Expression of insulin-like growth factor binding protein-6 in the vitreous and serum in a proliferative vitreoretinopathy rat model / 中华实验眼科杂志

ABSTRACT

Background Proliferative vitreoretinopathy (PVR) is one of the major causes of retinal detachment surgery failure.Based on proteomic studies of PVR vitreous,the insulin-like growth factor binding protein-6 (IGFBP-6) protein was specifically expressed in the vitreous and serum of PVR patients.Furthermore,its expression level is higher in the vitreous and serum in severe PVR patients than that in mild PVR patients.Objective This experiment was to detect the expression of IGFBP-6 in a PVR rat model.Methods Seventy 7-week old male SPF Wistar rats were included and were randomized into the PVR model group and control group.A mixture of RPE-J cell suspension(5 μl) and platelet-rich plasma (5 μl) was intravitreally injected in the left eyes of adult Wistar rats to establish the PVR model,and normal saline solution was administered in the same way in the control group.The rat eyes were clinically examined 1 week,2,3 and 4 weeks after injection,and PVR was graded based on the criteria of Francine.The animals were sacrificed after 1 week,2,4 or 8 weeks for the preparation of retinal sections and liver extraction.Expression levels of IGFBP-6 mRNA in the rat retina and liver were assayed by real-time Q-PCR.The expression of IGFBP-6 protein in the rat serum and vitreous was detected by ELISA.The use of animals complied with the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.Results Purified IGFBP-6 RNA was extracted from the liver and retina of Wistar rat and quantified by real-time Q-PCR.The expression level of IGFBP-6 mRNA in retina was (3.79± 1.33) × 10-4 in the PVR model rats,showing a significant decline in comparison with the control rats with a level of(8.32±2.96) × 10 4,4 weeks after injection (t =3.42,P＜0.01).The expression of IGFBP-6 mRNA in the 4th week was significantly lower than that of 1 week,2 or 8 weeks after the establishment of the PVR model(P＜0.05).No significant difference was found in the IGFBP-6 mRNA level in the liver between the PVR group and control group(27.60± 14.01 × 10 4 vs.25.01 ± 12.04 ×10-4,respectively),as well as among the different time points(P＞0.05).IGFBP-6 mRNA content in the retina was significantly reduced in grades 1,2 or 3 of the PVR groups compared with the control group(P＞0.05),but there was no significant difference among the different grades of PVR groups (P＞0.05).Concentrations of IGFBP-6 protein in grades 1,2 and 3 of the PVR model group were (221.00 ± 19.32),(229.63 ± 18.89) and (225.70 ± 26.71) μg/L,with a significant elevation in comparison with (173.25 ±21.11) μg/L of the control group (t =2.14,P＜0.05).However,there was no significant change among the different grades of PVR groups(t=1.24,1.46,P＞0.05).The concentrations of IGFBP-6 protein in the vitreous and serum were higher in PVR rat samples (vitreous225.44±19.36 μg/L;serum108.48 ± 15.78 μg/L) than in control rats (vitreous173.25 ± 21.11 μg/L,serum95.96 ±17.40 μg/L)(P＜0.05).Conclusions The concentrations of IGFBP-6 protein in the vitreous and serum increase in PVR rats.The results indicate that the increased IGFBP-6 in the vitreous might be a localized autocrine secretion of the eye.