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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

Developmental vessel regression does not depend on endothelial cell death.A, Overview of a wild-type postnatal day 6 (P6) mouse retina highlighting all regression profiles (blue lines). Regression profiles are vessel segments with collagen IV-positive vessel segments and negative for IsolectinB4. B, Quantification of number of regressing segments at P4, P6, and P8 retinas per vascularized area. C, Representative image of a P6 mouse retina labeled with Col.IV (green), cleaved caspase-3 (red) and IsolectinB4 (blue) showing regression profiles (white arrows) associated with cleaved caspase-3-positive cells (yellow arrows). D, Quantification of total numbers of cleaved caspase-3 events in entire P4, P6, and P8 mouse retinas, normalized for 100 μm2 of vascularized tissue. At P6, only 4.82% ± 0.76 (n = 5 retinas) of regression events are associated with caspase-3-positive labeled endothelial cells. Data given as mean ± SD. E, Confocal images of P6 wild-type retinas after 4h EdU-treatment (EdU, blue), endothelial cell nuclei (Erg, green) and blood vessels (ICAM2, red). F, Quantification of total number of endothelial cells, percentage of ETS related gene (Erg)- and 5-ethynyl-2'-deoxyuridine (EdU)-positive cells to total number of endothelial cells, and number of endothelial cells per vascularized area at specified mouse retina developmental stages. Mean ± SEM; n = 4 mice, 2 litters. Scale bars (A and E: 200 μm; C: 25 μm). The data used to make this figure can be found in S1 Data.
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pbio.1002125.g001: Developmental vessel regression does not depend on endothelial cell death.A, Overview of a wild-type postnatal day 6 (P6) mouse retina highlighting all regression profiles (blue lines). Regression profiles are vessel segments with collagen IV-positive vessel segments and negative for IsolectinB4. B, Quantification of number of regressing segments at P4, P6, and P8 retinas per vascularized area. C, Representative image of a P6 mouse retina labeled with Col.IV (green), cleaved caspase-3 (red) and IsolectinB4 (blue) showing regression profiles (white arrows) associated with cleaved caspase-3-positive cells (yellow arrows). D, Quantification of total numbers of cleaved caspase-3 events in entire P4, P6, and P8 mouse retinas, normalized for 100 μm2 of vascularized tissue. At P6, only 4.82% ± 0.76 (n = 5 retinas) of regression events are associated with caspase-3-positive labeled endothelial cells. Data given as mean ± SD. E, Confocal images of P6 wild-type retinas after 4h EdU-treatment (EdU, blue), endothelial cell nuclei (Erg, green) and blood vessels (ICAM2, red). F, Quantification of total number of endothelial cells, percentage of ETS related gene (Erg)- and 5-ethynyl-2'-deoxyuridine (EdU)-positive cells to total number of endothelial cells, and number of endothelial cells per vascularized area at specified mouse retina developmental stages. Mean ± SEM; n = 4 mice, 2 litters. Scale bars (A and E: 200 μm; C: 25 μm). The data used to make this figure can be found in S1 Data.

Mentions: Remodeling of primitive vascular networks through substantial regression of vessel segments is detectable as empty type IV collagen (Col.IV) matrix sleeves (Figs 1A and S1). The number of regression points per vascularized area increased only slightly as remodeling progressed during postnatal stages (Fig 1B), suggesting that regression profiles have a limited lifetime and therefore do not accumulate. Over the period analyzed, vessel regression was proportional to the total area vascularized. Programmed, vessel regression is mediated by endothelial cell apoptosis and correlates with macrophage activity [3,10]. To analyze whether developmental vessel regression in the retina involves endothelial cell death, we quantified the number of apoptotic endothelial cells (cleaved caspase 3) at different postnatal stages. We observed a mean of 78.1 ± 7.0 events (±SD, n = 8) in a whole 6-d post-natal (P6) retina, comprising approximately 16,000 endothelial cells (Fig 1C–1F and S1 Data). Although the total numbers of apoptotic endothelial cell events per retina increased over time, the ratio of apoptotic endothelial cells and the numbers of endothelial cell per vascularized retinal area remained surprisingly constant (Fig 1D–1F and S1 Data). Moreover, at P6, only 4.82% ± 0.76 (mean ± SD, n = 5) of the abundant regression profiles were associated with active endothelial cell apoptosis (Fig 1D and S1 Data). Thus, 95% of the regression events were not directly associated with endothelial apoptotic events, suggesting that vessel regression initiation or completion is largely unrelated to apoptosis in physiological vascular development in the mouse retina.


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)

Developmental vessel regression does not depend on endothelial cell death.A, Overview of a wild-type postnatal day 6 (P6) mouse retina highlighting all regression profiles (blue lines). Regression profiles are vessel segments with collagen IV-positive vessel segments and negative for IsolectinB4. B, Quantification of number of regressing segments at P4, P6, and P8 retinas per vascularized area. C, Representative image of a P6 mouse retina labeled with Col.IV (green), cleaved caspase-3 (red) and IsolectinB4 (blue) showing regression profiles (white arrows) associated with cleaved caspase-3-positive cells (yellow arrows). D, Quantification of total numbers of cleaved caspase-3 events in entire P4, P6, and P8 mouse retinas, normalized for 100 μm2 of vascularized tissue. At P6, only 4.82% ± 0.76 (n = 5 retinas) of regression events are associated with caspase-3-positive labeled endothelial cells. Data given as mean ± SD. E, Confocal images of P6 wild-type retinas after 4h EdU-treatment (EdU, blue), endothelial cell nuclei (Erg, green) and blood vessels (ICAM2, red). F, Quantification of total number of endothelial cells, percentage of ETS related gene (Erg)- and 5-ethynyl-2'-deoxyuridine (EdU)-positive cells to total number of endothelial cells, and number of endothelial cells per vascularized area at specified mouse retina developmental stages. Mean ± SEM; n = 4 mice, 2 litters. Scale bars (A and E: 200 μm; C: 25 μm). The data used to make this figure can be found in S1 Data.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4401640&req=5

pbio.1002125.g001: Developmental vessel regression does not depend on endothelial cell death.A, Overview of a wild-type postnatal day 6 (P6) mouse retina highlighting all regression profiles (blue lines). Regression profiles are vessel segments with collagen IV-positive vessel segments and negative for IsolectinB4. B, Quantification of number of regressing segments at P4, P6, and P8 retinas per vascularized area. C, Representative image of a P6 mouse retina labeled with Col.IV (green), cleaved caspase-3 (red) and IsolectinB4 (blue) showing regression profiles (white arrows) associated with cleaved caspase-3-positive cells (yellow arrows). D, Quantification of total numbers of cleaved caspase-3 events in entire P4, P6, and P8 mouse retinas, normalized for 100 μm2 of vascularized tissue. At P6, only 4.82% ± 0.76 (n = 5 retinas) of regression events are associated with caspase-3-positive labeled endothelial cells. Data given as mean ± SD. E, Confocal images of P6 wild-type retinas after 4h EdU-treatment (EdU, blue), endothelial cell nuclei (Erg, green) and blood vessels (ICAM2, red). F, Quantification of total number of endothelial cells, percentage of ETS related gene (Erg)- and 5-ethynyl-2'-deoxyuridine (EdU)-positive cells to total number of endothelial cells, and number of endothelial cells per vascularized area at specified mouse retina developmental stages. Mean ± SEM; n = 4 mice, 2 litters. Scale bars (A and E: 200 μm; C: 25 μm). The data used to make this figure can be found in S1 Data.
Mentions: Remodeling of primitive vascular networks through substantial regression of vessel segments is detectable as empty type IV collagen (Col.IV) matrix sleeves (Figs 1A and S1). The number of regression points per vascularized area increased only slightly as remodeling progressed during postnatal stages (Fig 1B), suggesting that regression profiles have a limited lifetime and therefore do not accumulate. Over the period analyzed, vessel regression was proportional to the total area vascularized. Programmed, vessel regression is mediated by endothelial cell apoptosis and correlates with macrophage activity [3,10]. To analyze whether developmental vessel regression in the retina involves endothelial cell death, we quantified the number of apoptotic endothelial cells (cleaved caspase 3) at different postnatal stages. We observed a mean of 78.1 ± 7.0 events (±SD, n = 8) in a whole 6-d post-natal (P6) retina, comprising approximately 16,000 endothelial cells (Fig 1C–1F and S1 Data). Although the total numbers of apoptotic endothelial cell events per retina increased over time, the ratio of apoptotic endothelial cells and the numbers of endothelial cell per vascularized retinal area remained surprisingly constant (Fig 1D–1F and S1 Data). Moreover, at P6, only 4.82% ± 0.76 (mean ± SD, n = 5) of the abundant regression profiles were associated with active endothelial cell apoptosis (Fig 1D and S1 Data). Thus, 95% of the regression events were not directly associated with endothelial apoptotic events, suggesting that vessel regression initiation or completion is largely unrelated to apoptosis in physiological vascular development in the mouse retina.

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