Abstract
Purpose:
Preterm birth seems to affect the retinal vascular system resulting in a lower threshold for the development of vascular diseases, such as retinopathy of prematurity (ROP). Oxygen-induced retinopathy (OIR) model is used widely for studying the pathogenesis of ROP. The general condition at birth and after birth of the termly born animal used in OIR model may be different from that of the preterm infant. So as to simulate the clinical features of preterm infants in animals and to provide some basic data for further studying the multiple effects of many risk factors on ROP, this study was designed to investigate the effect of preterm birth on the normal postnatal vascularization of the retina and OIR in neonatal rat.
Methods:
Newborn Sprague-Dawley (SD) rats were delivered prematurely at day 19 of gestation by caesarean section from pregnant female rats. After birth, preterm pups and surrogate mothers were housed in either room air or a chamber with cyclic oxygen for two weeks followed by 4-8 more days in room air. Naturally delivered term pups placed in room air or oxygen chamber were used as control. Retinas of pups in room air on postnatal day 4, 7, 10, 14, 18 and 22 as well as pups in oxygen chamber on day 14, 18 and 22 were dissected, whole-mounted and stained using Griffonia simplicifolia isolectin-B4 (GSA I-B4). On day 18, retinal cross-sections were stained with hematoxylin and eosin (H&E) to identify the preretinal neovascular tufts. Images were captured by fluorescence and light microscope. Avascular or neovascular areas of retinas were measured and compared.
Results:
Preterm rat pups had significantly larger retinal avascular areas than term rat pups on different postnatal days (P<0.001). After exposure to cyclic oxygen, preterm pups showed significantly larger retinal avascular areas on day 14 and 18 and larger retinal neovascular areas on day 18 than term pups (P<0.001, respectively). On day 22, residual retinopathy of preterm pups was more than term pups (P<0.01).
Conclusions:
Preterm birth induced by caesarean section had negative effects on normal retinal vascularization of rat pups. The immature vasculature of preterm pups was more easily susceptible to the damage of oxygen resulting in more severe and durable retinopathy than term pups.
Keywords: 698 retinal development •
688 retina •
635 oxygen