An optimized force-triggered density gradient sedimentation method for isolation of pelage follicle dermal papilla cells from neonatal mouse skin

BACKGROUND

The dermal papilla cells are a specialized population of mesenchymal cells located at the base of the hair follicle (HF), which possess the capacity to regulate HF morphogenesis and regeneration. However, lack of cell-type specific surface markers restricts the isolation of DP cells and application for tissue engineering purposes.

METHODS

We describe a novel force-triggered density gradient sedimentation (FDGS) method to efficiently obtain purified follicular DP-spheres cells from neonatal mouse back skin, utilizing only centrifugation and optimized density gradients.

RESULTS

Expression of characteristic DP cell markers, alkaline phosphatase, β-catenin, versican, and neural cell adhesion molecules, were confirmed by immunofluorescence. Further, the patch assays demonstrated that DP cells maintained their hair regenerative capacity in vivo. Compared with current methods, including microdissection and fluorescence-activated cell sorting, the FDGS technique is simpler and more efficient for isolating DP cells from neonatal mouse skin.

CONCLUSIONS

The FDGS method will improve the research potential of neonatal mouse pelage-derived DP cells for tissue engineering purposes.

Gellan gum-based hydrogels support the recreation of the dermal papilla microenvironment

The dermal papilla (DP), a specialized compartment within the hair follicle, regulates hair growth. However, human DP cells rapidly lose their inductivity in 2D-culture given the loss of positional and microenvironmental cues. Spheroids have been capable of recreating the 3D intercellular organization of DP cells, however, DP cell-matrix interactions are poorly represented. Considering the specific nature of the DP's extracellular matrix (ECM), we functionalized gellan gum (GG) with collagen IV-(HepIII) or fibronectin-(cRGDfC) derived peptide sequences to generate a 3D environment in which the phenotype and physiological functions of DP cells are restored. We further tuned the stiffness of the microenvironments by varying GG amount. Biomimetic peptides in stiffer hydrogels promoted the adhesion of DP cells, while each peptide and amount of polymer independently influenced the type and quantity of ECM proteins deposited. Furthermore, although peptides did not seem to have an influence, stiffer hydrogels improved the inductive capacity of DP cells after short term culture. Interestingly, independently of the peptide, these hydrogels supported the recapitulation of basic hair morphogenesis-like events when incorporated in an organotypic human skin in vitro model. Our work demonstrates that tailored GG hydrogels support the generation of a microenvironment in which both cell-ECM and cell-cell interactions positively influence DP cells towards the creation of an artificial DP.

A Cre knockin mouse reveals specific expression of Agouti gene in mesenchymal lineage cells in multiple organs and provides a unique tool for conditional gene targeting

The mouse Agouti gene encodes a paracrine signaling factor which promotes melanocytes to produce yellow instead of black pigment. It has been reported that Agouti mRNA is confined to the dermal papilla after birth in various mammalian species. In this study, we created and characterized a knockin mouse strain in which Cre recombinase was expressed in-frame with endogenous Agouti coding sequence. The Agouti-Cre mice were bred with reporter mice (Rosa26-tdTomato or Rosa26-ZsGreen) to trace the lineage of Agouti-expressing cells during development. In skin, the reporter was detected in some dermal fibroblasts at the embryonic stage and in all dermal fibroblasts postnatally. It was also expressed in all mesenchymal lineage cells in other organs/tissues, including eyes, tongue, muscle, intestine, adipose, prostate and testis. Interestingly, the reporter expression was excluded from epithelial cells in the above organs/tissues. In brain, the reporter was observed in the outermost meningeal fibroblasts. Our work helps to illustrate the Agouti expression pattern during development and provides a valuable mouse strain for conditional gene targeting in mesenchymal lineage cells in multiple organs.

The dermal papilla dilemma and potential breakthroughs in bioengineering hair follicles

The generation and growing of de novo hair follicles is the most daring hair replacement approach to treat alopecia. This approach has been explored at least since the 1960s without major success. Latest in the 1980s, the realization that the mesenchymal compartment of hair follicles, the dermal papilla (DP), is the crucial signaling center and element required for fulfilling this vision of hair follicle engineering, propelled research into the fibroblasts that occupy the DP. However, working with DP fibroblasts has been stubbornly frustrating. Decades of work in understanding the nature of DP fibroblasts in vitro and in vivo have led to the appreciation that hair follicle biology is complex, and the dermal papilla is an enigma. Functional DP fibroblasts tend to aggregate in 2D culture, while impaired DP cells do not. This fact has stimulated recent approaches to overcome the hurdles to DP cell culture by mimicking their natural habitat, such as growing DP fibroblasts in three dimensions (3D) by their self-aggregation, adopting 3D matrix scaffold, or bioprinting 3D microstructures. Furthermore, including keratinocytes in the mix to form hair follicle-like composite structures has been explored but remains a far cry from a useful and affordable method to generate human hair follicles in sufficient quantity and quality in a practical time frame for patients. This suggests that the current strategies may have reached their limitations in achieving successful hair follicle bioengineering for clinical applications. Novel approaches are required to overcome these barriers, such as focusing on embryonic cell types and processes in combination with emerging techniques.

Homeostases of epidermis and hair follicle, and development of basal cell carcinoma

Hedgehog signaling (Hh) plays a critical role in embryogenesis. On the other hand, its overactivity may cause basal cell carcinoma (BCC), the most common human cancer. Further, epidermal and hair follicle homeostases may have a key role in the development of BCC. This article describes the importance of different signaling pathways in the different stages of the two processes. The description of the homeostases brought up the importance of the Notch signaling along with the sonic hedgehog (Shh) and the Wnt pathways. Loss of the Notch signaling adversely affects the late stages of hair follicle formation and allows the bulge cells in the hair follicles to take the fate of the keratinocytes in the interfollicular epidermis. Further, the loss of Notch activity upregulates the Shh and Wnt activities, adversely affecting the homeostases. Notably, the Notch signaling is suppressed in BCC, and the peripheral BCC cells, which have low Notch activity, show drug resistance in comparison to the interior suprabasal BCC cells, which have high Notch activity.

Argan (Argania Spinosa) press cake extract enhances cell proliferation and prevents oxidative stress and inflammation of human dermal papilla cells

BACKGROUND

Hair follicle undergoes a growth cycle under the regulation of dermal papilla cells. Due to their enormous roles, these fibroblast cells have been used in various in vitro studies as a screening model to evaluate the effect of hair growth regulating agents.

OBJECTIVE

In the current study, we aim to check the hair growth potential effect of Argan press cake (APC) extracted using 50 or 80 % aqueous ethanol on human hair follicle dermal papilla cells (HFDPCs) and to determine the molecular mechanism.

METHODS

APC were applied to HFDPCs, then cell proliferation assays, mitochondrial biogenesis assay, and oxidative stress assay were assessed. DNA microarray was performed from the cells treated with our samples and minoxidil. Validation of the results was done using Quantitative Real-Time PCR with primers for hair-growth related genes. GC/MS analysis was used to determine the compounds contained in APC 50 and 80 %.

RESULTS

APC enhanced cell proliferation along with the stimulation of the ATP content. Additionally, APC had an anti-oxidant activity against H₂O₂ mediated oxidative stress preventing dermal papilla cell senescence. Consistent with this, global gene profiling analysis showed an activation of hair growth-related pathway, and a downregulation of inflammation- and oxidative stress-related genes by APC extracts. GC/MS analysis revealed that these extracts contained pure fatty acids, derived sugar chains, and pure compounds including tocopherols, squalene, and spinasterol.

CONCLUSION

Taken together, here we showed that APC extracts had an effect on stimulating hair growth while inhibiting the inflammation and the oxidative stress of HFDPCs and thus can potentially contribute to an anti-hair loss drug development.

Androgens downregulate BMP2 impairing the inductive role of dermal papilla cells on hair follicle stem cells differentiation

Hair follicle cyclical regeneration is regulated by epithelial-mesenchymal interactions. During androgenetic alopecia (AGA), hair follicle stem cells (HFSC) differentiation is impaired by deregulation of dermal papilla cells (DPC) secreted factors. We analyzed androgen influence on BMPs expression in DPC and their effect on HFSC differentiation to hair lineage. Androgens downregulated BMP2 and BMP4 in DPC spheroids. Addition of BMP2 restored alkaline phosphatase activity, marker of hair-inductivity in DPC, and DPC-induced HFSC differentiation, both inhibited by androgens. Concomitantly, in differentiating HFSC, an upregulation of BMPRIa and BMPRII receptors and nuclear β-catenin accumulation, indicative of Wnt/β-catenin pathway activation, were detected. Our results present BMP2 as an androgen-downregulated paracrine factor that contributes to DPC inductivity and favors DPC-induced HFSC differentiation to hair lineage, possibly through a crosstalk with Wnt/β-catenin pathway. A comprehensive understanding of androgen-deregulated DPC factors and their effects on differentiating HFSC would help to improve treatments for AGA.

Towards developing an organotypic model for the preclinical study and manipulation of human hair matrix-dermal papilla interactions

Organ culture of microdissected scalp hair follicles (HFs) has become the gold standard for human ex vivo hair research; however, availability is becoming very limited. Although various simplistic “HF-equivalent” in vitro models have been developed to overcome this limitation, they often fail to sufficiently mimic the complex cell–cell and cell–matrix interactions between epithelial and mesenchymal cell populations that underlie the specific growth processes occurring in a native HF. Here, we have attempted to overcome these limitations by developing a novel human hair research model that combines dermal papilla (DP) fibroblasts, cultured as 3-dimensional (3D) spheroids (DPS), with plucked anagen hair shafts (HS). We show that DPS express HF inductivity markers, such as alkaline phosphatase (ALP), versican and noggin, while plucked HSs retain substantial remnants of the anagen hair matrix. When cultured together, DPS adhere to and surround the plucked HS (HS-DPS), and significantly enhance HS expression of the differentiation marker keratin-85 (K85; p < 0.0001), while simultaneously decreasing the percentage of TUNEL + cells in the proximal HS (p = 0.0508). This simple model may offer a physiologically relevant first step toward evaluating HF differentiation in the human anagen hair matrix.

HIF-1α Stimulators Function Equally to Leading Hair Loss Agents in Enhancing Dermal Papilla Growth

INTRODUCTION

Androgenic alopecia (AGA) occurs due to progressive miniaturization of the dermal papilla (DP). During this process the hair follicle loses nutrition over time and eventually dies, causing the hair to fall out. Recent evidence suggests that hypoxia-inducible factor-1a (HIF-1α) modulation may counteract hair loss. This study aims to evaluate the proliferation of dermal papilla cells (DPCs) under the influence of a selection of commercially available topical hair loss drugs, compared to HIF-1α-stimulating agents.

MATERIALS AND METHODS

Using the hanging drop method, DPCs self-organized into spheroid shape, mirroring the three-dimensional (3D) structure of the DP in vivo. DP analogs were treated with established substances against AGA (minoxidil and caffeine) compared to HIF-1α-stimulating agents (deferoxamine [DFO] and deferiprone [DFP]), at 10 mM doses. DP analogs were simultaneously stained with 5-bromo-2'-deoxyuridine (BrdU) to evaluate impact of drug compounds on DP daughter cell production. Concurrently, fluorescent microscopy visualization of migration of daughter cells after 48 h in culture was performed.

RESULTS

DPC proliferation within the spheroid structure was significantly enhanced by caffeine, minoxidil, and the HIF-1α-stimulating agent DFP when compared to control. Highest proliferation was seen in the DFP-treated DP analogs. Migration of peripheral DP daughter cells was highest in control and DFO groups.

CONCLUSION

Here we demonstrate a significantly enhanced proliferative activity for both established substances against AGA (minoxidil and caffeine) and the HIF-1α-stimulating agent DFP in a 3D DPC spheroid culture model with equal results for DFP and minoxidil. These favorable characteristics make such compounds potential water-soluble alternatives to minoxidil.

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.

Ectodysplasin-A2 induces dickkopf 1 expression in human balding dermal papilla cells overexpressing the ectodysplasin A2 receptor

Androgenetic alopecia (AGA) is a common genetic disorder, and a X-chromosomal locus that contains the androgen receptor (AR) and ectodysplasin A2 receptor (EDA2R) genes represents a major susceptibility locus for AGA. In our previous study, we reported that ectodysplasin-A2 (EDA-A2) induces apoptosis in cultured human hair follicle (HF) cells and promotes the regression of HFs in mice. However, the role of the EDA-A2/EDA2R in AGA remains unknown, as the causative gene in this pathway has not yet been identified and potential functional connections between EDA-A2 signaling and the androgen pathway remain unclear. In this study, we investigated the expression of EDA2R in balding HFs and matched with non-balding HFs. The EDA2R level was upregulated in the balding dermal papilla (DP) cells compared with non-balding DP cells derived from patients with AGA. However, EDA2R was strongly expressed in both balding and non-balding outer root sheath (ORS) cells. We screened EDA-A2-regulated genes in balding DP cells and identified dickkopf 1 (DKK-1) as catagen inducer during the hair cycle. The mRNA and protein expression levels of DKK-1 were both upregulated by EDA-A2. In addition, DKK-1 expression was induced by EDA-A2 both in cultured human HFs and in mouse HFs. Moreover, the EDA-A2-induced apoptosis of DP and ORS cells was reversed by the antibody-mediated neutralization of DKK-1. Collectively, our data strongly suggest that EDA-A2 induces DKK-1 secretion and causes apoptosis in HFs by binding EDA2R, which is overexpressed in the bald scalp. EDA-A2/EDA2R signaling could inhibit hair growth through DKK-1 induction, and an inhibitor of EDA-A2/EDA2R signaling may be a promising agent for the treatment and prevention of AGA.

Destruction of the stem cell Niche, Pathogenesis and Promising Treatment Targets for Primary Scarring Alopecias

The Primary Scarring Alopecias are characterised by the irreversible destruction and fibrosis of hair follicles, leading to permanent and often disfiguring loss of hair. The pathophysiology of these diseases is not well understood. However, follicular-fibrosis and loss of the stem-cell niche appears to be a common theme. This review explores the pathogenesis of primary scarring alopecias, asking what happens to the stem cells of the hair follicle and how they may contribute to the progression of these diseases. Bulge-resident cells are lost (leading to loss of capacity for hair growth) from the follicle either by inflammatory-mediate apoptosis or through epigenetic reprogramming to assume a mesenchymal-like identity. What proportion of bulge cells is lost to which process is unknown and probably differs depending on the individual PCA and its specific inflammatory cell infiltrate. The formation of fibroblast-like cells from follicular stem cells may also mean that the cells of the bulge have a direct role in the pathogenesis. The identification of specific cells involved in the pathogenesis of these diseases could provide unique diagnostic and therapeutic opportunities to prevent disease progression by preventing EMT and specific pro-fibrotic signals.

Polygonum multiflorum extract support hair growth by elongating anagen phase and abrogating the effect of androgen in cultured human dermal papilla cells

Background

Dermal papilla cells (DPCs) play a key role in hair growth among the various cell types in hair follicles. Especially, DPCs determine the fate of hair follicle such as anagen to telogen transition and play a pivotal role in androgenic alopecia (AGA). This study was performed to elucidate the hair growth promoting effects of Polygonum multiflorum extract (PM extract) in cultured human DPCs and its underlying mechanisms.

Methods

The effects of PM extract on cultured DPCs were investigated. Cell viability and mitochondrial activity were measured by CCK-8 and JC-1 analysis, respectively. Western blotting, dot blotting, ELISA analysis, immunocytochemistry and real-time PCR analysis were also performed to elucidate the changes in protein and mRNA levels induced by PM extract. 3D cultured DPC spheroids were constructed for mimicking the in vivo DPs. The hair growth stimulatory effect of PM extract was evaluated using human hair follicle organ culture model.

Results

PM extract increased the viability and mitochondrial activity in cultured human DPCs in a dose dependent manner. The expression of Bcl2, an anti-apoptotic protein expressed dominantly in anagen was significantly increased and that of BAD, a pro-apoptotic protein expressed in early catagen was decreased by PM extract in cultured DPCs and/or 3D DPC spheroid culture. PM extract also decreased the expression of catagen inducing protein, Dkk-1. Growth factors including IGFBP2, PDGF and VEGF were increased by PM extract, revealed by dot blot protein analysis. We also have found that PM extract could reverse the androgenic effects of dihydrotestosterone (DHT), the most potent androgen. Finally, PM extract prolonged the anagen of human hair follicles by inhibiting catagen entry in human hair follicle organ culture model.

Conclusion

Our data strongly suggest that PM extract could promote hair growth by elongating the anagen and/or delaying the catagen induction of hair follicles through activation of DPCs.

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.

LncRNA-XIST promotes dermal papilla induced hair follicle regeneration by targeting miR-424 to activate hedgehog signaling

BACKGROUND

Alopecia is a highly prevalent disease characterizing by the loss of hair. Dermal papilla (DP) cells are the inducer of hair follicle regeneration, and in vitro three-dimensional (3D) culturing DP cells have been proven to induce hair follicle regeneration. However, the molecular mechanisms behind the regulation of 3D culturing DP cells remain unclear.

METHODS

3D-cultivated DP cells were used as in vitro cell model. DP sphere xenograft to nude mice was performed for in vivo study of hair follicle regeneration. qRT-PCR, Western blotting, and immunofluorescence were used for detecting the level of XIST, miR-424 and Hedgehog pathway-related proteins, respectively. H&E staining was used to examine hair neogenesis. Cell viability, proliferation and ALP activity were measured by MTT, CCK-8 and ELISA assays, respectively. Luciferase assays were used for studying molecular regulation between XIST, miR-424 and Shh 3'UTR.

RESULTS

XIST and Shh were up-regulated, and miR-424 was down-regulated in 3D DP cells. Molecular regulation studies suggested that XIST sponged miR-424 to promote Shh expression. Knockdown of XIST suppressed DP cell activity, cell proliferation, ALP activity and the expression of other DP markers by sponging miR-424. Knockdown of XIST suppressed Shh mediated hedgehog signaling by targeting miR-424. Moreover, the knockdown of XIST inhibited DP sphere induced in vivo hair follicle regeneration and hair development.

CONCLUSION

XIST sponges miR-424 to promote Shh expression, thereby activating hedgehog signaling and facilitating DP mediated hair follicle regeneration.

Isolation of Different Dermal Fibroblast Populations from the Skin and the Hair Follicle

The establishment of primary cells from fresh tissue is a widely used method for investigating human tissue in vitro. The skin harbors different cell populations in the dermis and the hair follicle, which can be isolated for downstream analysis. Here we describe the isolation of four dermal fibroblast populations from human haired skin and their maintenance in culture. The four cell populations for which isolation is described are papillary dermal fibroblast cells, reticular dermal fibroblast cells, hair follicle dermal sheath cells, and hair follicle dermal papilla cells.

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.

Ectodysplasin-A2 induces apoptosis in cultured human hair follicle cells and promotes regression of hair follicles in mice

Ectodysplasin is a ligand of the TNF family that plays a key role in ectodermal differentiation. EDA-A1 and EDA-A2 are two isoforms of ectodysplasin that differ only by the insertion of two amino acids and bind to two different receptors, ectodysplasin A receptor (EDAR) and ectodysplasin A2 receptor (EDA2R), respectively. Mutations of EDA-A1 and its receptor EDAR have been associated with hypohidrotic ecodermal dysplasia (HED). However, the role of EDA-A2 and the expression pattern of EDA2R in human hair follicles and in the mouse hair growth cycle have not been reported. In this study, we first investigated the expression of EDA2R in human hair follicles and in cultured follicular cells. EDA2R was strongly expressed in outer root sheath (ORS) cells and weakly expressed in dermal papilla (DP) cells. EDA-A2 induced the apoptosis of both ORS cells and DP cells via the activation of cleaved caspase-3. In addition, EDA2R was highly expressed in the late anagen phase compared with other phases in the hair growth cycle. Moreover, EDA-A2 induced apoptosis in cultured human hair follicle cells and in the mouse hair growth cycle, causing the premature onset of the catagen phase. Collectively, our results suggest that EDA-A2/EDA2R signaling could inhibit hair growth, and an inhibitor of EDA-A2/EDA2R signaling may be a promising agent for the treatment and prevention of hair loss.

Nuclear localization of Meis1 in dermal papilla promotes hair matrix cell proliferation in the anagen phase of hair cycle

The dermal papilla (DP) is a key mesenchymal compartment of hair follicles that orchestrates mesenchymal-epithelial interaction regulating hair growth cycles. In the present study, we demonstrate that a TALE-family transcription factor, Meis1, is selectively localized in the nucleus of the DP in the anagen phase of the hair cycle. By using an ex vivo organ culture of vibrissae follicles, conditional Meis1 loss causes retardation in hair growth, accompanied by defects in cell proliferation of hair matrix cells. This cell proliferation defect is partly rescued by the addition of culture supernatants derived from Meis1-sufficient but not -deficient DP cells. These findings indicate that nuclear Meis1 in DP activate genes involved in secretion of some unknown factors, which promote proliferation of hair matrix cells in the anagen phase of the hair cycle.

Lactoferrin promotes hair growth in mice and increases dermal papilla cell proliferation through Erk/Akt and Wnt signaling pathways

Hair loss affects men and women of all ages. Dermal papilla (DP) plays a crucial role in regulating the growth and cycling of hair follicles. Lactoferrin (LF) exhibits a wide range of biological functions, including antimicrobial activity and growth regulation. However, its effect on DP and its role in hair growth remain unknown. In this study, we found that bovine LF (bLF) promoted the proliferation of DP cells and enhanced the phosphorylation of Erk and Akt. The bLF-mediated proliferation was significantly blocked by the Erk phosphorylation inhibitor PD98059 or the Akt phosphorylation inhibitor LY294002. Moreover, biotin-labeled bLF could bind to DP cells, and the binding was independent of lipoprotein receptor-related protein 1, a known LF receptor. Importantly, bLF stimulated hair growth in both young and aged mice. Moreover, we also found that bLF significantly induced the expression of Wnt signaling-related proteins, including Wnt3a, Wnt7a, Lef1, and β-catenin. The bLF-mediated DP cell proliferation could be significantly reversed by the Wnt pathway inhibitor XAV939. Our findings suggest that bLF promotes hair growth in mice and stimulates proliferation of DP cells through Erk/Akt and Wnt signaling pathways. This study highlights a great potential of the use of bLF in developing drugs to treat hair loss.

Restoration of hair-inductive activity of cultured human follicular keratinocytes by co-culturing with dermal papilla cells

Hair follicle outer root sheath (ORS) cells can be expanded in vitro, but often lose receptivity to hair-inducing dermal signals. Recent studies have shown hair-inductive activity (trichogenicity) can be restored in rat ORS cells expanded with a fibroblast feeder by co-culturing with rat vibrissae dermal papilla (DP) cells. In this study, we investigated whether the trichogenicity of human ORS cells can be restored by co-culturing with human DP cells. ORS cells from human scalp hair follicles were cultured independently or with DP cells for 5 days and implanted into nude mice alongside freshly isolated neonatal mouse dermal cells. Although there was no hair induction when monocultured ORS cells were implanted, it was observed in co-cultured ORS cells. We also observed differential regulation of a number of genes in ORS cells co-cultured with DP cells compared to monocultured ORS cells as examined by microarray. Taken together, our data strongly suggest that human DP cells restore the trichogenicity of co-cultured ORS cells by influencing ORS gene expression through paracrine factors.

Engineering the niche for hair regeneration - A critical review

Recent progress in hair follicle regeneration and alopecia treatment necessitates revisiting the concepts and approaches. In this sense, there is a need for shedding light on the clinical and surgical therapies benefitting from nanobiomedicine. From this perspective, this review attempts to recognize requirements upon which new hair therapies are grounded; to underline shortcomings and opportunities associated with recent advanced strategies for hair regeneration; and most critically to look over hair regeneration from nanomaterials and pluripotent stem cell standpoint. It is noteworthy that nanotechnology is able to illuminate a novel path for reprogramming cells and controlled differentiation to achieve the desired performance. Undoubtedly, this strategy needs further advancement and a lot of critical questions have yet to be answered. Herein, we introduce the salient features, the hurdles that must be overcome, the hopes, and practical constraints to engineer stem cell niches for hair follicle regeneration.

Transmission electron microscopic and immunohistochemical observations of resting follicles of feathers in chicken show massive cell degeneration

The molting cycle of feathers includes an anagen (growth) stage, a likely catagen stage where the feather follicles degenerate, and a resting stage where fully grown feathers remain in their follicles and are functional before molting. However, the cytological changes involved in the resting and molting stages are poorly known, so the results of an ultrastructural analysis of these processes in adult chick feathers are presented here. The study showed that the dermal papilla shrinks, and numerous cells present increased heterochromatin and free collagen fibrils in the extracellular matrix. Degeneration of the germinal epithelium of the follicle-the papillary collar-occurs with an initial substantial contraction of cells followed by an increase in heterochromatin, vesicle and lipid accumulation, and membrane and organelle degeneration. Desmosomes are still present between degenerating epithelial cells, but ribosomes and tonofilaments disappear. This suggests that cell necrosis initially proceeds as a major contraction resembling apoptosis-a process termed necroptosis, which was previously also shown to occur during the formation of barbs and barbules in mature down and pennaceous feathers. This study suggests that, aside from apoptosis, the collar epithelium degenerates due to external factors, in particular the retraction of blood vessels supplying the dermal papilla. In contrast, revascularization of the dermal papilla triggers a new phase of feather growth (anagen).

Androgens and androgen receptor action in skin and hair follicles

Beyond sexual functions, androgens exert their action in skin physiology and pathophysiology. Skin cells are able to synthesize most active androgens from gonadal or adrenal precursors and the enzymes involved in skin steroidogenesis are implicated both in normal or pathological processes. Even when the role of androgens and androgen receptor (AR) in skin pathologies has been studied for decades, their molecular mechanisms in skin disorders remain largely unknown. Here, we analyze recent studies of androgens and AR roles in several skin-related disorders, focusing in the current understanding of their molecular mechanisms in androgenetic alopecia (AGA). We review the molecular pathophysiology of type 2 5α-reductase, AR coactivators, the paracrine factors deregulated in dermal papillae (such as TGF-β, IGF 1, WNTs and DKK-1) and the crosstalk between AR and Wnt signaling in order to shed some light on new promising treatments.

Hair Follicle-Associated Pluripotent (HAP) Stem Cells in Gelfoam® Histoculture for Use in Spinal Cord Repair

The stem cell marker, nestin, is expressed in the hair follicle, both in cells in the bulge area (BA) and the dermal papilla (DP). Nestin-expressing hair follicle-associated-pluripotent (HAP) stem cells of both the BA and DP have been previously shown to be able to form neurons, heart muscle cells, and other non-follicle cell types. The ability of the nestin-expressing HAP stem cells from the BA and DP to repair spinal cord injury was compared. Nestin-expressing HAP stem cells from both the BA and DP grew very well on Gelfoam^®. The HAP stem cells attached to the Gelfoam^® within 1 h. They grew along the grids of the Gelfoam^® during the first 2 or 3 days. Later they spread into the Gelfoam^®. After transplantation of Gelfoam^® cultures of nestin-expressing BA or DP HAP stem cells into the injured spinal cord (including the Gelfoam^®) nestin-expressing BA and DP cells were observed to be viable over 100 days post-surgery. Hematoxylin and eosin (H&E) staining showed connections between the transplanted cells and the host spine tissue. Immunohistochemistry showed many Tuj1-, Isl 1/2, and EN1-positive cells and nerve fibers in the transplanted area of the spinal cord after BA Gelfoam^® or DP Gelfoam^® cultures were transplanted to the spine. The spinal cord of mice was injured to effect hind-limb paralysis. Twenty-eight days after transplantation with BA or DP HAP stem cells on Gelfoam^® to the injured area of the spine, the mice recovered normal locomotion.

Establishment of an immortalized mouse dermal papilla cell strain with optimized culture strategy

Dermal papilla (DP) plays important roles in hair follicle regeneration. Long-term culture of mouse DP cells can provide enough cells for research and application of DP cells. We optimized the culture strategy for DP cells from three dimensions: stepwise dissection, collagen I coating, and optimized culture medium. Based on the optimized culture strategy, we immortalized primary DP cells with SV40 large T antigen, and established several immortalized DP cell strains. By comparing molecular expression and morphologic characteristics with primary DP cells, we found one cell strain named iDP6 was similar with primary DP cells. Further identifications illustrate that iDP6 expresses FGF7 and α-SMA, and has activity of alkaline phosphatase. During the process of characterization of immortalized DP cell strains, we also found that cells in DP were heterogeneous. We successfully optimized culture strategy for DP cells, and established an immortalized DP cell strain suitable for research and application of DP cells.

Establishment and characterization of five immortalized human scalp dermal papilla cell lines

Dermal papilla (DP) regulates the growth and cycling of hair follicles. Cultured DP cells are useful for the study of their role in relation to hair growth and regeneration. However, cultivation of human DP cells is tedious and difficult. In addition, cultured DP cells possess a relatively short replicative life span, requiring immortalized human DP cell lines. We previously established an immortalized human DP cell line, SV40T-hTERT-DPC, by introducing human telomerase reverse transcriptase (hTERT) gene into the transformed cell line, SV40T-DPC. In this study, we co-transfected the simian virus 40 large T antigen (SV40T-Ag) and hTERT into DP cells from scalp hair follicles from a male with androgenetic alopecia and established five immortalized DP cell lines and named KNU-101, KNU-102, KNU-103, KNU-201 and KNU-202. We then evaluated tumorigenicity, expression of DP markers, responses to androgen, Wnt3a and BMP4, and expression of DP signature genes. These cell lines displayed early passage morphology and maintained responses to androgen, Wnt and BMP. Furthermore, these cell lines expressed DP markers and DP signature genes. KNU cell lines established in this study are potentially useful sources for hair research.

Androgens modify Wnt agonists/antagonists expression balance in dermal papilla cells preventing hair follicle stem cell differentiation in androgenetic alopecia

In androgenetic alopecia, androgens impair dermal papilla-induced hair follicle stem cell (HFSC) differentiation inhibiting Wnt signaling. Wnt agonists/antagonists balance was analyzed after dihydrotestosterone (DHT) stimulation in androgen-sensitive dermal papilla cells (DPC) cultured as spheroids or monolayer. In both culture conditions, DHT stimulation downregulated Wnt5a and Wnt10b mRNA while the Wnt antagonist Dkk-1 was upregulated. Notably, tissue architecture of DPC-spheroids lowers Dkk-1 and enhances Wnt agonists' basal expression; probably contributing to DPC inductivity. The role of Wnt agonists/antagonists as mediators of androgen inhibition of DPC-induced HFSC differentiation was evaluated. Inductive DPC-conditioned medium supplemented with DKK-1 impaired HFSC differentiation mimicking androgens' action. This effect was associated with inactivation of Wnt/β-catenin pathway in differentiating HFSC by both DPC-conditioned media. Moreover, addition of WNT10b to DPC-medium conditioned with DHT, overcame androgen inhibition of HFSC differentiation. Our results identify DKK1 and WNT10b as paracrine factors which modulate the HFSC differentiation inhibition involved in androgen-driven balding.

Human platelet lysate versus minoxidil stimulates hair growth by activating anagen promoting signaling pathways

Minoxidil and human platelet lysate (HPL) are commonly used to treat patients with hair loss. However, the roles of HPL versus minoxidil in hair follicle biology largely remain unknown. Here, we hypothesized that bulge and dermal papilla (DP) cells may express specific genes, including Kras, Erk, Akt, Shh and β-catenin after exposure to minoxidil or HPL. The mouse hair follicles were isolated on day 10 after depilation and bulge or DP regions were dissected. The bulge and DP cells were cultured for 14days in DMEM/F12 medium. Then, the cells were treated with 100μM minoxidil and 10% HPL for 10 days. Nuclear morphology was identified using DAPi staining. Reverse transcriptase and real-time polymerase chain reaction (PCR) analysis were also performed to examine the expression of Kras, Erk, Akt, Shh and β-catenin mRNA levels in the treated bulge and DP regions after organ culture. Here, we found that minoxidil influences bulge and DP cell survival (P<0.05). Apoptosis in DP cells was also meaningfully decreased by HPL treatment (P=0.014). In addition, Kras, Akt, Erk, Shh and β-catenin mRNA levels were changed in response to minoxidil treatment in both bulge and DP cells. HPL mediated Erk upregulation in both bulge and DP cells (P<0.05), but Kras and Akt mRNA levels were not considerably different in the HPL-treated cells. β-catenin mRNA level was also significantly increased in the bulge region by HPL. We also found that Shh mRNA level was considerably higher in HPL-treated bulge cells than in minoxidil-treated bulge cells. In contrast, the expression of β-cateinin and Shh in the DP cells was not meaningfully increased after treatment with HPL. Our results suggest that minoxidil and HPL can promote hair growth by activating the main anagen inducing signaling pathways.

Acute Stress-Induced Changes in Follicular Dermal Papilla Cells and Mobilization of Mast Cells: Implications for Hair Growth

BACKGROUND

Stress is a known cause of hair loss in many species.

OBJECTIVE

In this study, we investigated the role of acute stress on hair growth using a rat model.

METHODS

Rats were immobilized for 24 hours and blood samples, and skin biopsies were taken. The effect of stress-serum on the in vitro proliferation of rat and human dermal papilla cells (hDPCs), as well as serum cortisol and corticotropin-releasing hormone levels, were measured. Mast cell staining was performed on the biopsied tissue. In addition, Western blot and quantitative real time polymerase chain reaction were used to assess mast cell tryptase and cytokine expression, respectively in rat skin biopsies.

RESULTS

Stress-serum treatment reduced significantly the number of viable hDPCs and arrested the cell cycle in the G1 phase, compared to serum from unrestrained rats (p<0.05, respectively). Moreover, restrained rats had significantly higher levels of cortisol in serum than unrestrained rats (p<0.01). Acute stress serum increased mast cell numbers and mast cell tryptase expression, as well as inducing interleukin (IL)-6 and IL-1β up-regulation.

CONCLUSION

These results suggest that acute stress also has an inhibitory effect on hair growth via cortisol release in addition to substance P-mast cell pathway.

Culture of Dermal Papilla Cells from Ovine Wool Follicles: An In Vitro Model for Papilla Size Determination

Common human balding or hair loss is driven by follicle miniaturization. Miniaturization is thought to be caused by a reduction in dermal papilla size. The molecular mechanisms that regulate papilla size are poorly understood, and their elucidation would benefit from a tractable experimental model. We have found that dermal papilla cells from sheep spontaneously aggregate in culture to form papilla-like structures. Here, we describe methods for microdissecting dermal papillae from wool follicles, for initiating and maintaining cultures of ovine papilla cells, and for using these cells in an in vitro assay to measure the effect of bioactive molecules on aggregate size.

Maintenance of Dermal Papilla Cells by Wnt-10b In Vitro

Dermal papilla cells (DPCs) are associated with development of hair follicles (HFs) and regulation of the hair cycle. However, primary DPCs are known to lose their ability to induce HFs after culture in standard media for fibroblasts. We examined a new culture condition for DPCs including addition of Wnt-10b, which promoted proliferation and maintained their HF induction ability for more than ten passages. These results suggest that Wnt-10b plays a pivotal role in proliferation and maintenance of DPCs in vitro.

Antimicrobial peptide lysozyme has the potential to promote mouse hair follicle growth in vitro

Lysozyme is a well-known antimicrobial peptide that exists widely in mammalian skin and it is also expressed by pilosebaceous units. However, the exact location of lysozyme in hair follicles and whether it exerts any direct effects on hair follicle growth are unclear. To determine whether lysozyme affected hair growth in vitro, micro-dissected mouse vibrissae follicles (VFs) were treated in serum-free organ culture for 3 days with lysozyme (1-10μg/ml). After that, the effects of lysozyme on dermal papilla (DP) cells were also investigated. Lysozyme was mainly identified in DP and dermal sheath regions of VF by immunochemistry. In addition, 5-10μg/ml lysozyme had a promoting effect on shaft production. It was also associated with significant proliferation of matrix keratinocytes by immunofluorescence observation. Furthermore, lysozyme promoted hair growth by increasing the levels of alkaline phosphatase and lymphoid enhancer factor 1 in DP, as determined by Western blotting. These results indicate that lysozyme is a promoter of VF growth via enhancing the hair-inductive capacity of DP cells during organ culture.

Epidermal stem cells and skin tissue engineering in hair follicle regeneration

The reconstitution of a fully organized and functional hair follicle from dissociated cells propagated under defined tissue culture conditions is a challenge still pending in tissue engineering. The loss of hair follicles caused by injuries or pathologies such as alopecia not only affects the patients' psychological well-being, but also endangers certain inherent functions of the skin. It is then of great interest to find different strategies aiming to regenerate or neogenerate the hair follicle under conditions proper of an adult individual. Based upon current knowledge on the epithelial and dermal cells and their interactions during the embryonic hair generation and adult hair cycling, many researchers have tried to obtain mature hair follicles using different strategies and approaches depending on the causes of hair loss. This review summarizes current advances in the different experimental strategies to regenerate or neogenerate hair follicles, with emphasis on those involving neogenesis of hair follicles in adult individuals using isolated cells and tissue engineering. Most of these experiments were performed using rodent cells, particularly from embryonic or newborn origin. However, no successful strategy to generate human hair follicles from adult cells has yet been reported. This review identifies several issues that should be considered to achieve this objective. Perhaps the most important challenge is to provide three-dimensional culture conditions mimicking the structure of living tissue. Improving culture conditions that allow the expansion of specific cells while protecting their inductive properties, as well as methods for selecting populations of epithelial stem cells, should give us the necessary tools to overcome the difficulties that constrain human hair follicle neogenesis. An analysis of patent trends shows that the number of patent applications aimed at hair follicle regeneration and neogenesis has been increasing during the last decade. This field is attractive not only to academic researchers but also to the companies that own almost half of the patents in this field.

Synergistic effect of PDGF and FGF2 for cell proliferation and hair inductive activity in murine vibrissal dermal papilla in vitro

BACKGROUND

The dermal papilla is composed of a small clump of mesenchymal cells, called dermal papilla cells (DPCs). DPCs closely interact with epidermal cells to give rise to hair follicles and shafts during hair follicle development and the hair cycle. DPCs are promising cell sources for hair regeneration therapy for alopecia patients. However, once DPCs are put into conventional two-dimensional culture conditions, they quickly lose their capability to produce hair follicles.

OBJECTIVE

We aimed to expand a sufficiently large population of DPCs that retain their hair inductive activity.

METHODS

Murine DPCs were cultured in the presence of platelet-derived growth factor-AA (PDGF-AA) and fibroblast growth factor 2 (FGF2). Expressions of follicular-related genes were analyzed by real time PCR and hair inductive activity was determined by patch assay and chamber assay in vivo.

RESULTS

FGF2 significantly increased the expression of platelet-derived growth factor receptor alpha (PDGFRα) in cultured vibrissal DPCs. PDGF-AA, a ligand of PDGFRα, promoted proliferation of DPCs synergistically when utilized with FGF2 and enhanced the expression of several follicular-related genes in DPCs. Hair reconstitution assays revealed that DPCs treated with both PDGF-AA and FGF-2 were able to maintain their hair inductive activity better than those treated with FGF2 alone.

CONCLUSION

Both cell proliferation and hair inductive activity in murine DPCs are maintained by the synergistic effect of FGF2 and PDGF-AA.

Hair Follicle Plasticity with Complemented Immune-modulation Following Follicular Unit Extraction

Background:

During hair transplantation as an effective therapy for androgenetic alopecia, hair follicles were typically trans-located from the nonaffected occipital to the balding frontal or vertex region of the scalp. Although this is an autologous intervention, the donor and recipient hair follicle tissue differ in composition and local environment.

Settings and Design:

In two case studies, we investigated the changes in hair follicle morphology and the immune status of scalp and body hair follicles from different origins transplanted to the eyebrows and the frontal scalp using follicular unit extraction.

Results:

Quantitative histomorphometry and immunohistochemistry revealed a transformation in hair follicle length and dermal papilla size of the scalp, chest and beard hair follicles, which had been re-extracted after a 6-month period posttransplantation. Furthermore, a significant infiltration of B and T lymphocytes as well as macrophages could be observed most prominently in the infundibulum of transplanted hair follicles.

Conclusion:

The presented results demonstrate that hair follicle units from different body sites are capable to replace miniaturized or degraded hair follicles in different recipient areas like scalp or eyebrows as they keep their intrinsic capability or acquire the potential to readjust plastically within the beneficiary skin region. The essential secretory crosstalk underlying the observed tissue remodeling is possibly mediated by the infiltrating immune cells.

Sox2 modulates the function of two distinct cell lineages in mouse skin

In postnatal skin the transcription factor Sox2 is expressed in the dermal papilla (DP) of guard/awl/auchene hair follicles and by mechanosensory Merkel cells in the touch domes of guard hairs. To investigate the consequences of Sox2 ablation in skin we deleted Sox2 in DP cells via Blimp1Cre and in Merkel cells via K14Cre. Loss of Sox2 from the DP did not inhibit hair follicle morphogenesis or establishment of the dermis and hypodermis. However, Sox2 expression in the DP was necessary for postnatal maintenance of awl/auchene hair follicles. Deletion of Sox2 via K14Cre resulted in a decreased number of Merkel cells but had no effect on other epithelial compartments or on the dermis. The reduced number of Merkel cells did not affect the number or patterning of guard hairs, nerve density or the interaction of nerve cells with the touch domes. We conclude that Sox2 is a marker of two distinct lineages in the skin and regulates the number of differentiated cells in the case of the Merkel cell lineage and hair follicle type in the case of the DP.

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Sox2 is a marker of two distinct lineages in the skin.

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Sox2 is required for postnatal maintenance of awl/auchene hair follicles.

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Loss of Sox2 results in a reduction in Merkel cells.

Canonical Wnts, specifically Wnt-10b, show ability to maintain dermal papilla cells

Although Wnts are expressed in hair follicles (HFs) and considered to be crucial for maintaining dermal papilla (DP) cells, the functional differences among them remain largely unknown. In the present study, we investigated the effects of Wnts (Wnt-3a, 5a, 10b, 11) on the proliferation of mouse-derived primary DP cells in vitro as well as their trichogenesis-promoting ability using an in vivo skin reconstitution protocol. Wnt-10b promoted cell proliferation and trichogenesis, while Wnt-3a showed those abilities to a limited extent, and Wnt-5a and 11 had no effects. Furthermore, we investigated the effects of these Wnts on cultured DP cells obtained from versican-GFP transgenic mice and found that Wnt-10b had a potent ability to sustain their GFP-positivity. These results suggest that canonical Wnts, specifically Wnt-10b, play important roles in the maintenance of DP cells and trichogenesis.

Valproic acid promotes human hair growth in in vitro culture model

BACKGROUND

β-Catenin, the transducer of Wnt signaling, is critical for the development and growth of hair follicles. In the absence of Wnt signals, cytoplasmic β-catenin is phosphorylated by glycogen synthase kinase (GSK)-3 and then degraded. Therefore, inhibition of GSK-3 may enhance hair growth via β-catenin stabilization. Valproic acid is an anticonvulsant and a mood-stabilizing drug that has been used for decades. Recently, valproic acid was reported to inhibit GSK-3β in neuronal cells, but its effect on human hair follicles remains unknown.

OBJECTIVES

To determine the effect of VPA on human hair growth.

METHODS

We investigated the effect of VPA on cultured human dermal papilla cells and outer root sheath cells and on an in vitro culture of human hair follicles, which were obtained from scalp skin samples of healthy volunteers. Anagen induction by valproic acid was evaluated using C57BL/6 mice model.

RESULTS

Valproic acid not only enhanced the viability of human dermal papilla cells and outer root sheath cells but also promoted elongation of the hair shaft and reduced catagen transition of human hair follicles in organ culture model. Valproic acid treatment of human dermal papilla cells led to increased β-catenin levels and nuclear accumulation and inhibition of GSK-3β by phosphorylation. In addition, valproic acid treatment accelerated the induction of anagen hair in 7-week-old female C57BL/6 mice.

CONCLUSIONS

Valproic acid enhanced human hair growth by increasing β-catenin and therefore may serve as an alternative therapeutic option for alopecia.

The Germinative Epithelium of Sheep Vibrissae and Wool Follicles has Extensive Proliferative Potential but is Dependent on the Dermal Papilla

AIM

To investigate the growth potential of keratinocytes derived from the germinative epithelium (GE) of ovine hair follicles. Stem cells from the outer root sheath (ORS) of hair follicles migrate to the GE in the lower follicle where they proliferate and differentiate to form the hair fiber. It has been suggested that the GE comprises transit-amplifying cells and that the duration of anagen is determined by their limited proliferative potential. However, we show here that keratinocytes derived from the GE of ovine follicles grow extensively in vitro, arguing against this hypothesis.

MATERIALS AND METHODS

Primary cultures of keratinocytes were initiated from microdissected GE tissue from ovine vibrissae and wool follicles. Clonal lines of keratinocytes were derived by limiting dilution. Their growth potential was determined by exhaustive serial passaging. Expression of differentiation markers was evaluated by real-time polymerase chain reaction.

RESULTS

Initiation of these cultures required that interaction between the GE and dermal papilla was maintained. However, the keratinocytes could subsequently be cloned and were grown as pure cell populations for 26-52 cell doublings. This proliferative potential is several orders of magnitude greater than required to maintain a single anagen phase. The keratinocytes were indistinguishable from ORS keratinocytes from the same follicles, expressing K14 while undifferentiated, and upregulating the epidermal and inner root sheath markers, loricrin and KRT27 on differentiation. Thus, these cells initially depend on papilla-derived signals to grow, but can revert to an ORS-like phenotype in vitro. Their extensive proliferative capacity shows that the GE is not an exclusively transit-amplifying cell population.