Intravitreal Delivery of VEGF-A₁₆₅-loaded PLGA Microparticles Reduces Retinal Vaso-Obliteration in an In Vivo Mouse Model of Retinopathy of Prematurity

ABSTRACT

Purpose: Retinopathy of prematurity (ROP) is a condition of abnormal retinal vascularization with reduced levels of vascular endothelial growth factor (VEGF) causing vaso-obliteration (Phase I), followed by abnormal neovascularization from increased VEGF (Phase II). We hypothesized that intravitreal pro-angiogenic VEGF-A in microparticle form would promote earlier retinal revascularization in an oxygen-induced ischemic retinopathy (OIR) mouse model.

Materials and Methods: Wildtype mice (39) were exposed to 77% oxygen from postnatal day 7 (P7) to P12. VEGF-A₁₆₅-loaded poly(lactic-co-glycolic acid) (PLGA) (n = 15) or empty PLGA (n = 14) microparticles were fabricated using a water-in-oil-in-water double emulsion method, and injected intravitreally at P13 into mice right eyes (RE). Left eyes (LE) were untreated. At P20, after retinal fluorescein angiography, vascular parameters were quantified. Retinal VEGF levels at P13 and flatmounts at P20 were performed separately.

Results: VEGF-A₁₆₅-loaded microparticles had a mean diameter of 4.2 μm. with a loading level of 8.6 weight.%. Retinal avascular area was reduced in VEGF-treated RE (39.5 ± 9.0%) compared to untreated LE (52.6 ± 6.1%, p < 0.0001) or empty microparticle-treated RE (p < 0.001) and untreated LEs (p = 0.001). Retinal arteries in VEGF-treated RE were less tortuous than untreated LE (1.08 ± 0.05 vs. 1.18 ± 0.08, p < 0.001) or empty-microparticles-treated RE (p = 0.02). Retinal arterial tortuosity was similar in the LE of VEGF and empty microparticle-treated mice (P > 0.05). Retinal vein width was similar in VEGF-treated and empty microparticle-treated RE (P > 0.9), which were each less dilated than their contralateral LE (p < 0.01). VEGF levels were higher in P13 OIR mice than RA mice (p < 0.0001). Retinal flatmounts showed vaso-obliteration and neovascularization.

Conclusions: Endogenous retinal VEGF is suppressed in OIR mice. Exogenous intravitreal VEGF-A₁₆₅-loaded microparticles in OIR mice reduced retinal vaso-obliteration and accelerated recovery from vein dilation and arterial tortuosity. This may be beneficial in preventing Phase II ROP without systemic effects.

KEYWORDS:

• Retinopathy of prematurity
• vascular endothelial growth factor
• microparticle
• oxygen-induced retinopathy
• retinal angiogenesis

Acknowledgments

The authors thank Ellen R. Wald, MD (Department of Pediatrics, University of Wisconsin) and Pam Kling, MD (Department of Pediatrics, University of Wisconsin) for their review of the manuscript. The authors also thank Nasim Jamali, PhD and Andrew Suscha for their assistance with retinal ELISA and flatmount studies.

Disclosure statement

No potential conflict of interest was reported by the authors.

Financial Support

University of Wisconsin Department of Pediatrics and School of Graduate Studies (to Mezu-Ndubuisi); NIH 1K25CA166178 and R01 HL129785 (to Gong). The work in NS lab is supported by an unrestricted award from Research to Prevent Blindness to the Department of Ophthalmology and Visual Sciences, Retina Research Foundation, P30 EY016665, EPA 83573701, and EY026078. NS is a recipient of RPB Stein Innovation Award.

Additional information

Funding

This work was supported by the University of Wisconsin Department of Pediatrics and School of Graduate Studies; National Eye Institute [EY026078, P30 EY016665]; Retina Research Foundation; NIH [1K25CA166178]; Environmental Protection Agency [EPA 83573701]; Research to Prevent Blindness; NIH [R01 HL129785].