Contrast of retinal structure and function developing of premature rats versus full-term newborn rats

Background

Premature birth is a high risk factor of abnormal development in the morphology and function of vision system.To observe the effect of premature birth on the structural and functional development of neonatal retina is of great importance.

Objective

This study aimed to compare the differences of retinal structure and function between premature rats and normal rats.

Methods

Twenty-eight gestational SD rats were randomized to bacterial lipopolysaccharide (LPS)-induced preterm (LP) group, mifepristone-induced preterm (RP) group, cesarean section-induced preterm (CP) group and normal control group, with 10-12 rats from each nest.LPS (20 μg/kg) or mifepristone (10 mg/kg) was injected on the 18 th day of gestation in the LP group and RP group, respectively, to establish premature birth rat models, and cesarean delivery was performed on the 19 th day of gestation in the CP group.Full-term newborn rats born in 22 days after gestation in the normal group.Systemic circulatory perfusion was carried out in the neonatal rats using normal saline solution and 4% triformal on postnetal 4, 7, 10 and 14 days and then the retinal sections of the left eyes were prepared for the hematoxylin and eosin staining to examin the retinal layers and cells counting.Electroretinogram (ERG) based on international standardization was recorded in the rats on postnetal 14, 21 and 28 days to evaluate the retinal function.All the results were compared between the premature rats and the normal rats.The use and care of the animals complied with the Regulations for the Administraion of Affair Concerning Experimental animals by State Science and Technology Commission.

Results

The number of neuroblast layers was more on postnetal 4-day and 7-day rats in the LP group, CP group and the RP group than those in the normal control group (LP: t=-7.07, -4.97, both at P<0.01; CP: t=-6.45, -3.61, both at P<0.01; RP: t=-6.38, -3.35, both at P=0.00). No significant difference was found in the number of inner and outer nuclear layers in postnetal 10-day and 14-day rats between the normal group and LP group, CP group or RP group (all at P>0.05). Compared with the normal group, the amplitudes of Rod-b wave, Max-a and b waves, oscillatory potentials (OPs), Cone-b wave and flicker ERG were not significantly changed on postnetal 14-day, 21-day and 28-day rats among the LP group, CP group and RP group (all at P>0.05). However, the latencies of Max-a and b waves were significantly extended on postnetal 14-day rats in the LP group (t =-3.94, -3.31, all at P<0.01), and the latencies of Rod-b wave, Max-b wave and Cone-b wave were prolonged in the CP group in comparison with the normal group (t=-2.42, -2.61, -2.16, all at P =0.02). Also, the latency of Max-b wave was extended in the RP group in comparison with the normal group (t=-3.67, P<0.01). In addition, the latencies of Max-a and b waves in 21-day rats and Max-b latency in 28-day rats in the LP group were significantly longer than those in the normal group (t =-3.18, -3.45, -3.61, all at P<0.01).

Conclusions

The developing lags of retinal structure and function propably are the anatomical basis of preterm children prone to retinal diseases.

Premature/chemically and surgery induced; Gestational age; Animals, newborn; Development; Retina; Electroretinogram; Structure; Rats, Sprague Dawley