Submitted on December 15, 2007
Revised on April 11, 2008
Accepted on April 11, 2008
Attenuation of Retinal Endothelial Cell Migration and Capillary Morphogenesis in the Absence of Bcl-2
Shuji Kondo1, Yixin Tang2, Elizabeth A Scheef3, Nader Sheibani3, and Christine M. Sorenson4*
1 The University of Tokushima Graduate School of Medical Sciences
2 University of Wisconsin school of Medicine and Public Health
3 University of Wisconsin School of Medicine and Public Health
4 University of Wisconsin Medical School
* To whom correspondence should be addressed. E-mail: cmsorenson{at}wisc.edu.
Apoptosis plays a critical role during development and in the maintenance of the vascular system. B cell leukemia lymphoma 2 (bcl-2) protects endothelial cells (EC) from apoptosis in response to a variety of stimuli. Previous work from this laboratory demonstrated attenuation of postnatal retinal vascular development and retinal neovascularization during oxygen-induced ischemic retinopathy in bcl-2 deficient (bcl-2-/-) mice. To gain further insight into the function of bcl-2 in the endothelium we isolated retinal EC from bcl-2+/+ and bcl-2-/- mice. Retinal EC lacking bcl-2 demonstrated reduced cell migration, tenascin-C expression, and adhesion to vitronectin and fibronectin. The bcl-2-/- retinal EC also failed to undergo capillary morphogenesis in Matrigel. In addition, using an ex vivo angiogenesis assay we observed reduced sprouting from aortic rings grown in culture from bcl-2-/- mice compared to bcl-2+/+ mice. Furthermore, re-expression of bcl-2 was sufficient to restore migration and capillary morphogenesis defects observed in bcl-2-/- retinal EC. Mechanistically, bcl-2-/- cells expressed significantly less endothelial nitric oxide synthase (eNOS), an important downstream effecter of proangiogenic signaling. This may be attributed to increased oxidative stress in the absence of bcl-2. In fact, incubation of retinal EC or aortic rings from bcl-2-/- mice with the antioxidant N-acetylcysteine rescued their capillary morphogenesis and sprouting defects. Thus, bcl-2-mediated cellular functions play important roles not only in survival but also in proangiogenic phenotype of EC with a significant impact on vascular development and angiogenesis.
