Cell Types Promoting Goosebumps Form a Niche to Regulate Hair Follicle Stem Cells.

Piloerection (goosebumps) requires concerted actions of the hair follicle, the arrector pili muscle (APM), and the sympathetic nerve, providing a model to study interactions across epithelium, mesenchyme, and nerves. Here, we show that APMs and sympathetic nerves form a dual-component niche to modulate hair follicle stem cell (HFSC) activity. Sympathetic nerves form synapse-like structures with HFSCs and regulate HFSCs through norepinephrine, whereas APMs maintain sympathetic innervation to HFSCs. Without norepinephrine signaling, HFSCs enter deep quiescence by down-regulating the cell cycle and metabolism while up-regulating quiescence regulators Foxp1 and Fgf18. During development, HFSC progeny secretes Sonic Hedgehog (SHH) to direct the formation of this APM-sympathetic nerve niche, which in turn controls hair follicle regeneration in adults. Our results reveal a reciprocal interdependence between a regenerative tissue and its niche at different stages and demonstrate sympathetic nerves can modulate stem cells through synapse-like connections and neurotransmitters to couple tissue production with demands.

Melanocyte transplantation to skin prepared by controlled PUVA-induced sunburn-like blistering for vitiligo treatment - A pilot clinical trial.

Vitiligo is a common acquired disease of pigment loss. In lesions recalcitrant to non-invasive treatment, transplantation of cultured autologous melanocytes is an emerging choice. Conventionally, the recipient site is often prepared by laser-mediated or mechanical dermabrasion. Such preparation procedures have disadvantages including prolonged transplantation duration, long period for reepithelialization and potential scarring. We propose a method of preparing recipient sites by psoralen and controlled ultraviolet A (PUVA)-induced blistering followed by transplanting suspended melanocytes. We introduced this method in 10 patients with segmental vitiligo on their recipient site 3 to 5 days before transplantation and blistering developed in 2 to 3 days afterwards. On the day of transplantation, the blister roof could be peeled off easily without bleeding and the recipient site preparation could be completed in 20 min. The recipient site became reepithelialized within 1 week. Progressive repigmentation was observed for up to 6 months, with an average of 65.06% repigmentation in the recipient site without scarring at the end of follow-up. Hence, preparation of the recipient site by controlled PUVA-induced sunburn-like blistering can potentially facilitate melanocyte transplantation and prevent scarring.

The cellular responses of corneal fibroblasts to cyclic stretching loads.

Mechanical signaling plays a crucial role in maintaining extracellular matrix (ECM) homeostasis in various structures. In this study, we investigated the responses of corneal fibroblasts to cyclic stretching loads using an in vitro cell culture system. Bovine corneal fibroblasts were cultured and subjected to equibiaxial cyclic strain of 15% for 72 h at a frequency of 0.25 Hz, with bovine skin fibroblasts used as a comparison. We explored various cellular behaviors, including morphological changes, cell proliferation, and metabolism in response to mechanical stretching loads. The expression of genes, protein secretion, and enzymatic activity for several major metalloproteinases was also determined through Q-PCR, Western blot, and gel zymography. Additionally, we investigated the involvement of mitogen-activated protein kinases (MAPKs) signaling pathways in the corneal fibroblasts when subjected to mechanical stimuli. Our findings revealed that, compared to skin fibroblasts, corneal fibroblasts were reluctant to morphological changes in response to a prolonged (72 h) and high-amplitude (15% of strain) cyclic stretching load. However, cyclic stretching loads stimulated the upregulation of MMP-2 expression in corneal fibroblasts via the MAPK signaling pathways involving extracellular signal-regulated kinase and p38. Together with a lack of upregulation in type I collagen expression, our results indicate the induction of the ECM degradation process in corneal fibroblasts in response to cyclic stretching. These findings emphasize the mechanoresponsive nature of corneal fibroblasts and shed light on the potential impact of intense mechanical stress on the cornea in both normal and pathological conditions such as keratoconus, providing valuable insights for understanding corneal mechanobiology.

Targeting ER protein TXNDC5 in hepatic stellate cell mitigates liver fibrosis by repressing non-canonical TGFß signalling.

BACKGROUND AND OBJECTIVES: Liver fibrosis (LF) occurs following chronic liver injuries. Currently, there is no effective therapy for LF. Recently, we identified thioredoxin domain containing 5 (TXNDC5), an ER protein disulfide isomerase (PDI), as a critical mediator of cardiac and lung fibrosis. We aimed to determine if TXNDC5 also contributes to LF and its potential as a therapeutic target for LF. DESIGN: Histological and transcriptome analyses on human cirrhotic livers were performed. Col1a1-GFPTg , Alb-Cre;Rosa26-tdTomato and Tie2-Cre/ERT2;Rosa26-tdTomato mice were used to determine the cell type(s) where TXNDC5 was induced following liver injury. In vitro investigations were conducted in human hepatic stellate cells (HSCs). Col1a2-Cre/ERT2;Txndc5fl/fl (Txndc5cKO ) and Alb-Cre;Txndc5fl/fl (Txndc5Hep-cKO ) mice were generated to delete TXNDC5 in HSCs and hepatocytes, respectively. Carbon tetrachloride treatment and bile duct ligation surgery were employed to induce liver injury/fibrosis in mice. The extent of LF was quantified using histological, imaging and biochemical analyses. RESULTS: TXNDC5 was upregulated markedly in human and mouse fibrotic livers, particularly in activated HSC at the fibrotic foci. TXNDC5 was induced by transforming growth factor ß1 (TGFß1) in HSCs and it was both required and sufficient for the activation, proliferation, survival and extracellular matrix production of HSC. Mechanistically, TGFß1 induces TXNDC5 expression through increased ER stress and ATF6-mediated transcriptional regulation. In addition, TXNDC5 promotes LF by redox-dependent JNK and signal transducer and activator of transcription 3 activation in HSCs through its PDI activity, activating HSCs and making them resistant to apoptosis. HSC-specific deletion of Txndc5 reverted established LF in mice. CONCLUSIONS: ER protein TXNDC5 promotes LF through redox-dependent HSC activation, proliferation and excessive extracellular matrix production. Targeting TXNDC5, therefore, could be a potential novel therapeutic strategy to ameliorate LF.

Depilatory laser miniaturizes hair by inducing bystander dermal papilla cell necrosis through thermal diffusion.

OBJECTIVES: Depilatory laser targeting melanin has been widely applied for the treatment of hypertrichosis. Both selective photothermolysis and thermal diffusion have been proposed for its effect, but the exact mechanism of permanent hair reduction remains unclear. In this study, we explore the role of thermal diffusion in depilatory laser-induced permanent hair loss and determine whether nonpigmented cells are injured by thermal diffusion. MATERIALS AND METHODS: C57BL/6 mice in anagen and telogen were treated with alexandrite laser (wavelength 755 nm, pulse duration 3 milliseconds, fluence 12 J/cm2 , spot size 12 mm), respectively. Histological analysis, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and transmission electron microscopic imaging were employed to evaluate the injury to hair follicle (HF) cells. The proliferation status of HF cells was examined by 5-bromo-2'-deoxyuridine pulse labeling. The number of HF stem cells was quantified by fluorescence-activated cell sorting. The size of the regenerated hair was determined by measuring its length and width. RESULTS: We found that irradiating C57BL/6 mice in anagen with alexandrite laser led to hair miniaturization in the next anagen. In addition to thermal disruption of melanin-containing cells in the precortex region, we also detected necrosis of the adjacent nonpigmented dermal papilla cells due to thermal diffusion. Dermal papilla cells decreased by 24% after laser injury, while the number of bulge stem cells remained unchanged. When the laser was delivered to telogen HFs where no melanin was present adjacent to the dermal papilla, thermal necrosis and cell reduction were not detected in the dermal papilla and no hair miniaturization was observed. CONCLUSION: Our results suggest that depilatory laser miniaturizes hair by inducing thermal necrosis of dermal papilla cells due to secondary thermal diffusion from melanin-containing precortex cells in the anagen hair bulbs.

Lower proximal cup and outer root sheath cells regenerate hair bulbs during anagen hair follicle repair after chemotherapeutic injury.

The cell dynamics and cell origin for anagen hair follicle (HF) repair following chemotherapeutic injury are unclear. We first mapped the HF response to cyclophosphamide (CYP) at natural anagen VI in mice. We found that 30-60 mg/kg of CYP leads to dose-dependent HF dystrophy that was spontaneously repaired with anagen resumption, while 120 mg/kg of CYP prematurely induced catagen/telogen entry. To explore how anagen HF repair is achieved in the dystrophic anagen pathway, we analysed the cell dynamics at 30 mg/kg of CYP. Hair bulbs first shrunk due to matrix cell apoptosis associated with DNA double-strand breaks. DNA damage was repaired, and ordered hair bulb structures were restored within 96 hours. Bulge stem cells did not undergo apoptosis nor proliferation. K5+ basal lower proximal cup cells and outer root sheath cells quickly replenished the cells in the germinative zone and regenerated the concentric layered structures of the lower HF segment. Therefore, anagen HFs are able to summon extra-bulge progenitor cells in close proximity to the damaged matrix for quick repair after CYP injury.

External light activates hair follicle stem cells through eyes via an ipRGC-SCN-sympathetic neural pathway.

Changes in external light patterns can alter cell activities in peripheral tissues through slow entrainment of the central clock in suprachiasmatic nucleus (SCN). It remains unclear whether cells in otherwise photo-insensitive tissues can achieve rapid responses to changes in external light. Here we show that light stimulation of animals' eyes results in rapid activation of hair follicle stem cells with prominent hair regeneration. Mechanistically, light signals are interpreted by M1-type intrinsically photosensitive retinal ganglion cells (ipRGCs), which signal to the SCN via melanopsin. Subsequently, efferent sympathetic nerves are immediately activated. Increased norepinephrine release in skin promotes hedgehog signaling to activate hair follicle stem cells. Thus, external light can directly regulate tissue stem cells via an ipRGC-SCN autonomic nervous system circuit. Since activation of sympathetic nerves is not limited to skin, this circuit can also facilitate rapid adaptive responses to external light in other homeostatic tissues.

Functional complexity of hair follicle stem cell niche and therapeutic targeting of niche dysfunction for hair regeneration.

Stem cell activity is subject to non-cell-autonomous regulation from the local microenvironment, or niche. In adaption to varying physiological conditions and the ever-changing external environment, the stem cell niche has evolved with multifunctionality that enables stem cells to detect these changes and to communicate with remote cells/tissues to tailor their activity for organismal needs. The cyclic growth of hair follicles is powered by hair follicle stem cells (HFSCs). Using HFSCs as a model, we categorize niche cells into 3 functional modules, including signaling, sensing and message-relaying. Signaling modules, such as dermal papilla cells, immune cells and adipocytes, regulate HFSC activity through short-range cell-cell contact or paracrine effects. Macrophages capacitate the HFSC niche to sense tissue injury and mechanical cues and adipocytes seem to modulate HFSC activity in response to systemic nutritional states. Sympathetic nerves implement the message-relaying function by transmitting external light signals through an ipRGC-SCN-sympathetic circuit to facilitate hair regeneration. Hair growth can be disrupted by niche pathology, e.g. dysfunction of dermal papilla cells in androgenetic alopecia and influx of auto-reacting T cells in alopecia areata and lichen planopilaris. Understanding the functions and pathological changes of the HFSC niche can provide new insight for the treatment of hair loss.

Proteomic Analysis Reveals Anti-Fibrotic Effects of Blue Light Photobiomodulation on Fibroblasts.

BACKGROUND AND OBJECTIVES: This study was aimed at determining the effects of blue light photobiomodulation on primary adult mouse dermal fibroblasts (AMDFs) and the associated signaling pathways. STUDY DESIGN/MATERIALS AND METHODS: Cultured AMDFs from adult C57BL/6 mice were irradiated by blue light from a light-emitting diode (wavelength = 463 ± 50 nm; irradiance = 5 mW/cm2 ; energy density = 4-8 J/cm2 ). The cells were analyzed using mass spectrometry for proteomics/phosphoproteomics, AlamarBlue assay for mitochondrial activity, time-lapse video for cell migration, quantitative polymerase chain reaction for gene expression, and immunofluorescence for protein expression. RESULTS: Proteomic/phosphoproteomic analysis showed inhibition of extracellular signal-regulated kinases/mammalian target of rapamycin and casein kinase 2 pathways, cell motility-related networks, and multiple metabolic processes, including carbon metabolism, biosynthesis of amino acid, glycolysis/gluconeogenesis, and the pentose phosphate pathway. Functional analysis demonstrated inhibition of mitochondrial activities, cell migration, and mitosis. Expression of growth promoting insulin-like growth factor 1 and fibrosis-related genes, including transforming growth factor ß1 (TGFß1) and collagen type 1 ɑ2 chain diminished. Protein expression of α-smooth muscle actin, an important regulator of myofibroblast functions, was also suppressed. CONCLUSIONS: Low-level blue light exerted suppressive effects on AMDFs, including suppression of mitochondrial activity, metabolism, cell motility, proliferation, TGFß1 levels, and collagen I production. Low-level blue light can be a potential treatment for the prevention and reduction of tissue fibrosis, such as hypertrophic scar and keloids. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

How chemotherapy and radiotherapy damage the tissue: Comparative biology lessons from feather and hair models.

Chemotherapy and radiotherapy are common modalities for cancer treatment. While targeting rapidly growing cancer cells, they also damage normal tissues and cause adverse effects. From the initial insult such as DNA double-strand break, production of reactive oxygen species (ROS) and a general stress response, there are complex regulatory mechanisms that control the actual tissue damage process. Besides apoptosis, a range of outcomes for the damaged cells are possible including cell cycle arrest, senescence, mitotic catastrophe, and inflammatory responses and fibrosis at the tissue level. Feather and hair are among the most actively proliferating (mini-)organs and are highly susceptible to both chemotherapy and radiotherapy damage, thus provide excellent, experimentally tractable model systems for dissecting how normal tissues respond to such injuries. Taking a comparative biology approach to investigate this has turned out to be particularly productive. Started in chicken feather and then extended to murine hair follicles, it was revealed that in addition to p53-mediated apoptosis, several other previously overlooked mechanisms are involved. Specifically, Shh, Wnt, mTOR, cytokine signalling and ROS-mediated degradation of adherens junctions have been implicated in the damage and/or reparative regeneration process. Moreover, we show here that inflammatory responses, which can be prominent upon histological examination of chemo- or radiotherapy-damaged hair follicle, may not be essential for the hair loss phenotype. These studies point to fundamental, evolutionarily conserved mechanisms in controlling tissue responses in vivo, and suggest novel strategies for the prevention and management of adverse effects that arise from chemo- or radiotherapy.

Anagen hair follicle repair: Timely regenerative attempts from plastic extra-bulge epithelial cells.

Anagen hair follicle repair (AHFR) is the regenerative scheme activated to restore the structure and hair growth following injuries to anagen hair follicles. Compared with telogen-to-anagen regeneration and hair follicle neogenesis, AHFR is a clinically important, yet relatively unexplored regenerative feature of hair follicles. Due to their highly proliferative character, germinative cells and matrix cells within hair bulbs are highly susceptible to injuries, such as chemotherapy and radiotherapy. Clinical and experimental observations suggest that damaged anagen hair follicles are able to repair themselves to resume anagen growth, bypassing premature catagen/telogen entry. Mechanistically, extra-bulge epithelial cells in the outer root sheath and the lower proximal cup are quickly mobilized for regeneration. These cells acquire stem cell-like properties, exhibiting high plasticity by breaking lineage restriction to regenerate all cell types in the lower segment of anagen hair follicles. Facilitating extra-bulge epithelial cells' mobilization ameliorates hair loss from chemo- and radiotherapy. On the other hand, quiescent bulge stem cells can also be activated, but only after more severe injuries and with slower activation dynamics. They show limited plasticity and regenerate part of the outer root sheath only. The dysrhythmic activation might render bulge stem cells susceptible to concomitant injuries due to their exit from quiescence.

Intravital multiphoton microscopic imaging platform for ocular surface imaging.

The purpose of this study is to provide an intravital noninvasive multiphoton microscopic platform for long-term ocular imaging in transgenic fluorescent mice with subcellular resolution. A multiphoton microscopic system with tunable laser output was employed. We designed a mouse holder incorporated with stereotaxic motorized stage for in vivo three-dimensional imaging of ocular surface in 3 transgenic mouse line with fluorescent protein (FP) expression to visualize distinct structures. With our imaging platform and the expression of FPs, we obtained the three-dimensional images across the whole cornea from epithelium to endothelium and in conjunctiva with subcellular resolution in vivo. Specified EGFP expression in corneal epithelium of K5-H2B-EGFP mice helped to identify both corneal and limbal epithelial cells while ubiquitous nuclear FP expression in R26R-GR mice allowed us to visualized nuclei of all cell types. Universal membrane-localized FP in mT/mG mice outlined all cell boundaries, nerve fibers, and capillaries. The simultaneously collected second harmonic generation signals from collagenous stroma provided architectural contrast. Time-lapsed recording enabled monitoring the mitotic activity of corneal epithelial cells and limbal epithelial cells. We developed an intravital multiphoton microscopic stereotaxic imaging platform and showed that, by incorporating FP-expressing transgenic mice, this platform enables in vivo 4-dimensional ophthalmic study at subcellular resolution.

HSD3B1 gene polymorphism and female pattern hair loss in women with polycystic ovary syndrome.

BACKGROUND/PURPOSE: Genetic variant of HSD3B1 1245 is known to augment androgen production at peripheral tissue as skin. This study aimed to investigate whether women with polycystic ovary syndrome inheriting this variant exhibit specific androgenic phenotypes. METHODS: A cross-sectional study of Taiwanese women with polycystic ovary syndrome, defined by Rotterdam criteria, at the reproductive endocrinology outpatient clinic in a university affiliated hospital. RESULTS: The presence of female pattern hair loss in women with polycystic ovary syndrome was significantly associated with an increased body mass index, decreased sex hormone binding globulin and high density lipoprotein cholesterol levels, elevated triglyceride levels, and increased prevalence of hypertension. Using stepwise multivariate logistic regression analysis, body mass index, triglyceride and HSD3B1 1245 AC or CC genotype were significantly related to female pattern hair loss in women with polycystic ovary syndrome after considering other variables. Overweight women with polycystic ovary syndrome had significantly higher risk of female pattern hair loss than normal-weight women with polycystic ovary syndrome. The presence of female pattern hair loss was higher in overweight women with polycystic ovary syndrome who comprised HSD3B1 AC or CC genotype compared with wild type. CONCLUSION: Carrying the HSD3B1 1245C allele and overweight are associated with the presence of female pattern hair loss in women with polycystic ovary syndrome.

Efficacy and Safety of a Low-Level Light Therapy for Androgenetic Alopecia: A 24-Week, Randomized, Double-Blind, Self-Comparison, Sham Device-Controlled Trial.

BACKGROUND: Previous studies have reported the benefits of low-level/light laser therapy (LLLT) for the promotion of hair regrowth. However, the effectiveness of LLLT for the treatment of androgenetic alopecia (AGA) is still a topic of debate. OBJECTIVE: To investigate the efficacy and safety of LLLT on hair regrowth in patients with AGA. METHODS: This 24-week, randomized, double-blind, self-comparison, sham device-controlled trial enrolled 100 patients with AGA. All participants were randomly assigned to receive the investigational LLLT on one side of the head and sham light treatment on the contralateral side, 3 times weekly for 30 minutes each, over a 24-week period. Global scalp photography, phototrichogram assessment, the investigator's global assessment (IGA) of hair regrowth, and the subject's assessment of the treatment satisfaction were used for evaluation. RESULTS: After 24 weeks of treatment, the LLLT-treated scalp exhibited significantly greater hair coverage than the sham light-treated side (14.2% vs. 11.8%, p < .001). A significantly greater improvement from baseline in hair thickness, hair count, hair coverage, and IGA were also observed in the LLLT-treated side than in the sham light-treated side at the 12- and 24-week visits. No serious adverse events were observed. CONCLUSION: The use of LLLT might be an effective, safe, well-tolerated treatment for AGA.

ABCG2 deficiency in skin impairs re-epithelialization in cutaneous wound healing.

The ATP-binding cassette transporter ABCG2 is expressed in the interfollicular epidermis and mediates the side-population phenotype in skin cells. However, the role of ABCG2 in skin is unclear. Increased expression levels of ABCG2 were found at the basal layer of transitional epidermis adjacent to cutaneous wounds in human patients, indicating that ABCG2 may be involved in regulating the wound healing process. To investigate the role of ABCG2 in cutaneous wound healing, full-thickness skin wounds were created in ABCG2 knockout (ABCG2-KO) and wild-type mice. The healing process was analysed and revealed that ABCG2 deficiency in skin results in delays in wound closure and impairments in re-epithelialization, as evidenced by reductions in both suprabasal differentiation and in p63-expressing keratinocytes migrating from transitional epidermis to epithelial tongues. The reduction in p63-expressing cells may be due to elevated levels of reactive oxygen species in ABCG2-KO epidermis, which can cause DNA damage and lead to proliferation arrest. To determine whether ABCG2 deficiency affects the potency of epidermal stem/progenitor cells (EPCs), transplantation studies were carried out, which demonstrated that ABCG2-KO EPCs display higher levels of γH2AX and lose the capacity to differentiate into suprabasal keratinocytes. A competitive repopulation assay confirmed that ABCG2 expression is critical for the proper expansion and differentiation of EPCs in cutaneous wounds. As EPCs are known to contribute to the healing of larger wounds, the current findings imply a functional role for ABCG2 in the expansion and differentiation of p63-expressing EPCs. Thus, ABCG2 deficiency in skin impairs re-epithelialization in cutaneous wound healing.

Inducible deletion of the Blimp-1 gene in adult epidermis causes granulocyte-dominated chronic skin inflammation in mice.

B lymphocyte-induced maturation protein-1 (Blimp-1) is a transcriptional repressor important for the differentiation and function of several types of immune cells. Because skin serves as a physical barrier and acts as an immune sentinel, we investigated whether Blimp-1 is involved in epidermal immune function. We show that Blimp-1 expression is reduced in skin lesions of some human eczema samples and in stimulated primary keratinocytes. Epidermal-specific deletion of PR domain containing 1, with ZNF domain (Prdm1), the gene encoding Blimp-1, in adult mice caused spontaneously inflamed skin characterized by massive dermal infiltration of neutrophils/macrophages and development of chronic inflammation associated with higher levels of cytokines/chemokines, including granulocyte colony-stimulating factor (G-CSF), and enhanced myelopoiesis in bone marrow. Deletion of Prdm1 in the epidermis of adult mice also led to stronger inflammatory reactions in a tape-stripping test and in a disease model of contact dermatitis. The elevated G-CSF produced by keratinocytes after deletion of Prdm1 in vitro was mediated by the transcriptional activation of FBJ osteosarcoma oncogene (Fos) and fos-like antigen 1 (Fosl1). Systemic increases in G-CSF contributed to the inflammatory responses, because deletion of the G-CSF gene [colony stimulating factor 3, (Csf3)] prevented neutrophilia and partially ameliorated the inflamed skin in Prdm1-deficient mice. Our findings indicate a previously unreported function for Blimp-1 in restraining steady-state epidermal barrier immunity.

Risk Factor Analysis for the Immunogenicity of Adalimumab Associated with Decreased Clinical Response in Chinese Patients with Psoriasis.

Although anti-drug antibodies against biologics have been associated with decreased clinical efficacy, the immunogenicity of biologics seems to vary between drugs, diseases and ethnicities. This study aims to investigate the predictors for the formation of anti-adalimumab antibodies (AAA) and the clinical consequences of AAA formation. In 53 Chinese psoriatic patients treated with adalimumab, AAA was detected in 50.9%. Differences in Psoriasis Area and Severity Index 75 (PASI75) response rates among patients with and without AAA were significant (44.4% vs. 88.5%; p = 0.001). Patients with AAA had significantly lower trough concentrations of adalimumab than those without AAA. Risk factor analysis showed that treatment interruption, low trough adalimumab concentration, absence of concomitant methotrexate use and biologics switching were associated with a higher AAA titre. The treatment pattern of biologics influences the risk of AAA formation, thereby leading to reduced efficacy of adalimumab.

Enhancing hair follicle regeneration by nonablative fractional laser: Assessment of irradiation parameters and tissue response.

BACKGROUND AND OBJECTIVE: Identification of methods to enhance anagen entry can be helpful for alopecia. Recently, nonablative laser has been proposed as a potential treatment for alopecia. However, how the laser parameters affect stem cell activity, hair cycles and the associated side effects have not been well characterized. Here we examine the effects of irradiation parameters of 1,550-nm fractional laser on hair cycles. STUDY DESIGN/MATERIALS AND METHODS: The dorsal skin of eight-week-old female C57BL/6 mice with hair follicles in synchronized telogen was shaved and irradiated with a 1,550-nm fractional erbium-glass laser (Fraxel RE:STORE (SR1500) Laser System, Solta Medical, U.S.A.) with varied beam energies (5-35 mJ) and beam densities (500-3500 microthermal zones/cm(2) ). The cutaneous changes were evaluated both grossly and histologically. Hair follicle stem cell activity was detected by BrdU incorporation and changes in gene expression were quantified by real-time PCR. RESULTS: Direct thermal injury to hair follicles could be observed early after irradiation, especially at higher beam energy. Anagen induction in the irradiated skin showed an all-or-non change. Anagen induction and ulcer formation were affected by the combination of beam energy and density. The lowest beam energy of 5 mJ failed to promote anagen entry at all beam densities tested. As beam energy increased from 10 mJ to 35 mJ, we found a decreasing trend of beam density that could induce anagen entry within 7-9 days with activation of hair follicle stem cells. Beam density above the pro-regeneration density could lead to ulcers and scarring followed by anagen entry in adjacent skin. Analysis of inflammatory cytokines, including TNF-α, IL-1ß, and IL-6, revealed that transient moderate inflammation was associated with anagen induction and intense prolonged inflammation preceded ulcer formation. CONCLUSION: To avoid side effects of hair follicle injury and scarring, appropriate combination of beam energy and density is required. Parameters outside the therapeutic window can result in either no anagen promotion or ulcer formation.

Visible red light enhances physiological anagen entry in vivo and has direct and indirect stimulative effects in vitro.

BACKGROUND AND OBJECTIVES: Hair follicles are located at the interface of the external and internal environments and their cycling has been shown to be regulated by intra- and extra-follicular factors. The aim of this study is to examine whether or how hair follicles respond to visible light. STUDY DESIGN/MATERIALS AND METHODS: We examined the effect of 3 mW red (630 nm, 1 J/cm(2)), 2 mW green (522 nm, 1 J/cm(2)), and 2 mW blue light (463 nm, 1 J/cm(2)) on telogen in mice for 3 weeks. The photobiologic effects of red light on cell proliferation of outer root sheath keratinocytes and dermal papilla cells were studied in vitro. RESULTS: We found that red light accelerated anagen entry faster than green and blue light in mice. Red light irradiation stimulated the proliferation of both outer root sheath keratinocytes and dermal papilla cells in a dose-dependent manner by promoting cell cycle progression. This stimulative effect was mediated via extracellular signal-regulated kinase phosphorylation in both cells. In a co-culture condition, dermal papilla cells irradiated by red light further enhanced keratinocyte proliferation, suggesting enhanced epithelial-mesenchymal interaction. In search for factors that mediated this paracrine effect, we found fibroblast growth factor 7 was upregulated in both mRNA and protein levels. The stimulative paracrine effect on keratinocytes was significantly inhibited by neutralizing antibody against fibroblast growth factor 7. CONCLUSIONS: These results suggest that hair follicles respond to visible light in vivo. Red light may promote physiological telogen to anagen transition by directly stimulating outer root sheath keratinocytes and indirectly by enhancing epithelial-mesenchymal interaction in vitro.

Hair Follicle Transit-Amplifying Cells Phagocytose Dead Cells after Radiotherapeutic and Chemotherapeutic Injuries for Timely Regeneration.

Efficient clearance of dead cells is critical for tissue regeneration after injuries. How dead cells are removed from the skin after radiotherapy and chemotherapy is unclear. In this study, we found that radiotherapeutic and chemotherapeutic damage induced extensive apoptosis of highly proliferative transit-amplifying cells in hair follicles. These apoptotic cells disappeared rapidly in the early stage of regenerative attempts, and the lost structures were regenerated with transient and low-level inflammation. Without the recruitment of macrophages as scavengers, the dying cells were engulfed directly by adjacent surviving transit-amplifying cells, which produced mature phagosomes through fusion with lysosomes in a manner similar to professional phagocytosis and remained active in proliferation. Autophagy did not contribute significantly to the clearance of engulfed cell debris. Perturbing phagocytosis in the transit-amplifying cells hindered apoptotic cell removal, delayed structural recovery, and aggravated hair loss. Therefore, transit-amplifying cells are capacitated with both proliferative and efferocytic functions that facilitate tissue regeneration after tissue injury.