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Melissa Liu, Xiaoguang Cao, Rafael Villasmil, Jingsheng Tuo, Defen Shen, Phyllis Silver, Chi-Chao Chan; Macrophage Polarization In C57BL/6 And Ccl2-/-/Cx3cr1-/- Mice. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2297.
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Age-related macular degeneration (AMD) is an immunologic disease. Activated macrophages have been shown to accumulate in or near AMD lesions and secrete chemokines and cytokines linked to AMD. Aberrant macrophage polarization towards pro-inflammatory M1 or pro-angiogenic M2 populations may play a role in the pathogenesis of AMD. The Ccl2-/-/Cx3cr1-/- mouse (DKO) develops focal AMD-like retinal and subretinal lesions, photoreceptor degeneration, retinal pigment epithelium abnormalities, and high A2E levels. We have reported that macrophages contribute to the AMD-like pathology in these mice. This study comparatively investigated macrophage polarization in DKO and C57BL/6 (WT) mice.
Splenic macrophages were isolated from WT and DKO mice and purified by CD11b+ selection using both magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). Macrophages were cultured under M1 (IFN-γ or LPS) or M2 (IL-4+IL-13) polarizing conditions. Cell culture supernatant was collected for ELISA and Griess Assay, and mRNA was extracted from cultured macrophages for RT-PCR to evaluate the expression of representative M1 and M2 markers.
Relative to WT, DKO macrophages demonstrated impaired ability to respond to M1 stimulation but similar ability to respond to M2 stimulation. IFN-γ significantly increased iNos expression in WT but not DKO macrophages (p<0.05). With LPS, DKO macrophages showed less upregulation of the pro-inflammatory cytokines Tnf-α, Il-1β, and IL-6 (p<0.05). Interestingly, expression of the anti-inflammatory molecules Il-10 and Arg1 did not vary significantly between WT and DKO macrophages.
The expression and secretion profiles of WT and DKO macrophages vary under different polarizing conditions. Naïve DKO macrophages have an impaired ability to respond to microenvironmental stimuli promoting M1 polarization. This difference between WT and DKO macrophages may contribute to aberrant systemic immune responses that play a role in AMD pathogenesis and the focal retinal degenerative lesions observed in DKO mice.
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