ABSTRACT
Objective To observe the apoptosis of retina and the expression of caspase-3 in mice with premature myopia and to explore the pathogenesis of premature myopia.Methods Together 60 newborn C57BL/6J mice were selected and divided randomly into three groups (n =20):P6 group (opening the eyelid on day 6 after birth),P10 group (opening the eyelid on day 10 after birth) and normal group (opening the eyelid naturally).The right eyes of mice in the P6 and P10 group were subjected to lighting exposure,and the left eyes were left untreated serving controls with its right eyes;while the eyes in the normal group open naturally without any treatment.Then the refraction was checked on day 15 through retinophotoscopy,and ocular axial length was measured by micrometer with electronic digital display.TUNEL assay was used to determine retinal apoptosis.Immunohistochemistry and Western blot were used to detect the expression of caspase-3 in mice retina.Results The right eyes developed significant myopia in the P6 group [(-7.55 ±0.15)D] and P10 group [(-5.25 ±0.10)D],while the eyes in the normal group did not suffer from myopia,and there was significant difference in the three groups (P ＜0.05).The average axial length of right eyes in the P6 group [(2.49 ± 0.08) mm] and the P10 group [(2.51 ±0.03)mm] was shorter than that in the normal group [(2.58 ± 0.04) mm],with significant difference (P ＜ 0.05).Immunohistochemistry showed that the expression of caspase-3 had a dramatically increase in ganglion cell layer and inner nuclear layer of retina of mice in P6 group and P10 group.TUNEL results showed that brown-stained positive apoptotic cells appeared in ganglion cell layer in the P6 and P10 group,while Western blot showed that the expression of caspase-3 protein in mouse retina in P6 group (gray value 52.70％) and P10 group (gray value 35.76％) was upregulated.Conclusion Early lighting exposure can induce premature myopia of mice,and the earlier the mice receive light,the higher the relative degree of myopia is;meanwhile during the process of premature myopia,ganglion cells and nuclear layer cells suffer apoptosis,as well as caspase-3 protein involves in the occurrence of apoptosis.