Mechanisms of Repair and Remodeling of the Retinal Vasculature by Vascular Progenitor Cells in a Mouse Model of Retinopathy of Prematurity (ROP)

Abstract

Purpose : We asked if intravitreal administration of the reparative cell populations, CD34⁺ cells (bone marrow-derived) and/or endothelial colony forming cells (ECFCs) (vascular wall-derived) could protect the retina in the oxygen-induced retinopathy (OIR) model by promoting vascular repair and remodeling.

Methods : OIR mouse model was used. Each pup received a single intravitreal injection of cells (human CD34⁺ isolated from peripheral blood, 10,000 cells; ECFCs-cord blood derived and expanded in culture, 100,000 cells; combination of CD34⁺ and ECFCs, 110,000 cells). Experimental groups differed based on injection/euthanasia times (P5/P12, P5/P17, P12/P17). Whole retinas were stained for collagen IV to assess vaso-obliteration (VO) and neovascularization (NV). Additional immunohistochemical studies were performed to localize distribution of injected vascular progenitor cells and to examine blood vessel maturity. Proteomic analysis was performed on isolated pup retinas.

Results : Maximum VO was seen in the saline and CD34⁺ pups of the P5/P12 group (Saline = 22.3 ± 0.4%; CD34⁺ = 23.4 ± 0.8%, p = 0.1), while ECFCs and Combination showed significant reduction (ECFCs =1 8.4 ± 1.3%, p < 0.05; Combination = 20.0 ± 0.7%, p < 0.05). Cell injection at P12 reduced VO in all groups when compared to saline (Saline = 13.9 ± 0.9%; CD34⁺ = 5.7 ± 1.0%, p < 0.05; ECFC = 8.1 ± 0.7%, p < 0.05; Combination = 7.4 ± 1.0%, p < 0.05) and reduced NV (Saline = 13.3 ± 1.3%; CD34⁺ = 3.5 ± 1.1%, p < 0.05; ECFC = 2.8 ± 0.7%, p < 0.05; Combination = 4.1 ± 0.6%, p < 0.05). Injection of either cell type alone at P5 did not prevent NV at P17; however, the combination of cells prevented NV. P5-injected ECFCs incorporated into, and stimulated Deep Vascular Plexus formation by P12. Proteomic analysis demonstrated that in OIR, FAK expression is increased by 14.3 ± 0.3% (p < 0.05), MMP2 by 25.2 ± 0.3% (p < 0.05) while PTEN is reduced by 15.7 ± 0.2% (p < 0.05). However, treatment with CD34⁺ cells, ECFCs or their combination returns their expression to normoxic levels.

Conclusions : CD34⁺ cells and ECFCs and their combination reduced retinal VO and NV. In a hyperoxic environment the combination of cells orchestrates acceleration of vascular remodeling (stabilization and ensheathment) via PTEN, MMP2 and FAK pathways.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.