Molecular Dissection of Mesenchymal–Epithelial Interactions in the Hair Follicle

Abstract

De novo hair follicle formation in embryonic skin and new hair growth in adult skin are initiated when specialized mesenchymal dermal papilla (DP) cells send cues to multipotent epithelial stem cells. Subsequently, DP cells are enveloped by epithelial stem cell progeny and other cell types to form a niche orchestrating hair growth. Understanding the general biological principles that govern the mesenchymal–epithelial interactions within the DP niche, however, has been hampered so far by the lack of systematic approaches to dissect the complete molecular make-up of this complex tissue. Here, we take a novel multicolor labeling approach, using cell type–specific transgenic expression of red and green fluorescent proteins in combination with immunolabeling of specific antigens, to isolate pure populations of DP and four of its surrounding cell types: dermal fibroblasts, melanocytes, and two different populations of epithelial progenitors (matrix and outer root sheath cells). By defining their transcriptional profiles, we develop molecular signatures characteristic for the DP and its niche. Validating the functional importance of these signatures is a group of genes linked to hair disorders that have been largely unexplored. Additionally, the DP signature reveals novel signaling and transcription regulators that distinguish them from other cell types. The mesenchymal–epithelial signatures include key factors previously implicated in ectodermal-neural fate determination, as well as a myriad of regulators of bone morphogenetic protein signaling. These findings establish a foundation for future functional analyses of the roles of these genes in hair development. Overall, our strategy illustrates how knowledge of the genes uniquely expressed by each cell type residing in a complex niche can reveal important new insights into the biology of the tissue and its associated disease states.

Novel In Vitro Culture Condition Improves the Stemness of Human Dermal Stem/Progenitor Cells

“…During in vitro culture, hDSPCs, which exhibited stem celllike characteristics in our previous study, gradually lose the expression of transcription factors associated with multipotency and self-renewal, such as SOX2 and NANOG for maintaining the characteristics of stem cells. Several previous reports suggested that the quality of the stem cells strongly depend on the culture method (Driskell et al, 2012;Grayson et al, 2007;Kuroda et al, 2010;Minchenko et al, 1994;Reiter et al, 2008;Ren et al, 2006;Rendl et al, 2005). Thus, we investigated whether hDSPCs retain their stemness in various culture conditions despite long-term culture.…”

“…It is also difficult to obtain adult stem cells because of their limited quantities in the tissue. According to some previous literatures, they are considered to be composed of 0.01% to 0.001% of the total cell number (Hill et al, 2012;Rendl et al, 2005;Riekstina et al, 2009;Shim et al, 2013;Wegner and Stolt, 2005;Wu et al, 2010). We found that hDSPCs in small quantity gradually lose pluripotency and the ability to proliferate once they are grown over long-term culture.…”

“…The four media evaluated were as follows: (i) DMEM containing 10% FBS; (ii) AmnioMAX C-100, which has been reported to maintain dermal papilla gene expression (Driskell et al, 2012;Rendl et al, 2005). (iii) skinderived precursor (SKP) medium containing fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) (Toma et al, 2001; and (iv) Hair follicle dermal papilla cell (HFDPC) growth medium supplemented with FGF2 and insulin (Reiter et al, 2008).…”

“…On the contrary, a few intracellular specific markers are identified in dermal stem cells. SOX2, a SRY transcription factor, plays an essential role in maintaining stemness in embryonic stem cells and some adult stem cells such as the dermal papilla cells (Rendl et al, 2005;Wegner and Stolt, 2005). NANOG, another embryonic stem cell marker, is also expressed in adult mesenchymal stem cell populations derived from bone marrow, adipose tissue, and dermis (Hill et al, 2012;Riekstina et al, 2009;Szade et al, 2011).…”

Development and Homeostasis of the Skin Epidermis

“…Loss of Nfatc1 stimulates bulge SC proliferation and anagen progression through loss of CDK4 repression (Horsley et al 2008). Transcriptional profiling showed that DP cells express a number of BMP receptors and several BMPs, the most potent being BMP6, promoting the maintenance of the DP-inductive properties upon in vitro culture (Rendl et al 2005(Rendl et al , 2008. Accordingly, conditional ablation of BMPR1a specifically in DP cells in vivo results in loss of the DP-inductive capacity in HF reconstitution assays (Rendl et al 2008).…”