Macrophages Inhibit Neovascularization in a Murine Model of Age-Related Macular Degeneration

Abstract

BackgroundAge-related macular degeneration (AMD) is the leading cause of blindness in people over 50 y of age in at least three continents. Choroidal neovascularization (CNV) is the process by which abnormal blood vessels develop underneath the retina. CNV develops in 10% of patients with AMD but accounts for up to 90% of the blindness from AMD.Although the precise etiology of CNV in AMD remains unknown, the macrophage component of the inflammatory response, which has been shown to promote tumor growth and support atherosclerotic plaque formation, is thought to stimulate aberrant angiogenesis in blinding eye diseases. The current theory is that macrophage infiltration promotes the development of neovascularization in CNV.Methods and FindingsWe examined the role of macrophages in a mouse model of CNV. IL-10 −/− mice, which have increased inflammation in response to diverse stimuli, have significantly reduced CNV with increased macrophage infiltrates compared to wild type. Prevention of macrophage entry into the eye promoted neovascularization while direct injection of macrophages significantly inhibited CNV. Inhibition by macrophages was mediated by the TNF family death molecule Fas ligand (CD95-ligand).ConclusionsImmune vascular interactions can be highly complex. Normal macrophage function is critical in controlling pathologic neovascularization in the eye. IL-10 regulates macrophage activity in the eye and is an attractive therapeutic target in order to suppress or inhibit CNV in AMD that can otherwise lead to blindness.

Macrophages in neovascular age-related macular degeneration: friends or foes?

“…It is possible, as suggested, that clodronate liposome treatment or other modalities may lead to death or injury of the endothelium, in addition to depletion of circulating monocytes. 71 This is an important consideration; clearly a modality that kills or inhibits the proliferation of the choroidal endothelium would be expected to reduce the severity of CNVMs, and its simultaneous effects on macrophages would be interesting but irrelevant. Whereas animals exposed to clodronate liposomes in other studies are viable, 65 and this delivery does not appear to cause widespread vascular dropout and tissue necrosis, it is feasible that the RPE and choriocapillaris are especially sensitive to this drug.…”

Monocyte/macrophages promote vasculogenesis in choroidal neovascularization in mice by stimulating SDF-1 expression in RPE cells

“…The number of macrophages in peripheral blood and tissues is markedly decreased by this drug, and the effects last for 24-48 h. It is believed to be a safe and stable method for monocyte-macrophage depletion [33]. However, it has been argued that choroidal endothelial cells may be susceptible to clodronate-lip, because liposomes may leak into the laser lesions [34]. In our study, it was true that liposome-DiO could be seen in the laser lesions on day 3, while none were encapsulated by ECs or RPE cells.…”

“…After cryoprotection in 30% sucrose in 0.1 M phosphate buffer overnight at 4°C, vertical sections were cut on a cryostat (12 μm; RM31; Leica, Heidelberger, Nussloch, Germany) and mounted on gelatin-coated slides. For sections from day 14, endothelial and vascular smooth muscle cells (VSMCs) derived from BMCs in CNV were identified by immunofluorescence, performed as described [20]. Serial cross sections were incubated with primary antibodies against CD31 (1:500), α-SMA (1:600; Neomarkers, Fremont, CA, USA), Texas Red or TRITC-conjugated secondary antibodies, and finally counterstained with DAPI.…”

“…To detect the mechanism, we also developed a model of monocyte-retinal pigmental epithelium (RPE) cells co-culture in vitro to survey the alteration of SDF-1. In addition, as clodronate-lip was suspected to inhibit experimental CNV by damaging local cells in the laser lesion [20], we firstly evaluated the effects of clodronate-lip before going into the present research.…”

The stereotypical molecular cascade in neovascular age-related macular degeneration: the role of dynamic reciprocity

“…Finally, do the conflicting results of previous studies of the role of macrophages in various models of NVAMD accurately mimic the disease in humans? [95][96][97][98] TGF-β is a multi-functional cytokine and is usually secreted in its latent form, thus allowing for sustained release throughout the repair process. 76 It can both stimulate and inhibit mitogenesis and stimulate angiogenesis, fibroblast differentiation, and matrix deposition.…”