TGF-beta is specifically expressed in human dermal papilla cells and modulates hair folliculogenesis

Hair Regeneration Methods Using Cells Derived from Human Hair Follicles and Challenges to Overcome

The hair follicle is a complex of mesenchymal and epithelial cells acquiring different properties and characteristics responsible for fulfilling its inductive and regenerative role. The epidermal and dermal crosstalk induces morphogenesis and maintains hair follicle cycling properties. The hair follicle is enriched with pluripotent stem cells, where dermal papilla (DP) cells and dermal sheath (DS) cells constitute the dermal compartment and the epithelial stem cells existing in the bulge region exert their regenerative role by mediating the epithelial-mesenchymal interaction (EMI). Many studies have developed and focused on various methods to optimize the EMI through in vivo and in vitro approaches for hair regeneration. The culturing of human hair mesenchymal cells resulted in the loss of trichogenicity and inductive properties of DP cells, limiting their potential application in de novo hair follicle generation in vivo. Epithelial stem cells derived from human hair follicles are challenging to isolate and culture, making it difficult to obtain enough cells for hair regeneration purposes. Mesenchymal stem cells and epithelial stem cells derived from human hair follicles lose their ability to form hair follicles during culture, limiting the study of hair follicle formation in vivo. Therefore, many attempts and methods have been developed to overcome these limitations. Here, we review the possible and necessary cell methods and techniques used for human hair follicle regeneration and the restoration of hair follicle cell inductivity in culture.

Deconvolving organogenesis in space and time via spatial transcriptomics in thick tissues

Organ development is guided by a space-time landscape that constraints cell behavior. This landscape is challenging to characterize for the hair follicle - the most abundant mini organ - due to its complex microscopic structure and asynchronous development. We developed 3DEEP, a tissue clearing and spatial transcriptomic strategy for characterizing tissue blocks up to 400 µm in thickness. We captured 371 hair follicles at different stages of organogenesis in 1 mm3 of skin of a 12-hour-old mouse with 6 million transcripts from 81 genes. From this single time point, we deconvoluted follicles by age based on whole-organ molecular pseudotimes to animate a stop-motion 3D atlas of follicle development along its trajectory. We defined molecular stages for hair follicle organogenesis and characterized the order of emergence for its structures, differential signaling dynamics at its top and bottom, morphogen shifts preceding and accompanying structural changes, and series of structural changes leading to the formation of its canal and opening. We further found that hair follicle stem cells and their niche are established and stratified early in organogenesis, before the formation of the hair bulb. Overall, this work demonstrates the power of increased depth of spatial transcriptomics to provide a four-dimensional analysis of organogenesis.

Establishment and functional characterization of immortalized rabbit dermal papilla cell lines

Hair follicle (HF) undergo periodic growth and development in mammals, which regulated by dermal papilla cells (DPCs) are reported to play an important role in HF morphogenesis and development. However, primary DPCs have low proliferative activity, age quickly, and fresh cell isolation is both time-consuming and laborious. In this study, we introduced the SV40 large T antigen (SV40T) into dissociated early passage rabbit vibrissae DPCs with lentiviral vectors and established seven immortalized DPC lines (R-1, R-2, R-3, R-4, R-5, R-6 and R-7). These cell lines displayed early passage morphology and high alkaline phosphatase activity. RT-PCR and immunofluorescence staining showed that all the immortalized cell lines expressed the DPC markers (α-SMA, IGF1, ALPL, FGF2, BMP2 and TGFβ2), but α-SMA was only expressed well in R-3, R-4, and R-7. Furthermore, it was found that R-7 was the only line to survive beyond 50 passages. Compared to melanoma cells, R-7 did not undergo malignant transformation. Karyotyping and cell growth viability analysis illustrated that the R-7 cell line preserved the basic characteristics of primary DPCs. The R-7 DPCs established have potential application for future hair research. The study provides the theoretical basis in the cell research of HF growth and development.

Vitamin D supplementation and immune-related markers: an update from nutrigenetic and nutrigenomic studies

Vitamin D is both a nutrient and a neurologic hormone that plays a critical role in modulating immune responses. While low levels of vitamin D are associated with increased susceptibility to infections and immune-related disorders, vitamin D supplementation has demonstrated immunomodulatory effects that can be protective against various diseases and infections. Vitamin D receptor is expressed in immune cells that have the ability to synthesise the active vitamin D metabolite. Thus, vitamin D acts in an autocrine manner in a local immunologic milieu in fighting against infections. Nutrigenetics and nutrigenomics are the new disciplines of nutritional science that explore the interaction between nutrients and genes using distinct approaches to decipher the mechanisms by which nutrients can influence disease development. Though molecular and observational studies have proved the immunomodulatory effects of vitamin D, only very few studies have documented the molecular insights of vitamin D supplementation. Until recently, researchers have investigated only a few selected genes involved in the vitamin D metabolic pathway that may influence the response to vitamin D supplementation and possibly disease risk. This review summarises the impact of vitamin D supplementation on immune markers from nutrigenetics and nutrigenomics perspective based on evidence collected through a structured search using PubMed, EMBASE, Science Direct and Web of Science. The research gaps and shortcomings from the existing data and future research direction of vitamin D supplementation on various immune-related disorders are discussed.

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.

Direct Reprograming of Mouse Fibroblasts into Dermal Papilla Cells via Small Molecules

The reprogramming of somatic fibroblasts into alternative cell linages could provide a promising source of cells for regenerative medicine and cell therapy. However, the direct conversion of fibroblasts into other functional cell types is still challenging. In this study, we show that dermal-papilla-cell-like cells (DPC-LCs) can be generated by treating fibroblasts, including L929 mouse fibroblast cell lines and somatic mouse fibroblasts, with small molecules. Based on alkaline phosphatase activity and other molecular markers, different compounds or their combinations are needed for converting the two different fibroblasts into DPC-LCs. Notably, we found that TTNPB alone can efficiently convert primary adult mouse fibroblasts into DPC-LCs. DPC-LCs generated from mouse fibroblasts showed a stronger hair-inducing capacity. Transcriptome analysis reveals that expression of genes associated with a hair-inducing capacity are increased in DPC-LCs. This pharmacological approach to generating functional dermal papilla cells may have many important implications for hair follicle regeneration and hair loss therapy.

Targeted deletion of TGFβ1 in basal keratinocytes causes profound defects in stratified squamous epithelia and aberrant melanocyte migration

Transforming Growth Factor Beta 1 (TGFβ1) is a multifunctional cytokine that regulates proliferation, apoptosis, and epithelial-mesenchymal transition of epithelial cells. While its role in cancer is well studied, less is known about TGFβ1 and regulation of epithelial development. To address this, we deleted TGFβ1 in basal keratinocytes of stratified squamous epithelia. Newborn mice with a homozygous TGFβ1 deletion had significant defects in proliferation and differentiation of the epidermis and oral mucosa, and died shortly after birth. Hair follicles were sparse in TGFβ1 depleted skin and had delayed development. Additionally, the Wnt pathway transcription factor LEF1 was reduced in hair follicle bulbs and nearly absent from the basal epithelial layer. Hemizygous knockout mice survived to adulthood but were runted and had sparse coats. The skin of these mice had irregular hair follicle morphology and aberrant hair cycle progression, as well as abnormally high melanin expression and delayed melanocyte migration. In contrast to newborn TGFβ1 null mice, the epidermis was hyperproliferative, acanthotic and inflamed. Expression of p63, a master regulator of stratified epithelial identity, proliferation and differentiation, was reduced in TGFβ1 null newborn epidermis but expanded in the postnatal acanthotic epidermis of TGFβ1 hemizygous mice. Thus, TGFβ1 is both essential and haploinsufficient with context dependent roles in stratified squamous epithelial development and homeostasis.

Recreation of a hair follicle regenerative microenvironment: Successes and pitfalls

The hair follicle (HF) is an exquisite skin appendage endowed with cyclical regenerative capacity; however, de novo follicle formation does not naturally occur. Consequently, patients suffering from extensive skin damage or hair loss are deprived of the HF critical physiological and/or aesthetic functions, severally compromising skin function and the individual's psychosocial well-being. Translation of regenerative strategies has been prevented by the loss of trichogenic capacity that relevant cell populations undergo in culture and by the lack of suitable human-based in vitro testing platforms. Here, we provide a comprehensive overview of the major difficulties associated with HF regeneration and the approaches used to overcome these drawbacks. We describe key cellular requirements and discuss the importance of the HF extracellular matrix and associated signaling for HF regeneration. Finally, we summarize the strategies proposed so far to bioengineer human HF or hair-bearing skin models and disclose future trends for the field.

Dexpanthenol Promotes Cell Growth by Preventing Cell Senescence and Apoptosis in Cultured Human Hair Follicle Cells

Dexpanthenol (D-panthenol) is a precursor of vitamin B5 (pantothenic acid) and is widely used for dietary supplements and topical applications. D-panthenol has long been used in hair care products for the purpose of anti-hair loss, its effects and the underlying mechanisms, however, were barely reported. In this study, the effects of D-panthenol on human hair follicle cells, including dermal papilla cells (hDPCs) and outer root sheath cells (hORSCs), were investigated. D-panthenol enhanced the cell viability, increasing the cellular proliferation marker Ki67 in cultured hDPCs. The markers for apoptosis (Caspase3/9) and cell senescence (p21/p16), reported to be expressed in aged or resting phase follicles, were significantly reduced by D-panthenol. Anagen-inducing factors (ALP; β-catenin; versican), which trigger or elongate the anagen phase, were stimulated by D-panthenol. On the other hand, D-panthenol reduced TGF-β1 expressions in both mRNA and protein levels. The expression of VEGF, which is important for peripheral blood vessel activation; was up-regulated by D-panthenol treatment. In cultured hORSCs, cell proliferation and viability were enhanced, while the mRNA expression of cell senescence markers (p21/p16) was significantly down-regulated. The expressions of both VEGF and its receptor (VEGFR) were up-regulated by D-panthenol. In conclusion, our data suggest that the hair growth stimulating activity of D-panthenol was exerted by increasing the cell viability, suppressing the apoptotic markers, and elongating the anagen phase in hair follicles.

TGF-β2 and collagen play pivotal roles in the spheroid formation and anti-aging of human dermal papilla cells

Dermal papilla cells (DPCs) tend to aggregate both in vitro and in vivo, which increases the hair inductivity of DPCs. However, the underlying mechanism of spheroid formation is unknown. We investigated whether collagen expression in human DPCs (hDPCs) is involved in the spheroid formation and hair inductivity of hDPCs and further examined the underlying molecular mechanism of collagen upregulation. The expression of diverse collagens, such as COL13A1 and COL15A1, was upregulated in three dimensional (3D)-cultured or intact DPCs, compared to 2D-cultured hDPCs. This collagen expression was a downregulated in aged hair follicle, and aged DPCs were difficult to aggregate. Blocking of COL13A1 and COL15A1 by small interfering RNA reduced aggregation, while induced senescence of hDPCs in vitro. Further, transforming growth factor-β2 (TGF-β2) expression decreases with aging, and is involved in regulating the expression of COL13A1 and COL15A1. Addition of recombinant TGF-β2 delayed cellular senescence, and recovered spheroid formation in aged hDPCs by upregulating collagen levels. On the contrary, knock-out of TGF-β2 induced the aging of DPCs, and inhibited spheroid formation. These results suggested that COL13A1 and COL15A1 expression is downregulated with aging in DPCs, and upregulation of collagen by TGF-β2 induces the spheroid formation of DPCs. Therefore, TGF-β2 supplement in DPC culture medium could enhance the maintenance and hair inductivity of DPCs.

Topical and nutricosmetic products for healthy hair and dermal antiaging using "dual-acting" (2 for 1) plant-based peptides, hormones, and cannabinoids

One of the side effects of oral antiaging retinoids is increased hair shedding. Retinoids promote the expression of TGF-β2 from fibroblasts, which stimulate collagen expression but silences keratinocytes. Since keratinocytes normally influence differentiation of dermal papilla cells at the base of the hair follicle, retinoids feasibly inhibit hair growth via the increased expression of TGF-β2, which inhibits Wnt/β-catenin signaling. Fortunately, the plant kingdom provides an array of alternatives as dual-acting nutricosmetics and topicals that work independently of TGF-β2 to confer dermal antiaging and hair health effects. These alternatives include "plant hormones" such as cytokinins and phytoestrogens. Many cytokinins are agonists of the G-coupled adenosine receptors. Partial agonism of adenosine receptors promotes collagen synthesis independently of TGF-β2 signaling. Adenosine expression is potentially also the mechanism of minoxidil in promotion of scalp hair growth. Because of crosstalk between adenosine and cannabinoid receptors it makes sense to try combinations of specific CB2 agonists and cytokinins (or phytoestrogens). However, dual-acting cosmetics including peptides with high numbers of positively charged amino acids, such as lysine or arginine, offer real potential as they can be processed from multiple botanical candidates, including almond, fenugreek, pea sprouts, soy, and seaweeds. The current review summarizes much of what is known about retinoid alternatives in the plant kingdom and identifies potentially fruitful new areas of research.

AP-1 and TGFß cooperativity drives non-canonical Hedgehog signaling in resistant basal cell carcinoma

Tumor heterogeneity and lack of knowledge about resistant cell states remain a barrier to targeted cancer therapies. Basal cell carcinomas (BCCs) depend on Hedgehog (Hh)/Gli signaling, but can develop mechanisms of Smoothened (SMO) inhibitor resistance. We previously identified a nuclear myocardin-related transcription factor (nMRTF) resistance pathway that amplifies noncanonical Gli1 activity, but characteristics and drivers of the nMRTF cell state remain unknown. Here, we use single cell RNA-sequencing of patient tumors to identify three prognostic surface markers (LYPD3, TACSTD2, and LY6D) which correlate with nMRTF and resistance to SMO inhibitors. The nMRTF cell state resembles transit-amplifying cells of the hair follicle matrix, with AP-1 and TGFß cooperativity driving nMRTF activation. JNK/AP-1 signaling commissions chromatin accessibility and Smad3 DNA binding leading to a transcriptional program of RhoGEFs that facilitate nMRTF activity. Importantly, small molecule AP-1 inhibitors selectively target LYPD3+/TACSTD2+/LY6D+ nMRTF human BCCs ex vivo, opening an avenue for improving combinatorial therapies.

Spatial association of SEMA3C with nerve endings/terminal Schwann cells in hair follicle isthmus region

Nerve endings and terminal Schwann cells (TSCs) specifically and densely surround hair follicle at isthmus area, forming a neuromuscular-junction-like structure called lanceolate complex. The interplay between neuronal components and epidermis in this specialized structure enables hair to properly sense complex stimuli from environments. However, how nerves precisely attach to and innervate this specific region during development remains to be elucidated. Here, we demonstrate that SEMA3C, a secreted protein member of semaphorin family responsible for axonal guidance, is localized right below sebaceous gland and in close approximation with nerve endings and TSCs processes all through the entire hair cycle. SEMA3C protein is deposited outside of epithelial cells and its expression is independent on the presence of nerve endings/TSCs. SEMA3C is also found in portions of dermal papilla at growth phase. The tight spatial association of SEMA3C with lanceolate complex suggests that it might play roles in establishment and/or maintenance of the lanceolate complex in hair follicle.

Hair Regeneration Potential of Human Dermal Sheath Cells Cultured Under Physiological Oxygen

We investigated the effect of oxygen tension on the proliferation and hair-inductive capacity of human dermal papilla cells (DPCs) and dermal sheath cells (DSCs). DPCs and DSCs were separately obtained from human hair follicles and each cultured under atmospheric/hyperoxic (20% O₂), physiological/normoxic (6% O₂), or hypoxic (1% O₂) conditions. Proliferation of DPCs and DSCs was highest under normoxia. Compared with hyperoxia, hypoxia inhibited proliferation of DPCs, but enhanced that of DSCs. In DPCs, hypoxia downregulated the expression of hair-inductive capacity-related genes, including BMP4, LEF1, SOX2, and VCAN. In DSCs, both normoxia and hypoxia upregulated SOX2 expression, whereas hypoxia downregulated BMP4 expression. Microarray analysis revealed that normoxia increased the expression of pluripotency-related genes, including SPRY, NR0B1, MSX2, IFITM1, and DAZL, compared with hyperoxia. In an in vivo hair follicle reconstitution assay, cultured DPCs and DSCs were transplanted with newborn mouse epidermal keratinocytes into nude mice using a chamber method. In this experiment, normoxia resulted in the most efficient induction of DPC hair follicles, whereas hypoxia caused the most efficient induction and maturation of DSC hair follicles. These results suggest that application of physiological/hypoxic oxygen tension to cultured human DSCs enhances proliferation and maintenance of hair inductivity for skin engineering and clinical applications. Impact statement Dermal sheath cells (DSCs) and dermal papilla cells (DPCs) are useful cell sources for cell-based regenerative therapy. This is the first report to describe that low-oxygen conditions are better for DSCs. Normoxic and hypoxic culture of DSCs is beneficial for expanding these hair follicular cells and advancing development of cell-based therapy for both wound healing and hair regeneration. The current study supports that optimized oxygen tension can be applied to use expanded human DPCs and DSCs for skin engineering and clinical applications.

Impact of Preservation Solutions on the Trichogenicity of Hair Micrografts Ascertained by Dermal Papilla Gene Expression

BACKGROUND

Appropriate storage of human hair follicle (HF) grafts during follicular unit excision (FUE) is crucial toward successful hair shaft implantation. Several commercial storage solutions are currently used to ensure ex vivo maintenance of follicular grafts viability and trichogenicity. However, quantitative experimental evidence demonstrating molecular changes in HF cells associated with the usage of different storage solutions is largely missing.

OBJECTIVE

To identify gene expression changes in HF cells caused by ex vivo storage of hair grafts in different preservation conditions.

METHODS

The authors performed gene expression analysis in dermal papilla (DP) isolated from HF stored under different temperatures and solutions. The expression signature of key genes controlling hair growth and cycling, apoptosis, inflammation, and senescence was assessed for (1) chilled versus room temperature (RT) and (2) DP cell medium, saline, Hypothermosol, platelet-rich plasma, and ATPv-supplemented saline.

RESULTS

The authors found chilled versus RT to prevent inflammatory cytokine signaling. Under chilled conditions, ATPv-supplemented saline was the best condition to preserve the expression of the trichogenic genes HEY1 and LEF1.

CONCLUSION

Data disclose DP gene expression analysis as a useful methodology to ascertain the efficacy of preserving solutions and elucidate about the best currently available option for FUE clinical practice.

Role of TGF-β in Skin Chronic Wounds: A Keratinocyte Perspective

Chronic wounds are characterized for their incapacity to heal within an expected time frame. Potential mechanisms driving this impairment are poorly understood and current hypotheses point to the development of an unbalanced milieu of growth factor and cytokines. Among them, TGF-β is considered to promote the broadest spectrum of effects. Although it is known to contribute to healthy skin homeostasis, the highly context-dependent nature of TGF-β signaling restricts the understanding of its roles in healing and wound chronification. Historically, low TGF-β levels have been suggested as a pattern in chronic wounds. However, a revision of the available evidence in humans indicates that this could constitute a questionable argument. Thus, in chronic wounds, divergences regarding skin tissue compartments seem to be characterized by elevated TGF-β levels only in the epidermis. Understanding how this aspect affects keratinocyte activities and their capacity to re-epithelialize might offer an opportunity to gain comprehensive knowledge of the involvement of TGF-β in chronic wounds. In this review, we compile existing evidence on the roles played by TGF-β during skin wound healing, with special emphasis on keratinocyte responses. Current limitations and future perspectives of TGF-β research in chronic wounds are discussed.

Self-organizing hair peg-like structures from dissociated skin progenitor cells: New insights for human hair follicle organoid engineering and Turing patterning in an asymmetric morphogenetic field

Human skin progenitor cells will form new hair follicles, although at a low efficiency, when injected into nude mouse skin. To better study and improve upon this regenerative process, we developed an in vitro system to analyse the morphogenetic cell behaviour in detail and modulate physical-chemical parameters to more effectively generate hair primordia. In this three-dimensional culture, dissociated human neonatal foreskin keratinocytes self-assembled into a planar epidermal layer while fetal scalp dermal cells coalesced into stripes, then large clusters, and finally small clusters resembling dermal condensations. At sites of dermal clustering, subjacent epidermal cells protruded to form hair peg-like structures, molecularly resembling hair pegs within the sequence of follicular development. The hair peg-like structures emerged in a coordinated, formative wave, moving from periphery to centre, suggesting that the droplet culture constitutes a microcosm with an asymmetric morphogenetic field. In vivo, hair follicle populations also form in a progressive wave, implying the summation of local periodic patterning events with an asymmetric global influence. To further understand this global patterning process, we developed a mathematical simulation using Turing activator-inhibitor principles in an asymmetric morphogenetic field. Together, our culture system provides a suitable platform to (a) analyse the self-assembly behaviour of hair progenitor cells into periodically arranged hair primordia and (b) identify parameters that impact the formation of hair primordia in an asymmetric morphogenetic field. This understanding will enhance our future ability to successfully engineer human hair follicle organoids.

Effect of Cinnamomum osmophloeum Kanehira Leaf Aqueous Extract on Dermal Papilla Cell Proliferation and Hair Growth

In this study, we explored the effect of the water extract of Cinnamomum osmophloeum Kanehira (COK) leaves on hair growth by in vitro and in vivo assays. Using an in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, it was found that the proliferation of rat vibrissae and human hair dermal papilla cells (hDPCs) was significantly enhanced by the COK leaf extract treatment. As determined by quantitative real-time polymerase chain reaction (RT-PCR), the messenger RNA (mRNA) levels of some hair growth–related factors including vascular endothelial growth factor, keratinocyte growth factor (KGF), and transforming growth factor-β2 were found to be higher in the cultured hDPCs exposed to COK leaf extract than those in the untreated control group. In the hair-depilated C57BL/6 mouse model, the stimulation of hair growth was demonstrated in the group of COK leaf extract treatment. Both photographical and histological observations revealed the promotion of the anagen phase in the hair growth cycle by the COK leaf extract in the C57BL/6 mice. Finally, the ultra performance liquid chromatography (UPLC) showed that the COK extract contained mostly cinnamic aldehyde and a small amount of cinnamic acid. The results suggest that the COK leaf extract may find use for the treatment of hair loss.

Use of human intra-tissue stem/progenitor cells and induced pluripotent stem cells for hair follicle regeneration

Background

The hair follicle (HF) is a unique miniorgan, which self-renews for a lifetime. Stem cell populations of multiple lineages reside within human HF and enable its regeneration. In addition to resident HF stem/progenitor cells (HFSPCs), the cells with similar biological properties can be induced from human-induced pluripotent stem cells (hiPSCs). As approaches to regenerate HF by combining HF-derived cells have been established in rodents and a huge demand exists to treat hair loss diseases, attempts have been made to bioengineer human HF using HFSPCs or hiPSCs.

Main body of the abstract

The aim of this review is to comprehensively summarize the strategies to regenerate human HF using HFSPCs or hiPSCs. HF morphogenesis and regeneration are enabled by well-orchestrated epithelial-mesenchymal interactions (EMIs). In rodents, various combinations of keratinocytes with mesenchymal (dermal) cells with trichogenic capacity, which were transplanted into in vivo environment, have successfully generated HF structures. The regeneration efficiency was higher, when epithelial or dermal HFSPCs were adopted. The success in HF formation most likely depended on high receptivity to trichogenic dermal signals and/or potent hair inductive capacity of HFSPCs. In theory, the use of epithelial HFSPCs in the bulge area and dermal papilla cells, their precursor cells in the dermal sheath, or trichogenic neonatal dermal cells should elicit intense EMI sufficient for HF formation. However, technical hurdles, represented by the limitation in starting materials and the loss of intrinsic properties during in vitro expansion, hamper the stable reconstitution of human HFs with this approach. Several strategies, including the amelioration of culture condition or compartmentalization of cells to strengthen EMI, can be conceived to overcome this obstacle. Obviously, use of hiPSCs can resolve the shortage of the materials once reliable protocols to induce wanted HFSPC subsets have been developed, which is in progress. Taking advantage of their pluripotency, hiPSCs may facilitate previously unthinkable approaches to regenerate human HFs, for instance, via bioengineering of 3D integumentary organ system, which can also be applied for the treatment of other diseases.

Short conclusion

Further development of methodologies to reproduce bona fide EMI in HF formation is indispensable. However, human HFSPCs and hiPSCs hold promise as materials for human HF regeneration.

Effects of mesenchymal stem cell therapy on alopecia areata in cellular and hair follicle organ culture models

Mesenchymal stem cell therapy (MSCT) has been suggested as a new therapeutic strategy for immunological disorders. There have been only a few attempts to treat alopecia areata (AA) with MSCT. MSCT efficacy and mechanism of action in treating AA are not known. We sought to investigate the effect of human hematopoietic mesenchymal stem cells (hHMSCs) on an in vitro model of AA and to explore relevant mechanisms that regulate efficacy. An AA-like environment was induced by pretreatment of human dermal papilla cells (hDPCs) with interferon gamma (IFN-γ). hHMSCs were administered to the hDPCs, and cell viability was determined. Similar studies were also conducted with human hair follicles (HFs) in culture. The change in expression of the Wnt/β-catenin pathway and JAK/STAT pathway-related molecules and growth factors in hHMSC-treated hDPCs was also examined by reverse transcription-PCR, Western blot assay and growth factor array. Immune privilege-related molecules were examined by immunohistochemistry in HF culture models. hHMSCs enhanced the cell viability of the hDPCs. hHMSCs activated several molecules in the Wnt/β-catenin signalling pathway, including ß-catenin and phosphorylated GSK3b, and decreased IFN-γ-induced expression of DKK1 in hDPCs. hHMSCs suppressed IFN-γ-induced expression of caspase-1, caspase-3 and IFN-γ receptor. hHMSCs induced the phosphorylation of STAT1 and STAT3 compared to controls and IFN-γ-pretreated hDPCs. hHMSC-treated HFs enhanced several growth factor mRNAs. hHMSC pretreatment modulated IFN-γ-induced expression of molecules related to HF immune privilege on HFs in organ culture. These data suggest MSCT may be a new potential therapeutic option in treating AA.

Review of Hair Follicle Dermal Papilla cells as in vitro screening model for hair growth

Hair disorders such as hair loss (alopecia) and androgen dependent, excessive hair growth (hirsutism, hypertrichosis) may impact the social and psychological well-being of an individual. Recent advances in understanding the biology of hair have accelerated the research and development of novel therapeutic and cosmetic hair growth agents. Preclinical models aid in dermocosmetic efficacy testing and claim substantiation of hair growth modulators. The in vitro models to investigate hair growth utilize the hair follicle Dermal Papilla cells (DPCs), specialized mesenchymal cells located at the base of hair follicle that play essential roles in hair follicular morphogenesis and postnatal hair growth cycles. In this review, we have compiled and discussed the extensively reported literature citing DPCs as in vitro model to study hair growth promoting and inhibitory effects. A variety of agents such as herbal and natural extracts, growth factors and cytokines, platelet-rich plasma, placental extract, stem cells and conditioned medium, peptides, hormones, lipid-nanocarrier, light, electrical and electromagnetic field stimulation, androgens and their analogs, stress-serum and chemotherapeutic agents etc. have been examined for their hair growth modulating effects in DPCs. Effects on DPCs' activity were determined from untreated (basal) or stress induced levels. Cell proliferation, apoptosis and secretion of growth factors were included as primary end-point markers. Effects on a wide range of biomolecules and mechanistic pathways that play key role in the biology of hair growth were also investigated. This consolidated and comprehensive review summarizes the up-to-date information and understanding regarding DPCs based screening models for hair growth and may be helpful for researchers to select the appropriate assay system and biomarkers. This review highlights the pivotal role of DPCs in the forefront of hair research as screening platforms by providing insights into mechanistic action at cellular level, which may further direct the development of novel hair growth modulators.

Study of gene expression alteration in male androgenetic alopecia: evidence of predominant molecular signalling pathways

BACKGROUND

Male androgenetic alopecia (AGA) is the most common form of hair loss in men. It is characterized by a distinct pattern of progressive hair loss starting from the frontal area and the vertex of the scalp. Although several genetic risk loci have been identified, relevant genes for AGA remain to be defined.

OBJECTIVES

To identify biomarkers associated with AGA.

METHODS

Molecular biomarkers associated with premature AGA were identified through gene expression analysis using cDNA generated from scalp vertex biopsies of hairless or bald men with premature AGA, and healthy volunteers.

RESULTS

This monocentric study reveals that genes encoding mast cell granule enzymes, inflammatory mediators and immunoglobulin-associated immune mediators were significantly overexpressed in AGA. In contrast, underexpressed genes appear to be associated with the Wnt/β-catenin and bone morphogenic protein/transforming growth factor-β signalling pathways. Although involvement of these pathways in hair follicle regeneration is well described, functional interpretation of the transcriptomic data highlights different events that account for their inhibition. In particular, one of these events depends on the dysregulated expression of proopiomelanocortin, as confirmed by polymerase chain reaction and immunohistochemistry. In addition, lower expression of CYP27B1 in patients with AGA supports the notion that changes in vitamin D metabolism contributes to hair loss.

CONCLUSIONS

This study provides compelling evidence for distinct molecular events contributing to alopecia that may pave the way for new therapeutic approaches.

The Contributory Roles of Th17 Lymphocyte and Cytotoxic T Lymphocyte at the Hair Bulge Region as Well as the Hair Bulb Area in the Chronic Alopecia Areata Patients

BACKGROUND

Alopecia areata (AA) is a T cell-mediated autoimmune disease that targets hair follicles and interrupts hair regrowth. The microenvironment of the effector T cells and their related cytokines may affect immunopathogenesis around the hair bulb/bulge.

OBJECTIVE

To determine the contributory roles of the effector T cell subsets and related cytokines to the pathogenesis of AA.

METHODS

We investigated the correlation between histopathological grades and four clinical prognostic factors in 331 patients with AA, and analyzed the topography of T cell infiltrates and related cytokines around the hair bulb/bulge according to histopathological grades through immunohistochemical and double immunofluorescence studies on a subset of AA specimens.

RESULTS

First, the groups with more severe histopathological grades were associated with earlier onset, longer duration, more hair loss, as well as poorer therapeutic outcomes. Second, the pattern of CD4 and CD8 expression around the hair bulb/bulge varied by histopathological grade, with staining density decreasing in the following order: type 1>type 2>type 3. In addition, interferon-γ and transforming growth factor-β1 expression appeared denser in the peribulbar area. Interestingly, the denser CCR6⁺ cells (Th17 cells) showed more infiltration than CCR5⁺ cells (Th1 cells) around the hair bulb/bulge as histopathological grade worsened.

CONCLUSION

The insidious destruction of bulge stem cells and hair bulb matrix stem cells results in more severe hair loss in patients with chronic AA, which is mediated by Th17 lymphocyte and cytotoxic T lymphocyte infiltration. Furthermore, Th17 lymphocytes may play an even more important role than cytotoxic T cells in the development of AA.

Characterization of Ovine Dermal Papilla Cell Aggregation

Context:

The dermal papilla (DP) is a condensation of mesenchymal cells at the proximal end of the hair follicle, which determines hair shaft size and regulates matrix cell proliferation and differentiation. DP cells have the ability to regenerate new hair follicles. These cells tend to aggregate both in vitro and in vivo. This tendency is associated with the ability of papilla cells to induce hair growth. However, human papilla cells lose their hair-inducing activity in later passage number. Ovine DP cells are different from human DP cells since they do not lose their aggregative behavior or hair-inducing activity in culture. Nonetheless, our understanding of ovine DP cells is still limited.

Aim:

The aim of this study was to observe the expression of established DP markers in ovine cells and their association with aggregation.

Subjects and Methods:

Ovine DP cells from three different sheep were compared. Histochemistry, immunoflourescence, and polymerase chain reaction experiments were done to analyze the DP markers.

Results:

We found that ovine DP aggregates expressed all the 16 markers evaluated, including alkaline phosphatase and versican. Expression of the versican V0 and V3 isoforms, neural cell adhesion molecule, and corin was increased significantly with aggregation, while hey-1 expression was significantly decreased.

Conclusions:

Overall, the stable expression of numerous markers suggests that aggregating ovine DP cells have a similar phenotype to papillae in vivo. The stability of their molecular phenotype is consistent with their robust aggregative behavior and retained follicle-inducing activity after prolonged culture. Their phenotypic stability in culture contrasts with DP cells from other species, and suggests that a better understanding of ovine DP cells might provide opportunities to improve the hair-inducing activity and therapeutic potential of human cells.

Role of peptide growth factors in the rhythm of change hair

The article presents current data on the role growth factors play in hair physiology. Based on a review of literature, the authors described the role growth factors play for initiating, suppressing the growth and differentiating hair follicles. According to them, each morphologic development stage of hair follicles is characterized by its own factor expression pattern. Referring to experimental and clinical studies, the authors describe the role some growth factors play for mechanisms promoting the development of androgynous and focal alopecia.

Vitamin D levels in multiple sclerosis patients: Association with TGF-β2, TGF-βRI, and TGF-βRII expression

AIM

A variety of evidence suggests that vitamin D can prevent the development of multiple sclerosis (MS). TGF-β pathway genes also play important roles in MS. Here, we aim to study whether vitamin D affects TGF-β pathway gene expression and Expanded Disability Status Scale (EDSS) scores in MS patients.

MAIN METHODS

A randomized clinical trial was conducted on 31 relapsing-remitting (RR) MS patients. Using real-time RT-PCR, we tested the levels of TGF-β2, TGF-βRI and TGF-βRII mRNAs in the RRMS patients before and after 8 weeks of supplementation with vitamin D.

KEY FINDINGS

Expression of TGF-β2 mRNA increased 2.84-fold, while TGF-βRI and TGF-βRII mRNA levels did not change after vitamin D treatment. In addition, these results revealed no correlation between the normalized expression of TGF-β2, TGF-βRI, or TGF-βRII and EDSS scores.

SIGNIFICANCE

Here, we demonstrate new evidence for the complex role of vitamin D in the pathogenesis, activity and progression of MS through the TGF-β signaling pathway.

Hair-growth stimulation by conditioned medium from vitamin D3-activated preadipocytes in C57BL/6 mice

AIMS

Recently, immature adipocyte lineage cells have been suggested as a potential hair-growth stimulator. Diverse studies have been attempted to find methods for the preconditioning of immature adipocyte lineage cells. The present study investigates the effect of conditioned medium (CM) from vitamin D3 (Vd3) pre-activated preadipocytes on hair-growth ability.

MAIN METHODS

To test the effect of CM from Vd3 pre-activated preadipocytes on hair-growth efficiency in mice, we compared the differences in hair regenerated after injecting CM from mouse preadipocytes pre-activated with or without Vd3. Next, to determine the regulating factors, the VEGF level was measured by ELISA and angiogenesis level was evaluated by IHC. Finally, the signaling mechanism was investigated by inhibitor kinase assay and western blotting.

KEY FINDINGS

The CM from Vd3 pre-activated preadipocyte injection markedly promoted the ability of hair regeneration in mice. The VEGF levels were increased by Vd3 treatment in vitro and the CM from Vd3 pre-activated preadipocytes significantly increased the angiogenesis in vivo, suggesting the involvement of angiognensis in the hair regeneration induced by CM from pre-activated preadipocytes. In signaling study, Vd3-enhanced VEGF production was reduced by an ERK1/2 inhibitor and the level of ERK1/2 phosphorylation was increased by treatment with Vd3.

SIGNIFICANCE

This has been the first report on CM from Vd3 pre-activated preadipocyte displaying stimulatory effects on hair growth via the enhancement of angiogenesis in a hairless-induced C57BL/6 mice.

Expression Patterns of Gli-1, Pleckstrin Homology-Like Domain, Family A, Member 1, Transforming Growth Factor-β1/β2, and p63 in Sebaceous and Follicular Tumors

Background

Certain epidermal appendage tumors, including hyperplasias (hamartomas), adenomas, benign epitheliomas, primordial epitheliomas, and malignant tumors, can exhibit any stage of differentiation. Several molecules associated with tumorigenesis, such as Gli-1, pleckstrin homology-like domain, family A, member 1 (PHLDA-1), transforming growth factor (TGF)-β1, TGF-β2, and p63, are associated with tumor grade and aggressive behavior in follicular and sebaceous tumors in ways that are not well understood.

Objective

The aim of this study was to elucidate the expression of Gli-1, PHLDA-1, TGF-β1/β2, and p63 in benign and malignant tumors of the hair and sebaceous glands and to determine their importance in the degree of tumor differentiation.

Methods

Immunohistochemistry was performed in follicular and sebaceous tumors using antibodies against Gli-1 (sebaceous tumor marker), PHLDA-1 (hair follicle outer root sheath [ORS] cell marker), p63, TGF-β1, and TGF-β2.

Results

Gli-1 was expressed in basaloid cells, sebocytes, and sebaceous carcinoma cells, and expression levels decreased as differentiation progressed. PHLDA-1 was expressed in ORS cells and some follicular tumor cells. Expression of p63 was observed in the nuclei of the outermost basaloid cells (seboblasts), poorly differentiated sebaceous carcinoma cells, and tumor cells toward the direction of the hair. Remarkably, TGF-β1 was expressed exclusively in the nuclei of benign and malignant follicular (hair) tumors, but not in sebaceous tumors, at levels that correlated with the degree of differentiation.

Conclusion

We propose that p63 and/or TGF-β1 are useful for predicting the degree of differentiation and malignant potential of sebaceous and follicular tumors and for distinguishing trichilemmal carcinoma from sebaceous carcinoma.

A review of adipocyte lineage cells and dermal papilla cells in hair follicle regeneration

Alopecia is an exceedingly prevalent problem effecting men and women of all ages. The standard of care for alopecia involves either transplanting existing hair follicles to bald areas or attempting to stimulate existing follicles with topical and/or oral medication. Yet, these treatment options are fraught with problems of cost, side effects, and, most importantly, inadequate long-term hair coverage. Innovative cell-based therapies have focused on the dermal papilla cell as a way to grow new hair in previously bald areas. However, despite this attention, many obstacles exist, including retention of dermal papilla inducing ability and maintenance of dermal papilla productivity after several passages of culture. The use of adipocyte lineage cells, including adipose-derived stem cells, has shown promise as a cell-based solution to regulate hair regeneration and may help in maintaining or increasing dermal papilla cells inducing hair ability. In this review, we highlight recent advances in the understanding of the cellular contribution and regulation of dermal papilla cells and summarize adipocyte lineage cells in hair regeneration.

Regenerative medicine and hair loss: how hair follicle culture has advanced our understanding of treatment options for androgenetic alopecia

Many of the current drug therapies for androgenetic alopecia were discovered serendipitously, with hair growth observed as an off-target effect when drugs were used to treat a different disorder. Subsequently, several studies using cultured cells have enabled identification of hair growth modulators with similar properties to the currently available drugs, which may also provide clinical benefit. In situations where the current therapeutics do not work, follicular unit transplantation is an alternative surgical option. More recently, the concept of follicular cell implantation, or hair follicle neogenesis, has been attempted, exploiting the inherent properties of cultured hair follicle cells to induce de novo hair growth in balding scalp. In this review, we discuss both the advances in cell culture techniques that have led to a wider range of potential therapeutics to promote hair growth, in addition to detailing current knowledge on follicular cell implantation, and the challenges in making this approach a reality.

Exogenous connective tissue growth factor preserves the hair-inductive ability of human dermal papilla cells

Connective tissue growth factor influences human dermal papilla cells' hair inductive ability through several signaling pathways.

Hair curvature: a natural dialectic and review

Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways, and others, can explain many alternatives and specific variations of hair bending phenotypes. Mechanisms for hair papilla budding or its division by bisection or fission can explain MPC formation. Epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) transitions, acting in collaboration with epithelial-mesenchymal communications are also considered as mechanisms affecting hair growth and its bending and twisting. These may be treated as sub-mechanisms of an overall development from neural-crest stem cell (NCSC) lineages to differentiated hair follicle (HF) cell types, thus providing a unified framework for hair growth and development.

Epidermal development in mammals: key regulators, signals from beneath, and stem cells

Epidermis is one of the best-studied tissues in mammals that contain types of stem cells. Outstanding works in recent years have shed great light on behaviors of different epidermal stem cell populations in the homeostasis and regeneration of the epidermis as well as hair follicles. Also, the molecular mechanisms governing these stem cells are being elucidated, from genetic to epigenetic levels. Compared with the explicit knowledge about adult skin, embryonic development of the epidermis, especially the early period, still needs exploration. Furthermore, stem cells in the embryonic epidermis are largely unstudied or ambiguously depicted. In this review, we will summarize and discuss the process of embryonic epidermal development, with focuses on some key molecular regulators and the role of the sub-epidermal mesenchyme. We will also try to trace adult epidermal stem cell populations back to embryonic development. In addition, we will comment on in vitro derivation of epidermal lineages from ES cells and iPS cells.

Strategies to enhance epithelial-mesenchymal interactions for human hair follicle bioengineering

Hair follicle morphogenesis and regeneration depend on intensive but well-orchestrated interactions between epithelial and mesenchymal components. Accordingly, the enhancement of this crosstalk represents a promising approach to achieve successful bioengineering of human hair follicles. The present article summarizes the techniques, both currently available and potentially feasible, to promote epithelial-mesenchymal interactions (EMIs) necessary for human hair follicle regeneration. The strategies include the preparation of epithelial components with high receptivity to trichogenic dermal signals and/or mesenchymal cell populations with potent hair inductive capacity. In this regard, bulge epithelial stem cells, keratinocytes predisposed to hair follicle fate or keratinocyte precursor cells with plasticity may provide favorable epithelial cell populations. Dermal papilla cells sustaining intrinsic hair inductive capacity, putative dermal papilla precursor cells in the dermal sheath/neonatal dermis or trichogenic dermal cells derived from undifferentiated stem/progenitor cells are promising candidates as hair inductive dermal cells. The most established protocol for in vivo hair follicle reconstitution is co-grafting of epithelial and mesenchymal components into immunodeficient mice. In theory, combination of individually optimized cellular components of respective lineages should elicit most intensive EMIs to form hair follicles. Still, EMIs can be further ameliorated by the modulation of non-cell autonomous conditions, including cell compartmentalization to replicate the positional relationship in vivo and humanization of host environment by preparing human stromal bed. These approaches may not always synergistically intensify EMIs, however, step-by-step investigation probing optimal combinations should maximally enhance EMIs to achieve successful human hair follicle bioengineering.

1α,25-dihydroxyvitamin D3 modulates the hair-inductive capacity of dermal papilla cells: therapeutic potential for hair regeneration

Dermal papilla cells (DPCs) have the potential to induce differentiation of epithelial stem cells into hair, and Wnt signaling is deeply involved in the initiation process. The functional limitation of expanded adult DPCs has been a difficult challenge for cell-based hair regrowth therapy. We previously reported that 1α,25-dihydroxyvitamin D(3) (VD(3)) upregulates expression of transforming growth factor (TGF)-β2 and alkaline phosphatase (ALP) activity, both features of hair-inducing human DPCs (hDPCs). In this study, we further examined the effects and signaling pathways associated with VD(3) actions on DPCs. VD(3) suppressed hDPC proliferation in a dose-dependent, noncytotoxic manner. Among the Wnt-related genes investigated, Wnt10b expression was significantly upregulated by VD(3) in hDPCs. Wnt10b upregulation, as well as upregulation of ALPL (ALP, liver/bone/kidney) and TGF-β2, by VD(3) was specific in hDPCs and not detected in human dermal fibroblasts. Screening of paracrine or endocrine factors in the skin indicated that all-trans retinoic acid (atRA) upregulated Wnt10b gene expression, although synergistic upregulation (combined atRA and VD(3)) was not seen. RNA interference with vitamin D receptor (VDR) revealed that VD(3) upregulation of Wnt10b, ALPL, and TGF-β2 was mediated through the genomic VDR pathway. In a rat model of de novo hair regeneration by murine DPC transplantation, pretreatment with VD(3) significantly enhanced hair folliculogenesis. Specifically, a greater number of outgrowing hair shafts and higher maturation of regenerated follicles were observed. Together, these data suggest that VD(3) may promote functional differentiation of DPCs and be useful in preserving the hair follicle-inductive capacity of cultured DPCs for hair regeneration therapies.