Ischemic stroke is the leading cause of neurological death and disability, and age remains the strongest non-modifiable risk factor: more than 75% of cases occur in people over 65. The penumbra is the tissue surrounding the infarct core, where blood flow is reduced but cells are still alive and can be saved by timely reperfusion. Until now, it has been defined by hemodynamic, cellular, or molecular criteria, but there was no transcriptome map that accounted for age and disease stage. This work stands apart from neighboring studies that examined either young animals, or single time points, or lacked spatial resolution.
The researchers used the 10x Visium platform for spatial gene expression profiling in brain sections from 20 mice: young (3–4 months) and old (19–20 months), after sham surgery or transient middle cerebral artery occlusion, on day 3 and day 14. In total, 62,958 high-quality spots were analyzed. Clustering identified 7 anatomical zones, including lesion sites at day 3 and day 14. Within the lesions, secondary clustering revealed a periphery and a core, with the periphery defined as the transcriptomic penumbra based on comparison with MRI and histology. Next, they integrated the data with previously published single-cell RNA-seq, applied RCTD deconvolution, CellChat ligand-receptor interaction analysis, and SCENIC regulatory network analysis.
The transcriptomic penumbra (TP) showed a clear "periphery around core" structure at all stages and in both age groups. In the acute phase (day 3), energy metabolism and synaptic transmission are suppressed in the TP, while inflammation and protein synthesis are activated; in the chronic phase (day 14), myelination and angiogenesis partially recover. Aging altered the dynamics: in old mice, the TP was larger at day 14, although the cellular composition was almost identical. Age suppressed genes for oxidative phosphorylation, lipid metabolism, synaptic and repair programs, but enhanced immune responses. Among cell types, neurons, oligodendrocytes, and choroid plexus cells showed the greatest age sensitivity. The analysis revealed a loss of reparative ligand-receptor pairs in old mice, including TNR/FN1/COL4A2-SDC4 in the acute phase and FGF1-FGFR1/2/3 in the chronic phase, as well as key transcription factors driving age-related microglial dysfunction.
This work provides the first spatiotemporal atlas of the stroke penumbra transcriptome that accounts for age. Unlike neighboring studies that were limited to young animals or a single time point, it covers both ages and two stages, making it possible to separate the effects of aging from those of time after stroke. It shows that aging acts not by changing cell composition but through intrinsic molecular failures, and that the penumbra in old mice does not disappear faster but even expands in the chronic stage, which contradicts expectations based solely on imaging.
The field could move toward integrating proteomic and post-translational data to test how mRNA changes translate into protein function. It would also be promising to study the dynamics of the infarct core and undamaged tissue, not just the penumbra. Functional validation of the identified candidate genes in cell and animal models will be the next step toward therapy, possibly combination therapy, to maximize tissue rescue in the elderly.
The results will influence ischemic stroke research, neurogeriatrics, and the development of targeted therapies aimed at saving the penumbra. The atlas will be useful for biomarker discovery and for testing hypotheses about the mechanisms of age-dependent worsening of outcomes.
Conduct functional experiments with knockout or pharmacological manipulation of the identified genes (e.g., Fgf1, Sdc4) in old mice to confirm their role in repair. It would also be worth extending the analysis to female animals and other stroke models.
This work directly addresses an unresolved problem in neuroscience: why the aged brain recovers worse after ischemia despite preservation of the penumbra. It shows that the key failures lie in energy metabolism, synaptic stability, and intercellular communication, not in cell death as such. This links aging to impaired plasticity and repair programs, which remains a central question in the study of age-related brain diseases.
In old mice, the transcriptomic penumbra turned out to be larger at day 14 after stroke, even though MRI showed no difference in infarct size compared with young mice. This means that tissue that looks dead on a scan may still retain molecular signs of salvageability.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.