Summary Pathologic angiogenesis mediated by abnormally polarized macrophages plays a central role in common age-associated diseases such as atherosclerosis, cancer and macular degeneration. Here we demonstrate that abnormal polarization in older macrophages is caused by programmatic changes that lead to reduced expression of ATP binding cassette transporter ABCA1. Downregulation of ABCA1 by microRNA-33 impairs the ability of macrophages to effectively efflux intracellular cholesterol, which in turn leads to higher levels of free cholesterol within senescent macrophages. Elevated intracellular lipid polarizes older macrophages to an abnormal, alternatively activated phenotype that promotes pathologic vascular proliferation. Mice deficient for Abca1, but not Abcg1, demonstrate an accelerated aging phenotype, whereas restoration of cholesterol efflux using LXR agonists or miR-33 inhibitors reverses it. Monocytes from older humans with age-related macular degeneration showed similar changes. These findings provide an avenue for therapeutic modulation of macrophage function in common age-related diseases.

SUMMARY Photoreceptor death is the endpoint of many blinding diseases. Identifying unifying pathogenic mechanisms in these diseases may offer global approaches for facilitating photoreceptor survival. We found that rod or cone photoreceptor-specific deletion of nicotinamide phosphoribosyltransferase (Nampt), the rate-limiting enzyme in the major NAD+ biosynthetic pathway beginning with nicotinamide, caused retinal degeneration. In both cases, we could rescue vision with nicotinamide mononucleotide (NMN). Significantly, retinal NAD+ deficiency was an early feature of multiple mouse models of retinal dysfunction, including light-induced degeneration, streptozotocin-induced diabetic retinopathy, and age-associated dysfunction. Mechanistically, NAD+ deficiency caused metabolic dysfunction and consequent photoreceptor death. We further demonstrate that the NAD+-dependent mitochondrial deacylases SIRT3/SIRT5 play important roles in retinal homeostasis and that NAD+ deficiency causes SIRT3 dysfunction. These findings demonstrate that NAD+ biosynthesis is essential for vision, provide a foundation for future work to further clarify the mechanisms involved, and identify a unifying therapeutic target for diverse blinding diseases.

Macrophage dysfunction plays a pivotal role during neovascular proliferation in diseases of ageing including cancers, atherosclerosis and blinding eye disease. In the eye, choroidal neovascularization (CNV) causes blindness in patients with age-related macular degeneration (AMD). Here we report that increased IL10, not IL4 or IL13, in senescent eyes activates STAT3 signalling that induces the alternative activation of macrophages and vascular proliferation. Targeted inhibition of both IL10 receptor-mediated signalling and STAT3 activation in macrophages reverses the ageing phenotype. In addition, adoptive transfer of STAT3-deficient macrophages into eyes of old mice significantly reduces the amount of CNV. Systemic and CD163+ eye macrophages obtained from AMD patients also demonstrate STAT3 activation. Our studies demonstrate that impaired SOCS3 feedback leads to permissive IL10/STAT3 signalling that promotes alternative macrophage activation and pathological neovascularization. These findings have significant implications for our understanding of the pathobiology of age-associated diseases and may guide targeted immunotherapy.

Endothelial cells (ECs) express fibroblast growth factor receptors (FGFRs) and are exquisitely sensitive to FGF signals. However, whether the EC or another vascular cell type requires FGF signaling during development, homeostasis, and response to injury is not known. Here, we show that Flk1-Cre or Tie2-Cre mediated deletion of FGFR1 and FGFR2 (Fgfr1/2Flk1-Cre or Fgfr1/ 2 Tie2-Cre mice), which results in deletion in endothelial and hematopoietic cells, is compatible with normal embryonic development. As adults, Fgfr1/2 Flk1-Cre mice maintain normal blood pressure and vascular reactivity and integrity under homeostatic conditions. However, neovascularization after skin or eye injury was significantly impaired in both Fgfr1/2Flk1-Cre and Fgfr1/2Tie2-Cre mice, independent of either hematopoietic cell loss of FGFR1/2 or vascular endothelial growth factor receptor 2 (Vegfr2) haploinsufficiency. Also, impaired neovascularization was associated with delayed cutaneous wound healing. These findings reveal a key requirement for cell-autonomous EC FGFR signaling in injuryinduced angiogenesis, but not for vascular homeostasis, identifying the EC FGFR signaling pathway as a target for diseases associated with aberrant vascular proliferation, such as age-related macular degeneration, and for modulating wound healing without the potential toxicity associated with direct manipulation of systemic FGF or VEGF activity.choroidal neovascularization | oxygen-induced retinopathy | retinopathy of prematurity | neoangiogenesis N eovascularization is critical for tissue repair and pathological conditions, including aberrant ocular angiogenesis and cancer (1-4). Although FGF signaling has been prominently implicated in these processes based on genetic inactivation experiments in mice and in vitro studies, the functional in vivo requirement of this pathway in the endothelial cell (EC) vs. other vascular cell types is not known (5-8).The FGF family is composed of 18 signaling ligands, which interact with four cell surface tyrosine kinase receptors. FGF receptor (FGFR) signaling regulates many biological processes, including survival, differentiation, proliferation, and angiogenesis through the activation of RAS-RAF-MAPK, PI3K, STAT, and PLC gamma pathways (6, 9). The EC response to FGF signals is well described in in vitro models of angiogenesis (10, 11). Moreover, previous gene expression analysis showed that Fgfr1 and Fgfr2 were the predominant Fgfrs in ECs (5), whereas Fgfr3 was sparsely detected (12, 13) and Fgfr4 expression was not reported (8). To this end, and given the critical role of FGFRs 1 and 2 during embryonic development, we tested the hypothesis that EC FGFR1/2 may play a key role during vascular development, homeostasis, and response to injury.Studies aimed at understanding the functional requirement of vascular FGF signaling have demonstrated a critical role in homeostasis and angiogenesis (14-16). In these studies, in vivo expression of an adenoviral-based soluble FGF trap (sFGFR) or a dominant inhibitor of all FGFRs (FGF...

Background: The Wnt signaling pathway is a cellular communication pathway that plays critical roles in development and disease. A major class of Wnt signaling regulators is the Dickkopf (Dkk) family of secreted glycoproteins. Although the biological properties of Dickkopf 1 (Dkk1) and Dickkopf 2 (Dkk2) are well characterized, little is known about the function of the related Dickkopf 3 (Dkk3) protein in vivo or in cell lines. We recently demonstrated that Dkk3 transcripts are upregulated during photoreceptor death in a mouse model of retinal degeneration. In this study, we characterized the activity of Dkk3 in Wnt signaling and cell death.