Promoting astrocyte-neuron triiodothyronine shuttling attenuates brain damage in neonatal hypoxic-ischemic...

BACKGROUND: Neonatal Hypoxic-Ischemic Encephalopathy (HIE) is a critical lifelong disabling neonatal disease with insufficient effective therapies. Signaling molecules derived from Astrocyte-Neuron Crosstalk have the potential to improve the prognosis, but relevant HIE research is limited. METHODS: We established hypoxic–ischemic brain damage (HIBD) in postnatal day 7 rat pups using the Rice–Vannucci model, and verified the injury both structurally and hemodynamically by histopathology and laser speckle contrast imaging. Whole-brain single-cell RNA sequencing was performed at P10, and proteomic profiling was conducted on astrocytes subjected to oxygen–glucose deprivation. We charted astrocyte diversity in situ using multiplex immunofluorescence. Thyroid hormones and signaling pathways were quantified by ELISA and Western blotting. Therapeutic efficacy was assessed by histopathology and the Morris water maze. RESULTS: A brain-wide single-cell transcriptomic atlas revealed a strong transcriptional coupling between astrocytes and neurons. Among astrocytes, we identified and functionally characterized a Dio2⁺Slc1a2⁺ subpopulation with metabolic and neuroprotective features, which was markedly depleted after HIBD. Pseudotime trajectories showed dynamic astrocyte state transitions over time, contextualizing the loss and reparative potential of the Dio2⁺ subpopulation. In vivo and in vitro, boosting astrocytic Dio2 or delivering exogenous Triiodothyronine(T3) enhanced neural repair and improved behavior across both early and long-term stages. CONCLUSIONS: We defined a previously unrecognized neuroprotective astrocyte subpopulation and revealed temporal heterogeneity in astrocytic inflammatory responses in HIE. We also identified a T3-mediated astrocyte–neuron crosstalk mechanism that mitigated HIBD, highlighting a tractable therapeutic avenue.