Doxycycline Effectively Inhibits Ocular Angiogenesis

Abstract

Purpose: : Doxycycline is a matrix metalloproteinase inhibitor and has been shown to suppress cerebral angiogenesis in a vascular endothelial growth factor–induced mouse model. Our purpose was to determine the effect of doxycycline (doxy) in ocular angiogenesis–related mouse models.

Methods: : A new model for studying pterygia was developed by injecting 10,000 human pterygial epithelial cells under the nasal limbal conjunctiva of athymic mice. Mice were given either plain water or doxy in their drinking water. Photographs of ocular lesions at six and twelve days after injection were compared. In the directed in vivo angiogenesis assay (DIVAA) model, silicone capsules (angioreactors) containing Matrigel with 10,000 pterygial epithelial cells were implanted under the skin of nude mice. Doxy was consumed via drinking water (or plain water), and after 11 days, fluorescein isothiocyanate–dextran (FITC–d) was injected into the mice tail veins. The extent of neovascularization (NV) within the capsules was quantified using a spectrofluorimeter. The mean relative fluorescence for six replicates was determined and Student's t–test was used to analyze the data. In a choroidal NV model (CNM), angiogenesis was induced by disrupting Bruch’s membrane with laser energy. Mice consumed doxy via drinking water (or plain water). The NV lesion volume was determined in choroid–RPE flat mounts labeled with Isolectin IB4, using confocal microscopy and Volocity^TM software for six or greater replicates.

Results: : The mice receiving 50 mg/kg/day of doxy for the pterygia model demonstrated a substantial reduction in lesion size. In the DIVAA experiment, doxycycline consumed at 30 mg/kg/day significantly reduced vessel growth by thirty percent (p< 0.004) when compared to plain water. The choroidal neovascular model demonstrated a fifty–four percent decrease in lesion size for those receiving doxy at 50 mg/kg/day (p< 3.85 x 10–6).

Conclusions: : Using three separate in vivo murine models, we conclude that oral administration of doxycycline can potentially inhibit angiogenesis in ocular diseases, especially pterygia and choroidal neovascularization. To the best of our knowledge, this is the first time this effect of doxycycline on choroidal neovascularization or pterygia has been demonstrated.

Keywords: pharmacology • neovascularization • Pterygium