Royal jelly regulates the proliferation of human dermal microvascular endothelial cells through the down-regulation of a photoaging-related microRNA.

Although royal jelly is believed to prevent skin aging, the underlying mechanism is not known in detail. In the present study, we investigated the plausibility of the involvement of microRNAs in the manifestation of this effect of royal jelly. The expression of microRNAs was determined by PCR array analysis and real-time PCR and the number of cells was counted with a cell counter. Using PCR array, we identified four microRNAs that were downregulated by royal jelly in cultured human dermal microvascular endothelial cells (HDMEC). Upon comparison of the expression of the four microRNAs between young and senescent facial skin, miR-129-5p was found to be significantly upregulated in senescent skin. Consistently, the expression of miR-129-5p in HDMEC was significantly increased by UVB radiation, suggesting that this microRNA is related to photoaging. The royal jelly treatment increased the number of HDMEC. Furthermore, forced overexpression of miR-129-5p resulted in significant decrease in the number of HDMEC, and its forced downregulation increased the number of cells. The number and density of vessels is reported to be decreased in aged skin. Our results indicate that miR-129-5p is induced in damaged endothelial cells upon exposure to UV radiation, which decreases the cell number. Furthermore, administration of royal jelly downregulated the expression of miR-129-5p in endothelial cells, and might prevent skin aging by maintaining the number of cells. The present study elucidates the mechanism of vessel aging caused by UV exposure and the anti-aging effects of royal jelly through the involvement of microRNA.