Microglia enhanced the angiogenesis, migration and proliferation of co-cultured RMECs

Abstract

BackgroundAttention is increasingly being given to microglia-related inflammation in neovascular diseases, such as diabetic retinopathy and age-related macular disease. Evidence shows that activated microglia contribute to disruption of the blood–retinal barrier, however, the mechanism is unclear. In this study, we aimed to clarify whether and how microglia affect the function of retinal microvascular endothelial cells (RMECs).MethodsWe activated microglia by Lipopolysaccharides (LPS) stimulation. After co-culturing static or activated microglia with RMECs using the Transwell system, we evaluated the function of RMECs. Vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor-BB (PDGF-BB) levels in the supernatant from the lower chamber were evaluated by ELISA. Angiogenesis, migration, and proliferation of RMECs were assessed by tube formation, wound healing, and WST-1 assays. The expression levels of tight junction proteins (ZO-1 and occludin) and endothelial markers (CD31 and CD34) were examined by Western blot analysis.ResultsWe successfully established an LPS-activated microglia model and co-culture system of static or activated microglia with RMECs. In the co-culture system, we showed that microglia, especially activated microglia stimulated VEGF-A and PDGF-BB expression, enhanced angiogenesis, migration, proliferation, and permeability, and altered the phenotype of co-cultured RMECs.ConclusionsMicroglia, especially activated microglia, play important roles in angiogenesis and maintenance of vascular function hemostasis in the retinal microvasculature. The mechanism needs further investigation and clarification.

Up-regulation of pro-angiogenic pathways and induction of neovascularization by an acute retinal light damage

“…In retinal neoangiogenesis, a pivotal role is also played by the microglia 13 . In fact, although the interaction between microglia and blood vessels is important for a healthy retinal environment, when pathophysiological conditions occur, this interface contributes to the progression of the diseases and it culminates in the breakdown of blood vessels and to the sprouting of new branches 47 .…”

“…In fact, although the interaction between microglia and blood vessels is important for a healthy retinal environment, when pathophysiological conditions occur, this interface contributes to the progression of the diseases and it culminates in the breakdown of blood vessels and to the sprouting of new branches 47 . Under stress conditions, microglia up-regulate the expression of VEGF 13,48 . We therefore hypothesized that the neovascularization phenomena were also related to microglia activation, which it is known to migrate to the photoreceptor layer and to the subretinal space in the light damaged model 19 .…”

“…Additional angiogenic factors include insulin like growth factor 1 (IGF-1), basic fibroblast growth factor (bFGF), tumour necrosis factor-a (TNF-α), angiopoietin-2 and matrix metalloproteinases (MMPs) 12 . Also microglia cells play important roles in angiogenesis and maintenance of vascular homeostasis in the retina 13 . Activated microglia increase oxidative stress damage in vitro and promote apoptosis in pericytes.…”

“…From the results described above it is possible to state that both VEGF and FGF are up-regulated and that they probably cooperate to promote angiogenesis. Activated microglia contribute to maintenance of vascular function and to angiogenesis in the retina 13 . In fact, it has been shown that activated microglia express VEGF 14 and promote Statistical analysis was performed by one-way ANOVA test followed by Tukey test.…”

Brain Microvascular Pericytes in Vascular Cognitive Impairment and Dementia

“…Microglia have been regarded as the main executor of inflammation after acute and chronic CNS disorders. The interaction between microglia and vascular cells -including pericytes -has important roles for vascular inflammation, angiogenesis, and BBB integrity (Ding et al, 2018;Thurgur and Pinteaux, 2019). Although endothelial cells are thought to be the main source of cytokines and chemokines which trigger microglial activation upon vascular inflammation, pericytes are also known to be key mediators in this process.…”