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Endothelium Expression of Bcl-2 Is Essential for Normal and Pathological Ocular Vascularization.

Zaitoun IS, Johnson RP, Jamali N, Almomani R, Wang S, Sheibani N, Sorenson CM - PLoS ONE (2015)

Bottom Line: In vitro studies indicated that in addition to modulating apoptosis, Bcl-2 expression also impacts endothelial and epithelial cell adhesion, migration and extracellular matrix production.However, studies delineating the cell autonomous role Bcl-2 expression plays in the endothelium during vascular development, pruning and remodeling, and neovascularization are lacking.Thus, Bcl-2 expression in the endothelium plays a significant role during postnatal retinal vascularization, and pathological choroidal but not retinal neovascularization, suggesting vascular bed specific Bcl-2 function in the endothelium.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI, 53705, United States of America.

ABSTRACT
Bcl-2 is an anti-apoptotic protein with important roles in vascular homeostasis and angiogenesis. Mice globally lacking Bcl-2 (Bcl-2 -/-) are small in stature and succumb to renal failure shortly after weaning as a result of renal hypoplasia/cystic dysplasia. We have shown that Bcl-2 -/- mice displayed attenuated retinal vascular development and neovascularization. In vitro studies indicated that in addition to modulating apoptosis, Bcl-2 expression also impacts endothelial and epithelial cell adhesion, migration and extracellular matrix production. However, studies delineating the cell autonomous role Bcl-2 expression plays in the endothelium during vascular development, pruning and remodeling, and neovascularization are lacking. Here we generated mice carrying a conditional Bcl-2 allele (Bcl-2Flox/Flox) and VE-cadherin-cre (Bcl-2EC mice). Bcl-2EC mice were of normal stature and lifespan and displayed some but not all of the retinal vascular defects previously observed in global Bcl-2 deficient mice. Bcl-2EC mice had decreased numbers of endothelial cells, decreased retinal arteries and premature primary branching of the retinal vasculature, but unlike the global knockout mice, spreading of the retinal superficial vascular layer proceeded normally. Choroidal neovascularization was attenuated in Bcl-2EC mice, although retinal neovascularization accompanying oxygen-induced ischemic retinopathy was not. Thus, Bcl-2 expression in the endothelium plays a significant role during postnatal retinal vascularization, and pathological choroidal but not retinal neovascularization, suggesting vascular bed specific Bcl-2 function in the endothelium.

No MeSH data available.


Related in: MedlinePlus

Premature primary branching in Bcl-2EC mice.Retinas from P21 mice were wholemount stained with anti-α-smooth muscle actin, Panel A (scale bar = 400 μm). The distance of primary (arrow) and secondary branches (arrowhead) for the center of the optic nerve were determined as shown in Panels B (**P< 0.001) and C (*P< 0.05) respectively. Panel D demonstrates the numbers of secondary branch points off the retinal arteries. In Panel E, photomicrographs were taken of retinal arteries near the optic nerve (scale bar = 200 μm). Please note symmetrical branching of retinal arteries from wild-type mice. Experiments were repeated with eyes from at least 5 mice with similar results.
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pone.0139994.g003: Premature primary branching in Bcl-2EC mice.Retinas from P21 mice were wholemount stained with anti-α-smooth muscle actin, Panel A (scale bar = 400 μm). The distance of primary (arrow) and secondary branches (arrowhead) for the center of the optic nerve were determined as shown in Panels B (**P< 0.001) and C (*P< 0.05) respectively. Panel D demonstrates the numbers of secondary branch points off the retinal arteries. In Panel E, photomicrographs were taken of retinal arteries near the optic nerve (scale bar = 200 μm). Please note symmetrical branching of retinal arteries from wild-type mice. Experiments were repeated with eyes from at least 5 mice with similar results.

Mentions: The processes involved in determination of retinal artery number are not well understood. We next examined whether Bcl–2 expression in endothelial cells impacted the number of major arteries or veins in the retina. Fig 2A demonstrates retinas from P21 wild-type and Bcl-2EC mice wholemount stained with SMA and collagen IV. Typically in wild-type mice we noted 5–6 retinal arteries (5.57 ± 0.17 arteries; Fig 2B). However, in the absence of endothelial Bcl–2 expression we noted a decreased number of retinal arteries (4.68 ± 0.78 arteries; Fig 2B), which coincided with decreased number of retinal veins (5±0 WT vs. 3.8± 0.3 Bcl-2EC; Fig 2C). Primary and secondary branching off of the retinal artery was also aberrant in Bcl-2EC mice. Primary branching occurred prematurely in the absence of endothelial Bcl–2 expression (Fig 3B), while secondary branching was observed at a greater distance from the optic nerve (Fig 3C) and demonstrated fewer secondary arterial branch points (Fig 3D) than in wild-type mice. Next we examined bifurcation of the retinal artery near the optic nerve at higher magnification (Fig 3E). Typically bifurcation of the retinal artery occurred near the optic nerve in wild-type mice. In contrast, in Bcl-2EC mice the branching of the retinal artery was aberrant, appearing as if branching occurs too late after the central retinal artery pierces the optic nerve. Thus, Bcl-2EC mice demonstrated decreased artery numbers and aberrant branching.


Endothelium Expression of Bcl-2 Is Essential for Normal and Pathological Ocular Vascularization.

Zaitoun IS, Johnson RP, Jamali N, Almomani R, Wang S, Sheibani N, Sorenson CM - PLoS ONE (2015)

Premature primary branching in Bcl-2EC mice.Retinas from P21 mice were wholemount stained with anti-α-smooth muscle actin, Panel A (scale bar = 400 μm). The distance of primary (arrow) and secondary branches (arrowhead) for the center of the optic nerve were determined as shown in Panels B (**P< 0.001) and C (*P< 0.05) respectively. Panel D demonstrates the numbers of secondary branch points off the retinal arteries. In Panel E, photomicrographs were taken of retinal arteries near the optic nerve (scale bar = 200 μm). Please note symmetrical branching of retinal arteries from wild-type mice. Experiments were repeated with eyes from at least 5 mice with similar results.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4622043&req=5

pone.0139994.g003: Premature primary branching in Bcl-2EC mice.Retinas from P21 mice were wholemount stained with anti-α-smooth muscle actin, Panel A (scale bar = 400 μm). The distance of primary (arrow) and secondary branches (arrowhead) for the center of the optic nerve were determined as shown in Panels B (**P< 0.001) and C (*P< 0.05) respectively. Panel D demonstrates the numbers of secondary branch points off the retinal arteries. In Panel E, photomicrographs were taken of retinal arteries near the optic nerve (scale bar = 200 μm). Please note symmetrical branching of retinal arteries from wild-type mice. Experiments were repeated with eyes from at least 5 mice with similar results.
Mentions: The processes involved in determination of retinal artery number are not well understood. We next examined whether Bcl–2 expression in endothelial cells impacted the number of major arteries or veins in the retina. Fig 2A demonstrates retinas from P21 wild-type and Bcl-2EC mice wholemount stained with SMA and collagen IV. Typically in wild-type mice we noted 5–6 retinal arteries (5.57 ± 0.17 arteries; Fig 2B). However, in the absence of endothelial Bcl–2 expression we noted a decreased number of retinal arteries (4.68 ± 0.78 arteries; Fig 2B), which coincided with decreased number of retinal veins (5±0 WT vs. 3.8± 0.3 Bcl-2EC; Fig 2C). Primary and secondary branching off of the retinal artery was also aberrant in Bcl-2EC mice. Primary branching occurred prematurely in the absence of endothelial Bcl–2 expression (Fig 3B), while secondary branching was observed at a greater distance from the optic nerve (Fig 3C) and demonstrated fewer secondary arterial branch points (Fig 3D) than in wild-type mice. Next we examined bifurcation of the retinal artery near the optic nerve at higher magnification (Fig 3E). Typically bifurcation of the retinal artery occurred near the optic nerve in wild-type mice. In contrast, in Bcl-2EC mice the branching of the retinal artery was aberrant, appearing as if branching occurs too late after the central retinal artery pierces the optic nerve. Thus, Bcl-2EC mice demonstrated decreased artery numbers and aberrant branching.

Bottom Line: In vitro studies indicated that in addition to modulating apoptosis, Bcl-2 expression also impacts endothelial and epithelial cell adhesion, migration and extracellular matrix production.However, studies delineating the cell autonomous role Bcl-2 expression plays in the endothelium during vascular development, pruning and remodeling, and neovascularization are lacking.Thus, Bcl-2 expression in the endothelium plays a significant role during postnatal retinal vascularization, and pathological choroidal but not retinal neovascularization, suggesting vascular bed specific Bcl-2 function in the endothelium.

View Article: PubMed Central - PubMed

Affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI, 53705, United States of America.

ABSTRACT
Bcl-2 is an anti-apoptotic protein with important roles in vascular homeostasis and angiogenesis. Mice globally lacking Bcl-2 (Bcl-2 -/-) are small in stature and succumb to renal failure shortly after weaning as a result of renal hypoplasia/cystic dysplasia. We have shown that Bcl-2 -/- mice displayed attenuated retinal vascular development and neovascularization. In vitro studies indicated that in addition to modulating apoptosis, Bcl-2 expression also impacts endothelial and epithelial cell adhesion, migration and extracellular matrix production. However, studies delineating the cell autonomous role Bcl-2 expression plays in the endothelium during vascular development, pruning and remodeling, and neovascularization are lacking. Here we generated mice carrying a conditional Bcl-2 allele (Bcl-2Flox/Flox) and VE-cadherin-cre (Bcl-2EC mice). Bcl-2EC mice were of normal stature and lifespan and displayed some but not all of the retinal vascular defects previously observed in global Bcl-2 deficient mice. Bcl-2EC mice had decreased numbers of endothelial cells, decreased retinal arteries and premature primary branching of the retinal vasculature, but unlike the global knockout mice, spreading of the retinal superficial vascular layer proceeded normally. Choroidal neovascularization was attenuated in Bcl-2EC mice, although retinal neovascularization accompanying oxygen-induced ischemic retinopathy was not. Thus, Bcl-2 expression in the endothelium plays a significant role during postnatal retinal vascularization, and pathological choroidal but not retinal neovascularization, suggesting vascular bed specific Bcl-2 function in the endothelium.

No MeSH data available.


Related in: MedlinePlus