Annexin A2 promotes choroidal neovascularization by increasing vascular endothelial growth factor expression in a rat model of argon laser coagulation-induced choroidal neovascularization.
BACKGROUND
Choroidal neovascularization (CNV) is a common cause of visual loss in the elderly patients with age-related macular degeneration and represents the growth of subretinal new vessels in the macular region. This study aimed to investigate the relationship between annexin A2 (ANXA2) and vascular endothelial growth factor (VEGF) in CNV.


METHODS
In a rat model of argon laser coagulation-induced CNV, the mRNA expressions of the annexins and VEGF protein expression in the retina were detected using fluorescent real-time polymerase chain reaction (PCR) and immunohistochemistry, respectively. The interactions between ANXA2 and VEGF in both a retinal pigment epithelial cell line RPE-J and the rat model of CNV were examined by means of RNA interference, real-time PCR, Western blotting, enzyme-linked immunosorbent assay (ELISA) and histopathological examinations.


RESULTS
Fundus fluorescein angiography (FFA) showed that argon laser coagulation of the retina induced stable CNV models in the rats. Two to three weeks after the coagulation, ANXA2 and VEGF expressions in the coagulated area in the retina and choroid increased to the peak level, while the other annexin members (ANXA4, ANXA5, ANXA7 and ANXA11) showed no obvious changes. In RPE-J cells and the CNV model, RNA interference of ANXA2 gene significantly lowered the VEGF protein and mRNA expressions, and application of an adenoviral vector containing ANXA2 gene markedly increased VEGF expressions in the rat model of CNV, but produced no significant effects on the expressions of the kinase insert domain-containing receptor (KDR) or the fms-like tyrosine kinase (Flt-1). The expression of KDR inhibited the increment in ANXA2 expression, but VEGF and Flt-1 did not directly affect ANXA2 expression.


CONCLUSIONS
Besides the role as a plasminogen and the receptor of tissue plasminogen activator, ANXA2, which is under regulation of KDR via a negative feedback mechanism, also participates in neovascularization by regulating VEGF expression through a positive feedback mechanism.
Zhao
Shi-hong
SH
Department of Ophthalmology, Changhai Hospital, Second Military Medical University, Shanghai 200433, China. zhaosh2001@sina.com
Pan
Dong-yan
DY
Zhang
Yuan
Y
Wu
Jin-hui
JH
Liu
Xin
X
Xu
Yu
Y
D000818:Animals; D017306:Annexin A2 / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D020256:Choroidal Neovascularization / Q000209:etiology* / Q000378:metabolism; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D017075:Laser Coagulation; D054020:Lasers, Gas; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011914:Rats, Inbred BN; D042461:Vascular Endothelial Growth Factor A / Q000032:analysis / Q000235:genetics / Q000502:physiology*
D017306:Annexin A2; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A