Generation of trichogenic adipose-derived stem cells by expression of three factors

Involvement of DKK1 secreted from adipose-derived stem cells in alopecia areata

Adipose-derived stem cells (ASCs) have shown efficacy in promoting hair growth, while DKK1 inhibits the WNT pathway, which is associated with hair loss. Our study focused on investigating the expression of DKK1 in alopecia areata (AA), a condition characterised by significant increases in the DKK1 levels in human and mouse ASCs. Treatment of interferon-γ increased the expression of DKK1 via STAT3 phosphorylation in ASCs. Treatment with recombinant DKK1 resulted in a decrease of cell growth in outer root sheath cells, whereas the use of a DKK1 neutralising antibody promoted hair growth. These results indicate that ASCs secrete DKK1, playing a crucial role in the progression and development of AA. Consequently, we generated DKK1 knockout (KO) ASCs using the Crispr/Cas9 system and evaluated their hair growth-promoting effects in an AA model. The DKK1 KO in ASCs led to enhanced cell motility and reduced cellular senescence by activating the WNT signalling pathway, while it reduced the expression of inflammatory cytokines by inactivating the NF-kB pathway. As expected, the intravenous injection of DKK1-KO-ASCs in AA mice, and the treatment with a conditioned medium derived from DKK1-KO-ASCs in hair organ culture proved to be more effective compared with the use of naïve ASCs and their conditioned medium. Overall, these findings suggest that DKK1 represents a novel therapeutic target for treating AA, and cell therapy using DKK1-KO-ASCs demonstrates greater efficiency.

Low Molecular Weight Collagen Peptide (LMWCP) Promotes Hair Growth by Activating the Wnt/GSK-3β/β-Catenin Signaling Pathway

Low molecular weight collagen peptide (LMWCP) is a collagen hydrolysate derived from fish. We investigated the effects of LMWCP on hair growth using human dermal papilla cells (hDPCs), human hair follicles (hHFs), patch assay, and telogenic C57BL/6 mice, while also examining the underlying mechanisms of its action. LMWCP promoted proliferation and mitochondrial potential, and the secretion of hair growth-related factors, such as EGF, HB-EGF, FGF-4, and FGF-6 in hDPCs. Patch assay showed that LMWCP increased the neogeneration of new HFs in a dose-dependent manner. This result correlated with an increase in the expression of dermal papilla (DP) signature genes such as, ALPL, SHH, FGF7, and BMP-2. LMWCP upregulated phosphorylation of glycogen synthase kinase-3β (GSK-3β) and β-catenin, and nuclear translocation of β-catenin, and it increased the expression of Wnt3a, LEF1, VEGF, ALP, and β-catenin. LMWCP promoted the growth of hHFs and increased the expression of β-catenin and VEGF. Oral administration of LMWCP to mice significantly stimulated hair growth. The expression of Wnt3a, β-catenin, PCNA, Cyclin D1, and VEGF was also elevated in the back skin of the mice. Furthermore, LMWCP increased the expression of cytokeratin and Keratin Type I and II. Collectively, these findings demonstrate that LMWCP has the potential to increase hair growth via activating the Wnt/β-catenin signaling pathway.

Effects of photobiomodulation at various irradiances on normal and dihydrotestosterone-treated human hair dermal papilla cells in vitro

Androgenetic alopecia (AGA) is the most common type of hair loss caused by dihydrotestosterone (DHT) binding to androgen receptors in dermal papilla cells (DPCs). Photobiomodulation (PBM) is a promising treatment for AGA but suffers from inconsistent outcomes and inconsistent effective light parameters. This study investigated the impact of red light at various irradiances on normal and DHT-treated DPCs. Our results suggested that red light at 8 mW/cm2 was most effective in promoting DPCs growth. Furthermore, a range of irradiances from 2 to 64 mW/cm2 modulated key signaling pathways, including Wnt, FGF, and TGF, in normal and DHT-treated DPCs. Interestingly, 8 mW/cm2 had a greater impact on these pathways in DHT-treated DPCs and altered the Shh pathway, suggesting that the effect of PBM varies with the cellular environment. This study highlights specific factors that influence PBM effectiveness and provides insight into the need for personalized PBM treatment approaches.

Hypoxia enhances the hair growth-promoting effects of embryonic stem cell-derived mesenchymal stem cells via NADPH oxidase 4

Human embryonic stem cell (hES)-derived mesenchymal stem cells (-MSCs) are an unlimited source of MSCs. The hair growth-promoting effects of diverse MSCs have been reported, but not that of hES-MSCs. In the present study, we investigated the hair growth-promoting effects of hES-MSCs and their underlying mechanisms. hES-MSCs or conditioned medium of hES-MSCs exhibited hair-growth effects, which increased the length of mouse vibrissae and human hair follicles. hES-MSCs accelerated the telogen-to-anagen transition in C3H mice and were more effective than adipose-derived stem cells. We further examined whether hypoxia could enhance the hair-growth promoting effects of hES-MSCs. The injection of hES-MSCs or conditioned medium (Hyp-CM) cultured under hypoxia (2% O₂) enhanced the telogen-to-anagen transition in C3H mice. Additionally, Hyp-CM increased the length of mouse vibrissae, human hair follicles, and the proliferation of human dermal papilla and outer root sheath cells. Moreover, fibroblast growth factor 7, interleukin 12B, and teratocarcinoma-derived growth factor 1 were upregulated under hypoxia, and the co-treatment with these three proteins increased the hair length and induced telogen-to-anagen transition. Hypoxia increased reactive oxygen species (ROS) production, and ROS scavenging attenuated the secretion of growth factors. NADPH oxidase 4 was primarily expressed in hES-MSCs and generated ROS under hypoxia. Collectively, our results suggest that hES-MSCs exhibit hair-growth effects, which is enhanced by hypoxia.

Effective and economical cell therapy for hair regeneration

We reviewed and summarized the latest reports on the characteristics of stem cells and follicular cells that are under development for hair loss treatment. Compared with conventional medicine, cell therapy could be effective in the long term with a single treatment while having mild adverse effects. Adipose-derived stem cells (ASCs) have the advantages of easy access and large isolation amount compared with dermal papilla cells (DPCs) and dermal sheath cup cells (DSCs), and promote hair growth through the paracrine effect. ASCs have a poor potential in hair neogenesis, therefore, methods to enhance trichogenecity of ASCs should be developed. DSCs can be isolated from the peribulbar dermal sheath cup, while having immune tolerance, and hair inductivity. Therefore, DSCs were first developed and finished the phase II clinical trial; however, the hair growth was not satisfactory. Considering that a single injection of DSCs is effective for at least 9 months in the clinical setting, they can be an alternative therapy for hair regeneration. Though DPCs are not yet studied in clinical trials, we should pay attention to DPCs, as hair loss is associated with gradual reduction of DPCs and DP cell numbers fluctuate over the hair cycle. DPCs could make new hair follicles with epidermal cells, and have an immunomodulatory function to enable allogeneic transplantation. In addition, we can expand large quantities of DPCs with hair inductivity using spheroid culture, hypoxia condition, and growth factor supplement. 'Off-the-shelf' DPC therapy could be effective and economical, and therefore promising for hair regeneration.

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.

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.

Epiregulin promotes hair growth via EGFR-medicated epidermal and ErbB4-mediated dermal stimulation

OBJECTIVES

EREG (epiregulin), a member of the epidermal growth factor (EGF) family, plays a role in inflammation, wound healing, normal physiology and malignancies. However, little is known about its function on hair growth.

MATERIALS AND METHODS

Cell growth assay, QPCR and immunostaining were carried out. Telogen-to-anagen transition and organ culture were conducted. ROS level was monitored by staining DCFDA.

RESULTS

We investigated the hair inductive effect of EREG and the mechanism of stimulation on DPCs and ORS cells during hair cycling. Whereas EREG promoted hair growth, EREG knockdown inhibited hair growth as evidenced by telogen-to-anagen transition and organ culture models. EREG was expressed in epidermal cells including ORS cells in vivo. EREG activated phospho-ErbB4 in DPCs during hair cycling and stimulated DPCs via ErbB4 activation in vitro. In terms of the underlying mechanism, reactive oxygen species (ROS) played a key role in DPC stimulation. EREG also activated phospho-EGF receptor (EGFR) in epidermal cells including matrix and ORS cells in vivo and stimulated ORS cells via EGFR activation in vitro.

CONCLUSIONS

EREG, which is released from ORS cells, activated EGFR and ErbB4 on epidermal cells and DPCs during hair cycling, respectively. As a result, EREG stimulated epidermal cells a positive feedback and DPCs via regulating ROS generation for hair growth. Therefore, EREG therapy may be a novel solution for hair loss treatment.

HB-EGF Improves the Hair Regenerative Potential of Adipose-Derived Stem Cells via ROS Generation and Hck Phosphorylation

Although adipose-derived stem cells (ASCs) have hair regenerative potential, their hair inductive capabilities are limited. The mitogenic and hair inductive effects of heparin binding-epidermal growth factor-like growth factor (HB-EGF) on ASCs were investigated in this study and the underlying mechanism of stimulation was examined. Cell growth, migration, and self-renewal assays, as well as quantitative polymerase chain reactions and immunostaining, were carried out. Telogen-to-anagen transition and organ culture using vibrissa follicles were also conducted. HB-EGF significantly increased ASC motility, including cell proliferation, migration, and self-renewal activity. The preconditioning of ASCs with HB-EGF induced telogen-to-anagen transition more rapidly in vivo, and injected PKH26-ASCs survived for longer periods of time. Conditioned medium obtained from HB-EGF-treated ASCs promoted hair growth in vivo, upregulating growth factors. In particular, thrombopoietin (THPO) also induced hair growth in vivo, stimulating dermal papilla cells (DPCs). Reactive oxygen species (ROS) appeared to play a key role in ASC stimulation as the inhibition of ROS generation and NOX4 knockout attenuated ASC stimulation and THPO upregulation by HB-EGF. In addition, the Hck phosphorylation pathway mediated the stimulation of ASCs by HB-EGF. In summary, HB-EGF increased the motility and paracrine effects of ASCs releasing THPO growth factor and THPO promoted hair growth-stimulating DPCs. ROS generation and Hck phosphorylation are key factors in HB-EGF-induced ASC stimulation. Therefore, combination therapy involving HB-EGF and ASCs may provide a novel solution for hair-loss treatment.

Sequential Transcriptome Changes in the Penumbra after Ischemic Stroke

To investigate the changes in the expression of specific genes that occur during the acute-to-chronic post-stroke phase, we identified differentially expressed genes (DEGs) between naive cortical tissues and peri-infarct tissues at 1, 4, and 8 weeks after photothrombotic stroke. The profiles of DEGs were subjected to the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and gene ontology analyses, followed by string analysis of the protein-protein interactions (PPI) of the products of these genes. We found 3771, 536, and 533 DEGs at 1, 4, and 8 weeks after stroke, respectively. A marked decrease in biological-process categories, such as brain development and memory, and a decrease in neurotransmitter synaptic and signaling pathways were observed 1 week after stroke. The PPI analysis showed the downregulation of Dlg4, Bdnf, Gria1, Rhoa, Mapk8, and glutamatergic receptors. An increase in biological-process categories, including cell population proliferation, cell adhesion, and inflammatory responses, was detected at 4 and 8 weeks post-stroke. The KEGG pathways of complement and coagulation cascades, phagosomes, antigen processing, and antigen presentation were also altered. CD44, C1, Fcgr2b, Spp1, and Cd74 occupied a prominent position in network analyses. These time-dependent changes in gene profiles reveal the unique pathophysiological characteristics of stroke and suggest new therapeutic targets for this disease.

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.