Collective Epithelial Migration Drives Kidney Repair after Acute Injury

Acute kidney injury (AKI) is a common and significant medical problem. Despite the kidney’s remarkable regenerative capacity, the mortality rate for the AKI patients is high. Thus, there remains a need to better understand the cellular mechanisms of nephron repair in order to develop new strategies that would enhance the intrinsic ability of kidney tissue to regenerate. Here, using a novel, laser ablation-based, zebrafish model of AKI, we show that collective migration of kidney epithelial cells is a primary early response to acute injury. We also show that cell proliferation is a late response of regenerating kidney epithelia that follows cell migration during kidney repair. We propose a computational model that predicts this temporal relationship and suggests that cell stretch is a mechanical link between migration and proliferation, and present experimental evidence in support of this hypothesis. Overall, this study advances our understanding of kidney repair mechanisms by highlighting a primary role for collective cell migration, laying a foundation for new approaches to treatment of AKI

Asymmetric inheritance of the apical domain and self-renewal of retinal ganglion cell progenitors depend on Anillin function.

Divisions that generate one neuronal lineage-committed and one self-renewing cell maintain the balance of proliferation and differentiation for the generation of neuronal diversity. The asymmetric inheritance of apical domains and components of the cell division machinery has been implicated in this process, and might involve interactions with cell fate determinants in regulatory feedback loops of an as yet unknown nature. Here, we report the dynamics of Anillin - an essential F-actin regulator and furrow component - and its contribution to progenitor cell divisions in the developing zebrafish retina. We find that asymmetrically dividing retinal ganglion cell progenitors position the Anillin-rich midbody at the apical domain of the differentiating daughter. anillin hypomorphic conditions disrupt asymmetric apical domain inheritance and affect daughter cell fate. Consequently, the retinal cell type composition is profoundly affected, such that the ganglion cell layer is dramatically expanded. This study provides the first in vivo evidence for the requirement of Anillin during asymmetric neurogenic divisions. It also provides insights into a reciprocal regulation between Anillin and the ganglion cell fate determinant Ath5, suggesting a mechanism whereby the balance of proliferation and differentiation is accomplished during progenitor cell divisions in vivo.journal articleresearch support, non-u.s. gov't2015 Mar 012015 02 05importe

Hemodynamic Forces Sculpt Developing Heart Valves through a KLF2-WNT9B Paracrine Signaling Axis.

Hemodynamic forces play an essential epigenetic role in heart valve development, but how they do so is not known. Here, we show that the shear-responsive transcription factor KLF2 is required in endocardial cells to regulate the mesenchymal cell responses that remodel cardiac cushions to mature valves. Endocardial Klf2 deficiency results in defective valve formation associated with loss of Wnt9b expression and reduced canonical WNT signaling in neighboring mesenchymal cells, a phenotype reproduced by endocardial-specific loss of Wnt9b. Studies in zebrafish embryos reveal that wnt9b expression is similarly restricted to the endocardial cells overlying the developing heart valves and is dependent upon both hemodynamic shear forces and klf2a expression. These studies identify KLF2-WNT9B signaling as a conserved molecular mechanism by which fluid forces sensed by endothelial cells direct the complex cellular process of heart valve development and suggest that congenital valve defects may arise due to subtle defects in this mechanotransduction pathway.journal articleresearch support, non-u.s. gov'tresearch support, n.i.h., extramural2017 11 062017 10 19importe

Mechanotransduction in cardiovascular morphogenesis and tissue engineering.

Cardiovascular morphogenesis involves cell behavior and cell identity changes that are activated by mechanical forces associated with heart function. Recently, advances in in vivo imaging, methods to alter blood flow, and computational modelling have greatly advanced our understanding of how forces produced by heart contraction and blood flow impact different morphogenetic processes. Meanwhile, traditional genetic approaches have helped to elucidate how endothelial cells respond to forces at the cellular and molecular level. Here we discuss the principles of endothelial mechanosensitity and their interplay with cellular processes during cardiovascular morphogenesis. We then discuss their implications in the field of cardiovascular tissue engineering.journal articlereview2019 Aug2019 10 03importe

Fusion Bonding Behavior of Plasticized Corn Proteins in Fused Deposition Modeling Process

International audienceThe processing of natural biopolymers by Fused Deposition Modeling (FDM) opens perspectives for applications in food and health domains by taking advantages of their edibility, biocompatibility and bioresorbability. Glycerol plasticized zeins (proteins from maize kernels) present thermomechanical properties matching the extrusion step requirements of FDM (at T-printing= 130 degrees C for 20% of glycerol). The present work focuses on the fusion-bonding step of the process between adjacent filaments. Mechanisms at the root of the thermal bonding of amorphous polymers at T>T-g are governed by melt's surface tension (Gamma, driving force) and viscosity (eta, limiting force). In addition, healing phenomenon, assessed by the degree of healing, Dh, increases with time as Dh proportional to t(1/4). It originates from the diffusion of polymer chains across the interface in accordance with the reptation theory. Dynamic rheological properties of molten extruded filaments of plasticized zeins were determined in a pre-heated oscillatory rheometer at 130 degrees C, with |eta*|(gamma)over dot=1.6(s-1) ranging from 0.6 to 0.8kPa.s. Gamma was estimated from the evolution of the fusion-bonding neck growth between two extrudates (polymer sintering model). The 0.1mm.s(-1) bonding rate observed at 130 degrees C allowed estimating a melt surface tension of 30-40mN.m(-1). Concurrently surface energy measurements were conducted on solid plasticized zein at 20 degrees C using the sessile drop method: By varying liquids deposited on zein-based surface and following Owens and Wendt's approach, gamma(SV) was found to amount to 39.2 +/- 1.6mN.m(-1), with the dispersive component gamma(d)(SV) = 4.2 +/- 0.4mN.m(-1) and the polar one gamma(p)(SV) = 35.0 +/- 1.2mN.m(-1). These values were used to extrapolate a melt surface tension using the typical surface tension dependence d gamma/dT approximate to-0.05mN.m(-1).K-1 like for synthetic polymers following the Eotvos' law. The extrapolated values at 130 degrees C were in agreement with those obtained from fusion-bonding experiments

Fusion Bonding Behavior of Plasticized Corn Proteins in Fused Deposition Modeling Process

International audienc

The Zebrafish Anillin-eGFP Reporter Marks Late Dividing Retinal Precursors and Stem Cells Entering Neuronal Lineages.

Monitoring cycling behaviours of stem and somatic cells in the living animal is a powerful tool to better understand tissue development and homeostasis. The tg(anillin:anillin-eGFP) transgenic line carries the full-length zebrafish F-actin binding protein Anillin fused to eGFP from a bacterial artificial chromosome (BAC) containing Anillin cis-regulatory sequences. Here we report the suitability of the Anillin-eGFP reporter as a direct indicator of cycling cells in the late embryonic and post-embryonic retina. We show that combining the anillin:anillin-eGFP with other transgenes such as ptf1a:dsRed and atoh7:gap-RFP allows obtaining spatial and temporal resolution of the mitotic potentials of specific retinal cell populations. This is exemplified by the analysis of the origin of the previously reported apically and non-apically dividing late committed precursors of the photoreceptor and horizontal cell layers

Anillin-eGFP marks all cycling cells of the maturing retinal layers.

<p>(A-E) Optical section from a z-stack (frontal view) through the retina of a 48 hpf, <i>anillin</i>:<i>anillin-eGFP/ptf1a</i>:<i>dsRed</i> transgenic zebrafish that have been counterstained with DAPI (A) and pH3-antibody (A,D). (C) Only 34% of the Anillin-eGFP positive cell nuclei are pH3 immunoreactive at 48 hpf (n = 8 retinas). The black horizontal line shows the median while the crosses show the average. The box limits indicate the 25th and 75th percentiles as determined by R software; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles, data points are plotted as open circles. Asterisks in (B) and (E) highlight cells that are (<i>ptf1a</i>)dsRed (magenta) and Anillin-eGFP (green) positive, only few of which are also pH3 positive (yellow in D). The arrow in (B) and (E) points at the midbody between dividing daughter cells (asterisk) during late cytokinesis. (F,G) Optical section from a z-stack (frontal view) through the retina of an 60 hpf, <i>anillin</i>:<i>anillin-eGFP/ptf1a</i>:<i>dsRed</i> transgenic zebrafish that have been counterstained with DAPI (grey) and Rx2-antibody (blue). The arrowhead points at the cycling, Anillin-eGFP positive and Rx2-immunoreactive cell located at the base of the outer limiting membrane. ONL, outer nuclear layer; INL, inner nuclear layer; ac, amacrine cell; ph, photoreceptors; mg, Müller glia cell bodies (intermingling with the ac bodies).</p

Anillin-eGFP labelled cell division activity is restricted to the CMZ at 3 dpf and at 5 dpf.

<p>(A-C) Optical section from a z-stack taken in the transversal plane (frontal view as represented in the top panel of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170356#pone.0170356.g004" target="_blank">Fig 4</a>) through the central retina of an <i>anillin</i>:<i>anillin-eGFP</i> transgenic zebrafish fixed at 48 hpf (A), 60 hpf (B) or 3 dpf (C). Counterstaining with DAPI (grey) marks the cell nuclei and the three retinal cell layers. (D) Left: Anillin-eGFP positive cells were counted, which were allocated to the three retinal nuclear layers of the central retina (excluding the CMZ delineated by the dotted line). Anillin-eGFP positive cells were counted per embryo (48hpf, n = 3 apical = 22±4, non-apical = 11±4; 60 hpf, n = 3, apical = 20±4, non-apical = 13±0; 3dpf, n = 3, apical = 3±3, non-apical = 3±1,5). Right: Overlay of a confocal image with a schematic view representing the different locations of Anillin-eGFP positive cells within the central retina: apical, in the outer nuclear layer (ONL) and non-apical in the inner nuclear layer (INL). Error bars represent standard deviation. GCL: ganglion cell layer. (E) Two-photon z-stack projection (z-sections 1 μm apart) of a retina from a 5 dpf zebrafish showing Anillin-eGFP positive cells (green) in the CMZ. The cell nuclei (magenta) were labelled with DAPI. The image represents a dorsal view.</p

Anillin-eGFP in the CMZ marks transit-amplifying progenitors entering restricted neuronal lineages.

<p>Top panel: view of the retina in the transversal plane (eye position 90° relative to the viewer). The blue line across the retina corresponds to the sagittal view (optical z-section) in the top panel of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0170356#pone.0170356.g003" target="_blank">Fig 3</a>. (A-C) and (E-I) represent two optical sections from confocal z-stacks through the retina of a 48 hpf (A-C) and 3 dpf (E-I) zebrafish taken in the transversal plane. The squared dotted bracket in (A) and (E) delineates the CMZ domains. The squared bracket in (A-C) and (E-H) delineates cells within the CMZ that are both Anillin-eGFP (green) and Rx2 immunoreactive (blue). (D) As the stem cell niche develops, the percentage of Rx2 immunoreative cells that are also Anillin-eGFP positive in the CMZ domain decreases over time from 20% to 11,4%. The arrows in (F-I) point at two dividing, Anillin-eGFP (green) positive cells and at their nuclei (I). (F,G) One of the two cells is also (<i>ptf1a</i>)dsRed positive and non-apically located. Ph, photoreceptors; ac, amacrine cells; hc, horizontal cells; mg, Müller glial cell. ONL, outer nuclear layer; INL, inner nuclear layer; ONL, outer nuclear layer.</p