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Sassan Azarian, Rosemarie Cepeda, Jun Liu, Shifeng Pan, Nicholas Ng, Bijan Etemad-Gilbertson, Shelby Giza, Jimmy Elliott, Viral Kansara, Bruce Jaffee; Activation of the Wnt Pathway in a Corneal Neovascularization Model. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2405.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the involvement of the Wnt pathway in the mouse corneal neovascularization model (CoNV). CoNV is a commonly-used, well-established model for acute NV that has so far responded to all clinically viable anti-angiogenic treatments. Wnt has been implicated in angiogenesis and may be a therapeutic target for ocular NV diseases, such as wet AMD.
CoNV was induced by corneal abrasion, and visualized by injection of ConA-FITC (IV) and fluorescence microscopy (FM) of corneal flatmounts. For gene expression analysis, RNA was isolated from freshly dissected corneas and analyzed by Taqman. The progression of NV was assessed in timecourse studies, with analyses by both FM and by a VEGF Taqman assay. For efficacy studies with anti-angiogenic treatments, mice were subjected to corneal abrasion on day 0 (D0) and dosed on D0-D5 with either a) an anti-VEGF polyclonal antibody ( IP), b) PTK787, an oral VEGFR2 inhibitor (PO), and appropriate controls (N = 8-12 mice/group). For assessment of efficacy, CoNV at D6 was visualized by FM and the area was quantified with Axiovision software. The activity of the Wnt pathway was monitored by an axin2 Taqman assay.
Analyses by FM and by the VEGF Taqman assay indicated that CoNV was clearly visible in abraded mice compared to that in naive controls, and that it was progressive with time. Treatment with anti-angiogenics significantly inhibited neovascularization in the CoNV model by different administration routes (IP, PO, or topical). Preliminary Taqman data showed an early, brief, but significant increase in axin2 gene expression level: peak activity, which was 5x over baseline, was seen 1 hour after abrasion and returned to baseline between 4 and 7 hours up to at least 10 days.
The mouse CoNV is a robust model for acute angiogenesis that is amendable to genetic manipulation. In this model NV is observed to be progressive by FM and by gene expression, and can be pharmaceutically inhibited with known anti-angiogenic treatments. Preliminary analysis of axin2 gene expression revealed a significant peak early on, indicating activation of Wnt pathway prior to manifestation of new blood vessels in this model. Current studies are investigating whether activation of Wnt is directly related to angiogenesis.
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