\ngradients have not yet been addressed. The main reason for this is the lack of\r\nan assay that offers diverse haptotactic environments, hence allowing the study\r\nof DC migration as a response to different signals of immobilized guidance cue.\r\nIn this work, we developed an in vitro assay that enables us to\r\nquantitatively assess DC haptotaxis, by combining precisely controllable\r\nchemokine photo-patterning with physically confining migration conditions. With this tool at hand, we studied the influence of CCL21 gradient properties and\r\nconcentration on DC haptotaxis. We found that haptotactic gradient sensing\r\ndepends on the absolute CCL21 concentration in combination with the local\r\nsteepness of the gradient. Our analysis suggests that the directionality of\r\nmigrating DCs is governed by the signal-to-noise ratio of CCL21 binding to its\r\nreceptor CCR7. Moreover, the haptotactic CCL21 gradient formed in vivo\r\nprovides an optimal shape for DCs to recognize haptotactic guidance cue.\r\nBy reconstitution of the CCL21 gradient in vitro we were also able to\r\nstudy the influence of CCR7 signal termination on DC haptotaxis. To this end,\r\nwe used DCs lacking the G-protein coupled receptor kinase GRK6, which is\r\nresponsible for CCL21 induced CCR7 receptor phosphorylation and\r\ndesensitization (Zidar et al., 2009). We found that CCR7 desensitization by\r\nGRK6 is crucial for maintenance of haptotactic CCL21 gradient sensing in vitro\r\nand confirm those observations in vivo.\r\nIn the context of the organism, immobilized haptotactic guidance cues\r\noften coincide and compete with soluble chemotactic guidance cues. During\r\nwound healing, fibroblasts are exposed and influenced by adhesive cues and\r\nsoluble factors at the same time (Wu et al., 2012; Wynn, 2008). Similarly,\r\nmigrating DCs are exposed to both, soluble chemokines (CCL19 and truncated\r\nCCL21) inducing chemotactic behavior as well as the immobilized CCL21. To\r\nquantitatively assess these complex coinciding immobilized and soluble\r\nguidance cues, we implemented our chemokine photo-patterning technique in a\r\nmicrofluidic system allowing for chemotactic gradient generation. To validate\r\nthe assay, we observed DC migration in competing CCL19/CCL21\r\nenvironments.\r\nAdhesiveness guided haptotaxis has been studied intensively over the\r\nlast century. However, quantitative studies leading to conceptual models are\r\nlargely missing, again due to the lack of a precisely controllable in vitro assay. A\r\nrequirement for such an in vitro assay is that it must prevent any uncontrolled\r\ncell adhesion. This can be accomplished by stable passivation of the surface. In\r\naddition, controlled adhesion must be sustainable, quantifiable and dose\r\ndependent in order to create homogenous gradients. Therefore, we developed a novel covalent photo-patterning technique satisfying all these needs. In\r\ncombination with a sustainable poly-vinyl alcohol (PVA) surface coating we\r\nwere able to generate gradients of adhesive cue to direct cell migration. This\r\napproach allowed us to characterize the haptotactic migratory behavior of\r\nzebrafish keratocytes in vitro. Furthermore, defined patterns of adhesive cue\r\nallowed us to control for cell shape and growth on a subcellular scale.@eng" bibo_authorlist: - foaf_Person: foaf_givenName: Jan foaf_name: Schwarz, Jan foaf_surname: Schwarz foaf_workInfoHomepage: http://www.librecat.org/personId=346C1EC6-F248-11E8-B48F-1D18A9856A87 dct_date: 2016^xs_gYear dct_isPartOf: - http://id.crossref.org/issn/2663-337X dct_language: eng dct_publisher: Institute of Science and Technology Austria@ dct_title: Quantitative analysis of haptotactic cell migration@ ...