Fig. 1.

Old blood induces aging-like changes in vascular mRNA expression profile Panel A: Principal component analysis (PCA) plot of mRNA expression profiles in aorta samples derived from isochronic parabiont young mice [Y–(Y)], isochronic parabiont aged mice [A–(A)] and heterochronic parabiont young mice [Y–(A)]. The profiles from Y–(Y) mice (green) cluster separately from clusters representing A–(A) mice (red) and Y–(A) mice (yellow) in the space of the first three principal components. The A–(A) and Y–(A) expression profiles were more similar and clustered less discriminately in the PCA, indicating the impact of old blood on the aorta transcriptome in young mice. PC1, PC2, and PC3: Principal components 1, 2, and 3, respectively. Panel B: The heat map is a graphic representation of normalized expression values of genes that are differentially expressed both in aorta samples derived from isochronic parabiont aged mice [A–(A)] and heterochronic parabiont young mice [Y–(A)] as compared to those in aorta samples obtained from isochronic parabiont young mice [Y–(Y)]. The expression values for these genes in aorta samples obtained from heterochronic parabiont aged mice [A–(Y)] are also shown. Hierarchical clustering analysis reveals groups of genes whose expression is similarly up- or down-regulated in aortas of both A–(A) mice and Y–(A) mice but is unaffected by the presence of young blood in A–(Y) mice. Panel C: Volcano plot depicting differentially expressed genes comparing aortic samples derived from Y–(Y) and Y–(A) mice. Stratified p-values are plotted against expression fold changes for results obtained in Y–(A) samples normalized to Y–(Y) samples. Colored points refer to genes whose expression is significantly altered in Y–(A) mice