Natural killer cells promote neutrophil extracellular traps and restrain macular degeneration in mice.

Neovascular age-related macular degeneration (nvAMD) is the leading cause of blindness in the elderly population. Although it is known that nvAMD is associated with focal inflammation, understanding of the precise immune components governing this process remains limited. Here, we identified natural killer (NK) cells as a prominent lymphocyte population infiltrating the perivascular space of choroidal neovascularization (CNV) lesions in patients with nvAMD and in mouse models. Olink proteomic analysis and single-cell RNA sequencing combined with knockout studies demonstrated the involvement of C-C chemokine receptor 5 (CCR5) in NK cell recruitment and extravasation at the CNV sites of mice. Depletion of NK cells or inhibition of activating receptor NK group 2, member D (NKG2D) inhibited the formation of neutrophil extracellular traps, increased vascular leakage, and exacerbated pathological angiogenesis, indicating that NK cells restrain pathogenesis in this mouse model. Age is the strongest risk factor for AMD, and we show that NK cells from aged human donors exhibited a less cytotoxic phenotype. NK cells from old mice exhibited compromised protective effects in the CNV mouse model. In addition, interleukin-2 complex-mediated expansion of NK cells improved CNV formation in mice. Collectively, our study highlights NK cells as a potential therapeutic target for patients with nvAMD.

Protein Phosphatase 2A Mediates YAP Activation in Endothelial Cells Upon VEGF Stimulation and Matrix Stiffness.

Angiogenesis is an essential process during development. Abnormal angiogenesis also contributes to many disease conditions such as tumor and retinal diseases. Previous studies have established the Hippo signaling pathway effector Yes-associated protein (YAP) as a crucial regulator of angiogenesis. In ECs, activated YAP promotes endothelial cell proliferation, migration and sprouting. YAP activity is regulated by vascular endothelial growth factor (VEGF) and mechanical cues such as extracellular matrix (ECM) stiffness. However, it is unclear how VEGF or ECM stiffness signal to YAP, especially how dephosphorylation of YAP occurs in response to VEGF stimulus or ECM stiffening. Here, we show that protein phosphatase 2A (PP2A) is required for this process. Blocking PP2A activity abolishes VEGF or ECM stiffening mediated YAP activation. Systemic administration of a PP2A inhibitor suppresses YAP activity in blood vessels in developmental and pathological angiogenesis mouse models. Consistently, PP2A inhibitor also inhibits sprouting angiogenesis. Mechanistically, PP2A directly interacts with YAP, and this interaction requires proper cytoskeleton dynamics. These findings identify PP2A as a crucial mediator of YAP activation in ECs and hence as an important regulator of angiogenesis.