Figure 4. Brain Capillaries Sense and Adopt Cues in the Circulatory Milieu, with Aged Plasma Exposure Recapitulating the Normal Aging Transcriptomic Signature.

(A) Schematic of the aged mouse plasma (AMP) acute infusion paradigm in young mice.

(B) tSNE of AMP- and PBS-treated BECs from young (3 months) mice after CCA, using the top-9 correlation components. AMP- and PBS-treated cells show comparable distributions of A, C, and V identities, suggesting plasma infusions do not significantly alter native segmental identities.

(C) Expression bar plots of canonical A-C-V marker genes in AMP- and PBS-treated BECs, with segmental identities defined by unbiased clustering in (B).

(D) Volcano plot depicting up- and downregulated genes with AMP treatment in capillaries (compared to PBS control). Genes marked in red are significant (FDR < 0.1). FDR values are calculated only with genes showing an average log₂FC > 0.1. Genes labeled red are FDR <0.1.

(E) Dotted heatmap of top 60 DEGs ranked by the signed-FDR value (product of log₂FC*⁻log₁₀(FDR)). Color indicates the average log₂FCof AMP/PBS, while the dot size represents degree of statistical significance. DEGs with FDR < 0.1 for at least one vessel segment are listed and ordered by hierarchically clustering (dot size = 0 indicates FDR > 0.1).

(F) Scatterplot of genes and their log₂FCin both aged/young and AMP/PBS treatment in capillaries. The 153 genes commonly up- (blue) or downregulated (green) in both groups (FDR <0.1 in both) are labeled. These DEGs may be modulated by plasma factors upregulated in normal aging. Inset shows the same genes (red) on a scatterplot of the signed-FDR value (product of log₂FC*⁻log10(FDR)) for normal aging and AMP.

(G) Top pathways over-represented by DEGs upregulated in both normal aging and with AMP treatment (149 intersecting DEGs).