Hyperoxia-Induced Proliferative Retinopathy: Early Interruption of Retinal Vascular Development with Severe and Irreversible Neurovascular Disruption

Abstract

Bronchopulmonary dysplasia (BPD) is a major cause of neonatal morbidity in premature infants, occurring as a result of arrested lung development combined with multiple postnatal insults. Infants with BPD exposed to supplemental oxygen are at risk of retinopathy of prematurity as well. Thus, we studied the effects of hyperoxia on the retinal vasculature in a murine model of BPD. The retinal phenotype of this model, which we termed hyperoxia-induced proliferative retinopathy (HIPR), shows severe disruption of retinal vasculature and loss of vascular patterning, disorganized intra-retinal angiogenesis, inflammation and retinal detachment. Neonatal mice were subjected to 75% oxygen exposure from postnatal day (P)0 to P14 to model BPD, then allowed to recover in room air for 1 (P15), 7 (P21), or 14 days (P28). We quantified retinal thickness, protein levels of HIF-1α, NOX2, and VEGF, and examined the cellular locations of these proteins by immunohistochemistry. We examined the retinal blood vessel integrity and inflammatory markers, including macrophages (F4/80) and lymphocytes (CD45R). Compared to controls, normal retinal vascular development was severely disrupted and replaced by a disorganized sheet of intra-retinal angiogenesis in the HIPR mice. At all time-points, HIPR showed persistent hyaloidal vasculature and a significantly thinner central retina compared to controls. HIF-1α protein levels were increased at P15, while VEGF levels continued to increase until P21. Intra-retinal fibrinogen was observed at P21 followed by sub-retinal deposition in at P28. Inflammatory lymphocytes and macrophages were observed at P21 and P28, respectively. This model presents a severe phenotype of disrupted retinal vascular development, intra-retinal angiogenesis inflammation and retinal detachment.

Risk Factors of Retinopathy of Prematurity Associated with Delayed Retinal Vascular Development

“…We found that many factors may be involved in this Phase I of ROP, causing a greater delay in vascular development (31).…”

Photoreceptor oxidative stress in hyperoxia-induced proliferative retinopathy accelerates rd8 degeneration

“…We previously reported significant disruption of the retinal vascular development, with persistent hyaloidal vessels in B6J HIPR [ 14 ]. Comparing the B6J and B6N strains in HIPR, retinal flat mounts stained with IB4, an endothelial cell marker, were assessed at P21 and P28.…”

“…The C57BL/6N mice carry the rd8 mutation while the C57BL/6J mice carry the wild-type Crb1 gene [ 15 , 16 ]. We have recently characterized the retinopathy in the HIPR model [ 14 , 17 , 18 ]. Briefly, newborn pups are placed in a Plexiglas chamber with an oxygen controller (Pro-Ox 110; Biospherix, Lacona, NY) and exposed to 75% oxygen from birth to P14.…”

“…We used the hyperoxia-induced proliferative (HIPR) model [14], where new-born pups are placed in high oxygen (75%) for 14 days. In the current study, we compared the effects of HIPR in two mouse strains: C57BL/6J (B6J) and C57BL/6N (B6N).…”

“…Given the importance of Crb1 in regulating Rac1 and limiting the production of photoreceptor superoxide, we sought to explore the effect of neonatal hyperoxia and neonatal proliferative retinopathy on mice carrying the rd8 mutation. We used the hyperoxia-induced proliferative (HIPR) model [ 14 ], where new-born pups are placed in high oxygen (75%) for 14 days. In the current study, we compared the effects of HIPR in two mouse strains: C57BL/6J (B6J) and C57BL/6N (B6N).…”