Potential Role of Cyr61 Induced Degeneration of Human Müller Cells in Diabetic Retinopathy

Abstract

The degeneration of Müller cells has been recognized to involve in the pathogenesis of diabetic retinopathy. However, the mechanism is not yet clear. This study is to explore the potential role of Cyr61, a secreted signaling protein in extracellular matrix, in inducing human Müller cell degeneration in diabetic retinopathy (DR). Twenty patients with proliferative diabetic retinopathy (PDR) and twelve non-diabetic patients were recruited for this study. Vitreous fluid was collected during vitrectomy surgery for Cyr61 ELISA. Human Müller cell line MIO-M1 were cultured to be subconfluent, and then treated with glucose (0–20 mM) or Cyr61 (0–300 ng/ml). Cyr61 expression induced by increasing concentrations of glucose was evaluated by RT-qPCR and Western blot. Effects of Cyr61 on Müller cells viability, migration and apoptosis were observed by MTT assay, Transwell assay, and TUNEL assay. Vitreous Cyr61 levels were observed to be 8-fold higher in patients with PDR (3576.92±1574.58 pg/mL), compared with non-diabetic controls (436.14±130.69 pg/mL). Interestingly, the active PDR group was significantly higher than the quiescent PDR group (P<0.01). In retinal Müller cells culture, high glucose significantly and dose-dependently elevated Cyr61 expression at both mRNA and protein levels. Cyr61 at high concentrations dose-dependently inhibited the viability and migration of Müller cells. TUNEL assay further revealed that high concentration of Cyr61 significantly promoted the cell apoptosis. In conclusion, these findings demonstrated for the first time that the expression of Cyr61 was elevated by high glucose in Müller cells, and Cyr61 inhibited cell viability and migration while induced apoptosis, suggesting the potential role of Cyr61 in Müller cell degeneration. The elevated Cyr61 levels in vitreous fluid of PDR patients further support its role in diabetic retinopathy (DR).

Changes and related factors of blood CCN1 levels in diabetic patients

“…You et al reported the occurrence of higher levels of CCN1 in the vitreous humor of patients with proliferative diabetic retinopathy (PDR) compared to patients without diabetes (5). This observation has been consistently confirmed by Zhang et al (9), Choi et al (10), and Zhou et al (11). Additionally, it was observed that the vascular activity in patients with PDR significantly affected the vitreous levels of CCN1 (11,12).…”

“…Additionally, it was observed that the vascular activity in patients with PDR significantly affected the vitreous levels of CCN1 (11,12). Zhou et al observed that CCN1 levels were significantly higher in patients with active PDR than in patients with quiescent PDR (11); additionally, Zhang et al found that vitreous CCN1 levels were higher in patients with PDR who had extensive neovascularization in the retina than in those with limited neovascularization (9). However, CCN1 levels were higher in the PDR group than in the control group, regardless of the PDR status (11,12).…”

Association of serum Cyr61 levels with peripheral arterial disease in subjects with type 2 diabetes

“…Cysteine-rich angiogenic inducer 61 (Cyr61), belonging to the CCN family, is a 40 kD secreted extracellular matrix (ECM)- related signalling protein that can regulate cell proliferation, adhesion, differentiation and extracellular matrix production [ 7 – 9 ]. Cyr61 is maintained at a low level under normal conditions, but is usually elevated in various states of disease, such as colitis, rheumatoid arthritis, Graves’ orbitopathy, diabetic retinopathy and atherosclerosis [ 10 – 15 ]. Downregulation of Cyr61 expression in carotid balloon injury rats can mitigate the proliferation of vascular smooth muscle cells, thereby attenuating vascular intimal hyperplasia [ 16 ].…”

Association of serum Cyr61 levels with peripheral arterial disease in patients with type 2 diabetes

“…Cysteine-rich angiogenic inducer 61 (Cyr61), belongs to CCN family, is a 40 kD secreted extracellular matrix (ECM)-related signaling protein that can regulate cell proliferation, adhesion, differentiation and extracellular matrix production [7][8][9]. Cyr61 is maintained at a low level under normal conditions, but is usually elevated in various status of disease, such as colitis, rheumatoid arthritis, Graves' orbitopathy, diabetic retinopathy and atherosclerosis [10][11][12][13][14][15]. Moreover, inhibition of Cyr61 expression in carotid balloon injury rats can mitigated the proliferation of vascular smooth muscle cells, thereby attenuating vascular intimal hyperplasia [16].…”