The Matricellular Protein Cysteine-Rich Protein 61 (Cyr61/CCN1) Prevents Blood Vessel Loss and Induces Blood Vessel Regrowth in a Mouse Model of Oxygen-Induced Retinopathy

Abstract

Purpose: : Structural and functional damage to existing blood vessels and inappropriate development of new vessels are hallmark features of ischemic retinopathies (IR). Yet while the histological features of IR are well characterized many key modulators remain unknown. Previously, we showed that the inducible matricellular protein, cysteine-rich protein 61 (Cyr61/CCN1), is required for proper angiogenesis and vasculogenesis during fetal tissue development. Cyr61 protein acts through activation of Notch and Wnt signaling pathways to provide blood vessel stability and/or growth. This study investigates the expression pattern of Cyr61/CCN1 during retinal vascular development and its effects on retinal angiogenesis in the mouse model of oxygen-induced retinopathy (OIR).

Methods: : Expression pattern of the Cyr61 gene was examined during retinal vessel development and upon induction of OIR. Tissue localization of Cyr61 was performed on whole mount retinas and in radial sections. Recombinant (r) Cyr61 protein was injected into the vitreous of neonatal mice undergoing OIR at either P7 or P12. Mice were sacrificed at post natal day 17 and the degree of angiogenesis was evaluated by retinal flat mounts and cross sections.

Results: : Postnatal development of retinal vessels was associated with increased expression of the Cyr61 mRNA with a progressive decrease in expression as the retina became fully vascularized. Cyr61 immunoreactivity localized to both the superficial and deep retinal vessel layers. Development of preretinal neovasularization in the OIR model was associated with decreased expression of the Cyr61mRNA. Intravitreal injection of rCyr61 increased tight junction formation, reduced areas of vaso-obliteration and the development of preretinal neovascularization compared to control saline injected pups.

Conclusions: : The ability of Cyr61 to limit vessel loss and enhance vessel regrowth suggests its possible therapeutic potential in preventing or reducing the risk of IR.

Keywords: retinopathy of prematurity • extracellular matrix • ischemia