Enzyme digestion to isolate and culture human scalp dermal papilla cells: a more efficient method

Force-triggered density gradient sedimentation and cocktail enzyme digestion treatment for isolation of single dermal papilla cells from follicular unit extraction harvesting human hair follicles

BACKGROUND

Hair follicles (HFs) are dynamic structures which are readily accessible within the skin that contain various pools of stem cells with broad regenerative potential, such as dermal papilla cells (DPCs), dermal sheath cells, and epithelial HF stem cells. DPCs act as signalling centres for HF regeneration. The current method for isolating human DPCs are inefficient. These methods struggle to obtain freshly isolated original DPCs and do not maintain the characteristics of DPCs effectively.

METHODS

In this study, two simple but more efficient methods were explored. Force-triggered density gradient sedimentation (FDGS) and cocktail enzyme digestion treatment (CEDT) were used to isolate purified DP spheres from human HFs, obtaining purified freshly isolated original DPCs from DP spheres. The expression profiles of isolated DPCs were tested, and gene expression of DPC-specific markers were analyzed using immunofluorescence staining, RT-qPCR and western blot.

RESULTS

The 10% Ficoll PM400 was determined as the optimal concentration for FDGS method. Primary DPCs, DSCs and HFSCs were isolated simultaneously using the FDGS and CEDT method. The expression profiles of fresh DPCs isolated using the FDGS and CEDT methods were similar to those of traditionally isolated DPCs. DP-specific markers were expressed at significantly higher levels in freshly isolated DPCs than in traditionally isolated DPCs.

CONCLUSIONS

Compared to traditional methods, the presented laboratory protocols were able to isolate fresh DPCs with high efficiency, thereby improving their research potential.

Exosomes derived from mouse vibrissa dermal papilla cells promote hair follicle regeneration during wound healing by activating Wnt/β-catenin signaling pathway

Hair follicle (HF) regeneration during wound healing continues to present a significant clinical challenge. Dermal papilla cell-derived exosomes (DPC-Exos) hold immense potential for inducing HF neogenesis. However, the accurate role and underlying mechanisms of DPC-Exos in HF regeneration in wound healing remain to be fully explained. This study, represents the first analysis into the effects of DPC-Exos on fibroblasts during wound healing. Our findings demonstrated that DPC-Exos could stimulate the proliferation and migration of fibroblasts, more importantly, enhance the hair-inducing capacity of fibroblasts. Fibroblasts treated with DPC-Exos were capable of inducing HF neogenesis in nude mice when combined with neonatal mice epidermal cells. In addition, DPC-Exos accelerated wound re-epithelialization and promoted HF regeneration during the healing process. Treatment with DPC-Exos led to increased expression levels of the Wnt pathway transcription factors β-catenin and Lef1 in both fibroblasts and the dermis of skin wounds. Specifically, the application of a Wnt pathway inhibitor reduced the effects of DPC-Exos on fibroblasts and wound healing. Accordingly, these results offer evidence that DPC-Exos promote HF regeneration during wound healing by enhancing the hair-inducing capacity of fibroblasts and activating the Wnt/β-catenin signaling pathway. This suggests that DPC-Exos may represent a promising therapeutic strategy for achieving regenerative wound healing.

Histological characteristics of hair follicles at different hair cycle and in vitro modeling of hair follicle-associated cells of yak (Bos grunniens)

To adapt to the extreme conditions of plateau environments, yaks have evolved thick hair, making them an ideal model for investigating the mechanisms involved in hair growth. We can gain valuable insights into how hair follicles develop and their cyclic growth in challenging environments by studying yaks. However, the lack of essential data on yak hair follicle histology and the absence of in vitro cell models for hair follicles serve as a limitation to such research objectives. In this study, we investigated the structure of skin tissue during different hair follicle cycles using the yak model. Additionally, we successfully established in vitro models of hair follicle-associated cells derived from yak skin, including dermal papilla cells (DPCs), preadipocytes, and fibroblasts. We optimized the microdissection technique for DPCs culture by simplifying the procedure and reducing the time required. Furthermore, we improved the methodology used to differentiate yak preadipocytes into mature adipocytes, thus increasing the differentiation efficiency. The introduction of yak as a natural model provides valuable research resources for exploring the mechanisms of hair growth and contributes to a deeper understanding of hair follicle biology and the development of regenerative medicine strategies.

Back to the Future: From Appendage Development Toward Future Human Hair Follicle Neogenesis

Hair disorders such as alopecia and hirsutism often impact the social and psychological well-being of an individual. This also holds true for patients with severe burns who have lost their hair follicles (HFs). HFs stimulate proper wound healing and prevent scar formation; thus, HF research can benefit numerous patients. Although hair development and hair disorders are intensively studied, human HF development has not been fully elucidated. Research on human fetal material is often subject to restrictions, and thus development, disease, and wound healing studies remain largely dependent on time-consuming and costly animal studies. Although animal experiments have yielded considerable and useful information, it is increasingly recognized that significant differences exist between animal and human skin and that it is important to obtain meaningful human models. Human disease specific models could therefore play a key role in future therapy. To this end, hair organoids or hair-bearing skin-on-chip created from the patient’s own cells can be used. To create such a complex 3D structure, knowledge of hair genesis, i.e., the early developmental process, is indispensable. Thus, uncovering the mechanisms underlying how HF progenitor cells within human fetal skin form hair buds and subsequently HFs is of interest. Organoid studies have shown that nearly all organs can be recapitulated as mini-organs by mimicking embryonic conditions and utilizing the relevant morphogens and extracellular matrix (ECM) proteins. Therefore, knowledge of the cellular and ECM proteins in the skin of human fetuses is critical to understand the evolution of epithelial tissues, including skin appendages. This review aims to provide an overview of our current understanding of the cellular changes occurring during human skin and HF development. We further discuss the potential implementation of this knowledge in establishing a human in vitro model of a full skin substitute containing hair follicles and the subsequent translation to clinical use.

Maintaining Hair Inductivity in Human Dermal Papilla Cells: A Review of Effective Methods

The dermal papilla comprises mesenchymal cells in hair follicles, which play the main role in regulating hair growth. Maintaining the potential hair inductivity of dermal papilla cells (DPCs) and dermal sheath cells during cell culture is the main factor in in vitro morphogenesis and regeneration of hair follicles. Using common methods for the cultivation of human dermal papilla reduces the maintenance requirements of the inductive capacity of the dermal papilla and the expression of specific dermal papilla biomarkers. Optimizing culture conditions is therefore crucial for DPCs. Moreover, exosomes appear to play a key role in regulating the hair follicle growth through a paracrine mechanism and provide a functional method for treating hair loss. The present review investigated the biology of DPCs, the molecular and cell signaling mechanisms contributing to hair follicle growth in humans, the properties of the dermal papilla, and the effective techniques in maintaining hair inductivity in DPC cultures in humans as well as hair follicle bioengineering.

Generation of Hair Follicle Germs In Vitro Using Human Postnatal Skin Cells

Modeling organoids with hair follicle germ-like properties provides an opportunity for developing strategies for alopecia drug discovery and replacement therapy, as well as investigating the molecular mechanisms underlying human hair follicle regeneration in vitro. Hair follicle germ reconstruction in vitro is based on dermal papilla hair-inducing abilities and the plasticity of skin epidermal keratinocytes. The current protocol describes a highly efficient approach suitable for adult human skin cell applications. This method allows to obtain hair follicle germs using tissues from one donor. Isolated and cultured for 2 weeks, adult hair follicle dermal papilla cells and skin epidermal keratinocytes self-organize in hanging drop cultures generating organoids that exhibit the features of folliculogenesis onset.

Low-level PDT treatment modulated photoaging mediated by UVA irradiation through regulating Bach2

OBJECTIVE

To investigate low-level ALA-PDT (Aminolevulinic acid photodynamic therapy) effects on photorejuvenation in vitro and in vivo, exploring the basic mechanism of Bach2 involved in PDT treatment in photoaging.

METHOD

Photoaging model was established by UVA chronic irradiation in human fibroblasts and mice skins. Cell viability was determined by MTS assay and cell senescence was detected by SA-β-gal activity. PDT treatment and Bach2 knockdown with adenovirus in fibroblasts were confirmed by Western blot.

RESULTS

UVA chronic irradiation induced photoaging in vitro and in vivo. Treatment of low-level PDT reduced photoaging by decreasing SA-β-gal activity and cell senescence-related proteins levels of p16 and p21 in fibroblasts. Moreover, low-level PDT treatment accompany with Bach2 accumulation increased in fibroblasts and in mice skin tissues. Bach2 knockdown with adenovirus induced cell senescence and Bach2 depletion with PDT treatment some extent decreased SA-β-gal activity, but was with no significant change of Bach2 itself and p16 protein levels in fibroblasts.

CONCLUSION

Low-level PDT treatment decreased skin photoaging which might be through up-regulating Bach2.

Isolating Dermal Papilla Cells from Human Hair Follicles Using Microdissection and Enzyme Digestion

The dermal papilla (DP) is a cluster of mesenchymal cells located at the bottom of the hair follicle. Cells within the DP interact with numerous other cell types within the follicle, including epithelial stem cells, matrix cells, and melanocytes, regulating their function. The diameter of the DP is directly proportional to the width of the hair shaft, and a decrease in both cell number and DP size is observed in hair loss conditions such as androgenetic alopecia. Conversely, microdissected ex vivo DP can instruct growth of de novo hair follicles. The study of DP cells and their role in human hair growth is often hampered by the technical challenge of DP isolation and culture. Here we describe a method used within our research group for isolating DP from human hair follicles.

Hair Growth Promoting Effect of 4HGF Encapsulated with PGA Nanoparticles (PGA-4HGF) by β-Catenin Activation and Its Related Cell Cycle Molecules

Poly-γ-glutamic acid (γ-PGA)-based nanoparticles draw remarkable attention as drug delivery agents due to their controlled release characteristics, low toxicity, and biocompatibility. 4HGF is an herbal mixture of Phellinus linteus grown on germinated brown rice, Cordyceps militaris grown on germinated soybeans, Polygonum multiflorum, Ficus carica, and Cocos nucifera oil. Here, we encapsulated 4HGF within PGA-based hydrogel nanoparticles, prepared by simple ionic gelation with chitosan, to facilitate its penetration into hair follicles (HFs). In this study, we report the hair promoting activity of 4HGF encapsulated with PGA nanoparticles (PGA-4HGF) and their mechanism, compared to 4HGF alone. The average size of spherical nanoparticles was ~400 nm in diameter. Continuous release of PGA-4HGF was observed in a simulated physiological condition. As expected, PGA-4HGF treatment increased hair length, induced earlier anagen initiation, and elongated the duration of the anagen phase in C57BL/6N mice, compared with free 4HGF treatment. PGA-4HGF significantly increased dermal papilla cell proliferation and induced cell cycle progression. PGA-4HGF also significantly increased the total amount of β-catenin protein expression, a stimulator of the anagen phase, through induction of cyclinD1 and CDK4 protein levels, compared to free 4HGF treatment. Our findings underscore the potential of PGA nanocapsules to efficiently deliver 4HGF into HFs, hence promoting hair-growth. Therefore, PGA-4HGF nanoparticles may be promising therapeutic agents for hair growth disorders.

Effects of low-dose ALA-PDT on fibroblast photoaging induced by UVA irradiation and the underlying mechanisms

OBJECTIVES

To investigate the effects of low-dose aminolevulinic acid photodynamic therapy (ALA-PDT) on photoaging in human dermal fibroblasts (HDFs) and to explore the mechanism of Nuclear factor erythroid 2-related factor 2(Nrf2)-mediated photorejuvenation in vitro.

METHODS

A photoaging model was established through repeated exposure of HDFs to UVA. Total superoxide dismutase (SOD) expression was detected by a SOD activity assay. Nrf2 was knocked down through adenovirus infection, and successful knockdown was confirmed by Western blot analysis and quantitative polymerase chain reaction.

RESULTS

Sustained exposure to UVA induced photoaging in HDFs. Total SOD activity was significantly increased by low-dose aminolevulinic acid (ALA)-PDT. Upon application of low doses of ALA-PDT to photoaging HDFs, Nrf2 was translocated to the nucleus; in addition, the expression of Nrf2, transforming growth factor-β1 (TGF-β1), type I and III collagen (COL1 and COL3), heme oxygenase 1 (HO-1), and p-ERK was increased, while the expression of matrix metalloproteinase 9 (MMP-9) was decreased. However, after Nrf2 was knocked down in HDFs, the expression of TGF-β1, COL1, COL3, and HO-1 was significantly decreased, while the expression of MMP-9 was increased.

CONCLUSION

This study revealed that low-dose ALA-PDT decreases UVA-mediated photoaging through an Nrf2-mediated antioxidant effect.

Methods for the isolation and 3D culture of dermal papilla cells from human hair follicles

The dermal papilla is a cluster of mesenchymal cells located at the base of the hair follicle which have a number of important roles in the regulation of hair growth. As a consequence, in vitro models of these cells are widely used to study the molecular mechanisms which underlie hair follicle induction, growth and maintenance. While dermal papilla from rodent hair follicles can be digested prior to cell isolation, the unique extracellular matrix composition found in human dermal papilla renders enzymes such as trypsin and collagenase insufficient for digestion of the dermal papilla into a single cell suspension. As such, to grow human dermal papilla cells in vitro, the papilla has to first be isolated via a micro-dissection approach from the follicle. In this article we describe the micro-dissection and culture methods, which we use within our laboratory, for the study of human dermal papilla cells.

Knockout of p16INK4a promotes aggregative growth of dermal papilla cells

OBJECTIVE

Dermal papilla cells (DPCs) are located in the hair follicles and play an important role in hair growth. These cells have the ability to induce hair follicle formation when they display aggregative behavior. DPCs derived from the androgenetic alopecia (AGA) area undergo premature senescence in vitro, associated with p16INK4a expression. The aim of the current study was to investigate the expression of p16INK4a in aggregative and non-aggregative DPCs and the effect of p16INK4a down-regulation in these cells by adenovirus-mediated RNA interference (RNAi).

METHOD

DPCs were isolated and cultured from healthy human scalp. p16INK4a gene and protein were detected in aggregative and non-aggregative cells. Expression of p16INK4a in DPCs was silenced by infection with rAd5-CDKN1A-1p2shRNA. Cell fate was monitored after infection. The growth of cells was measured by MTT assay. Cell cycle was evaluated by flow cytometry (FCM).

RESULTS

DPCs were isolated by digestion and showed aggregative behavior for six passages. The expression of p16INK4a showed a clear upward trend in non-aggregative cells when compared with aggregative group. p16INK4a expression was silenced by rAd5-CDKN1A-1p2shRNA (p<0.05). The p16INK4a-silenced cells grew more rapidly and exhibited a trend towards aggregative growth. There was an increase in the proportion of cells in G1 phase, while those in S phase were reduced after p16INK4a gene silencing (p<0.05).

CONCLUSION

Our results suggest that p16INK4a plays an important role in the premature senescence and aggregative behavior of DPCs. These observations can lead to novel therapeutic strategies for treatment of AGA.

Hair Germ Model In Vitro via Human Postnatal Keratinocyte-Dermal Papilla Interactions: Impact of Hyaluronic Acid

Hair follicle (HF) reconstruction in vitro is a promising field in alopecia treatment and human HF development research. Here, we combined postnatal human dermal papilla (DP) cells and skin epidermal keratinocytes (KCs) in a hanging drop culture to develop an artificial HF germ. The method is based on DP cell hair-inducing properties and KC self-organization. We evaluated two protocols of aggregate assembling. Mixed HF germ-like structures demonstrated the initiation of epithelial-mesenchymal interaction, including WNT pathway activation and expression of follicular markers. We analyzed the influence of possible DP cell niche components including soluble factors and extracellular matrix (ECM) molecules in the process of the organoid assembling and growth. Our results demonstrated that soluble factors had little impact on HF germ generation and Ki67⁺ cell score inside the organoids although BMP6 and VD3 maintained effectively the DP identity in the monolayer culture. Aggrecan, biglycan, fibronectin, and hyaluronic acid (HA) significantly stimulated cell proliferation in DP cell monolayer culture without any effect on DP cell identity. Most of ECM compounds prevented the formation of cell aggregates while HA promoted the formation of larger organoids. In conclusion, our model could be suitable to study cell-cell and cell-niche interactions during HF reconstruction in vitro.

Effect of Extremely Low Frequency Electromagnetic Field on MAP2 and Nestin Gene Expression of Hair Follicle Dermal Papilla Cells

Introduction

In recent years, the extremely low frequency electromagnetic field (ELF-EMF) has attracted a great deal of scientific interest. The ELF-EMF signal is able to control ion transport across ion channels and therefore induce cell differentiation.

Aim

The purpose of this study was to investigate the effect of ELF-EMF (50 Hz, 1 mT) on MAP2 and Nestin gene expression of dermal papilla mesenchymal cells (DPCs).

Methods

In order to examine the effect of chemical and electromagnetic factors on gene expression, 4 experimental groups, namely chemical (cell exposure to chemical signals), EMF (exposing cells to ELF-EMF), chemical-EMF (subjecting cells to chemical signals and ELF-EMF) and control (with no treatment) groups, were prepared, treated for 5 days, and studied. To assess the effect of extended test time on the expression of neural differentiation markers (Nestin and MAP2), an EMF group was prepared and treated for a period of 14 consecutive days. The beneficial role of EMF in inducing neural differentiation was shown by real-time PCR analysis.

Results

The higher expression of MAP2 after 14 days compared to that after 5 days and decrease of cell proliferation on days 5 to 20 were indicative of the positive effect of extending treatment time on neural differentiation by evaluation of gene expression in EMF group.

Identification of Wnt/β-catenin signaling pathway in dermal papilla cells of human scalp hair follicles: TCF4 regulates the proliferation and secretory activity of dermal papilla cell

It is clear that the dermal papilla cell (DPC), which is located at the bottom of the hair follicle, is a special mesenchymal component, and it plays a leading role in regulating hair follicle development and periodic regeneration. Recent studies showed that the Wnt signaling pathway through β-catenin (canonical Wnt signaling pathway) is an essential component in maintaining the hair-inducing activity of the dermal papilla and growth of hair papilla cells. However, the intrinsic pathways and regulating mechanism are largely unknown. In the previous work, we constructed a cDNA subtractive library of DPC and first found that the TCF4 gene, as a key factor of Wnt signaling pathway, was expressed as the upregulated gene of the hair follicle in low-passage DPC. This study was to explore the role of TCF4 in regulating the proliferation and secretory activity of DPC. We constructed a pcDNA3.0-TCF4 expression vector and transfected it into DPC to achieve stable expression by bangosome 2000. Furthermore, we used the method of chemosynthesis to synthesize three pairs of TCF4 siRNA and transfected them into DPC. Meanwhile, we compared the transfection group and non-transfection group. We first proposed that there was expression difference in TCF4 in DPC under different biological condition. This study may have a high impact on the molecular mechanism of follicular lesions and provide a new vision for the treatment of clinic diseases.

Hair follicle: a novel source of multipotent stem cells for tissue engineering and regenerative medicine

The adult body harbors powerful reservoirs of stem cells that enable tissue regeneration under homeostatic conditions or in response to disease or injury. The hair follicle (HF) is a readily accessible mini organ within the skin and contains stem cells from diverse developmental origins that were shown to have surprisingly broad differentiation potential. In this review, we discuss the biology of the HF with particular emphasis on the various stem cell populations residing within the tissue. We summarize the existing knowledge on putative HF stem cell markers, the differentiation potential, and technologies to isolate and expand distinct stem cell populations. We also discuss the potential of HF stem cells for drug and gene delivery, tissue engineering, and regenerative medicine. We propose that the abundance of stem cells with broad differentiation potential and the ease of accessibility makes the HF an ideal source of stem cells for gene and cell therapies.

Restoration of the intrinsic properties of human dermal papilla in vitro

The dermal papilla (DP) plays pivotal roles in hair follicle morphogenesis and cycling. However, characterization and/or propagation of human DPs have been unsatisfactory because of the lack of efficient isolation methods and the loss of innate characteristics in vitro. We hypothesized that culture conditions sustaining the intrinsic molecular signature of the human DP could facilitate expansion of functional DP cells. To test this, we first characterized the global gene expression profile of microdissected, non-cultured human DPs. We performed a 'two-step' microarray analysis to exclude the influence of unwanted contaminants in isolated DPs and successfully identified 118 human DP signature genes, including 38 genes listed in the mouse DP signature. The bioinformatics analysis of the DP gene list revealed that WNT, BMP and FGF signaling pathways were upregulated in intact DPs and addition of 6-bromoindirubin-3'-oxime, recombinant BMP2 and basic FGF to stimulate these respective signaling pathways resulted in maintained expression of in situ DP signature genes in primarily cultured human DP cells. More importantly, the exposure to these stimulants restored normally reduced DP biomarker expression in conventionally cultured DP cells. Cell growth was moderate in the newly developed culture medium. However, rapid DP cell expansion by conventional culture followed by the restoration by defined activators provided a sufficient number of DP cells that demonstrated characteristic DP activities in functional assays. The study reported here revealed previously unreported molecular mechanisms contributing to human DP properties and describes a useful technique for the investigation of human DP biology and hair follicle bioengineering.

Hair follicle regeneration in skin grafts: current concepts and future perspectives

The repair and management of full-thickness skin defects resulting from burns and chronic wounds remain a significant unmet clinical challenge. For those skin defects exceeding 50%-60% of total body surface area, it is impractical to treat with autologous skin transplants because of the shortage of donor sites. The possibility of using tissue-engineered skin grafts for full-thickness wound repair is a promising approach. The primary goal of tissue-engineered skin grafts is to restore lost barrier function, but regeneration of appendages, such as hair follicles, has to be yet achieved. The successful regeneration of hair follicles in immunodeficient mice suggests that creating human hair follicles in tissue-engineered skin grafts is feasible. However, many limitations still need to be explored, particularly enriching isolated cells with trichogenic capacity, maintaining this ability during processing, and providing the cells with proper environmental cues. Current advances in hair follicle regeneration, in vitro and in vivo, are concisely summarized in this report, and key requirements to bioengineer a hair follicle are proposed, with emphasis on a three-dimensional approach.

Molecular biological and immunohistological characterization of canine dermal papilla cells and the evaluation of culture conditions

The dermal papilla (DP) plays pivotal roles in hair follicle morphogenesis and cycling. However, our understanding of the biology of the canine DP is extremely limited. The aim of this study was to elucidate molecular biological and immunohistochemical characteristics of canine DP cells and determine appropriate conditions for in vitro expansion. Histological investigation revealed that the canine DP expressed biomarkers of human and rodent DP, including alkaline phosphatase (ALP) and versican. When microdissected, canine DP, but not fibroblasts, strongly expressed the DP-related genes for alkaline phosphatase, Wnt inhibitory factor 1 and lymphoid enhancer-binding factor 1, confirming successful isolation. The growth rate of isolated canine DP cells was moderate in conventional culture conditions for rodent and human DP; however, AmnioMAX-C100 complete medium allowed more efficient cultivation. Dermal papilla marker gene expression was maintained in early passage cultured DP cells, but gradually lost after the third passage. Approaches to mimic the in vivo DP environment in culture, such as supplementation of keratinocyte-conditioned medium or use of extracellular matrix-coated dishes, moderately ameliorated loss of DP gene expression in canine DP cells. It is possible that constituent factors in AmnioMAX may influence culture. These findings suggested that further refinements of culture conditions may enable DP cell expansion without impairing intrinsic properties and, importantly, demonstrated that AmnioMAX-cultured early passage canine DP cells partly maintained the biological characteristics of in vivo canine DP cells. This study provides crucial information necessary for further optimization of culture conditions of canine DP.

Versican targeting by RNA interference suppresses aggregative growth of dermal papilla cells

BACKGROUND

Dermal papilla cells (DPCs) are specialized fibroblasts found in the hair follicle papilla, which are associated with the development and cycle regulation of hair follicles (HFs). DPCs exhibit a multilayer aggregative growth character, which is closely related to induction of HF formation. Versican, a large chondroitin sulphate proteoglycan and one of the major components of the extracellular matrix, is involved in the formation of HF.

METHODS

To confirm the relationship between versican and the aggregative growth of DPCs, we first induced and established an aggregative cell model in DPCs in vitro, with cells taken to passage 8. Simultaneously, aggregative passage 2 DPCs and nonaggregative passage 8 DPCs were selected as parallel controls. RNA interference (RNAi) targeted to versican was used in passage 2 DPCs using a lentiviral vector. Reverse transcriptase (RT)-PCR and western blotting were used to assay the expression of versican in DPCs.

RESULTS

RNAi targeted to versican efficiently suppressed the aggregative growth of passage 2 DPCs, and the inhibitory effect was significant 3 days after RNAi treatment. The mRNA and protein levels of versican were also downregulated in passage 2 DPCs, and were lower than levels in nonaggregative passage 8 DPCs. Notably, the aggregative growth of nonaggregative passage 8 DPCs was restored after induction in a 1 : 1 v/v mixture of fresh DMEM and medium recycled from a previous passage.

CONCLUSION

Versican is a key gene for the aggregative growth of DPCs, and might be significant in the regeneration of HF.

Review of hair follicle dermal cells

Hair follicle stem cells in the epithelial bulge are responsible for the continual regeneration of the hair follicle during cycling. The bulge cells reside in a niche composed of dermal cells. The dermal compartment of the hair follicle consists of the dermal papilla and dermal sheath. Interactions between hair follicle epithelial and dermal cells are necessary for hair follicle morphogenesis during development and in hair reconstitution assays. Dermal papilla and dermal sheath cells express specific markers and possess distinctive morphology and behavior in culture. These cells can induce hair follicle differentiation in epithelial cells and are required in hair reconstitution assays either in the form of intact tissue, dissociated freshly prepared cells or cultured cells. This review will focus on hair follicle dermal cells since most therapeutic efforts to date have concentrated on this aspect of the hair follicle, with the idea that enriching hair-inductive dermal cell populations and expanding their number by culture while maintaining their properties, will establish an efficient hair reconstitution assay that could eventually have therapeutic implications.

Dermal papilla cells induce keratinocyte tubulogenesis in culture

The ability of dermal papilla (DP) cells to induce hair growth was reported in many studies. However, early stages of hair follicle development and signals that govern this process are poorly understood. Therefore, an in vitro model may be a convenient system to study epithelial-mesenchymal interactions and early stages of epidermal morphogenesis, especially in humans. To investigate the role of DP cells in epidermal morphogenesis we modified the method of isolation of DP cells from hair follicle of human scalp and developed the three-dimensional model of epidermal morphogenesis. Isolated DP cells were able to differentiate in adipogenic and osteogenic directions and retained activity of alkaline phosphatase (AP) for seven passages in culture. DP cells were able to induce tubule-like structures in three-dimensional model in vitro and to reorganize collagen matrix. Prolonged cultivation of DP cells has been a big problem because of the loss of hair follicle-inducing ability and growth activity after several passages. To solve this problem we immortalized DP cells by the transfection of the human telomerase reverse transcriptase cDNA (hTERT). Immortalized DP-hTERT cells retained AP activity and demonstrated low ability to osteogenic differentiation. The conditioned medium collected from actively proliferated cells as well as DP-hTERT cells themselves were capable to induce tubulogenesis after prolonged keratinocyte cultivation.

Hair follicle neogenesis induced by cultured human scalp dermal papilla cells

AIM

To develop a method by which human hair follicle dermal papilla (DP) cells can be expanded in vitro while preserving their hair-inductive potential for use in follicular cell implantation, a cellular therapy for the treatment of hair loss.

MATERIALS & METHODS

DP cells were isolated from scalp hair follicles in biopsies from human donors. DP cell cultures were established under conditions that preserved their hair-inductive potential and allowed for significant expansion. The hair-inductive potential of cells cultured for approximately 36 doublings was tested in an in vivo flap-graft model. In some experiments, DiI was used to label cells prior to grafting.

RESULTS

Under the culture conditions developed, cultures established from numerous donors reproducibly resulted in an expansion that averaged approximately five population doublings per passage. Furthermore, the cells consistently induced hair formation in an in vivo graft assay. Grafted DP cells appeared in DP structures of newly formed hairs, as well as in the dermal sheath and in the dermis surrounding follicles. Induced hair follicles persisted and regrew after being plucked 11 months after grafting.

CONCLUSION

A process for the propagation of human DP cells has been developed that provides significant expansion of cells and maintenance of their hair-inductive capability, overcoming a major technical obstacle in the development of follicular cell implantation as a treatment for hair loss.

The mesenchymal component of hair follicle neogenesis: background, methods and molecular characterization

Hair follicle morphogenesis and regeneration occur by an extensive and collaborative crosstalk between epithelial and mesenchymal skin components. A series of pioneering studies, which revealed an indispensable role of follicular dermal papilla and dermal sheath cells in this crosstalk, has led workers in the field to study in detail the anatomical distribution, functional properties, and molecular signature of the trichogenic dermal cells. The purpose of this paper was to provide a practical summary of the development and recent advances in the study of trichogenic dermal cells. Following a short review of the relevant literature, the methods for isolating and culturing these cells are summarized. Next, the bioassays, both in vivo and in vitro, that enable the evaluation of trichogenic properties of tested dermal cells are described in detail. A list of trichogenic molecular markers identified by those assays is also provided. Finally, this methods review is completed by defining some of the major questions needing resolution.

Angiogenin is expressed in human dermal papilla cells and stimulates hair growth

The perifollicular vasculature undergoes hair-cycle dependent expansion and degeneration. Multiple soluble factors derived from dermal papilla cells (DPCs) may act on surrounding blood vessels to influence angiogenesis, growth and differentiation, and thereby regulate cyclic hair growth. The goal of this study was to examine the expression of angiogenin, a potent angiogenic factor, in human DPCs, and to determine its role in hair growth. Reverse transcription polymerase chain reaction (RT-PCR), western blotting, immunofluorescence and ELISA analyzes were used to investigate the expression of angiogenin in human DPCs, while semi-quantitative RT-PCR was used to assess angiogenin mRNA expression in murine skin phased at different stages of the hair cycle. We detected angiogenin expression in DPCs, where it was found to be localized to the cytoplasm. Angiogenin mRNA was expressed in murine skin in a hair-cycle dependent manner, with maximum levels observed at the late anagen. Local injection of angiogenin promoted skin angiogenesis and induced anagen VI. In vitro studies showed that angiogenin significantly enhanced the elongation of hair follicles, and stimulated DPCs and ORS keratinocytes to proliferate. Taken together, these findings show that angiogenin is expressed in human DPCs, where it might contribute to hair growth directly, by stimulating DPCs and ORS keratinocytes to proliferate, or indirectly, by inducing local vascularization.

Hair follicle reformation induced by dermal papilla cells from human scalp skin

To investigate the possibility of hair follicle reformation induced by dermal papilla cells in vivo and in vitro. Dermal papilla cells, dermal sheath cells obtained from human scalp skin by enzyme digestion were mixed with collagen to form mesenchymal cell-populated collagen gels. Superior and inferior epithelial cells and bulb matrical cells were then cultured on these gels by organotypic culture to recombine bilayer artificial skins. Dermal papilla cells and outer root sheath keratinocytes were mingled together and transplanted under subcutaneous tissue of the dorsal skin of nude mice. The results of histologic examination was observed with HE stain. These recombinants by organotypic culture all reformed bilayer structure like nature skin. Hair follicle-like structure reformation was found in dermal sheath cell-populated collagen gel when combined with superior or inferior epithelial cells. Dermal papilla cells also induced superior and inferior epithelial cells to form hair follicle on nude mice. Low passage dermal papilla cells mixed with hair follicle epithelial cells reformed many typical hair follicle structures and produced hair fibres after transplantation on nude mice. The dermal part of hair follicle, such as dermal papilla cells and dermal sheath cells, has the ability to induce hair follicle formation by interaction with the epithelial cells of hair follicle.