Murine Hair Research Articles

Expression of p63 and its association with cell proliferation at different stages of murine hair follicle cycle

Expression of p63 and its association with cell proliferation at different stages of murine hair follicle cycle

Hair Follicle Stem Cell Faith Is Dependent on Chromatin Remodeling Capacity Following Low-Dose Radiation.

The main function of the skin, to protect against the environment, is supported by the activity of different stem cell populations. The main focus of this study was elucidating the coping mechanisms of stem cells against the stimulation of constant exposure to genotoxic stresses, both endogenous and exogenous, to ensure long-term function. Investigation of various mouse strains, differing in their DNA repair capacity, enables us to clarify fractionated low-dose irradiation (LDR)-induced consequences for different stem cell populations of the murine hair follicle (HF) in their physiological stem cell niche. Using microscopic techniques combined with flow cytometry, we could show that LDR induces accumulation of persisting; pKu70-independent 53BP1-foci ("chromatin-alterations") in heterochromatic regions of the HF stem cells (HFSCs). These remaining chromatin-alterations result in varying stem cell consequences. CD34-positive HFSCs react by ataxia telangiectasia mutated-dependent, premature senescence, which correlates with global chromatin compaction, whereby apoptosis is prevented by the activity of DNA-dependent protein kinase catalytic subunit. However, distinctively highly damaged HFSCs seem to be sorted out of the niche by differentiation, transferring their chromatin-alterations to more proliferative G protein-coupled receptor 5-positive stem cells. Consequentially, the loss of basal HFSCs is compensated by increased proliferation within the stem cell pool. Despite the initial success of these mechanisms in stem cell population maintenance, the combined effect of the chromatin-alterations and the modification in stem cell pool composition may lead to downstream long-term functional loss of tissue or organs. Stem Cells 2018;36:574-588.

Murine Hair Follicle Derived Stem Cell Transplantation onto the Cornea Using a Fibrin Carrier.

The goal of this protocol is to establish a procedure for cultivating stem cells on a fibrin carrier to allow for eventual transplantation to the eye. The ability to transfer stem cells to a patient is critical for treatment for a variety of disorders and wound repair. We took hair follicle stem cells from the vibrissae of transgenic mice expressing a dual reporter gene under the control of the Tet-on system and the keratin 12 promoter (Meyer- Blazejewska et al., 2011 ). A clonal growth assay was performed to enrich for stem cells. Once holoclones formed they were transferred onto a fibrin carrier and cultivated to obtain a confluent epithelial cell layer. Limbal stem cell deficient (LSCD) mice were used as the transplant recipient in order to test for successful grafting and eventual differentiation into a corneal epithelial phenotype.

Topical Inhibition of the Electron Transport Chain Can Stimulate the Hair Cycle

Abstract While many signaling pathways have been implicated in control of activation of adult hair follicle stem cells and the hair cycle, less is known about cell intrinsic mechanisms of stem cell control. We previously identified lactate production as a key cell intrinsic regulator of hair follicle stem cell activity, suggesting that cellular metabolism is important in stem cell activation. Others have used transgenic methods to suggest that transgenic blockade of the Electron Transport Chain (ETC) leads to degeneration of the hair follicle. Here, we show that pharmacological abrogation of ETC activity, as opposed to complete ablation of ETC, can promote hair cycle activation without significant cell toxicity. Furthermore, metabolic data suggest that ETC inhibition leads to increased pyruvate accessibility for the Ldh enzyme and therefore increased lactate production, which we previously showed can promote hair cycle activation. Finally, this type of ETC inhibition can even be used to accelerate the hair cycle in aged mice. These results point toward an unexpected and safe method to promote hair follicle stem cell activation.

Dominant-negative Sox18 function inhibits dermal papilla maturation and differentiation in all murine hair types

SOX family proteins SOX2 and SOX18 have been reported as being essential in determining hair follicle type; however, the role they play during development remains unclear. Here, we demonstrate that Sox18 regulates the normal differentiation of the dermal papilla of all hair types. In guard (primary) hair dermal condensate (DC) cells, we identified transient Sox18 in addition to SOX2 expression at E14.5, which allowed fate tracing of primary DC cells until birth. Similarly, expression of Sox18 was detected in the DC cells of secondary hairs at E16.5 and in tertiary hair at E18.5. Dominant-negative Sox18 mutation (opposum) did not prevent DC formation in any hair type. However, it affected dermal papilla differentiation, restricting hair formation especially in secondary and tertiary hairs. This Sox18 mutation also prevented neonatal dermal cells or dermal papilla spheres from inducing hair in regeneration assays. Microarray expression studies identified WNT5A and TNC as potential downstream effectors of SOX18 that are important for epidermal WNT signalling. In conclusion, SOX18 acts as a mesenchymal molecular switch necessary for the formation and function of the dermal papilla in all hair types.

Dickkopf‐1 is involved in dexamethasone‐mediated hair follicle regression

The stress-related neurohormones including glucocorticoids (GCs) are secreted by hair follicles (HFs), and GCs suppress murine hair growth in vivo. In this study, we found that dexamethasone (Dex), a synthetic GC, increased the expression of dickkopf-1 (DKK1), a known catagen inducer, in dermal papilla (DP) cells, but not in follicular keratinocytes. The neutralizing DKK1 antibody significantly attenuated the Dex-induced inhibition of human hair shaft elongation. In addition, the neutralizing Dkk1 antibody delayed Dex-induced catagen in mice. Collectively, our data strongly suggest that stress-related neurohormones cause DP cells to secrete DKK1, thereby leading to stress-associated disturbances in hair growth.

Maintaining hair follicle stem cell identity in a dish.

Identifying and mimicking the signals that regulate stem cell self‐renewal, differentiation and maintenance in a petri dish is crucial to faithfully recapitulate stem cell behaviour in vitro . In this issue, Chacon‐Martinez et al (2017) describe novel culture conditions that allow the long‐term expansion and maintenance of functional murine hair follicle stem cells. This exciting discovery provides a faithful platform to study hair follicle stem cells in vitro and potentially perform drug screening for skin and hair follicle disorders.

JAK-STAT Signaling Jump Starts the Hair Cycle

Legrand et al show that JAK/STAT5 signaling in the dermal papilla is required for anagen onset in the murine hair cycle. Interestingly, others have shown that JAK-inhibition is able to induce telogen-to-anagen transition in wild-type mice. This apparent contradiction highlights the complexity of interactions within the hair follicle, and encourages further discussion on the role of JAK-STAT signaling in the various stem cell niches of the hair follicle.

Mutations in TSPEAR, Encoding a Regulator of Notch Signaling, Affect Tooth and Hair Follicle Morphogenesis.

Despite recent advances in our understanding of the pathogenesis of ectodermal dysplasias (EDs), the molecular basis of many of these disorders remains unknown. In the present study, we aimed at elucidating the genetic basis of a new form of ED featuring facial dysmorphism, scalp hypotrichosis and hypodontia. Using whole exome sequencing, we identified 2 frameshift and 2 missense mutations in TSPEAR segregating with the disease phenotype in 3 families. TSPEAR encodes the thrombospondin-type laminin G domain and EAR repeats (TSPEAR) protein, whose function is poorly understood. TSPEAR knock-down resulted in altered expression of genes known to be regulated by NOTCH and to be involved in murine hair and tooth development. Pathway analysis confirmed that down-regulation of TSPEAR in keratinocytes is likely to affect Notch signaling. Accordingly, using a luciferase-based reporter assay, we showed that TSPEAR knock-down is associated with decreased Notch signaling. In addition, NOTCH1 protein expression was reduced in patient scalp skin. Moreover, TSPEAR silencing in mouse hair follicle organ cultures was found to induce apoptosis in follicular epithelial cells, resulting in decreased hair bulb diameter. Collectively, these observations indicate that TSPEAR plays a critical, previously unrecognized role in human tooth and hair follicle morphogenesis through regulation of the Notch signaling pathway.

Regeneration of Murine Hair Follicles is Inhibited by Low-Dose-Rate Gamma Irradiation.

To determine whether the effects of low-dose-rate gamma (γ) irradiation are identifiable in the regeneration of murine hair follicles, we irradiated whole bodies of C57BL/10JHir mice in the first telogen phase of the hair cycle with 137Cs γ-rays. The mice were examined for effects on hair follicles, including number, morphology, and pigmentation in the second anagen phase. Effects of γ-radiation on melanocyte stem cells were also investigated by the indirect immunolabeling of tyrosinase-related protein 2 (TRP2). Irradiated skin showed a decrease in hair follicle density and the induction of curved hair follicles along with the presence of white hairs and hypopigmented hair bulbs. There was a small, but not significant, change in the number of TRP2-positive melanocyte stem cells in the hair bulge region of the irradiated skin. These results suggest that low-dose rate γ-irradiation does not deplete melanocyte stem cells, but can damage stem cells and progenitors for both keratinocytes and melanocytes, thereby affecting the structure and pigmentation of regenerated hair follicles in the 2nd anagen phase.

Roles of two sphingomyelin synthase isoforms in murine hair

Roles of two sphingomyelin synthase isoforms in murine hair

Stabilization of β-Catenin Does Not Increase Dermal Papilla Cell Number in the Hair Follicle

Stabilization of β-Catenin Does Not Increase Dermal Papilla Cell Number in the Hair Follicle

Repair of traumatized mammalian hair cells via sea anemone repair proteins.

Mammalian hair cells possess only a limited ability to repair damage after trauma. In contrast, sea anemones show a marked capability to repair damaged hair bundles by means of secreted repair proteins (RPs). Previously, it was found that recovery of traumatized hair cells in blind cavefish was enhanced by anemone-derived RPs; therefore, the ability of anemone RPs to assist recovery of damaged hair cells in mammals was tested here. After a 1h incubation in RP-enriched culture media, uptake of FM1-43 by experimentally traumatized murine cochlear hair cells was restored to levels comparable to those exhibited by healthy controls. In addition, RP-treated explants had significantly more normally structured hair bundles than time-matched traumatized control explants. Collectively, these results indicate that anemone-derived RPs assist in restoring normal function and structure of experimentally traumatized hair cells of the mouse cochlea.

Activation of β-Catenin Signaling in CD133-Positive Dermal Papilla Cells Drives Postnatal Hair Growth.

The hair follicle dermal papilla (DP) contains a unique prominin-1/CD133-positive (CD133+) cell subpopulation, which has been shown to possess hair follicle-inducing capability. By assaying for endogenous CD133 expression and performing lineage tracing using CD133-CreERT2; ZsGreen1 reporter mice, we find that CD133 is expressed in a subpopulation of DP cells during the growth phase of the murine hair cycle (anagen), but is absent at anagen onset. However, how CD133+ DP cells interact with keratinocytes to induce hair regenerative growth remains unclear. Wnt/β-catenin has long been recognized as a major signaling pathway required for hair follicle morphogenesis, development, and regeneration. Nuclear Wnt/β-catenin activity is observed in the DP during the hair growth phase. Here we show that induced expression of a stabilized form of β-catenin in CD133+ DP cells significantly accelerates spontaneous and depilation-induced hair growth. However, hair follicle regression is not affected in these mutants. Further analysis indicates that CD133+ DP-expressed β-catenin increases proliferation and differentiation of epithelial matrix keratinocytes. Upregulated Wnt/β-catenin activity in CD133+ DP cells also increases the number of proliferating DP cells in each anagen follicle. Our data demonstrate that β-catenin signaling potentiates the capability of CD133+ DP cells to promote postnatal hair growth.

Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function.

Cochlear hair cells convert sound-induced vibration into electrical signals. FAM65B mutations cause hearing loss by an unknown mechanism. Using biochemistry and stochastic optical reconstruction microscopy (STORM), we show here that Fam65b oligomers form a circumferential ring near the basal taper of the mechanically sensitive stereocilia of murine hair cells. Taperin, a second protein near the taper, forms a dense-core-like structure that is disrupted in the absence of Fam65b. Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected and stereocilia deteriorate. Yeast-two-hybrid screens identify RhoC as a Fam65b binding partner. RhoC co-localizes with Fam65b in stereocilia and regulates Fam65b oligomerization. Binding to RhoC and oligomerization are critical for Fam65b function. Our findings thus reveal a highly organized compartment near the base of stereocilia that is critical for hair cell function and affected in disease.

Age-associated decrease in GDNF and its cognate receptor GFRα-1 protein expression in human skin.

Glial cell line-derived neurotrophic factor (GDNF) and its cognate receptor (GFRα-1) are expressed in normal human skin. They are involved in murine hair follicle morphogenesis and cycling control. We hypothesize that 'GDNF and GFRα-1 protein expression in human skin undergoes age-associated alterations. To test our hypothesis, the expression of these proteins was examined in human skin specimens obtained from 30 healthy individuals representing three age groups: children (5-18years), adults (19-60years) and the elderly (61-81years). Immunofluorescent and light microscopic immunohistologic analyses were performed using tyramide signal amplification and avidin-biotin complex staining methods respectively. GDNF mRNA expression was examined by RT-PCR analysis. GDNF mRNA and protein as well as GFRα-1 protein expressions were detected in normal human skin. We found significantly reduced epidermal expression of these proteins with ageing. In the epidermis, the expression was strong in the skin of children and declined gradually with ageing, being moderate in adults and weak in the elderly. In children and adults, the expression of both GDNF and GFRα-1 proteins was strongest in the stratum basale and decreased gradually towards the surface layers where it was completely absent in the stratum corneum. In the elderly, GDNF and GFRα-1 protein expression was confined to the stratum basale. In the dermis, both GDNF and GFRα-1 proteins had strong expressions in the fibroblasts, sweat glands, sebaceous glands, hair follicles and blood vessels regardless of the age. Thus there is a decrease in epidermal GDNF and GFRα-1 protein expression in normal human skin with ageing. Our findings suggest that the consequences of this is that GFRα-1-mediated signalling is altered during the ageing process. The clinical and therapeutic ramifications of these observations mandate further investigations.

691 Topical curcumin promotes induction of the murine hair cycle

691 Topical curcumin promotes induction of the murine hair cycle

684 First indications that peri-follicular macrophages contribute to the regulation of catagen initiation and progression in the murine hair follicle

684 First indications that peri-follicular macrophages contribute to the regulation of catagen initiation and progression in the murine hair follicle

700 Oncostatin M is upstream of JAK-STAT signaling during the murine hair cycle

700 Oncostatin M is upstream of JAK-STAT signaling during the murine hair cycle

Sulforaphane promotes murine hair growth by accelerating the degradation of dihydrotestosterone.

Dihydrotestosterone (DHT) causes the regression of human hair follicles in the parietal scalp, leading to androgenic alopecia (AGA). Sulforaphane (SFN) increases the expression of DHT degrading enzymes, such as 3α-hydroxysteroid dehydrogenases (3α-HSDs), and, therefore, SFN treatment may improve AGA. To determine the effects of SFN on hair growth, we administered SFN (10 mg/kg BW, IP) or vehicle (DMSO) to ob/ob mice for six weeks and examined hair regeneration and the plasma levels of testosterone and DHT. We also tested the effects of SFN on the expression of two forms of 3α-HSD, aldo-keto reductase 1c21 and dehydrogenase/reductase (SDR family) member 9, both in vitro and in vivo. SNF significantly enhanced hair regeneration in ob/ob mice. The mice treated with SFN showed lower plasma levels of testosterone and DHT than those treated with vehicle. SFN increased the mRNA and protein levels of the two forms of 3α-HSD in the liver of the mice and in cultured murine hepatocyte Hepa1c1c7 cells. These results suggest that SFN treatment increases the amount of 3α-HSDs in the liver, accelerates the degradation of blood DHT, and subsequently blocks the suppression of hair growth by DHT.