The expression of chondroitin sulfate proteoglycans in the retinas of retinitis pigmentosa rats

Abstract

Objective To study the expression of chondroitin sulfate proteoglycans (CSPGs) in retinal pigment epithelium cell degeneration rat induced by sodium iodate (NaIO3) intraperitoneal injection.Methods In this experimental study,a total of 24 Sprague-Dawley (SD) rats were used.And divided into control group,7 days group,14 days group and 28 days group,with 6 rats in each group.NaIO3 (3％,100 mg/kg) was intraperitoneally injected in 18 rats to establish the retinal degeneration models.HE and Tunel assay were performed to evaluate the retinal degeneration.The expression of CSPGs in rat retinas was detected by immunofluorescence; the expression of Versican mRNA was analyzed by retrovirus-polymerase chain reaction (RT-PCR).The macrophage-specific antigen CD68,secreted by microglia,was detected by an immunohistochemical method.The data was statistically analyzed by one-way ANOVA and independent samples t test.Results HE showed morphological retinal degeneration in rats after NaIO3 injection.The apoptosis of photoreceptors appeared more severe with the development of retinal degeneration in rat retinas after NaIO3 injection.The apoptosis rates were (21.0±3.5)％,(323±2.3)％ and (41.7±2.6)％ in 7 days.14 days and 28 days groups,respectively.after NaIO3 injection,with statistically significant differences between each group (F=205.27,P＜0.01).CS-56 and CD68 appeared in the choroid,photoreceptor outer segment debris zone (DZ),the internuclear layer (INL) and the ganglion cell layer (GCL) 7 days after NaIO3 injection and spread to the outer nuclear layer (ONL) 14 days after NaIO3 injection.Twenty-eight days after NaIO3 injection,CSPGs continued to expand to the outer plexiform layers (OPL).With the passage of time after NaIO3 injection,CS-56 fluorescence and CD68 intensity became stronger in each layer.CD68 intensity was 1.33±0.52,2.67±0.82,4.00±1.10 and 7.17±1.33 in normal rat retinas,7 days,14 days and 28 days after NaIO3 injection,and there were statistically significant differences between each group (F=38.45,P＜0.01).The expression of Versican mRNA,the N-terminal fragment of CSPGs,in the retinal degeneration animals was 1.02±0.06,which was significantly higher than in the control rats (0.23±0.02) (t=-26.05,P＜0.01).Conclusion With the passage of time after NaIO3 injection,the range of CSPGs continued to expand and the expression intensity became stronger in rat retinas.The same distribution of CSPGs and microglia suggested that microglia constitute a source of CSPGs in the degenerating rat retina. Key words: Proteochondroitin Sulfates; Iodates; Retinitis; pigmentosa; Microglia