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Updated: May 28, 2026
Oxygen-Induced Retinopathy Model for Ischemic Retinal Diseases in Rodents
Published on: September 16, 2020
Persistent inhibition of oxygen-induced retinal neovascularization by anthrax lethal toxin
Jennifer L Bromberg-White1, Elissa Boguslawski, Daniel Hekman
1Laboratory of Cancer and Developmental Cell Biology, Van Andel Research Institute, Grand Rapids, Michigan 49503, USA.
Purpose:
To evaluate the role of mitogen-activated protein kinase kinase (MKK) signaling in a mouse model of oxygen-induced retinopathy (OIR) that mimics retinopathy of prematurity (ROP).
Methods:
Postnatal day 7 mice were exposed to elevated oxygen for 5 days to induce retinopathy. Anthrax lethal toxin (LeTx), an MKK inhibitor, was injected into the vitreous after restoration to normoxia, and its effects on vascular growth were analyzed by whole mount immunofluorescence and confocal microscopy. Pericyte coverage was determined by PDGFR-β and α-SMA staining. Macrophage presence was determined by F4/80 staining. Vitreal cytokine secretion was measured by ELISA and multianalyte profiling.
Results:
Intravitreal injection of LeTx over a restricted time interval after return to normoxic conditions blocked the progression of OIR. This block was independent of vascular endothelial growth factor (VEGF) release and did not alter the release of cytokines and growth factors associated with OIR. VEGFR2 expression and activation were similarly unaffected. LeTx had no statistically significant effect on macrophage recruitment. LeTx sensitivity correlated with vessel maturity, extent of hypoxia, and growth of the deep vascular plexus network.
Conclusions:
Correlation among pericyte coverage, deep vascular plexus growth, and hypoxia after LeTx treatment indicate immature vessels in a hypoxic environment are preferentially sensitive to LeTx-mediated MKK inhibition. The persistence of VEGF without concomitant induction of neovascular growth or revascularization of vaso-obliterated zones suggests MKK inhibition causes an inability of the cells that are present, or a failure to recruit cells able, to respond to proangiogenic stimuli. These results indicate the inhibition of MKK signaling presents a novel strategy for the inhibition of vascular retinopathies such as OIR and ROP.
Insights
Inhibiting mitogen-activated protein kinase kinase (MKK) signaling with anthrax lethal toxin (LeTx) blocked oxygen-induced retinopathy (OIR) progression in mice. This novel strategy targets immature vessels in hypoxic conditions, offering a new approach for treating vascular retinopathies like OIR and retinopathy of prematurity (ROP).
Area of Science:
- Ophthalmology
- Vascular Biology
- Molecular Signaling
Background:
- Retinopathy of prematurity (ROP) and oxygen-induced retinopathy (OIR) are leading causes of childhood blindness.
- Abnormal neovascularization in the retina underlies these conditions, driven by complex signaling pathways.
- Mitogen-activated protein kinase kinase (MKK) signaling is implicated in cellular responses to stress and growth factors.
Purpose of the Study:
- To investigate the role of MKK signaling in a mouse model of OIR.
- To determine if inhibiting MKK signaling can prevent or reverse OIR progression.
- To explore the underlying mechanisms of MKK inhibition's effects on retinal neovascularization.
Main Methods:
- Mice were exposed to hyperoxia to induce OIR, followed by intravitreal injection of anthrax lethal toxin (LeTx), an MKK inhibitor.
- Vascular growth, pericyte coverage, and macrophage infiltration were assessed using immunofluorescence and specific staining.
- Vitreal cytokine and growth factor levels were measured via ELISA and multianalyte profiling.
Main Results:
- Intravitreal LeTx administration effectively blocked OIR progression when given during normoxia after hyperoxic exposure.
- The inhibitory effect of LeTx was independent of vascular endothelial growth factor (VEGF) and did not significantly alter cytokine profiles or macrophage recruitment.
- LeTx sensitivity was associated with vessel maturity, hypoxia extent, and deep vascular plexus development, suggesting a specific targeting of immature, hypoxic vessels.
Conclusions:
- MKK inhibition, specifically by LeTx, presents a promising therapeutic strategy for managing vascular retinopathies like OIR and ROP.
- The mechanism involves rendering immature, hypoxic vessels unresponsive to proangiogenic stimuli, thereby preventing aberrant neovascularization.
- Further research into MKK signaling pathways could lead to novel treatments for blinding retinal diseases.
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