Validation of differential age-related gene expression in individual tissue samples. qRT-PCR was performed on RNA from epidermal suction blisters of 18 healthy female volunteers (9 young and 9 old volunteers). The heatmap shows processed ΔCt values. Gene expression differences of individual samples are indicated relative to the gene-specific, age-independent average expression level over all samples (blue: lower ΔCt, red: higher ΔCt). Numbers in the left colum indicate fold-change differences in gene expression between young and old, as determined by transcriptome sequencing. P values were determined by a Mann-Whitney U test and indicate the significance for differential gene expression. The line between VCL and RHPN2 separates genes with a ≥2-fold change in gene expression from genes with a <2-fold change.