Sustained-release endotoxin. A model for inducing corneal neovascularization.

Area of Science:

• Ophthalmology
• Vascular Biology
• Biomaterials

Background:

• The rabbit corneal pocket assay is a standard model for studying angiogenesis.
• There is a growing need for reliable models to investigate angiogenesis inhibitors.

Purpose of the Study:

• To modify the rabbit corneal pocket assay for stimulating neovascularization using endotoxin-eluting implants.
• To evaluate the efficacy of different endotoxin concentrations in inducing corneal neovascularization.

Main Methods:

• Sustained-release polymer pellets (ethylene vinyl acetate copolymer - Elvax) were prepared with varying endotoxin (Escherichia coli lipopolysaccharide) concentrations (1-40%).
• Implants were inserted into intrastromal corneal pockets in New Zealand rabbits.
• Neovascularization was quantified using slit-lamp biomicroscopy.

Main Results:

• Endotoxin loads of 15% induced significant neovascularization (0.21 mm/day) with minimal edema.
• Concentrations of 7.5% and 20% also showed neovascularization, while 1% had a lower response.
• Higher loads (30-40%) caused severe edema, hindering accurate measurements. Vessel regression was observed upon implant removal.

Conclusions:

• The modified rabbit corneal assay using endotoxin-Elvax implants provides a tunable model for studying angiogenesis.
• This method is suitable for identifying both stimulators and inhibitors of new blood vessel formation in the cornea.