The Suppression of the Cell Adhesion Protein CEACAM1 by the Anti-Angiogenetic Aptamer Macugen® Is Dose Dependant

Abstract

Purpose:: A limited chemical burn starts early VEGF induced events of neovascularization.The human carcinoembryonic antigen-related adhesion molecule 1 (CEACAM1) stimulates proliferation of human microvascular endothelial cells. Data suggest that CEACAM1 is a major effector of VEGF¹⁶⁵ in the early microvessel formation.We have in earlier studies (ARVO 2006) showed the expression of VEGF¹⁶⁵ in the rabbit cornea. Pegaptanib (Macugen®) is an RNA-aptamer that blocks VEGF¹⁶⁵ selectively. We found it interesting to study the effect of Macugen® on the expression of CEACAM1 in a corneal wound model.

Methods:: 20 New Zealand White male rabbits were used. The animals received, in the right eye, subconjunctival injection of either 0,5 ml solute only, 0,9 mg of Macugen® 18 mg/ml, 0,45 mg of Macugen® 9mg/ml or 2 mg of triamcinolone, all given15 minutes preoperatively. The group with 0,9 mg of Macugen® also received an injection with the same dose 24 hours postoperatively. The right cornea was 15 min after the injection inflicted with a alkali wound in anaesthesia. A filter paper, 5 mm in diameter, soaked in 1 N NaOH, was placed on the cornea for 60 seconds. The wound area was rinsed with BSS. The rabbits were sacrificed after 48 hours.The corneas were excised with a scleral rim, fixed in 4% formaldehyde and embedded in paraffin. Left eyes served as controls. Sections were double stained with hematoxyline and immunohistochemically for PCNA. RNA was isolated from ten-µm paraffin sections from the limbal parts and analysed with RT-PCR for CEACAM1.

Results:: In the PCNA stained sections there were no difference of expression between the first two groups (control, Macugen® high) Results from PCNA staining in group 3 and 4 will be presented. In the triamcinolone treated group the inflammatory response was markedly reduced. RT-PCR showed expression of CEACAM1 in right corneas of group 1 and 2 . There were no expression in left, untreated eyes. In group 3 (Macugen® low) and 4 (triamcinolone) there were no evidence of CEACAM1 expression in right or left corneas.

Conclusions:: Macugen® in a lower dose and triamcinolone inhibit the expression of the cell adhesion protein CEACAM1 in the limbal area of alkali wounded corneas. CEACAM1 serves as a major effector of VEGF in the early microvessel formation and pegaptanib in low concentration may be an effective prophylactic treatment for corneal neovascularization.

Keywords: neovascularization • cornea: basic science • wound healing