NFAT1⁺ microglia promote antiinflammatory polarization and angiogenesis via the HAS3-HA-LYVE1 axis to improve...

Neuroinflammation and angiogenesis are central to post-stroke repair. However, the cellular and molecular mechanisms regulating these events remain incompletely understood. The nuclear factor of activated T cells-1 (NFAT1) is implicated in inflammation and vascular remodeling, yet its role in ischemic stroke is unclear.

We established Nfat1-deficient (Nfat1^-/-) and Nfat1^+/+ stroke mice to investigate the role of NFAT1 in post-stroke inflammation and repair. Neurological outcomes, infarct volume, neuronal injury, synaptic protein expression, neuroinflammation, angiogenesis, and cerebral blood flow were assessed by behavioral test, magnetic resonance imaging (MRI), Nissl staining, western blotting, ELISA, immunofluorescence, and laser speckle imaging, respectively. ChIP, dual-luciferase, and mechanistic assays identified NFAT1 downstream targets and signaling pathways. Conditioned medium experiments examined the impact of Nfat1^+/+ primary microglia on endothelial cell behavior. NFAT1-overexpressing microglia were transplanted to assess therapeutic efficacy in vivo.

Nfat1^-/- stroke mice showed worsened neurological function, increased neuronal damage, and reduced expression of antiinflammatory and proangiogenic factors (interleukin (IL)-10, tumor growth factor (TGF)-β, VEGFA, and FGF2). NFAT1 deficiency impaired microglial polarization (CD163⁺ and CD206⁺), angiogenesis, and blood perfusion. NFAT1 upregulated HAS3 and LYVE1, promoting HA-LYVE1 autocrine/paracrine signaling and activation of the Wnt/β-catenin pathway, which facilitated antiinflammatory polarization. Conditioned medium experiments confirmed that Nfat1^+/+ microglia enhanced endothelial cell proliferation, migration, and tube formation. NFAT1-overexpressing microglia therapy enhanced antiinflammatory responses and angiogenesis, improved neurological recovery (e.g. Garcia score at day 35 increased by 0.87 points versus control), and reduced infarct size (corrected infarct area decreased by 27.29 units) in stroke mice.

Microglial NFAT1 drives antiinflammatory polarization and angiogenesis via the HAS3-HA-LYVE1-Wnt/β-catenin axis, ultimately improving stroke recovery. These findings reveal a previously unrecognized mechanism of neurovascular repair and highlight NFAT1⁺ microglia as a promising therapeutic target for ischemic stroke.