Abu El-Asrar Ahmed M, Nawaz Mohd Imtiaz, De Hertogh Gert, Alam Kaiser, Siddiquei Mohammad Mairaj, Van den Eynde Kathleen, Mousa Ahmed, Mohammad Ghulam, Geboes Karel, Opdenakker Ghislain
Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
Laboratory of Histochemistry and Cytochemistry, University of Leuven, KU Leuven, Belgium.
Mol Vis. 2014 Sep 10;20:1209-24. eCollection 2014.
The calcium-binding protein S100A4 is implicated in cancer cell invasion and metastasis, the stimulation of angiogenesis, the progression of fibrosis, and inflammatory disorders. We investigated the expression of S100A4 and correlated it with clinical disease activity as well as with the levels of osteopontin (OPN), soluble syndecan-1, and vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR). To reinforce the findings at the functional level, we examined the expressions of S100A4 and OPN in the retinas of diabetic rats and in human retinal microvascular endothelial cells (HRMECs) following exposure to VEGF and the proinflammatory cytokine tumor necrosis factor-α (TNF-α).
Vitreous samples from 30 PDR and 30 nondiabetic patients, epiretinal membranes from 14 patients with PDR, the retinas of rats, and HRMECs were studied by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, western blot analysis, and co-immunoprecipitation.
ELISA revealed a significant increase in the expressions of S100A4, OPN, soluble syndecan-1, and VEGF in vitreous samples from PDR patients compared to nondiabetic controls (p = 0.001; <0.001; <0.001; <0.001, respectively). Significant positive correlations were found between the levels of S100A4, OPN (r = 0.52, p = <0.001), soluble syndecan-1 (r = 0.37, p = 0.012), and VEGF (r = 0.29, p = 0.044). In epiretinal membranes, S100A4 was expressed in the vascular endothelial cells and stromal CD45-expressing leukocytes. A significant positive correlation was detected between the number of blood vessels expressing CD31 and the number of stromal cells expressing S100A4 (r = 0.77, p = 0.001). Western blot analysis revealed a significant increase in the expressions of S100A4 and both intact and cleaved OPN in vitreous samples from PDR patients compared to nondiabetic controls, as well as in the retinas of diabetic rats. Co-immunoprecipitation studies revealed a positive interaction between S100A4 and the receptor for advanced glycation end products (RAGE) in the retinas of diabetic rats. TNF-α-but not VEGF-induced the upregulations of S100A4 and both intact and cleaved OPN in HRMECs.
S100A4 represents a valuable vitreous marker molecule in the pathogenesis of PDR and might become a new target for the treatment of PDR.
钙结合蛋白S100A4与癌细胞侵袭和转移、血管生成的刺激、纤维化进展及炎症性疾病有关。我们研究了增殖性糖尿病视网膜病变（PDR）中S100A4的表达，并将其与临床疾病活动以及骨桥蛋白（OPN）、可溶性syndecan - 1和血管内皮生长因子（VEGF）水平相关联。为了在功能水平上强化研究结果，我们检测了糖尿病大鼠视网膜以及人视网膜微血管内皮细胞（HRMECs）在暴露于VEGF和促炎细胞因子肿瘤坏死因子-α（TNF-α）后S100A4和OPN的表达。
采用酶联免疫吸附测定（ELISA）、免疫组织化学、蛋白质印迹分析和免疫共沉淀法，对30例PDR患者和30例非糖尿病患者的玻璃体样本、14例PDR患者的视网膜前膜、大鼠视网膜以及HRMECs进行研究。
ELISA显示，与非糖尿病对照组相比，PDR患者玻璃体样本中S100A4、OPN、可溶性syndecan - 1和VEGF的表达显著增加（分别为p = 0.001；<0.001；<0.001；<0.001）。S100A4水平与OPN（r = 0.52，p = <0.001）、可溶性syndecan - 1（r = 0.37，p = 0.012）和VEGF（r = 0.29，p = 0.044）之间存在显著正相关。在视网膜前膜中，S100A4在血管内皮细胞和表达基质CD45的白细胞中表达。表达CD31的血管数量与表达S100A4的基质细胞数量之间存在显著正相关（r = 0.77，p = 0.001）。蛋白质印迹分析显示，与非糖尿病对照组相比，PDR患者玻璃体样本以及糖尿病大鼠视网膜中S100A4、完整和裂解的OPN表达均显著增加。免疫共沉淀研究显示，糖尿病大鼠视网膜中S100A4与晚期糖基化终产物受体（RAGE）之间存在正向相互作用。TNF-α而非VEGF诱导HRMECs中S100A4以及完整和裂解OPN的上调。
S100A4是PDR发病机制中有价值的玻璃体标志物分子，可能成为PDR治疗的新靶点。
