Department of Neonatology, Children's Hospital of Zhengzhou

Retinopathy of prematurity (ROP) is a major cause of blindness and visual impairment in children in both developing and developed countries around the world. ROP is a multifactorial disease characterized by perturbation of normal vascular development in the retina. The pathogenesis of ROP is hypothesized to consist of two distinct phases of which the second phase is characterized by hypoxia-induced up-regulation of vascular endothelial growth factor (VEGF) and retinal neovascularization.

Recent studies have shown a relationship between the β-adrenergic system and angiogenesis. This relationship has been observed in several diseases, like infantile hemangiomas, ROP, and neoplasias. Studies in animal models have shown that norepinephrine stimulates VEGF expression and secretion in retinal cells. In oxygen induced retinopathy, blockage of β-adrenergic receptors (β-AR) can inhibit the angiogenic cascade and interfere with further proliferation of retinal vasculature. Also, angiogenesis seems to be impaired in β-Argene deficient mice, when exposed to hypoxia and other stimuli, but this function is restored after gene therapy.

An association between ROP and infantile hemangiomas was observed over 50 years ago with a higher prevalence of ROP in children with hemangiomas. Studies have also shown that β-AR blockage reduces VEGF levels and favors the regression of infantile hemangiomas. The treatment of choice in threshold stages of ROP is laser photocoagulation and/or intravitreal bevacizumab injections, but management of early stages of ROP, until now has been expectant, with ophthalmologic follow-up but no therapeutic interventions to prevent its progression.

Propranolol is a non-selective β-AR blocker, with equal affinity for β1 and β2 receptors. It has a systemic effect, and acts in different tissues. In vivo models of proliferative retinopathies have shown a strong inhibitory role of β-AR on vascular changes. In particular, β2-AR seems to be the most involved in these responses

. Propranolol has shown to be highly effective in inhibiting both the increase of VEGF expression caused by a hypoxic insult, and the consequent neovascular Response. Studies have shown that propranolol reduces the overproduction of VEGF in oxygen induced retinopathy, but VEGF levels remain unchanged in the normal retina. Assuming in human preterm newborns with ROP that VEGF overexpression and retinal neovascularization in response to hypoxia might involve b-AR activation, we design prospective randomized study to assess the effect of oral propranolol on the progression of early stages of ROP in very low birth weight infants.