Establishment of an in vitro organoid model of dermal papilla of human hair follicle

Abstract

Human hair dermal papilla (DP) cells are specialized mesenchymal cells that play a pivotal role in hair regeneration and hair cycle activation. The current study aimed to first develop three-dimensional (3D) DP spheroids (DPS) with or without a silk-gelatin (SG) microenvironment, which showed enhanced DP-specific gene expression, resulting in enhanced extracellular matrix (ECM) production compared with a monolayer culture. We tested the feasibility of using this DPS model for drug screening by using minoxidil, which is a standard drug for androgenic alopecia. Minoxidil-treated DPS showed enhanced expression of growth factors and ECM proteins. Further, an attempt has been made to establish an in vitro 3D organoid model consisting of DPS encapsulated by SG hydrogel and hair follicle (HF) keratinocytes and stem cells. This HF organoid model showed the importance of structural features, cell-cell interaction, and hypoxia akin to in vivo HF. The study helped to elucidate the molecular mechanisms to stimulate cell proliferation, cell viability, and elevated expression of HF markers as well as epithelial-mesenchymal crosstalks, demonstrating high relevance to human HF biology. This simple in vitro DP organoid model system has the potential to provide significant insights into the underlying mechanisms of HF morphogenesis, distinct molecular signals relevant to different stages of the hair cycle, and hence can be used for controlled evaluation of the efficacy of new drug molecules.

Epidermal Stem Cells in Hair Follicle Cycling and Skin Regeneration: A View From the Perspective of Inflammation

“…There are also new data suggesting that apoptotic cells are not inert: they may trigger genes associated with wound healing, proliferation, and a decrease in inflammation in adjacent cells (Medina et al, 2020). It is known that the signaling pathways of inflammation and cell death are interconnected through RIPK-1 and RIPK-3, including the situation of wound healing, as shown in several studies (Takahashi et al, 2014;Godwin et al, 2015;Moriwaki et al, 2015;Gupta et al, 2018). Such intersections can also occur in the HF.…”

Tissue engineering strategies for human hair follicle regeneration: How far from a hairy goal?

“…Thus, from an in vitro tissue engineering perspective, mimicking in vivo contribution of both HFSC and DP seems critical to establish a successful HF regeneration strategy. Accordingly, several studies evidenced a boost of HF induction when combining the epithelial component (HFSCs ± keratinocytes) with the inductive DPCs within engineered germs . Even though, bulge‐specific cell molecular markers allow direct HFSC isolation from mouse and human HF —as opposed to human DPCs—HFSCs have poor proliferative ability and tend to differentiate during culture passaging .…”

“…Additionally, two recent studies have achieved growth of mouse hair in vivo after transplantation of in vitro formed structures, either consisting of mouse adult DP and epidermal cells, or of mouse iPSCs, encapsulated in hydrogel matrices. Different artificial 3D microenvironments composed of silk‐gelatin, hyaluronic acid, and collagen were shown to improve hair germs for hair regenerative medicine. In a similar approach, human HF resembling vellus hair were recreated in vitro from a mixture of DP cells, keratinocytes and melanocytes in a collagen matrix, and named “microfollicles.” Presently, researchers are joining efforts to develop more complex structures that can mimic the DP tridimensional morphology while providing a spatiotemporal delivery of molecular cues needed for human hair morphogenesis.…”

“…Accordingly, several studies evidenced a boost of HF induction when combining the epithelial component (HFSCs ± keratinocytes) with the inductive DPCs within engineered germs. 59,60 Even though, bulge-specific cell molecular markers allow direct HFSC isolation from mouse and human HF 33,61 -as opposed to human DPCs-HFSCs have poor proliferative ability and tend to differentiate during culture passaging. 62 Therefore, committed progenitors or keratinocyte precursors are being alternatively used as an epithelial component for HF tissue engineering.…”

Evaluating hair growth promoting effects of candidate substance: A review of research methods

“…In this system, certain known hair growth-modulating molecules (i.e., calcitriol, cyclosporin A) alter the folliculoid microspheres, protein and gene expression associated with hair growth. A similar three-dimensional model, consisting of human DP cell spheroids encapsulated by silk gelatin hydrogel and HFSCs and keratinocytes [32], has been used to simulate the expression of various DP cell genes in the spheroids of HFs in vitro.…”