The roles of vitreal macrophages and circulating leukocytes in retinal neovascularization.
OBJECTIVE
To analyze the roles of vitreal macrophages and circulating leukocytes in retinal vascular growth.


METHODS
Bone marrow (BM) cells from green fluorescent protein (GFP) transgenic mice were transplanted into postnatal day (P)1 mice after irradiation. The mice were exposed to 76% to 78% oxygen (P7-P12), to initiate oxygen-induced retinopathy (OIR). The eyes were collected at P8, P17, and P30, to analyze the engraftment of GFP-positive cells in the retina. GFP-positive peritoneal macrophages, clodronate liposomes, or control liposomes were injected into the eyes at P5 or P12 to examine the effects at P8 or P17. The number of Iba1-positive vitreal macrophages was quantified from histologic sections at P12 and P17.


RESULTS
Few transplanted GFP-positive cells were found in the retina at P8 in both wild-type and OIR mice. However, their number increased at P17 during retinal neovascularization in OIR. Most GFP-positive cells were Iba1-positive microglia, which comprised a minority of the total retinal microglia. Intravitreal injection of peritoneal macrophages showed only incidental migration of these cells into the wild-type retinas (P8), whereas the engraftment was more robust, typically around the neovascularization, in OIR mice (P17). Furthermore, native macrophages in the vitreous cavity became fewer (37.7% reduction) during neovascularization in OIR at P17. The selective depletion of vitreal macrophages by clodronate liposomes at P12 reduced retinal neovascularization in OIR mice by 59.0% at P17.


CONCLUSIONS
Vitreal macrophages are attracted to the site of pathologic angiogenesis triggered by retinal ischemia, where they actively participate in vascular development.
Department of Ophthalmology, Nagoya University School of Medicine, Nagoya, Japan.
Keiko
K
Kataoka
Koji M
KM
Nishiguchi
Hiroki
H
Kaneko
Nico
N
van Rooijen
Shu
S
Kachi
Hiroko
H
Terasaki
D000818:Animals; D016026:Bone Marrow Transplantation; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D004002:Clodronic Acid / Q000633:toxicity; D004195:Disease Models, Animal; D049452:Green Fluorescent Proteins / Q000235:genetics; D058449:Intravitreal Injections; D007962:Leukocytes / Q000502:physiology*; D008212:Lymphocyte Depletion; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008840:Microfilament Proteins; D017628:Microglia / Q000378:metabolism; D010100:Oxygen / Q000633:toxicity; D010587:Phagocytosis / Q000502:physiology; D015861:Retinal Neovascularization / Q000378:metabolism* / Q000473:pathology; D012171:Retinal Vessels / Q000378:metabolism* / Q000473:pathology; D014822:Vitreous Body / Q000166:cytology*
C491049:Aif1 protein, mouse; D002135:Calcium-Binding Proteins; D008840:Microfilament Proteins; D004002:Clodronic Acid; D049452:Green Fluorescent Proteins; D010100:Oxygen