Sostdc1 Secreted from Cutaneous Lymphatic Vessels Acts as a Paracrine Factor for Hair Follicle Growth

Abstract

In our previous study, we found that lymphatic vessels stimulate hair follicle growth through paracrine effects on dermal papilla cells. However, the paracrine factors secreted from cutaneous lymphatic vessels that can activate dermal papilla cells are still unknown. In this study, we investigated whether lymphatic endothelial cells might secrete paracrine factors that activate dermal papilla cells in vitro. We found that Sostdc1 was more expressed in lymphatic endothelial cells compared with blood vascular endothelial cells. In addition, Sostdc1 expression levels were significantly increased during the anagen phase in the back skin of C57BL/6J mice, as compared to the telogen phase. We also observed that incubation of dermal papilla cells with 200 ng/mL Sostdc1 for 72 h induced the expression levels of Lef-1, a downstream target of Wnt signaling. Taken together, our results reveal that Sostdc1, a BMP antagonist, secreted from cutaneous lymphatic vessels, may act as a paracrine factor for hair follicle growth.

Keywords: Sostdc1; dermal papilla cells; hair follicle growth; lymphatic vessels.

Figure 1

Sostdc1 is highly expressed in lymphatic endothelial cells compared with blood vascular endothelial cells. (A,B) The expression of Sostdc1 in matched pairs of human LECs and BECs was determined by microarray (A) and by qRT-PCR (B). (C) Sostdc1 protein levels were measured by ELISA in conditioned media of control (CON-CM) and conditioned media of LECs (LEC-CM). Results are expressed as mean ± standard error of the mean (SEM). Data were analyzed using a two-tailed unpaired t-test. * p < 0.05 compared to the control group.

Figure 2

Lymphatic vessels express Sostdc1. Immunofluorescent staining of 10-µm frozen sections of back skin (anagen phase, postnatal day 8) for Prox1 (lymphatic-specific transcription factor, green) and Sostdc1 (red). Nuclear staining with Hoechst 33342 (blue). White arrows indicate the bulge area (Bu). Scale bars: 20 μm.

Figure 3

Sostdc1 expression levels were significantly increased during the anagen phase. (A) LECs were incubated with 400 ng/mL VEGF-C for 24 h, followed by qRT-PCR to assess Sostdc1 expression. (B) Total RNA was isolated from the back skin of female C57BL/6 mice and Sostdc1 expression was determined by qRT-PCR. (C) DPCs were treated with the indicated concentrations of Sostdc1 for 72 h and Lef-1 mRNA expression was determined by qRT-PCR. (D) DPCs were incubated with 50% LEC-CM-Sostdc1 shRNA or LEC-CM-scrambled shRNA for 48 h. Total RNA was isolated and mRNA expression levels of WNT7b, BMP2 and BMP4 were measured by qRT-PCR. Results are expressed as mean ± SEM. Data were analyzed using a two-tailed unpaired t-test. * p < 0.05, ** p < 0.01 compared to the control group.