Bovine Retinal Microvascular Pericytes Research Articles

Overexpression of integrin-linked kinase in bovine retinal microvascular pericytes induced by glucose

目的 研究高糖培养的牛视网膜微血管周细胞的凋亡和整合蛋白连接酶(ILK)表达的变化及二者的关系.方法 原代培养周细胞,用流式细胞Annexin V检测周细胞的凋亡,用免疫细胞化学和Western blot检测牛视网膜微血管周细胞ILK的表达.结果 用30 mmol/L D-葡萄糖培养24、48、72 h后,牛视网膜微血管周细胞凋亡显著增加,分别为47.6%、58.4%和68.7%且具有时间依赖性.用5 mmol/L D-葡萄糖培养72 h后未见周细胞ILK表达.在30 mmol/L D-葡萄糖或5 μmol/L H2O2条件下培养72 h后,周细胞形态发生改变,ILK表达显著增强,主要分布在细胞质;Western blot检测发现30 mmol/L D-葡萄糖培养的条件下周细胞ILK蛋白水平随时间延长显著增加.结论 高糖可以诱导视网膜微血管周细胞凋亡,高糖条件下周细胞ILK过表达可能参与周细胞的损伤。

The effects of caspase-3 in apoptosis of cultured retinal microvascular pericytes induced by advanced glycation end products

One of the earliest changes observed in the development of diabetic retinopathy (DR) is the selective loss of pericytes and acellular capillaries. We tested the hypothesis that advanced glycation end products (AGE) might be involved in the disappearance of retinal pericytes by apoptosis and further investigated the activity and effect of caspase-3 at the same time. Cultured bovine retinal microvascular pericytes (BRPs) were exposed to various concentrations of advanced glycation end products-bovine serum albumin (AGE, 0.47, 1.88, 7.50 micromol/L) for 4 days. We assayed the degree of pericytes apoptosis by fluorescence activated cell sorting, and further measured the caspase-3 activity and the effect of selective caspase-3 inhibitor Z-DEVD-fmk on apoptosis and the of ratio Bcl-2/Bax expression. The results showed that AGE could induce significantly the apoptosis of BRPs in a dose-dependent manner compared with controls (r = 0.867, P < 0.01), associated with an increase in intracellular caspase-3 activity. Selective caspase-3 inhibitor Z-DEVD-fmk inhibited pericyte apoptosis induced by AGE. These data suggest that the pericyte loss in DR involves an apoptotic process, and that activation of caspase-3 are associated with apoptotic process, which can provide new therapeutic perspectives in diabetic retinopathy.

Angiotensin II stimulates migration of retinal microvascular pericytes: involvement of TGF-beta and PDGF-BB.

We studied the promigratory effect of angiotensin II (ANG II) on cultured bovine retinal microvascular pericytes. ANG II stimulated migration of pericytes by 86% at 10(-8) M, but this effect was lost at 10(-4) M. Migratory responses were inhibited by the ANG II type 1 (AT(1)) receptor antagonist losartan but not by PD-123319, an AT(2) antagonist. Addition of PD-123319 to the 10(-4) M ANG II dose restored migratory responses. The promigratory effect of ANG II (10(-7) M) was reduced by 59% in absence of gradient. Although ANG II augmented the latent matrix metalloproteinase-2 (MMP-2) activity of the pericyte by 35%, it also doubled tissue inhibitors of MMPs. ANG II-induced migration was not altered by a broad-spectrum MMP inhibitor (GM6001); it was inhibited by ~50% by antibodies against transforming growth factor (TGF)-beta(1/2/3) and was abolished by antibodies against platelet-derived growth factor (PDGF)-BB. We conclude that ANG II induces chemotactic responses on retinal microvascular pericytes acting through the AT(1) receptor. This effect is opposed by the AT(2) receptor. ANG II-induced chemotaxis is mediated by PDGF-BB and involves TGF-beta, but it is independent of MMP activity. It is also independent of vascular endothelial growth factor (VEGF) because VEGF did not stimulate pericyte migration. ANG II can contribute to the regulation of retinal neovascularization by stimulating pericyte migration.

Aldose Reductase Inhibition Prevents Glucose-induced Apoptosis in Cultured Bovine Retinal Microvascular Pericytes

The pathogenesis of pericyte loss, an initial deficit in the early stage of diabetic retinopathy, remains unclear. Polyol pathway hyperactivity has been implicated in the pathogenesis of diabetic retinopathy, and recent studies have suggested that apoptosis may be involved in pericyte loss. The present study was conducted to investigate whether high glucose induces apoptosis in cultured bovine retinal pericytes. The effect of an aldose reductase inhibitor, SNK-860, was also examined. After a 5 day incubation with various concentrations of glucose (5.5–40m M) in the presence or absence of SNK-860, the cell viability and the percentages of dead cells were measured, and staining with the TUNEL method and Hoechst 33342, and DNA electrophoresis were performed. High glucose reduced the viability and increased the percentages of dead cells. TUNEL-positive cells were observed in pericytes under high glucose, but not in those under 5.5m M glucose. In the staining of nuclei with Hoechst 33342, the percentage of apoptotic cells in total cells counted under high glucose was higher than that under 5.5m M glucose. DNA electrophoresis of pericytes cultured with high glucose demonstrated a ‘ladder pattern’. Hyperosmolarity also induced apoptosis in pericytes, but less than that by high glucose. SNK-860 inhibited the glucose-induced apoptosis in pericytes. These observations suggest that the pericyte loss in diabetic retinopathy involves an apoptotic process, and that the polyol pathway hyperactivity plays an important role in inducing apoptosis in pericytes by high glucose.

Altered endothelin-1 induced contraction and second messenger generation in bovine retinal microvascular pericytes cultured in high glucose medium

Altered endothelin-1 induced contraction and second messenger generation in bovine retinal microvascular pericytes cultured in high glucose medium

Altered endothelin-1 induced contraction and second messenger generation in bovine retinal microvascular pericytes cultured in high glucose medium

The effect of simulated hyperglycaemia on bovine retinal pericytes was studied following culture of these cells for 10 days under normal (5 mmol/l) and elevated (25 mmol/l) glucose conditions in the absence of endothelial cells. Pericytes cultured under high ambient glucose exhibited both a delayed and reduced contractile response following stimulation with endothelin-1. Stimulation with 10(-7) mol/l endothelin-1 for 30 s caused significant contraction in cells grown in both 5 mmol/l and 25 mmol/l glucose. The former also contracted significantly with 10(-8) mol/l endothelin-1. Further, at all concentrations tested, statistical comparison of the time course of contraction showed a significant difference (p < 0.02) in the reduction of planimetric surface area between the two cell groups. Since neither binding of endothelin-1 nor the number of receptors for this peptide were significantly different (p > 0.1) between bovine retinal pericytes grown for 10 days under normo- or hyperglycaemic conditions, it became apparent that the altered contractility in bovine retinal pericytes following culture in high glucose must be due to post-binding intracellular disturbance(s). Indeed, both basal and 15 s post-stimulation with 10(-8) mol/l endothelin-1, levels of inositol trisphosphate were significantly reduced (p < 0.05 and p < 0.02, respectively) in pericytes cultured for 10 days in 25 mmol/l glucose. These results show that endothelial-independent alterations in contractility of pericytes occur when they are grown in conditions which simulate hyperglycaemia. The results also suggest that the observed attenuation in response to endothelin-1 stimulation evident in pericytes grown under simulated hyperglycaemic conditions is not due to alterations in peptide binding.

Inhibition of bovine retinal microvascular pericyte proliferation in vitro by adenosine.

Adenosine acts on bovine retinal microvascular pericytes through one or more adenosine receptor subtypes present on the cell surface. Retinal pericytes cultured in medium containing adenosine at concentrations from 10(-6) to 10(-4) M showed significant reduction in proliferation following several days in vitro compared with control cultures. The effects of adenosine were mimicked by polyadenylic acid and inhibited by 8-phenyltheophylline, indicating involvement of a cell surface receptor. Metabolites of adenosine had no effect on pericyte proliferation. An A2 adenosine receptor-specific analogue also inhibited pericyte growth, suggesting that inhibition by adenosine is mediated by A2-receptors and might involve a transient increase in adenosine 3',5'-cyclic monophosphate levels. The results of the present study demonstrate that in addition to demonstrated stimulatory effects on capillary endothelial cells, adenosine also has a direct inhibitory effect on retinal pericytes. We hypothesize a dual function of adenosine within the capillary wall resulting in loss of inhibition of endothelial cells and suggest a role for this nucleoside in pathological neovascularization processes such as proliferative diabetic retinopathy.

The effect of endothelin 1 on the retinal microvascular pericyte

The effect of the highly vasoactive peptide endothelin 1 (ET1) was tested on bovine retinal microvascular pericytes propagated in vitro. Specific binding of 125I-ET1 to retinal pericytes was documented by autoradiography. ET1 caused contraction of pericytes at a concentration of 0.1 n M which was accompanied by increases in inositol phosphates. Exposure of pericytes to 10 n M ET1 resulted in the aggregation and realignment of muscle-specific actins into bundles which were oriented parallel to the long axis of the cell, and ET1 was also mitogenic to pericytes in the presence of low levels of fetal calf serum. These observations suggest that ET1 may play an important role in endothelial cell-pericyte interactions within the microvasculature of the retina and that it may be involved in the autoregulation of retinal blood flow.

ATP causes retinal pericytes to contract in vitro

We evaluated the contractility of bovine retinal microvascular pericytes in culture by permeabilizing the cells with 0.1% Triton X-100 and measuring their response to MgATP. Sequential photographs of the cells were taken over 20 min and their surface areas were measured. Our study directly demonstrates that pericytes are contractile cells, which respond to MgATP in a dose-dependent fashion over a relatively short time course (minutes). Pericytes did not contract in response to GTP, pyrophosphate or beta, gamma-methylene ATP. Immunofluorescence study showed the presence of muscle actin in Triton X-100-treated cells before and after contraction, indicating preservation of this cytoskeletal protein even after treatment with the detergent. Similar experiments on human umbilical vein endothelial cells, bovine lens epithelial cells and human retinal pigment epithelial cells showed that these cells were significantly less contractile than retinal pericytes. That pericytes show substantial contraction over a short time course indicates that these cells may play a major role in regulating blood flow in the microcirculation.

Collagens of the retinal microvascular basement membrane and of retinal microvascular cells in vitro

We have analysed the collagens present in vascular basement membranes isolated from bovine retinal and cerebral microvessels and bovine renal glomeruli, and from the non-vascular basement membrane of bovine lens capsule. These are compared with the collagens produced by cultured bovine retinal microvascular pericytes and lens epithelial cells, and by canine retinal microvascular endothelial cells, in vitro. Biochemical and immunocytochemical analyses indicate that all of the vascular basement membrane preparations have an identical collagenous composition, consisting of the same polypeptides present in lens capsule (primarily type IV collagen), together with other polypeptides that are identified as type I, and a small amount of type III collagen. Identification of the latter is based on two-dimensional gel electrophoresis in the presence and absence of a reducing agent. Immunocytochemical studies, however, demonstrate type I, type IV and some type V collagen in the basement membranes of the isolated microvessels. The cultured microvascular cells produce predominantly type I collagen molecules, but they also produce other collagen peptides that appear to be type IV, and, at least in some experiments, small amounts of type III collagen. The biochemical identification of collagens type I and IV is confirmed by immunocytochemistry. However, results with anti-type I collagen and procollagen antibodies in cultured pericytes vary with antibodies from different sources. The quantities of the type IV peptides produced by the cultured cells also vary in different experiments.