Platelet-derived growth factor-AA-inducible epiregulin promotes elongation of human hair shafts by enhancing proliferation and differentiation of follicular keratinocytes

Epiregulin ameliorates ovariectomy-induced bone loss through orchestrating the differentiation of osteoblasts and osteoclasts

Epiregulin plays a role in a range of biological activities including malignancies. This study aims to investigate the potential contribution of epiregulin to bone cell differentiation and bone homeostasis. The data showed that epiregulin expression was upregulated during osteogenesis but downregulated during adipogenesis. Functionally, epiregulin promoted osteoblast differentiation while inhibiting adipocyte differentiation from mesenchymal progenitor cells. Epidermal growth factor receptor (EGFR), one of the two known receptors for epiregulin, exerted opposing effects compared to epiregulin. Intriguingly, silencing EGFR almost completely abolished the dysregulation of osteoblast and adipocyte differentiation induced by epiregulin, suggesting that EGFR is indispensable for mediating epiregulin function. Further mechanistic exploration indicated that epiregulin/EGFR signaled via the inactivation of mechanistic target of rapamycin complex 1 (mTORC1) pathway. Moreover, epiregulin downregulated RANKL expression in bone marrow stromal cells (BMSCs) and inhibited the differentiation of bone marrow osteoclast precursor cells into osteoclasts. Treatment of ovariectomized female mice with recombinant epiregulin increased osteoblasts and bone formation, decreased osteoclasts and bone resorption, and ameliorated cancellous bone loss. Consistently, epiregulin treatment improved the potential of BMSCs to differentiate into osteoblasts. Collectively, this study has identified a critical role of epiregulin in regulating osteoblast differentiation through EGFR-mediated inactivation of the mTORC1 pathway, as well as osteoclast differentiation via a mechanism associated with RANKL signaling. Additionally, it highlights the potential of epiregulin as a strategy for combating osteoporosis.

dEREGulated pathways: unraveling the role of epiregulin in skin, kidney, and lung fibrosis

The epidermal growth factor receptor (EGFR) signaling pathway is an evolutionary conserved mechanism to control cell behavior during tissue development and homeostasis. Deregulation of this pathway has been associated with abnormal cell behavior, including hyperproliferation, senescence, and an inflammatory cell phenotype, thereby contributing to pathologies across a variety of organs, including the kidneys, skin, and lungs. To date, there are seven distinct EGFR ligands described. Although binding of these ligands to the receptor is cell type-specific and spatio-temporally controlled with distinct affinities and kinetics, epiregulin (EREG) stands out as a long-acting EGFR ligand that emerges under pathological conditions, particularly in tissue fibrosis. Although EREG has been extensively studied in cancer, its contribution to the maladaptive remodeling of tissue is elusive. The aim of this review is to highlight the role of EREG in skin, kidney, and lung fibrosis and to discuss opportunities for therapeutic intervention.

New Plant Extracts Exert Complementary Anti-Hair Loss Properties in Human In Vitro and Ex Vivo Models

BACKGROUND

Hair loss is linked to dysfunction of the growth (anagen), regression (catagen) and rest (telogen) phases of the hair follicle (HF) cycle.

AIMS

To evaluate the effects of a Silybum marianum extract (SME), manganese PCA (MnPCA), and a Lespedeza capitata extract (LCE) on markers of hair growth and anchorage in human follicle dermal papilla cells (HFDPCs), and to investigate the ability of a topical serum containing these active ingredients to improve HF growth in an ex vivo human scalp skin model.

METHODS

In HFDPCs, we assessed receptor tyrosine kinase phosphorylation and Wnt/β-catenin pathway activation; quantified versican, vascular endothelial growth factor (VEGF) and Dickkopf-1 (DDK1) secretion; and evaluated 5α-reductase (5αR) activity. Using scalp skin biopsies from two female donors, we measured hair shaft elongation, analyzed hair matrix keratinocyte proliferation and apoptosis, and determined HF cycle stage and score.

RESULTS

Compared to untreated HFDPCs, SME upregulated phosphorylation of growth factor receptors (EGFR:1.9 × and PDGFR: 2.8 ×) and their downstream effectors (ERK, GSK3, Akt, and STAT: 1.2-2.0 ×); MnPCA enhanced versican (33.0 ×) and VEGF (3.3 ×) secretion, and stimulated the Wnt/β-catenin pathway (+80%); and LCE reduced DKK1 secretion (-72%) and 5αR activity (dihydrotestosterone/testosterone ratio: -60%). Compared to untreated scalp skin biopsies, the serum enhanced hair shaft elongation (+102%), and significantly prolonged the anagen phase by improving hair cycle scores and stimulating hair matrix keratinocyte proliferation (+58%).

CONCLUSIONS

SME, MnPCA, and LCE displayed complementary anti-hair loss properties. The serum combining these active ingredients may be useful in hair loss treatment.

Possible role of epiregulin from dermal fibroblasts in the keratinocyte hyperproliferation of psoriasis

Psoriasis, an immune-mediated inflammatory disease, is characterized by keratinocyte hyperproliferation. Tumor necrosis factor (TNF)-α, interleukin (IL)-23, and IL-17A play critical roles in the pathogenesis of psoriasis. IL-17A secreted by T-helper 17 acts more directly against keratinocytes than TNF-α or IL-23 do. Regarding the receptors of cytokines, fibroblasts also express receptors against IL-17A and TNF-α, and induce the production of growth factors. Epiregulin (EREG), an epidermal growth factor receptor ligand, is produced by both keratinocytes and fibroblasts. EREG enhances keratinocyte proliferation and differentiation. We hypothesized that fibroblasts stimulated with IL-17A and/or TNF-α may play a role in epidermal hyperproliferation through the production of epidermal growth factors in psoriasis. The mRNA expression of EREG was found to be significantly upregulated by co-stimulation with IL-17A and TNF-α (mean, 49.2-fold). Furthermore, the stimulation with TNF-α alone, but not IL-17A alone, induced significant increases. Immunofluorescent staining demonstrated that the protein expression level of EREG was also increased in fibroblasts stimulated with these cytokines. Stimulation with EREG significantly enhanced keratinocyte proliferation in vitro. In human psoriatic patients' skin, immunofluorescence staining of EREG showed significantly high intensity in the dermis of lesional skin. In conclusion, cytokine stimulation with TNF-α and IL-17A induces the overexpression of EREG from dermal fibroblasts in the lesional skin of psoriasis, and plays a role in epidermal hyperproliferation.

Epiregulin promotes hair growth via EGFR-medicated epidermal and ErbB4-mediated dermal stimulation

OBJECTIVES

EREG (epiregulin), a member of the epidermal growth factor (EGF) family, plays a role in inflammation, wound healing, normal physiology and malignancies. However, little is known about its function on hair growth.

MATERIALS AND METHODS

Cell growth assay, QPCR and immunostaining were carried out. Telogen-to-anagen transition and organ culture were conducted. ROS level was monitored by staining DCFDA.

RESULTS

We investigated the hair inductive effect of EREG and the mechanism of stimulation on DPCs and ORS cells during hair cycling. Whereas EREG promoted hair growth, EREG knockdown inhibited hair growth as evidenced by telogen-to-anagen transition and organ culture models. EREG was expressed in epidermal cells including ORS cells in vivo. EREG activated phospho-ErbB4 in DPCs during hair cycling and stimulated DPCs via ErbB4 activation in vitro. In terms of the underlying mechanism, reactive oxygen species (ROS) played a key role in DPC stimulation. EREG also activated phospho-EGF receptor (EGFR) in epidermal cells including matrix and ORS cells in vivo and stimulated ORS cells via EGFR activation in vitro.

CONCLUSIONS

EREG, which is released from ORS cells, activated EGFR and ErbB4 on epidermal cells and DPCs during hair cycling, respectively. As a result, EREG stimulated epidermal cells a positive feedback and DPCs via regulating ROS generation for hair growth. Therefore, EREG therapy may be a novel solution for hair loss treatment.