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Updated: Aug 21, 2026
Depletion and Reconstitution of Macrophages in Mice
Published on: August 1, 2012
Macrophage depletion diminishes lesion size and severity in experimental choroidal neovascularization
Diego G Espinosa-Heidmann1, Ivan J Suner, Eleut P Hernandez
1Bascom Palmer Eye Institute, Department of Ophthalmology, The University of Miami School of Medicine, Miami, Florida, USA.
Insights
Macrophage depletion using clodronate liposomes (CL(2)MDP-lip) significantly reduced choroidal neovascularization (CNV) severity in a mouse model. This supports the role of macrophages in AMD pathogenesis.
Area of Science:
- Ophthalmology
- Immunology
- Pathogenesis of Age-Related Macular Degeneration (AMD)
Background:
- Macrophage recruitment to the choroid is implicated in the development of choroidal neovascularization (CNV), a key process in AMD.
- Understanding the role of macrophages in CNV pathogenesis is crucial for developing effective AMD treatments.
Purpose of the Study:
- To investigate whether clodronate liposomes (CL(2)MDP-lip), a macrophage-depleting agent, can reduce the severity of laser-induced CNV in a mouse model.
- To determine the impact of blood monocyte and choroidal macrophage depletion on neovascularization.
Main Methods:
- Laser-induced CNV was performed in aged C57BL/6 mice.
- Macrophages were depleted using intraperitoneal and subcutaneous injections of CL(2)MDP-lip.
- CNV severity was assessed by measuring lesion size, vascularity, and cellularity using flatmount analysis and histopathology.
Main Results:
- CL(2)MDP-lip treatment effectively depleted circulating monocytes and choroidal macrophages.
- Macrophage-depleted mice showed a significant reduction in CNV area, vascularity, and cellularity compared to controls.
- Histopathology confirmed smaller diameter and thickness of CNV lesions in the treated group.
Conclusions:
- Macrophage depletion using CL(2)MDP-lip effectively reduces the size, cellularity, and vascularity of CNV lesions.
- These findings support the hypothesis that macrophages play a significant role in the pathogenesis and severity of CNV in AMD.
Purpose:
Macrophage recruitment to the choroid has been proposed to contribute to the pathogenesis of choroidal neovascularization (CNV) in AMD. The study was conducted to determine whether treatment with clodronate liposomes (CL(2)MDP-lip), which cause depletion of blood monocytes and lymph node macrophages, diminishes the severity of neovascularization in a mouse model of laser-induced CNV.
Methods:
Laser-induced CNV was performed in female 16-month-old C57BL/6 mice. Macrophages were depleted by use of CL(2)MDP-lip intraperitoneally and subcutaneously 72 and 24 hours before and every 2 to 3 days after laser injury. Control mice received injections of either PBS alone or PBS liposomes. Blood monocyte and choroidal macrophage depletion were documented by flow cytometry and choroidal flatmount preparation analysis, respectively. Two weeks after laser injury, mice were injected intravenously with fluoresceinated dextran. The right eyes were removed and prepared for flatmount analysis of CNV surface area (in relative disc areas or DA), vascularity (relative fluorescence), and cellularity (propidium iodide stain). The mice were then perfused with 10% formaldehyde, and the left eyes were removed for histopathology. The means of the various parameters for four CNV lesions per eye were calculated. Fluorescein angiography was also performed.
Results:
Flow cytometry of circulating monocytes and immunohistochemical analysis of choroidal macrophage density confirmed the effective depletion of blood monocytes and choroidal macrophages respectively in CL(2)MDP-lip-treated mice. Compared with the control, flatmount analysis of macrophage depleted mice demonstrated a significant reduction in size of the CNV area (2.8 +/- 0.5 DA vs. 1.4 +/- 0.1 DA; P < 0.043). The treated group also revealed less vascularity (1.6 +/- 0.1 units vs. 1.1 +/- 0.0 units; P < 0.0092) and cellularity of CNV lesions (3.3 +/- 0.6 DA vs. 1.7 +/- 0.1 DA, P < 0.04). Histopathology revealed that, in the macrophage-depleted group, CNV was smaller in diameter (1270 +/- 73 pixels vs. 770 +/- 82 pixels, P < 0.0006) and thickness (120 +/- 7 pixels vs. 96 +/- 7 pixels, P < 0.019).
Conclusions:
Macrophage depletion using CL(2)MDP-lip reduces size, cellularity, and vascularity of CNV. This observation supports the hypothesis that macrophages contribute to the severity of CNV lesions.
