The Role of the Different VEGF-Isoforms in Scar Formation After Glaucoma Filtration Surgery

Abstract

Purpose: : We previously showed that in vitro pegaptanib (Macugen^TM, Pfizer) addition inhibited endothelial cells (HUVEC) in a dose-dependent way, whereas human Tenon fibroblasts (HTF) were only inhibited at the highest dose. Bevacizumab, on the other hand, was able to inhibit both HUVEC and HTF dose-dependently. In a rabbit model of trabeculectomy, a single injection of bevacizumab was able to reduce angiogenesis as well as fibrosis. A single pegaptanib injection only temporarily improved the surgical outcome by reducing angiogenesis, without effecting inflammation and fibrosis. Therefore, we checked whether repeated injections of pegaptanib can more efficiently improve the surgical outcome. Also, we aimed at further elucidating the role of the different VEGF-isoforms on the process of wound healing in vivo and in vitro.

Methods: : The effect of the different VEGF-isoforms (VEGF₁₂₁ & VEGF₁₆₅ (R&D Systems), and VEGF₁₈₉ (Cell Sciences)) on HUVEC and HTF in vitro was determined by a WST-1 assay. In a group of 12 rabbits, injections (0,3mg; 90 µl) were given every 2 days subconjunctivally until day 14. The outcome of the treatment was investigated 15 and 30 days after surgery by analysis of angiogenesis (CD31), inflammation (CD45) and fibrosis (Sirius Red).

Results: : In vitro

Conclusions: : Addition of VEGF₁₂₁ and VEGF₁₆₅ stimulated HUVEC proliferation, while VEGF₁₂₁ and VEGF₁₈₉ increased the growth of HTF in vitro. Repeated injections of pegaptanib improved surgery outcome by reducing angiogenesis on day 15 and 30 after surgery, however no differences were visible in inflammation and fibrosis. These data indicate that VEGF-isoforms play a differential role in ocular wound healing. VEGF₁₆₅ may affect blood vessels, whereas the other isoforms may be more important in inflammation and fibrosis.

Keywords: vascular endothelial growth factor • wound healing