Opposite roles of CCR2 and CX3CR1 macrophages in alkali-induced corneal neovascularization.
OBJECTIVE
The purpose of this study was to investigate the role of infiltrating macrophages in the development of experimental corneal neovascularization.


METHODS
Corneal neovascularization was induced by alkali injury in mice deficient in a macrophage-tropic chemokine receptor, CCR2 or CX3CR1, or in mice treated with clodronate-liposomes (Cl2MDP-lip), which can selectively deplete monocytes/macrophages. Corneal neovascularization 2 weeks after alkali injury was assessed by immunostaining with anti-CD31 antibody. Intracorneal expression of proangiogenic and antiangiogenic factors was determined by reverse transcription-polymerase chain reaction.


RESULTS
CCR2-deficient mice exhibited reduced alkali-induced corneal neovascularization with reduced macrophage infiltration, whereas CX3CR1-deficient mice developed a more severe form of alkali-induced corneal neovascularization with reduced macrophage infiltration. Selective macrophage depletion by Cl2MDP-lip treatment failed to affect alkali-induced corneal neovascularization as evidenced by immunohistochemical analysis using anti-CD31 antibody, whereas intracorneal macrophage infiltration was markedly reduced. Alkali injury enhanced the expression of proangiogenic molecules, including matrix metalloproteinase-2, matrix metalloproteinase-9, and tumor necrosis factor alpha, and antiangiogenic factors, including a disintegrin and metalloprotease with thrombospondin (ADAMTS)-1, thrombospondin-1, and thrombospondin-2. Cl2MDP-lip-treated mice exhibited a reduction in the messenger RNA expression of these molecules.


CONCLUSIONS
Because CCR2- and CX3CR1-expressing macrophages exhibit opposite activities in angiogenesis, depletion of macrophages as a whole may not have apparent effects on alkali-induced corneal neovascularization.
Department of Ophthalmology, Clinical Immunology Key Laboratory of Jiangsu Province, the First Affiliated Hospital of Soochow University, Suzhou, China. lupeirong@yahoo.com.hk
Peirong
P
Lu
Longbiao
L
Li
Gaoqin
G
Liu
Nico
N
van Rooijen
Naofumi
N
Mukaida
Xueguang
X
Zhang
D000468:Alkalies; D000818:Animals; D002057:Burns, Chemical / Q000473:pathology; D000073883:CX3C Chemokine Receptor 1; D004002:Clodronic Acid / Q000008:administration & dosage; D003315:Cornea / Q000378:metabolism / Q000473:pathology; D065306:Corneal Injuries; D016510:Corneal Neovascularization / Q000139:chemically induced* / Q000378:metabolism* / Q000473:pathology; D015536:Down-Regulation; D005126:Eye Burns / Q000473:pathology; D008081:Liposomes; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D054390:Receptors, CCR2 / Q000172:deficiency / Q000378:metabolism*; D019707:Receptors, Chemokine / Q000172:deficiency / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000468:Alkalies; D000073883:CX3C Chemokine Receptor 1; C515335:Ccr2 protein, mouse; C471885:Cx3cr1 protein, mouse; D008081:Liposomes; D054390:Receptors, CCR2; D019707:Receptors, Chemokine; D014409:Tumor Necrosis Factor-alpha; D004002:Clodronic Acid; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9