Explore the evidence
Experimental evidence has shown that Ang-2 and VEGF work together to drive vascular instability characterised by vascular leakage, neovascularisation, and inflammation.1

Clinical relevance
Ang-2 levels are elevated in retinal and choroidal vascular diseases, whereas Ang-1 levels remain balanced.2,3
Preclinical evidence
Studies have shown that Ang-2 increases inflammation and vascular leakage, and facilitates the effects of VEGF.3-5 Review the evidence below.

Vascular leakage and neovascularisation
MOUSE SKIN MODEL MILES ASSAY
Ang-2 may act as a facilitator of VEGF-induced vascular leakage5
Visualisation of
vascular leakage

Adapted from Benest AV, et al. PLoS One. 2013;8:e70459.
Quantification of
vascular leakage

Wild type Ang-2–deficient mice
**p<0.01. Error bars represent means±SD.
Adapted from Benest AV, et al. PLoS One. 2013;8:e70459.

VEGF-induced vascular leakage is attenuated in Ang-2–deficient mice.
SPONTANEOUS CNV MOUSE MODEL†
Ang-2 inhibition promotes sustained reduction of vascular leakage from CNV lesions5

Reduction in CNV leakage area is more prolonged with Ang-2 inhibition than with VEGF inhibition.
TEER ASSAY* USING HUMAN ENDOTHELIAL CELLS
Inhibition of Ang-2 or addition of Ang-1 improves endothelial cell barrier integrity3


*Quantitative technique to measure the integrity of tight junction dynamics of endothelial (and epithelial) monolayers.
Adapted from Regula JT, et al. EMBO Mol Med. 2016;8(11):1265-88.

VEGF-A reduces the integrity of endothelial cell tight junctions.

Inhibition of Ang-2 or addition of Ang-1 improves barrier integrity.


Inflammation
Ang-2 promotes leukocyte adhesion and transmigration.6,7

Adapted from Augustin HG, et al. Nat Rev Mol Cell Biol. 2009;10:165–77.
During inflammation, cytokines such as TNF-α induce the expression of adhesion molecules on the endothelial cell surface, mediating leukocyte tethering and rolling. Ang-2 acts as an amplifier to activate and sensitise vascular endothelial cells to inflammatory cytokines, regulating the transition from leukocyte rolling to firm adhesion and facilitating leukocyte migration across the vascular endothelium, into tissues such as the retina.
MOUSE DORSAL SKINFOLD CHAMBER MODEL
Leukocyte adhesion
Wild type

Error bars represent means±SD.
Reprinted from Nature Medicine, 12(2), Fiedler U, et al., Angiopoietin-2 sensitizes endothelial cells to TNF-alpha and has a crucial role in the induction of inflammation, 235–9, Copyright (2006), with permission from Springer Nature.
Ang-2–deficient

Error bars represent means±SD.
Reprinted from Nature Medicine, 12(2), Fiedler U, et al., Angiopoietin-2 sensitizes endothelial cells to TNF-alpha and has a crucial role in the induction of inflammation, 235–9, Copyright (2006), with permission from Springer Nature.

Leukocyte adhesion is defective in Ang-2–deficient mice, suggesting an important role of Ang-2 in the inflammatory response.

AMD, age-related macular degeneration; Ang, angiopoietin; CNV, choroidal neovascularisation; DR, diabetic retinopathy; EC, endothelial cell; FA, fluorescein angiography; FFA, fundus fluorescein angiography; nAMD, neovascular age-related macular degeneration; RVO, retinal vein occlusion; TEER, transendothelial electrical resistance; Tie, tyrosine kinase with immunoglobulin-like domains; TNF-α, tumour necrosis factor alpha; VEGF, vascular endothelial growth factor.
References
- Saharinen P, et al. Nat Rev Drug Discov. 2017;16:635–61
- Regula JT, et al. EMBO Mol Med. 2019;11:e10666
- Regula JT, et al. EMBO Mol Med. 2016;8:1265–88
- Benest AV, et al. PLoS One. 2013;8:e70459
- Chakravarthy U, et al. Presented at ARVO May 2020, Virtual Meeting
- Augustin HG, et al. Nat Rev Mol Cell Biol. 2009;10:165–77
- Fiedler U, et al. Nat Med. 2006;12:235–9