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The conditional inactivation of the beta-catenin gene in endothelial cells causes a defective vascular pattern and increased vascular fragility.

Cattelino A, Liebner S, Gallini R, Zanetti A, Balconi G, Corsi A, Bianco P, Wolburg H, Moore R, Oreda B, Kemler R, Dejana E - J. Cell Biol. (2003)

Bottom Line: We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered.These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability.We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts.

View Article: PubMed Central - PubMed

Affiliation: FIRC Institute of Molecular Oncology, 16-20139, Milan, Italy.

ABSTRACT
Using the Cre/loxP system we conditionally inactivated beta-catenin in endothelial cells. We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered. In addition, in many regions, the vascular lumen was irregular with the formation of lacunae at bifurcations, vessels were frequently hemorrhagic, and fluid extravasation in the pericardial cavity was observed. Cultured beta-catenin -/- endothelial cells showed a different organization of intercellular junctions with a decrease in alpha-catenin in favor of desmoplakin and marked changes in actin cytoskeleton. These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability. We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts. This may become more marked when the vessels are exposed to high or turbulent flow, such as at bifurcations or in the beating heart, leading to fluid leakage or hemorrhages.

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Phenotypic defects in endothelial β-catenin– embryos. (A and B) E9.5 embryos after whole-mount immunohistochemistry with anti-PECAM antibodies. No major differences can be observed in the vascular phenotype of control (A) and mutant (B) embryos at this stage. (C–J) E10.5 embryos. Although major vitelline vessels are visible in control embryos after dissection (C, arrows), the mutant yolk sac appeares paler (D). In E–H, K, and L, whole-mount staining for PECAM was performed. In E (control) and F (mutant), note the difference in diameter of vitelline (vv) and major vessels (arrowheads) in the yolk sac. In both control (G) and mutant embryos (H), PECAM and nuclear fast red staining of yolk sac sections shows essentially indistinguishable vessels with the presence of endothelial (e), mesothelial (m), blood (b), and endodermal cells (n). (I–L) Umbilical vessels (uv) in 10.5 (I and J) and 11.5 embryos (K and L). In the mutants, umbilical vessels are smaller in diameter, ramified, or anastomosed (J and L) as compared with the control (I and K). h, heart; em, embryo; pl, placenta. Bars, 100 μm.
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fig2: Phenotypic defects in endothelial β-catenin– embryos. (A and B) E9.5 embryos after whole-mount immunohistochemistry with anti-PECAM antibodies. No major differences can be observed in the vascular phenotype of control (A) and mutant (B) embryos at this stage. (C–J) E10.5 embryos. Although major vitelline vessels are visible in control embryos after dissection (C, arrows), the mutant yolk sac appeares paler (D). In E–H, K, and L, whole-mount staining for PECAM was performed. In E (control) and F (mutant), note the difference in diameter of vitelline (vv) and major vessels (arrowheads) in the yolk sac. In both control (G) and mutant embryos (H), PECAM and nuclear fast red staining of yolk sac sections shows essentially indistinguishable vessels with the presence of endothelial (e), mesothelial (m), blood (b), and endodermal cells (n). (I–L) Umbilical vessels (uv) in 10.5 (I and J) and 11.5 embryos (K and L). In the mutants, umbilical vessels are smaller in diameter, ramified, or anastomosed (J and L) as compared with the control (I and K). h, heart; em, embryo; pl, placenta. Bars, 100 μm.

Mentions: At E9.5, endothelial β-catenin mutant mice were morphologically indistinguishable from control littermates and showed a similar vascular pattern in the embryo proper as well as in the yolk sac (Fig. 2, A and B; unpublished data). However, at E10.5, the β-catenin mutant mice had pale and less perfused yolk sacs (Fig. 2, C and D). In the yolk sac of mutant embryos, the primary vascular plexus was present and correctly organized, whereas the vitelline vessels presented a smaller diameter (Fig. 2, E and F). The average diameter of the vitelline vessels connecting the embryo to the yolk sac (Fig. 2, E and F, arrows) was 60 ± 30 μm in the β-catenin mutant mice and 145 ± 10 μm in the control. The maximum diameter of the vitelline vessels in the yolk sac (Fig. 2, E and F, arrowheads) was 82 ± 18 μm in the mutant and 170 ± 20 μm in the control (numbers obtained out of five embryos). The number of branches was not significantly different for the same vessel length comparing mutant and control embryos (6.3 ± 1.1 primary branches in the mutant and 5.3 ± 1.5 in the control for 2 mm length of the major vitelline vessel, measured out of three embryos). Histological sections of the yolk sac showed the presence of endodermal (n), endothelial (e), mesothelial (m), and nucleated blood cells (b) in both control (Fig. 2 G) and mutant (Fig. 2 H) mice. Umbilical vessels were often increased in number, presented a markedly smaller diameter, and were abnormally branched or anastomosed, as compared with controls (Fig. 2, I–L).


The conditional inactivation of the beta-catenin gene in endothelial cells causes a defective vascular pattern and increased vascular fragility.

Cattelino A, Liebner S, Gallini R, Zanetti A, Balconi G, Corsi A, Bianco P, Wolburg H, Moore R, Oreda B, Kemler R, Dejana E - J. Cell Biol. (2003)

Phenotypic defects in endothelial β-catenin– embryos. (A and B) E9.5 embryos after whole-mount immunohistochemistry with anti-PECAM antibodies. No major differences can be observed in the vascular phenotype of control (A) and mutant (B) embryos at this stage. (C–J) E10.5 embryos. Although major vitelline vessels are visible in control embryos after dissection (C, arrows), the mutant yolk sac appeares paler (D). In E–H, K, and L, whole-mount staining for PECAM was performed. In E (control) and F (mutant), note the difference in diameter of vitelline (vv) and major vessels (arrowheads) in the yolk sac. In both control (G) and mutant embryos (H), PECAM and nuclear fast red staining of yolk sac sections shows essentially indistinguishable vessels with the presence of endothelial (e), mesothelial (m), blood (b), and endodermal cells (n). (I–L) Umbilical vessels (uv) in 10.5 (I and J) and 11.5 embryos (K and L). In the mutants, umbilical vessels are smaller in diameter, ramified, or anastomosed (J and L) as compared with the control (I and K). h, heart; em, embryo; pl, placenta. Bars, 100 μm.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172846&req=5

fig2: Phenotypic defects in endothelial β-catenin– embryos. (A and B) E9.5 embryos after whole-mount immunohistochemistry with anti-PECAM antibodies. No major differences can be observed in the vascular phenotype of control (A) and mutant (B) embryos at this stage. (C–J) E10.5 embryos. Although major vitelline vessels are visible in control embryos after dissection (C, arrows), the mutant yolk sac appeares paler (D). In E–H, K, and L, whole-mount staining for PECAM was performed. In E (control) and F (mutant), note the difference in diameter of vitelline (vv) and major vessels (arrowheads) in the yolk sac. In both control (G) and mutant embryos (H), PECAM and nuclear fast red staining of yolk sac sections shows essentially indistinguishable vessels with the presence of endothelial (e), mesothelial (m), blood (b), and endodermal cells (n). (I–L) Umbilical vessels (uv) in 10.5 (I and J) and 11.5 embryos (K and L). In the mutants, umbilical vessels are smaller in diameter, ramified, or anastomosed (J and L) as compared with the control (I and K). h, heart; em, embryo; pl, placenta. Bars, 100 μm.
Mentions: At E9.5, endothelial β-catenin mutant mice were morphologically indistinguishable from control littermates and showed a similar vascular pattern in the embryo proper as well as in the yolk sac (Fig. 2, A and B; unpublished data). However, at E10.5, the β-catenin mutant mice had pale and less perfused yolk sacs (Fig. 2, C and D). In the yolk sac of mutant embryos, the primary vascular plexus was present and correctly organized, whereas the vitelline vessels presented a smaller diameter (Fig. 2, E and F). The average diameter of the vitelline vessels connecting the embryo to the yolk sac (Fig. 2, E and F, arrows) was 60 ± 30 μm in the β-catenin mutant mice and 145 ± 10 μm in the control. The maximum diameter of the vitelline vessels in the yolk sac (Fig. 2, E and F, arrowheads) was 82 ± 18 μm in the mutant and 170 ± 20 μm in the control (numbers obtained out of five embryos). The number of branches was not significantly different for the same vessel length comparing mutant and control embryos (6.3 ± 1.1 primary branches in the mutant and 5.3 ± 1.5 in the control for 2 mm length of the major vitelline vessel, measured out of three embryos). Histological sections of the yolk sac showed the presence of endodermal (n), endothelial (e), mesothelial (m), and nucleated blood cells (b) in both control (Fig. 2 G) and mutant (Fig. 2 H) mice. Umbilical vessels were often increased in number, presented a markedly smaller diameter, and were abnormally branched or anastomosed, as compared with controls (Fig. 2, I–L).

Bottom Line: We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered.These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability.We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts.

View Article: PubMed Central - PubMed

Affiliation: FIRC Institute of Molecular Oncology, 16-20139, Milan, Italy.

ABSTRACT
Using the Cre/loxP system we conditionally inactivated beta-catenin in endothelial cells. We found that early phases of vasculogenesis and angiogenesis were not affected in mutant embryos; however, vascular patterning in the head, vitelline, umbilical vessels, and the placenta was altered. In addition, in many regions, the vascular lumen was irregular with the formation of lacunae at bifurcations, vessels were frequently hemorrhagic, and fluid extravasation in the pericardial cavity was observed. Cultured beta-catenin -/- endothelial cells showed a different organization of intercellular junctions with a decrease in alpha-catenin in favor of desmoplakin and marked changes in actin cytoskeleton. These changes paralleled a decrease in cell-cell adhesion strength and an increase in paracellular permeability. We conclude that in vivo, the absence of beta-catenin significantly reduces the capacity of endothelial cells to maintain intercellular contacts. This may become more marked when the vessels are exposed to high or turbulent flow, such as at bifurcations or in the beating heart, leading to fluid leakage or hemorrhages.

Show MeSH
Related in: MedlinePlus