Extracellular Vesicles from Activated Dermal Fibroblasts Stimulate Hair Follicle Growth Through Dermal Papilla-Secreted Norrin

Abstract

Dermal papilla cells (DPCs) play a pivotal role in the regulation of hair follicle (HF) growth, formation, and cycling, mainly through paracrine mechanisms. In the last decade, extracellular vesicles (EVs) have been recognized as a new paracrine mechanism that can modify the physiological state of recipient cells by transferring biological material. Herein, we investigated the effect of EVs isolated from stimulated human dermal fibroblasts (DFs) on DPC activation and HF growth. We found that these EVs (st-EVs) enhanced HF growth ex vivo. Comparative transcriptomic analysis on DPCs identified specific activation of the NDP gene, encoding the non-Wnt ligand Norrin. We found that Norrin was secreted by st-EVs-stimulated DPCs activating in a noncell autonomous manner β-catenin pathway in follicular keratinocytes (human HF keratinocyte [HHFK]) and hair growth ex vivo. Although Norrin-specific receptor Frizzled4 was barely detected in HHFK, we found its presence in DF-EVs. Accordingly, DF-EVs provided Frizzled4 to potentiate Norrin effects ex vivo. Our study identifies DF-EVs as efficient activators of DPCs and Norrin as a novel modulatory player in HF physiopathology. STEM CELLS 2019;37:1166-1175 SIGNIFICANCE STATEMENTDermal papilla cells (DPCs) control the growth and regeneration of hair follicles (HFs) via cellcell interactions and extracellular molecules. These data demonstrate that activated dermal fibroblasts (DFs) secrete specific extracellular vesicles (st-EVs) that enhance HF growth ex vivo. DPCs treated with st-EVs secrete Norrin, a non-Wnt ligand that activates the β-catenin pathway of recipient human hair follicular keratinocytes. DF-EVs contain Norrin-specific Frizzled4 receptor that is barely detected in human HF keratinocytes. Combinatory treatment of Norrin and DF-EVs is sufficient to recapitulate the stimulating effect ex vivo of st-EVs on HF growth. The study identifies Norrin as a novel modulatory player in HF physiopathology.

Macrophage-Derived Extracellular Vesicle Promotes Hair Growth

“…In the current study, MAC-EVs were shown to have the capacity to induce proliferation of DP cells, which was further confirmed by upregulated PCNA expression. This result is in line with a study showing the activated fibroblast-derived EVs could induce cell proliferation signaling in DP cells [43]. This could be very useful for large-scale production of DP cells in vitro for research studies and DP cells therapies [47,48], as cultured DP cells lose their ability of inducing and maintaining the HF.…”

“…These results collectively demonstrated that MAC-EVs contain enriched amounts of Wnts, associated with the membrane, which could readily activate the Wnt/β-catenin signaling pathway in DP cells on interaction with their membrane. A recent study showed that activated fibroblast EVs delivered the Frizzled4 receptors to DP cells and activated the Wnt/β-catenin signaling pathway in DP cells [43].…”

Do hair follicles operate as primitive, multifocal kidney‐like excretory (mini‐) organs?

“…The activity of such ABC transporters, which typically pump defined molecules out of a cell, could also determine which compounds are explicitly not embedded into the HS. Furthermore, given that dermal papilla fibroblasts can engage in substantial release of exosomes, it is conceivable that some molecules destined for extrusion reach precortical hair matrix keratinocytes packaged into exosomes and/or microvesicles released by the HF mesenchyme.…”

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“…As studies have previously established that extracellular vesicle secretion from dermal cell populations promotes hair growth in vivo , partly through though β‐catenin signaling, researchers from the laboratory of Daniel Aberdam (Université de Paris, Brive, France) sought to investigate the molecular mechanism and the critical mediating molecules. In their recent Stem Cells article , le Riche et al used transcriptomic and functional analyses to demonstrate how extracellular vesicles derived from stimulated human dermal fibroblasts (DFs) prompted the secretion of Norrin, a non‐conventional ligand of the Wnt/β‐catenin pathway, from DPCs through the transport of the Norrin‐specific receptor Frizzled4. Secreted Norrin then activated the β‐catenin pathway in human hair follicular keratinocytes and promoted ex vivo hair growth from scalp tissue hair follicles, therefore highlighting DF extracellular vesicles as a DPC activator and Norrin as a novel regulator of hair follicle physiopathology.…”

“…However, this knowledge may also aid the development of enhanced skin replacements and wound healing strategies for sufferers of deep skin injuries, which entail the destruction of the regenerative elements of the skin. In our second Featured Article this month in Stem Cells , le Riche et al describe how the secretion of Norrin, a non‐Wnt ligand, by DPCs treated with extracellular vesicles derived from stimulated human dermal fibroblasts fosters enhanced hair follicle growth through the activation of the β‐catenin pathway in keratinocytes . In a Related Article from Stem Cells Translational Medicine , Leirós et al establish an essential role for DPCs as a vital component of hair follicle stem cell‐containing engineered skin substitutes that provided for enhanced wound healing, improved aesthetic effects, and the generation of hair bud‐like structures .…”