Then, we confirmed the down-regulated expressions of ABCC4, PTGER3, BCEH, HPGD, and MOXD1 in normal group, while AR, CXCR2, HSD17B2, ODC1, PI3, PLAU and THBS2 were up-regulated in skin aging group (Figure 5A, 5B). This evidence concerns the gene HPGD and skin aging.