Abstract
Purpose. The aim of this study was to investigate and quantify changes in the newborn rats retinal layers during the hyperoxia (80% O2) exposure using fractal analysis. Materials and Methods. This study was conducted on two groups of 20 newborn rats: a control (normal) group (10 rats) and an experimental group (10 rats). The control group was composed of 10 newborn rats, which were placed at 12 hours after birth, in a pediatric incubator, together with their mother, in conditions of normoxia for 21 days. The experimental group consisted of 10 newborn rats, which were placed at 12 hours after birth, in a pediatric incubator with their mother, in conditions of normoxia for 7 days, then 7 days of hyperoxia (80% O2) for 22.5 hours/day, and then 7 days in conditions of normoxia. Slaughtering of the rats was performed on day 21 and the eye globes were harvested in order to perform histopathological examinations. The fractal analyses of the retinal digital images were performed using the fractal analysis software Image J, and the fractal dimensions were calculated using the standard box-counting method. Results. Microscopic examination revealed a normal development of the retina in the control group. In the experimental group, all the animals exposed to hyperoxia revealed both structural and vascular abnormalities on entire retina. Conclusions. The results showed that the fractal analysis is a valuable tool to quantify histoarchitectural changes in the newborn rats retinal layers during the hyperoxia (80% O2).
Highlights
In the last few decades important efforts have been directed to understand various aspects of the newborn rats retinal layers, for clinical diagnostics and treatment [1,2,3,4].The rat’s retina is immature at birth, being comparable with that from human fetuses of 26 weeks, and allows tracking its development postnatally [1]
All histological sections made showed a normal aspect of the retinal vessels and retinal layers (Figure 1)
Some remarks can be obtained concerning the results from Table 1: (i) the average of fractal dimensions (D) of the pathological retinal layers is slightly lower than the normal cases; (ii) the fractal analysis was in agreement with the histological observations
Summary
In the last few decades important efforts have been directed to understand various aspects of the newborn rats retinal layers, for clinical diagnostics and treatment [1,2,3,4].The rat’s retina is immature at birth, being comparable with that from human fetuses of 26 weeks, and allows tracking its development postnatally [1]. Exposure to oxigen of rat pups retina, during the first days after birth, develops an oxygen-induced retinopathy (OIR), similar to human retinopathy of prematurity (ROP) [2,3,4]. The cycle hyperoxia-normoxia mimics ischemia-reperfusion and leads to retinal neovascularization [2,3,4, 10,11,12]. This experimental model could be useful in the study of angiogenesis occurring in other potentially blinding retinal diseases (e.g., diabetes), cancer, and degenerative diseases and in the study of the effect of some substances with
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