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Dynamic endothelial cell rearrangements drive developmental vessel regression.

Franco CA, Jones ML, Bernabeu MO, Geudens I, Mathivet T, Rosa A, Lopes FM, Lima AP, Ragab A, Collins RT, Phng LK, Coveney PV, Gerhardt H - PLoS Biol. (2015)

Bottom Line: Patterning of functional blood vessel networks is achieved by pruning of superfluous connections.The cellular and molecular principles of vessel regression are poorly understood.Establishing and analyzing the first axial polarity map of all endothelial cells in a remodeling vascular network, we propose that balanced movement of cells maintains the primitive plexus under low shear conditions in a metastable dynamic state.

View Article: PubMed Central - PubMed

Affiliation: Vascular Biology Laboratory, London Research Institute-Cancer Research UK, Lincoln's Inn Laboratories, London, United Kingdom; Instituto de Medicina Molecular, Faculdade de Medicina Universidade de Lisboa, Lisboa, Portugal.

ABSTRACT
Patterning of functional blood vessel networks is achieved by pruning of superfluous connections. The cellular and molecular principles of vessel regression are poorly understood. Here we show that regression is mediated by dynamic and polarized migration of endothelial cells, representing anastomosis in reverse. Establishing and analyzing the first axial polarity map of all endothelial cells in a remodeling vascular network, we propose that balanced movement of cells maintains the primitive plexus under low shear conditions in a metastable dynamic state. We predict that flow-induced polarized migration of endothelial cells breaks symmetry and leads to stabilization of high flow/shear segments and regression of adjacent low flow/shear segments.

No MeSH data available.


Related in: MedlinePlus

Extensive cell rearrangements drive developmental vessel regression.A, Schematic of ISV disconnection from the aorta. B,S4 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(kdrl:mCherry-CAAX) zebrafish embryo injected with pTol2:fli1ep:eGFP-CAAX, showing the dynamic behavior of endothelial cells during the process of intersegmental vessel regression (white arrow), triggered by the anastomosis of a venous sprout (blue arrow). C,S5 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(Fli1a:dsRedEx); Tg(Fli1a:nEGFP) zebrafish embryo showing the dynamic behavior of endothelial cell nuclei during vessel regression (white arrow). The regressing endothelial cell (asterisk) is viable and undergoes mitosis a later stage, originating two daughter endothelial cells (asterisk a and b). D, Confocal images of regression profiles in a wild-type P6 mouse retina labeled with lumen (ICAM2), junctions (ZO1), and basement membrane (Col.IV). Vessel segments range from a normal stable vessel segment (left panel), stenosis lumen/junction, disconnected lumen, and complete absence of lumen (right panel). E, Proposed four-step model for vessel regression. Step 1: selection of the regressing branch, Step 2: lumen stenosis in the regressing vessel, Step 3: junction/lumen remodeling during endothelial cell retraction, and Step 4: integration of regressing endothelial cells in neighboring vessel segments leaving an empty basement membrane. (dlav: dorsolateral anastomotic vessel; isv: intersegmental vessel; da: dorsal aorta; pcv: posterior cardinal vein). Scale bars (B and C: 20 μm; D: 10 μm).
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pbio.1002125.g004: Extensive cell rearrangements drive developmental vessel regression.A, Schematic of ISV disconnection from the aorta. B,S4 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(kdrl:mCherry-CAAX) zebrafish embryo injected with pTol2:fli1ep:eGFP-CAAX, showing the dynamic behavior of endothelial cells during the process of intersegmental vessel regression (white arrow), triggered by the anastomosis of a venous sprout (blue arrow). C,S5 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(Fli1a:dsRedEx); Tg(Fli1a:nEGFP) zebrafish embryo showing the dynamic behavior of endothelial cell nuclei during vessel regression (white arrow). The regressing endothelial cell (asterisk) is viable and undergoes mitosis a later stage, originating two daughter endothelial cells (asterisk a and b). D, Confocal images of regression profiles in a wild-type P6 mouse retina labeled with lumen (ICAM2), junctions (ZO1), and basement membrane (Col.IV). Vessel segments range from a normal stable vessel segment (left panel), stenosis lumen/junction, disconnected lumen, and complete absence of lumen (right panel). E, Proposed four-step model for vessel regression. Step 1: selection of the regressing branch, Step 2: lumen stenosis in the regressing vessel, Step 3: junction/lumen remodeling during endothelial cell retraction, and Step 4: integration of regressing endothelial cells in neighboring vessel segments leaving an empty basement membrane. (dlav: dorsolateral anastomotic vessel; isv: intersegmental vessel; da: dorsal aorta; pcv: posterior cardinal vein). Scale bars (B and C: 20 μm; D: 10 μm).

Mentions: To directly observe cell dynamics during the process of vessel regression, we studied regression of intersegmental vessels (ISVs) during remodeling of arterial to venous ISVs in the zebrafish embryo. After the first angiogenic phase, ISVs are originated from endothelial sprouts arising from the aorta. A second angiogenic phase occurs at a later stage in development, in which secondary sprouts arising from the posterior cardinal vein (PCV) either connect with the arterial ISVs, triggering disconnection from the aorta, or instead form precursors of the zebrafish lymphatic system (Fig 4A) [15]. We generated mosaic endothelial expression of membrane-bound eGFP in Tg(kdrl:mCherry-CAAX) embryos to observe the dynamics of single endothelial cells during regression of the connection of ISVs to the aorta (Fig 4B and S4 Movie). Where venous sprouts connected to the ISV (Fig 4Bii), we observed subsequent disconnection and retraction of the arterial cells from the aorta (Fig 4Biii, iv). Similar to the mouse retina observations, the disconnection of the ISVs occurred without evident endothelial cell death (S4 Movie). Cell tracking using a zebrafish transgenic line labeling endothelial nuclei (Fig 4C and S5 Movie) also revealed migration of cells with no sign of apoptosis during and after regression. In the shown example, the regressing cell proliferates after regression (Fig 4Cv), confirming that cells involved in regression remain active and viable. When comparing vessel regression in the mouse retina and the zebrafish ISV, we could observe striking similarities in the cellular arrangements during the different phases of vessel regression (Fig 4D). On the basis of these observations, we schematized the cellular and junctional rearrangements underlying vessel branch regression (Fig 4E). We propose that vessel regression entails four distinct steps: (1) an initial selection step, which precedes and triggers the morphological alterations during regression; (2) a stenosis step, in which the lumen is focally constricted or collapsed; (3) a retraction step, in which endothelial cells migrate and retract processes, associated with junctional remodeling; (4) a resolution step, which comprises the final loss of any endothelial processes in this branch, leaving only basement membrane and pericyte(s) behind (Figs 4E and S4).


Dynamic endothelial cell rearrangements drive developmental vessel regression.

Franco CA, Jones ML, Bernabeu MO, Geudens I, Mathivet T, Rosa A, Lopes FM, Lima AP, Ragab A, Collins RT, Phng LK, Coveney PV, Gerhardt H - PLoS Biol. (2015)

Extensive cell rearrangements drive developmental vessel regression.A, Schematic of ISV disconnection from the aorta. B,S4 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(kdrl:mCherry-CAAX) zebrafish embryo injected with pTol2:fli1ep:eGFP-CAAX, showing the dynamic behavior of endothelial cells during the process of intersegmental vessel regression (white arrow), triggered by the anastomosis of a venous sprout (blue arrow). C,S5 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(Fli1a:dsRedEx); Tg(Fli1a:nEGFP) zebrafish embryo showing the dynamic behavior of endothelial cell nuclei during vessel regression (white arrow). The regressing endothelial cell (asterisk) is viable and undergoes mitosis a later stage, originating two daughter endothelial cells (asterisk a and b). D, Confocal images of regression profiles in a wild-type P6 mouse retina labeled with lumen (ICAM2), junctions (ZO1), and basement membrane (Col.IV). Vessel segments range from a normal stable vessel segment (left panel), stenosis lumen/junction, disconnected lumen, and complete absence of lumen (right panel). E, Proposed four-step model for vessel regression. Step 1: selection of the regressing branch, Step 2: lumen stenosis in the regressing vessel, Step 3: junction/lumen remodeling during endothelial cell retraction, and Step 4: integration of regressing endothelial cells in neighboring vessel segments leaving an empty basement membrane. (dlav: dorsolateral anastomotic vessel; isv: intersegmental vessel; da: dorsal aorta; pcv: posterior cardinal vein). Scale bars (B and C: 20 μm; D: 10 μm).
© Copyright Policy
Related In: Results  -  Collection

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pbio.1002125.g004: Extensive cell rearrangements drive developmental vessel regression.A, Schematic of ISV disconnection from the aorta. B,S4 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(kdrl:mCherry-CAAX) zebrafish embryo injected with pTol2:fli1ep:eGFP-CAAX, showing the dynamic behavior of endothelial cells during the process of intersegmental vessel regression (white arrow), triggered by the anastomosis of a venous sprout (blue arrow). C,S5 Movie still images from time-lapse confocal imaging at 48 h post-fertilization of a transgenic Tg(Fli1a:dsRedEx); Tg(Fli1a:nEGFP) zebrafish embryo showing the dynamic behavior of endothelial cell nuclei during vessel regression (white arrow). The regressing endothelial cell (asterisk) is viable and undergoes mitosis a later stage, originating two daughter endothelial cells (asterisk a and b). D, Confocal images of regression profiles in a wild-type P6 mouse retina labeled with lumen (ICAM2), junctions (ZO1), and basement membrane (Col.IV). Vessel segments range from a normal stable vessel segment (left panel), stenosis lumen/junction, disconnected lumen, and complete absence of lumen (right panel). E, Proposed four-step model for vessel regression. Step 1: selection of the regressing branch, Step 2: lumen stenosis in the regressing vessel, Step 3: junction/lumen remodeling during endothelial cell retraction, and Step 4: integration of regressing endothelial cells in neighboring vessel segments leaving an empty basement membrane. (dlav: dorsolateral anastomotic vessel; isv: intersegmental vessel; da: dorsal aorta; pcv: posterior cardinal vein). Scale bars (B and C: 20 μm; D: 10 μm).
Mentions: To directly observe cell dynamics during the process of vessel regression, we studied regression of intersegmental vessels (ISVs) during remodeling of arterial to venous ISVs in the zebrafish embryo. After the first angiogenic phase, ISVs are originated from endothelial sprouts arising from the aorta. A second angiogenic phase occurs at a later stage in development, in which secondary sprouts arising from the posterior cardinal vein (PCV) either connect with the arterial ISVs, triggering disconnection from the aorta, or instead form precursors of the zebrafish lymphatic system (Fig 4A) [15]. We generated mosaic endothelial expression of membrane-bound eGFP in Tg(kdrl:mCherry-CAAX) embryos to observe the dynamics of single endothelial cells during regression of the connection of ISVs to the aorta (Fig 4B and S4 Movie). Where venous sprouts connected to the ISV (Fig 4Bii), we observed subsequent disconnection and retraction of the arterial cells from the aorta (Fig 4Biii, iv). Similar to the mouse retina observations, the disconnection of the ISVs occurred without evident endothelial cell death (S4 Movie). Cell tracking using a zebrafish transgenic line labeling endothelial nuclei (Fig 4C and S5 Movie) also revealed migration of cells with no sign of apoptosis during and after regression. In the shown example, the regressing cell proliferates after regression (Fig 4Cv), confirming that cells involved in regression remain active and viable. When comparing vessel regression in the mouse retina and the zebrafish ISV, we could observe striking similarities in the cellular arrangements during the different phases of vessel regression (Fig 4D). On the basis of these observations, we schematized the cellular and junctional rearrangements underlying vessel branch regression (Fig 4E). We propose that vessel regression entails four distinct steps: (1) an initial selection step, which precedes and triggers the morphological alterations during regression; (2) a stenosis step, in which the lumen is focally constricted or collapsed; (3) a retraction step, in which endothelial cells migrate and retract processes, associated with junctional remodeling; (4) a resolution step, which comprises the final loss of any endothelial processes in this branch, leaving only basement membrane and pericyte(s) behind (Figs 4E and S4).

Bottom Line: Patterning of functional blood vessel networks is achieved by pruning of superfluous connections.The cellular and molecular principles of vessel regression are poorly understood.Establishing and analyzing the first axial polarity map of all endothelial cells in a remodeling vascular network, we propose that balanced movement of cells maintains the primitive plexus under low shear conditions in a metastable dynamic state.

View Article: PubMed Central - PubMed

Affiliation: Vascular Biology Laboratory, London Research Institute-Cancer Research UK, Lincoln's Inn Laboratories, London, United Kingdom; Instituto de Medicina Molecular, Faculdade de Medicina Universidade de Lisboa, Lisboa, Portugal.

ABSTRACT
Patterning of functional blood vessel networks is achieved by pruning of superfluous connections. The cellular and molecular principles of vessel regression are poorly understood. Here we show that regression is mediated by dynamic and polarized migration of endothelial cells, representing anastomosis in reverse. Establishing and analyzing the first axial polarity map of all endothelial cells in a remodeling vascular network, we propose that balanced movement of cells maintains the primitive plexus under low shear conditions in a metastable dynamic state. We predict that flow-induced polarized migration of endothelial cells breaks symmetry and leads to stabilization of high flow/shear segments and regression of adjacent low flow/shear segments.

No MeSH data available.


Related in: MedlinePlus