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Release of cellular tension signals self-restorative ventral lamellipodia to heal barrier micro-wounds.

ABSTRACT: Basic mechanisms by which cellular barriers sense and respond to integrity disruptions remain poorly understood. Despite its tenuous structure and constitutive exposure to disruptive strains, the vascular endothelium exhibits robust barrier function. We show that in response to micrometer-scale disruptions induced by transmigrating leukocytes, endothelial cells generate unique ventral lamellipodia that propagate via integrins toward and across these "micro-wounds" to close them. This novel actin remodeling activity progressively healed multiple micro-wounds in succession and changed direction during this process. Mechanical probe-induced micro-wounding of both endothelia and epithelia suggests that ventral lamellipodia formed as a response to force imbalance and specifically loss of isometric tension. Ventral lamellipodia were enriched in the Rac1 effectors cortactin, IQGAP, and p47Phox and exhibited localized production of hydrogen peroxide. Together with Apr2/3, these were functionally required for effective micro-wound healing. We propose that barrier disruptions are detected as local release of isometric tension/force unloading, which is directly coupled to reactive oxygen species-dependent self-restorative actin remodeling dynamics.

SUBMITTER: Martinelli R

PROVIDER: S-EPMC3639391 | biostudies-literature | 2013 Apr

REPOSITORIES: biostudies-literature

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Release of cellular tension signals self-restorative ventral lamellipodia to heal barrier micro-wounds.

Martinelli Roberta R Kamei Masataka M Sage Peter T PT Massol Ramiro R Varghese Laya L Sciuto Tracey T Toporsian Mourad M Dvorak Ann M AM Kirchhausen Tomas T Springer Timothy A TA Carman Christopher V CV

The Journal of cell biology 20130401 3

Basic mechanisms by which cellular barriers sense and respond to integrity disruptions remain poorly understood. Despite its tenuous structure and constitutive exposure to disruptive strains, the vascular endothelium exhibits robust barrier function. We show that in response to micrometer-scale disruptions induced by transmigrating leukocytes, endothelial cells generate unique ventral lamellipodia that propagate via integrins toward and across these "micro-wounds" to close them. This novel actin ...[more]

PMID: 23629967

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Project description:Recently we observed that endothelial cells cultured in tightly confluent monolayers display frequent local lamellipodia, and that thrombin, an agent that increases endothelial permeability, reduces lamellipodia protrusions. This led us to test the hypothesis that local lamellipodia contribute to endothelial barrier function. Movements of subcellular structures containing GFP-actin or VE-cadherin-GFP expressed in endothelial cells were recorded using time-lapse microscopy. Transendothelial electrical resistance (TER) served as an index of endothelial barrier function. Changes in both lamellipodia dynamics and TER were assessed during baseline and after cells were treated with either the barrier-disrupting agent thrombin, or the barrier-stabilizing agent sphingosine-1-phosphate (S1P). The myosin II inhibitor blebbistatin was used to selectively block lamellipodia formation, and was used to test their role in the barrier function of endothelial cell monolayers and isolated, perfused rat mesenteric venules. Myosin light chain (MLC) phosphorylation was assessed by immunofluorescence microscopy. Rac1 and RhoA activation were evaluated using G-LISA assays. The role of Rac1 was tested with the specific inhibitor NSC23766 or by expressing wild-type or dominant negative GFP-Rac1. The results show that thrombin rapidly decreased both TER and the lamellipodia protrusion frequency. S1P rapidly increased TER in association with increased protrusion frequency. Blebbistatin nearly abolished local lamellipodia protrusions while cortical actin fibers and stress fibers remained intact. Blebbistatin also significantly decreased TER of cultured endothelial cells and increased permeability of isolated rat mesenteric venules. Both thrombin and S1P increased MLC phosphorylation and activation of RhoA. However, thrombin and S1P had differential impacts on Rac1, correlating with the changes in TER and lamellipodia protrusion frequency. Overexpression of Rac1 elevated, while NSC23766 and dominant negative Rac1 reduced barrier function and lamellipodia activity. Combined, these data suggest that local lamellipodia, driven by myosin II and Rac1, are important for dynamic changes in endothelial barrier integrity.

Project description:BACKGROUND:Thalamic dysfunction has been implicated in overall chronic neurological dysfunction after traumatic brain injury (TBI), however little is known about the underlying histopathology. In experimental diffuse TBI (dTBI), we hypothesize that persisting histopathological changes in the ventral posteromedial (VPM) nucleus of the thalamus is indicative of progressive circuit reorganization. Since circuit reorganization in the VPM impacts the whisker sensory system, the histopathology could explain the development of hypersensitivity to whisker stimulation by 28days post-injury; similar to light and sound hypersensitivity in human TBI survivors. METHODS:Adult, male Sprague-Dawley rats underwent craniotomy and midline fluid percussion injury (FPI) (moderate severity; 1.8-2.0atm) or sham surgery. At 1d, 7d, and 28days post-FPI (d FPI) separate experiments confirmed the cytoarchitecture (Giemsa stain) and evaluated neuropathology (silver stain), activated astrocytes (GFAP), neuron morphology (Golgi stain) and microglial morphology (Iba-1) in the VPM. RESULTS:Cytoarchitecture was unchanged throughout the time course, similar to previously published data; however, neuropathology and astrocyte activation were significantly increased at 7d and 28d and activated microglia were present at all time points. Neuron morphology was dynamic over the time course with decreased dendritic complexity (fewer branch points; decreased length of processes) at 7d FPI and return to sham values by 28d FPI. CONCLUSIONS:These data indicate that dTBI results in persisting thalamic histopathology out to a chronic time point. While these changes can be indicative of either adaptive (recovery) or maladaptive (neurological dysfunction) circuit reorganization, they also provide a potential mechanism by which maladaptive circuit reorganization could contribute to the development of chronic neurological dysfunction. Understanding the processes that mediate circuit reorganization is critical to the development of future therapies for TBI patients.

Project description:IntroductionExtracellular vesicles from mesenchymal stromal cells (MSC-EVs) have shown promise in wound healing. Their use in diabetic wounds specifically, however, remains pre-clinical and their efficacy remains uncertain less clear. A systematic review of preclinical studies is needed to determine the efficacy of MSC-EVs in the treatment of diabetic wounds to accelerate the clinical translation of this cell-based therapy.MethodsPubMed and Embase were searched (to June 23, 2020). All English-language, full-text, controlled interventional studies comparing MSC-EVs to placebo or a "no treatment" arm in animal models of diabetic wounds were included. Study outcomes, including wound closure (primary outcome), scar width, blood vessel number and density, and re-epithelialisation were pooled using a random effects meta-analysis. Risk of bias (ROB) was assessed using the SYRCLE tool for pre-clinical animal studies.ResultsA total of 313 unique records were identified from our search, with 10 full text articles satisfying inclusion criteria (n = 136 animals). The administration of MSC-EVs improved closure of diabetic wounds compared to controls with a large observed effect (Standardized Mean Difference (SMD) 5.48, 95% Confidence Interval (CI) 3.55-8.13). Healing was further enhanced using MSC-EVs enriched in non-coding RNAs or microRNAs compared to controls (SMD 9.89, 95%CI 7.32-12.46). Other outcomes, such as blood vessel density and number, scar width, and re-epithelialisation were improved with the administration of MSC-EVs, with a large effect. ROB across studies was unclear.ConclusionMSC-EVs, particularly following enrichment for specific RNAs, are a promising treatment for diabetic wounds in pre-clinical studies and translation to the clinical domain appears warranted.RegistrationPROSPERO #CRD42020199327 [248]. Forest plot demonstrating increased wound closure rates of diabetic wounds receiving genetically modified MSC-EVs that were enriched for specific RNAs. DFO = deferoxamine. Control groups were inactive (no treatment or saline) except for 3 studies which used hydrogels without MSC-EVs as control (Li M 2016; Shi 2017; Tao 2016).

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Release of cellular tension signals self-restorative ventral lamellipodia to heal barrier micro-wounds.

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Release of cellular tension signals self-restorative ventral lamellipodia to heal barrier micro-wounds.

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