Pre-aggregation of scalp progenitor dermal and epidermal stem cells activates the WNT pathway and promotes hair follicle formation in in vitro and in vivo systems

Yiqun Su,Xin Xu,Zhiwei Xie,Jie Wen,Chang Liu,Qun Zhang,Xunwei Wu,Chuan Ma,Junrong Zhu

doi:10.1186/s13287-019-1504-6

Abstract

BackgroundBillions of dollars are invested annually by pharmaceutical companies in search of new options for treating hair loss conditions; nevertheless, the challenge remains. One major limitation to hair follicle research is the lack of effective and efficient drug screening systems using human cells. Organoids, three-dimensional in vitro structures derived from stem cells, provide new opportunities for studying organ development, tissue regeneration, and disease pathogenesis. The present study focuses on the formation of human hair follicle organoids.MethodsScalp-derived dermal progenitor cells mixed with foreskin-derived epidermal stem cells at a 2:1 ratio aggregated in suspension to form hair follicle-like organoids, which were confirmed by immunostaining of hair follicle markers and by molecular dye labeling assays to analyze dermal and epidermal cell organization in those organoids. The hair-forming potential of organoids was examined using an in vivo transplantation assay.ResultsPre-aggregation of dermal and epidermal cells enhanced hair follicle formation in vivo. In vitro pre-aggregation initiated the interactions of epidermal and dermal progenitor cells resulting in activation of the WNT pathway and the formation of pear-shape structures, named type I aggregates. Cell-tracing analysis showed that the dermal and epidermal cells self-assembled into distinct epidermal and dermal compartments. Histologically, the type I aggregates expressed early hair follicle markers, suggesting the hair peg-like phase of hair follicle morphogenesis. The addition of recombinant WNT3a protein to the medium enhanced the formation of these aggregates, and the Wnt effect could be blocked by the WNT inhibitor, IWP2.ConclusionsIn summary, our system supports the rapid formation of a large number of hair follicle organoids (type I aggregates). This system provides a platform for studying epithelial-mesenchymal interactions, for assessing inductive hair stem cells and for screening compounds that support hair follicle regeneration.

Highlights

Billions of dollars are invested annually by pharmaceutical companies in search of new options for treating hair loss conditions; the challenge remains
Cell preparation Human fetal dermal (FDer) (derived from EGA 15–18 weeks old scalp tissues) and adult dermal (ADer) progenitor cells were derived from frozen aliquots that had been used in our previous study [18], and have been shown to have multiple differentiation potentials [18, 32]
Pre-aggregation of dermal and epidermal cells enhances hair follicle formation in vivo Hair follicles are composed of epidermal and dermal compartments, and their crosstalk plays an important role in their morphogenesis [12, 22]

Summary

Introduction

Billions of dollars are invested annually by pharmaceutical companies in search of new options for treating hair loss conditions; the challenge remains. That was the first report of an in vitro generation of human hair follicle organoids; the dermal cells had not been expanded in culture and the droplet method is not practical to generate large-scale organoids for research and clinical applications such as screening assays. Further signals sent between dermal condensates and the overlaying epidermal placodes regulate the behavior of both cell populations and orchestrate the formation of hair follicles and dermal papillae [22, 24, 25]. The present study was aimed to investigate whether transplantation of pre-aggregating epidermal and dermal cells can enhance hair formation in vivo, to determine whether those cells can aggregate to form hair structures in vitro, and to study the role of the WNT signaling pathway during the aggregation

Methods

Results

Conclusion