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Release of Pro-Inflammatory/Angiogenic Factors by Retinal Microvascular Cells Is Mediated by Extracellular Vesicles
Elena Beltramo1, Aurora Mazzeo1, Massimo Porta1
1Department of Medical Sciences, University of Turin, 10126 Torino, Italy.
Abstract:
The interactions between the neuronal and vascular sides of the retina during diabetic retinopathy (DR) have gained increasing attention. Microglia is responsible for the immune response to inflammation inside the retina, which could be mediated by paracrine signals carried by extracellular vesicles (EVs). We aimed to characterize EVs released from immortalized human microglial cells in inflammation and investigate their effects on the retinal microvasculature and the anti-inflammatory potential of thiamine in this context. M1 pro-inflammatory polarization in microglia was induced through a cytokine cocktail. EVs were isolated from the supernatants, characterized, and used to stimulate human retinal endothelial cells (HRECs) and pericytes (HRPs). Microvascular cell functions and their release of pro-inflammatory/angiogenic factors were assessed. M1-derived EVs showed increased content of miR-21, miR-155, CCL2, MMP2, and MMP9, and enhanced apoptosis, proliferation, migration, and ROS production in HRPs and HRECs. IL-1β, IL-6, MMP9, CCL2, and VEGF release increased in HRPs exposed to M1-derived EVs, while HRECs showed augmented IL-6, Ang2, VEGF, and PDFG-B. Addition of thiamine to M1-microglial cultures reverted most of these effects. In conclusion, M1-derived EVs stimulate functional changes and secretion of pro-inflammatory/angiogenic molecules in microvascular cells, exacerbating inflammatory damage and retinopathy features. Thiamine added to microglia exerts anti-inflammatory effects.
Insights
Inflammatory microglia release extracellular vesicles (EVs) that damage retinal microvasculature in diabetic retinopathy (DR). Thiamine treatment reduced these harmful EV effects, suggesting a potential therapeutic strategy for DR.
Area of Science:
- Ophthalmology
- Immunology
- Cell Biology
Background:
- Diabetic retinopathy (DR) involves complex interactions between retinal neurons and vasculature.
- Microglia play a key role in retinal inflammation, potentially releasing extracellular vesicles (EVs) that mediate damage.
Purpose of the Study:
- To characterize EVs from inflamed human microglia.
- To investigate the impact of these EVs on retinal microvascular cells.
- To assess thiamine's anti-inflammatory potential in this context.
Main Methods:
- Human microglial cells were polarized to M1 pro-inflammatory state.
- Extracellular vesicles (EVs) were isolated and characterized.
- Retinal endothelial cells (HRECs) and pericytes (HRPs) were stimulated with M1-derived EVs.
- Cell functions and inflammatory factor release were assessed.
- Thiamine was added to M1-microglial cultures.
Main Results:
- M1-derived EVs contained increased miR-21, miR-155, CCL2, MMP2, and MMP9.
- These EVs induced apoptosis, proliferation, migration, and ROS production in HRPs and HRECs.
- EV exposure increased pro-inflammatory and angiogenic factors (IL-1β, IL-6, MMP9, CCL2, VEGF, Ang2, PDGF-B) in microvascular cells.
- Thiamine treatment largely reversed these detrimental effects.
Conclusions:
- Microglia-derived EVs in an inflammatory state promote microvascular dysfunction and exacerbate DR features.
- Thiamine demonstrates anti-inflammatory effects by modulating microglial EV release and their impact on retinal vasculature.
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