Abstract
Purpose: :
Objective of the present study was to investigate the interactions among complement activation, chemokines and angiogenic growth factors that occur in vivo during the development of laser-induced choroidal neovascularization (CNV).
Methods: :
A combination of following approaches was used to establish a link between membrane attack complex (MAC) - the end product of complement activation, chemokine (CCL2) and growth factor (VEGF) during the development of CNV. We first investigated the sequential expression of MAC, CCL2 and VEGF during laser-induced CNV. CNV was induced in C57BL/6 mice by laser treatment. Time dependent expression of CCL2 and VEGF in RPE-choroid was investigated by real-time RT-PCR and ELISA. MAC deposition and CNV formation was detected using immunohistochemical staining of RPE-choroid-scleral flat mounts. Next to determine the cross-talk between MAC, CCL2 and VEGF during laser-induced CNV, C57BL/6 mice were injected separately with neutralizing antibodies against C6, CCL2 and VEGF via intraperitoneal and subretinal routes to block the bioactivity of MAC, CCL2 and VEGF respectively.
Results: :
Increased MAC deposition was detected at 1 hour post-laser, whereas CCL2 levels increased at 3 hour post-laser and VEGF levels were up-regulated by day 3 post-laser. Blocking MAC formation inhibited CCL2 and VEGF expression, and also limited CNV formation; while neutralization of CCL2 bioactivity did not affect MAC deposition; however it reduced VEGF expression and CNV formation. When the bioactivity of VEGF was blocked, CNV formation was significantly inhibited, but MAC deposition and CCL2 levels were not affected.
Conclusions: :
Taken together, our results demonstrate that during the course of laser-induced CNV, MAC regulates the production of CCL2 and facilitates choroidal angiogenesis by inducing VEGF production. Understanding the interplay between MAC, CCL2 and VEGF is critical to gain insight into the pathogenesis of CNV and to the development of an effective therapy.
Keywords: age-related macular degeneration • choroid: neovascularization • inflammation