Human placental extract activates a wide array of gene expressions related to skin functions

Abstract

As skin aging is one of the most common dermatological concerns in recent years, scientific research has promoted treatment strategies aimed at preventing or reversing skin aging. Breakdown of the extracellular matrix (ECM), such as collagen and elastin fibers, in the skin results in decreased skin elasticity and tension. Cutaneous cells, especially fibroblasts in the dermis layer of the skin, mainly produce ECM proteins. Although clinical studies have demonstrated that placental extract (PE) has positive effects on skin health, the molecular mechanisms by which PE acts against skin aging are still largely unknown. In this study, we performed RNA-sequence analysis to investigate whether human PE (HPE) alters ECM-related gene expression in normal human dermal fibroblast (NHDF) cells. Gene ontology analysis showed that genes related to extracellular matrix/structure organization, such as COL1A1, COL5A3, ELN, and HAS2 were highly enriched, and most of these genes were upregulated. We further confirmed that the HPE increased the type I collagen, proteoglycan versican, elastin, and hyaluronan levels in NHDF cells. Our results demonstrate that HPE activates global ECM-related gene expression in NHDF cells, which accounts for the clinical evidence that the HPE affects skin aging.

Figure 1

HPE increases collagen levels both at mRNA and protein levels. (a) Schematic diagram of HPE treatment procedure. (b and c) Effects of HPE on PIP production and COL1A1 mRNA expression in cultured NHDF cells. Cells were treated with or without HPE for 72 h. *p < 0.05, ***p < 0.001, or ns, not significant, compared to the control, 0 mg/mL HPE, by ANOVA followed by Fisher’s LSD test.

Figure 2

HPE globally affects gene expression levels in NHDF cells. (a) Volcano plot of differentially expressed genes of HPE-treated NHDF cells. Red, black, and green dots represent upregulated, non-differentially expressed, and down-regulated genes, respectively. (b) Six selected genes from DEGs were validated by qPCR. GAPDH gene was used as the reference. White or black bars indicate control (ctrl) or HPE-treated samples, respectively. *p < 0.05, **p < 0.01, or ***p < 0.001, ****p < 0.0001 compared to the control sample by Unpaired Student’s t-test. (c) The levels of 6 selected genes show the correlation between the results of RNA-seq and qPCR (correlation coefficient = 0.8334).

Figure 3

Gene ontology (GO) enrichment analyses revealed ECM enhancing functions by HPE. (a) Top 5 significantly enriched GO terms in the BP (green), MF (orange), and CC (blue). (b) DEGs under the top identified BP, MF, and CC. Red and blue bars represent up and downregulated genes, respectively. (c) Pie charts show percentages and numbers of upregulated (red) and downregulated (blue) DEGs in BP, MF, and CC. BP: Biological process; MF: Molecular function; CC: Cellular components.

Figure 4

HPE affects the production of ECM components in NHDF cells. The amount of proteoglycan versican, elastin and hyaluronan in culture supernatants of NHDF cells after HPE treatment were measured by ELISA. White or black bars indicate control (ctrl) or HPE-treated samples, respectively. *p < 0.05, **p < 0.01, or ***p < 0.001, ****p < 0.0001 compared to the control sample by unpaired Student’s t-test.