Feasibility of adipose-derived therapies for hair regeneration: Insights based on signaling interplay and clinical overview.

Dermal white adipose tissue (dWAT) is a dynamic component of the skin and closely interacts with the hair follicle. Interestingly, dWAT envelops the hair follicle during anagen and undergoes fluctuations in volume throughout the hair cycle. dWAT-derived extracellular vesicles can significantly regulate the hair cycle, and this provides a theoretical basis for utilizing adipose tissue as a feasible clinical strategy to treat hair loss. However, the amount and depth of the available literature are far from enough to fully elucidate the prominent role of dWAT in modulating the hair growth cycle. This review starts by investigating the hair cycle-coupled dWAT remodeling and the reciprocal signaling interplay underneath. Then, it summarizes the current literature and assesses the advantages and limitations of clinical research utilizing adipose-derived therapies for hair regeneration.

A highly resistant structure between the cuticle and the cortex of human hair III: Characterzation of the structure CARB.

OBJECTIVE: It was previously reported that a highly resistant structure, which functions as a barrier against the penetration of dyes, is present at the interface between the cuticle and the cortex of human hair. That structure was named CARB, cuticle anchored resistant base. The goal of this study was to clarify the formation and composition of the structure CARB. METHODS: Cuticular substructures were observed from the keratinized area of each hair to its root end. The positions where the CARB structure appeared were isolated, and the barrier ability before and after that structure was evaluated. The distributions of glycolipid and cystine were measured using a nano-IR and a transmission electron microscope (TEM). RESULTS: Cuticular substructures were fully constructed several mm from the hair bulb of the hairs observed. The results show that keratinization at the distal side of the cuticle cell precedes that of the proximal side, and CARB is fully constructed last among the substructures. Glycolipid was preferentially distributed at CARB in the keratinized area. The cystine content of CARB is lower than that of the A-layer; however, it is slightly higher than that of the exocuticle and the inner layer. CONCLUSION: These results demonstrate that CARB is produced in the final stage of keratinization of the cuticle layers. The rich contents of glycolipid and cystine might contribute to its resistant property.

OBJECTIF: Il a été précédemment rapporté qu'une structure hautement résistante, qui fonctionne comme une barrière contre la pénétration des colorants, est présente à l'interface entre la cuticule et le cortex des cheveux humains. Cette structure a été baptisée « CARB ¼ pour cuticle anchored resistant base (base résistante ancrée dans la cuticule). L'objectif de cette étude était de clarifier la formation et la composition de la structure CARB. MÉTHODES: Des sous-structures cuticulaires ont été observées à partir de la zone kératinisée de chaque cheveu jusqu'à sa racine. Les positions où apparaissait la structure CARB ont été isolées et la capacité de barrière avant et après cette structure a été évaluée. Les distributions des glycolipides et de la cystine ont été mesurées à l'aide d'un spectromètre infrarouge nanométrique (nano-IR) et d'un microscope électronique à transmission (MET). RÉSULTATS: Les sous-structures cuticulaires étaient entièrement construites à plusieurs mm du bulbe capillaire des cheveux observés. Les　résultats montrent que la kératinisation du côté distal de la cellule cuticulaire précède celle du côté proximal, et la structure CARB est entièrement construite en dernier dans les sous-structures. Les glycolipides étaient distribués de préférence dans la structure CARB dans la zone kératinisée. La teneur en cystine de la structure CARB est inférieure à celle de la couche A ; cependant, elle est légèrement supérieure à celle de l'exocuticule et de la couche interne. CONCLUSION: Ces résultats démontrent que la structure CARB est produite à l'étape finale de la kératinisation des couches cuticulaires. Le riche contenu en glycolipides et cystine pourrait contribuer à sa propriété résistante.

Investigation of the molecular signature of greying hair shafts.

OBJECTIVE: Hair greying (i.e. canitie) is a physiological process occurring with the loss of melanin production and deposition within the hair shafts. Many studies reported the oxidation as the main biological process underlying this defect of pigmentation. Even though the overall appearance and biomechanical properties of hairs are reported to be altered with greying, there is a lack of information about molecular modifications occurring in grey hair shafts. The aim of this study was thus to investigate the molecular signature and associated changes occurring in greying hair shafts by confocal Raman microspectroscopy. METHODS: This study was conducted on pigmented, intermediate (i.e. grey) and unpigmented hairs taken from 29 volunteers. Confocal Raman microspectroscopy measurements were acquired directly on hair shafts. RESULTS: Automatic classification of Raman spectra revealed 5 groups displaying significant differences. Hence, the analysis of the molecular signature highlighted the existence of 3 sub-groups within grey hair: light, medium and dark intermediate. Among molecular markers altered in the course of greying, this study identified for the first time a gradual modification of lipid conformation (trans/gauche ratio) and protein secondary structure (α-helix/ß-sheet ratio), referring respectively to an alteration of barrier function and biomechanical properties of greying hair. CONCLUSION: This study thus reports for the first time a highly specific molecular signature as well as molecular modifications within grey hair shaft.

OBJECTIF: Le grisonnement du cheveu (i.e. canitie) est un processus physiologique correspondant à l'altération de la production et du dépôt des pigments de mélanine au sein de la tige pilaire. De nombreuses études identifient l'oxydation en tant que principal phénomène à l'origine de ce défaut de pigmentation. L'apparence globale et les propriétés biomécaniques des cheveux grisonnants sont également rapportées comme étant altérées. Cependant, il existe un manque d'information concernant les modifications moléculaires ayant lieu dans la tige pilaire grisonnante. Le but de cette étude était donc d'investiguer par microspectroscopie confocale Raman la signature moléculaire de la tige pilaire grisonnante ainsi que les changements biologiques associés. MÉTHODES: Cette étude a été réalisée sur des cheveux pigmentés, intermédiaires (i.e. gris) et non pigmentés, prélevés sur 29 volontaires. Les mesures par microspectroscopie Raman confocale ont directement été acquises sur la tige pilaire. RÉSULTATS: Une classification automatique des spectres Raman a permis de révéler 5 groupes présentant des différences significatives. Ainsi, l'analyse de la signature moléculaire spectrale identifie 3 sous-groupes au sein des cheveux gris : intermédiaires clairs, moyens et foncés. Parmi les marqueurs moléculaires altérés au cours du grisonnement, cette étude identifie pour la première fois une modification graduelle de la conformation des lipides (ratio trans /gauche) et de la structure secondaire des protéines (ratio hélice α/feuillets ß). Ces marqueurs correspondent respectivement à l'altération de la fonction barrière et des propriétés biomécaniques des cheveux gris. CONCLUSION: Cette étude met en évidence pour la première fois une signature moléculaire extrêmement précise ainsi que des modifications moléculaires en lien avec le grisonnement de la tige pilaire.

Ethnic hair: Thermoanalytical and spectroscopic differences.

BACKGROUND: The aim of this study is to characterize and detect the possible differences among the hair of three different ethnicities: African, Asiatic and Caucasian. MATERIALS AND METHODS: The differences in water adsorption/desorption behaviour of hairs were studied using a thermogravimetric balance and compared with the analysis of the lipid distribution and order using synchrotron-based Fourier transform infrared microspectroscopy. Besides, the thermal thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses on human hair were executed. RESULTS: Differences in the diffusion coefficients were evidenced. African hair exhibited increased permeability. Caucasian hair displayed a higher water absorption capability with increasing humidity but with a slow diffusion rate. The Asian fibre appeared to be more resistant to hydration changes. The spectroscopic analysis showed notable differences in the cuticle lipids. The African cuticle exhibited more lipids with a lower order bilayer. The outmost layer of Caucasian fibres contained more ordered lipids, and the Asian fibres show a very low level of lipids on the cuticle region. The DSC results indicate no difference in the thermal stability and TG showed higher water content in the Caucasian fibre and a possible lower cysteine disulphide bond content in the African hair matrix. CONCLUSION: The triple approach demonstrated the permeability differences among the ethnic fibres and their correlation with the properties of their cuticle lipids. These differences could have particular relevance to the hair care cosmetic market.

A combination of pyridine-2, 4-dicarboxylic acid diethyl ester and resveratrol stabilizes hypoxia-inducible factor 1-alpha and improves hair density in female volunteers.

OBJECTIVE: The aim of this study was first to demonstrate that a combination of pyridine-2, 4-dicarboxylic acid diethyl ester and resveratrol could synergize in vitro on biological pathways associated with hair growth and then to demonstrate the benefit on hair density in a clinical study. METHODS: The effects of pyridine-2, 4-dicarboxylic acid diethyl ester and resveratrol directly on the hypoxic inducible factor-1α protein (HIF-1α) and related genes expression were demonstrated on keratinocytes in culture in vitro using western-blot analysis and real time quantitative polymerase chain reaction analysis. The effect of resveratrol against oxidative stress induced by hydrogen peroxide treatment was studied in hair follicle and hair matrix cells in vitro using the sensitive probe Dichloro-dihydro-fluorescein diacetate (DCFH-DA). Finally, a randomized clinical study on hair density was conducted on 79 Caucasian female subjects to assess the effect of this combination of actives. RESULTS: Pyridine-2, 4-dicarboxylic acid diethyl ester and resveratrol stabilized HIF-1a protein and increased the expression of HIF-1α target genes. Resveratrol significantly reduced the oxygen peroxide-induced oxidative stress generated in hair follicle and hair matrix cells. The clinical study showed that a topical treatment with the combination significantly increased the hair density on women from 1.5 months. CONCLUSION: In addition to the antioxidant properties of resveratrol, the association of pyridine-2, 4-dicarboxylic acid diethyl ester and resveratrol revealed a synergistic effect on the HIF-1α pathway. The results of the clinical study confirmed the importance of such a combination to increase the hair density.

L'alopécie peut affecter 50% des femmes au cours de leur vie ce qui induit une perte de leur estime de soi et une diminution de leur qualité de vie. Au-delà des solutions chirurgicales et des traitements pouvant induire des effets secondaires potentiellement dangereux, il y a un besoin d'améliorer l'efficacité des produits cosmétiques qui permettent de prévenir la chute des cheveux tout en préservant la sécurité des patients. Ainsi, nous avons sélectionné une combinaison de pyridine-2, 4-dicarboxylic acide diethyle ester et de resvératrol pour activer des voies biologiques associées à la croissance du cheveu. Nous avons d'abord montré, in vitro, que la combinaison de pyridine-2, 4-dicarboxylic acide diethyle ester et de resvératrol permet de stabiliser la protéine HIF-1α conduisant ainsi à un effet synergique sur l'expression de gènes clés de la voie HIF-1α. Nous avons aussi démontré, in vitro, que le resvératrol permet de protéger significativement les follicules pileux et les cellules de la matrice du stress oxydatif induit par traitement au peroxide d'hydrogène. En final, une étude clinique randomisée mesurant la densité capillaire a été réalisée sur 79 femmes caucasiennes. Cette étude montre qu'une application topique d'une solution contenant de 5% pyridine-2, 4-dicarboxylic acide diethyle ester et 0.25% de resvératrol augmentent significativement la densité capillaire chez les femmes après 1.5 mois. En conclusion, ces résultats démontrent l'intérêt de stimuler la voie HIF-1α tout en protégeant les cheveux et le scalp du stress oxydatif afin d'améliorer la croissance des cheveux chez les femmes.

Wanted, dead and alive: Why a multidisciplinary approach is needed to unlock hair treatment potential.

Human recorded history is littered with attempts to improve the perceived appearance of scalp hair. Throughout history, treatments have included both biological and chemical interventions. Hair "quality" or "perceived appearance" is regulated by multiple biological intervention opportunities: adding more hairs by flipping follicles from telogen to anagen, or delaying anagen follicles transiting into catagen; altering hair "apparent amount" by modulating shaft diameter or shape; or, in principle, altering shaft physical properties changing its synthesis. By far the most common biological intervention strategy today is to increase the number of hairs, but to date this has proven difficult and has yielded minimal benefits. Chemical intervention primarily consists of active material surface deposition to improve shaft shine, fibre-fibre interactions and strength. Real, perceptible benefits will best be achieved by combining opportunity areas across the three primary sciences: biology, chemistry and physics. Shaft biogenesis begins with biology: proliferation in the germinative matrix, then crossing "Auber's Critical Line" and ceasing proliferation to synthesize shaft components. Biogenesis then shifts to oxidative chemistry, where previously synthesized components are organized and cross-linked into a shaft. We herein term the crossing point from biology to chemistry as "The Orwin Threshold." Historically, hair biology and chemistry have been conducted in different fields, with biological manipulation residing in biomedical communities and hair shaft chemistry and physics within the consumer care industry, with minimal cross-fertilization. Detailed understanding of hair shaft biogenesis should enable identification of factors necessary for optimum hair shaft production and new intervention opportunities.

Exploring some characteristics (density, anagen ratio, growth rate) of human body hairs. Variations with skin sites, gender and ethnics.

OBJECTIVE: To determine, in vivo, the density, growth rate and percentage of anagen phase follicles of body hairs present on five different skin sites (axilla, cheek, chin, leg, upper-lip) of women and men from four different ethnics (African, Caucasian, Chinese, North African). The same characteristics of terminal hairs from the nape of all subjects were recorded as references. METHODS: The photo-trichogram technique was used on all skin sites (of different sizes) at variable times (2 or 3 days) post shaving of small skin areas (a few cm2 ). Digital photographs were then analysed through a dedicated software that allows to record the density of body hairs (N cm-2 ), the % of growing hairs (Anagen phase) and their growth rates (in µm day-1 ). RESULTS: The densities of terminal hairs (on nape) found on all subjects were similar to those previously observed on much larger populations. The same ranking of a decreased density of body hairs in the five skin sites was observed in men, irrespective with ethnics. Body hairs seem homogeneously distributed among ethnics on armpit and leg with slight gender-related differences. In men, a significantly higher anagen phase percentage (> 85%) is found on terminal hairs, cheek and upper-lip region in Caucasians and North Africans, as compared to African and Chinese men. The technique used cannot precisely determine the very thin hairs present on the faces of all women. The anagen phase percentage appears higher in all women on leg and armpit. Hair body growth rates ranged from 180 to 485 µm day-1 and were found, on axilla, close to those of terminal hairs. CONCLUSION: The abundance of body hairs, in the studied skin sites, appears similar, irrespective with ethnic groups, whereas their functional characteristics (anagen ratio, growth rate) are more driven by individual/gender influences. RÉSUMÉ: Objectif Déterminer, in vivo, la densité, la vitesse de pousse et le pourcentage de follicules en phase anagènes des poils corporels présents sur 5 sites cutanés différents (l'aisselle, la joue, le menton, la jambe, la lèvre supérieure) de femmes et d'hommes issus de 4 groupes ethniques différents (Africain, Caucasien, Chinois, Nord-africain). Ces mêmes caractéristiques ont été enregistrées pour les cheveux (poils terminaux) en nuque de tous les sujets en tant que références. Méthodes la technique du photo-trichogramme a été utilisée sur tous les sites cutanés (de tailles différentes) après un temps variable (2 ou 3 jours) suivant le rasage de petites zones cutanées (quelques cm-2 ). Les photographies numériques ont été alors analysées par un logiciel spécifique qui permet d'enregistrer la densité de poils corporels (N.cm-2 ), le pourcentage de poils en phase de croissance (la phase Anagène) et leur vitesse de pousse (en µm/jour). Résultats la densité de cheveux (en nuque) trouvée sur tous les sujets était semblable à celle précédemment observée sur des populations beaucoup plus larges. On retrouve chez les hommes le même classement entre les 5 sites cutanés en termes de densité de poils corporels, indépendamment du groupe ethnique étudié. Les poils corporels semblent distribués de manière homogène parmi les membres d'un groupe ethnique sur l'aisselle et la jambe avec des légères différences liées au genre. Chez les hommes, les Caucasiens et les Nord-Africains présentent un pourcentage de poils terminaux en phase anagène significativement plus élevé (>85%) sur la joue et la région de la lèvre supérieure que les hommes Africains et Chinois. La technique utilisée ne permet pas précisément de déterminer la présence de poils très minces sur les visages des femmes. Le pourcentage de poils en phase anagène paraît plus élevé chez les femmes sur la jambe et l'aisselle. Les vitesses de pousse des poils corporels s'étendent de 180 à 485 µm/jours et se trouvent, sur les aisselles, proches de celles des cheveux. Conclusion la densité de poils corporels, dans les sites cutanés étudiés, présente une variabilité de sites indépendante du groupe ethnique considéré, tandis que leurs caractéristiques fonctionnelles (le ratio de poils en phase anagène, la vitesse de pousse) sont plus dirigées par des influences d'individu/genre.

Expression profiling and bioinformatic analyses suggest new target genes and pathways for human hair follicle related microRNAs.

BACKGROUND: Human hair follicle (HF) cycling is characterised by the tight orchestration and regulation of signalling cascades. Research shows that micro(mi)RNAs are potent regulators of these pathways. However, knowledge of the expression of miRNAs and their target genes and pathways in the human HF is limited. The objective of this study was to improve understanding of the role of miRNAs and their regulatory interactions in the human HF. METHODS: Expression levels of ten candidate miRNAs with reported functions in hair biology were assessed in HFs from 25 healthy male donors. MiRNA expression levels were correlated with mRNA-expression levels from the same samples. Identified target genes were tested for enrichment in biological pathways and accumulation in protein-protein interaction (PPI) networks. RESULTS: Expression in the human HF was confirmed for seven of the ten candidate miRNAs, and numerous target genes for miR-24, miR-31, and miR-106a were identified. While the latter include several genes with known functions in hair biology (e.g., ITGB1, SOX9), the majority have not been previously implicated (e.g., PHF1). Target genes were enriched in pathways of interest to hair biology, such as integrin and GnRH signalling, and the respective gene products showed accumulation in PPIs. CONCLUSIONS: Further investigation of miRNA expression in the human HF, and the identification of novel miRNA target genes and pathways via the systematic integration of miRNA and mRNA expression data, may facilitate the delineation of tissue-specific regulatory interactions, and improve our understanding of both normal hair growth and the pathobiology of hair loss disorders.

What is a Caucasian 'fine' hair? Comparing instrumental measurements, self-perceptions and assessments from hair experts.

OBJECTIVE: To determine the various factors contributing to what Caucasian women describe as 'fine hair'. METHODS: Three complementary approaches were used, namely self-evaluation by the volunteer, assessment by a sensorial expert and instrumental measurements, in order to determine some of the possible parameters taken into account by Caucasian women when they describe the notion of fine hair. One hundred fifty one women of Caucasian origin participated in the study. They varied in age, and varied in that some considered themselves as having fine hair, and others not. The instrumental measurements carried out included hair diameter measurements, hair density measurements, hair breakage force, hair flexibility and scalp sebum levels. RESULTS: From six parameters defined initially, four parameters were found to be in common with the three approaches: hair abundance (density), hair thickness, hair resistance and the volume of the hair on the head. The commonly used term 'body' was only common to self and expert evaluation, whereas the influence of curliness was only common to expert evaluation and instrumental measurements. CONCLUSIONS: This study has shown close agreement between sensorial and instrumental findings, and also illustrates how the women participating can subtly and adequately describe their own hair. It is important to note that the words 'fine hair' describes a lot more than just physically thin hair fibres. Ageing is an additional factor that clearly impacts certain parameters associated with 'fine hair' among the volunteers.

Towards a body hair atlas of women of caucasian ethnicity.

OBJECTIVE: A preliminary study was conducted in 17 female volunteers (mean age 29.8 years) to gain deeper insights into the characteristics of terminal Caucasian female body hair of different body parts. The focus on Caucasian women was driven by the high number of different scalp hair phenotypes in this ethnicity and intended to identify relevant differences between body areas to improve body hair removal approaches. METHODS: Multiple growth parameters and structural parameters were assessed for hair on the upper arm, forearm, upper leg, lower leg, axilla and intimate area and compared to scalp data. RESULTS: In particular, macroscopic and much less microscopic or hair surface properties differ strikingly in the investigated body areas. Hair density on the body is much lower than on scalp with the highest hair density in the axilla and intimate area. Multihair follicular units are described for scalp but were also found to a smaller proportion in the axilla and the intimate area. Substantial percentages of hair triplets are only found on the scalp and intimate area. Hair diameter is highest in the intimate area, followed by axillary and lower leg hair and correlates with a faster hair growth rate. The angle of emerging hair is smallest in the intimate area, axilla and on the lower leg. Hair shafts on the lower leg and in the axilla have most overlapping cuticle layers, but independent of body region, no significant differences in the mean thickness of cuticle layers were detectable. In addition, no differences were found in the mean distance between cuticle layer edges along the hair shaft and the hair surface roughness. Hair on the scalp, forearm, upper arm and upper leg had an almost round shape, whereas hair of the lower leg, intimate area and axilla had more elliptical shape. Hairs on the arm showed the highest luminance values and no visible medulla. The darkest hairs were in the axilla and intimate area containing the highest level of visible medulla in hair shafts. CONCLUSION: To our knowledge, this is the first systematic study comparing terminal hair properties in all cosmetically relevant body regions in Caucasian women.

Oxidative stress--a key emerging impact factor in health, ageing, lifestyle and aesthetics.

Oxidative stress is the resultant damage that arises due to redox imbalances, more specifically an increase in destructive free radicals and reduction in protection from antioxidants and the antioxidant defence pathways. Oxidation of lipids by reactive oxygen species (ROS) can damage cellular structures and result in premature cell death. At low levels, ROS-induced oxidative stress can be prevented through the action of antioxidants, however, when ROS are present in excess, inflammation and cytotoxicity eventually results leading to cellular oxidative stress damage. Increasing evidence for the role of oxidative stress in various diseases including neurological, dermatological, and cardiovascular diseases is now emerging. Mitochondria are the principal source (90%) of ROS in the cell, with superoxide radicals being generated when molecular oxygen is combined with free electrons. Given the key role of mitochondria in the generation of cellular oxidative stress it is worth considering this organelle and the process in more detail and to provide methods of intervention.

The impact of oxidative stress on hair.

Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to detoxify the reactive intermediates or to repair the resulting damage. Reactive oxygen species or free radicals are highly reactive molecules that can directly damage lipids, proteins, and DNA. They are generated by a multitude of endogenous and environmental challenges, while the body possesses endogenous defense mechanisms. With age, production of free radicals increases, while the endogenous defense mechanisms decrease. This imbalance leads to progressive damage of cellular structures, presumably resulting in the aging phenotype. While the role of oxidative stress has been widely discussed in skin aging, little focus has been placed on its impact on hair condition. Moreover, most literature on age-related hair changes focuses on alopecia, but it is equally important that the hair fibers that emerge from the scalp exhibit significant age-related changes that have equal impact on the overall cosmetic properties of hair. Sources of oxidative stress with impact on the pre-emerging fiber include: oxidative metabolism, smoking, UVR, and inflammation from microbial, pollutant, or irritant origins. Sources of oxidative stress with impact on the post-emerging fiber include: UVR (enhanced by copper), chemical insults, and oxidized scalp lipids. The role of the dermatologist is recognition and treatment of pre- and post-emerging factors for lifetime scalp and hair health.

The role of oxidative damage in poor scalp health: ramifications to causality and associated hair growth.

The oxidative stress element of unhealthy scalp leads to compromised pre-emergent hair formation and poorly formed hair as it grows. Only cosmetic solutions can minimize the impact of unhealthy hair and to achieve healthy looking and feeling hair, the scalp health must be normalized first. The objectives of this research were to both investigate whether oxidative stress was a relevant aetiological element in scalp dandruff and seborrhoeic dermatitis and whether scalp condition affects the quality of hair that grows from it. Further, this research was designed to determine whether an effective anti-dandruff shampoo would repair and protect the scalp and pre-emergent hair from oxidative stress. This study demonstrated that oxidative stress is an aetiological element relevant to the dandruff condition and that a potentiated ZPT shampoo effectively improves scalp condition, including a reduction in oxidative stress. The compromised hair condition associated with dandruff is concomitantly improved when the scalp condition is improved. It appears that there is a direct link between hair quality and scalp health.

Dermal ß-Catenin Is Required for Hedgehog-Driven Hair Follicle Neogenesis.

Hair follicle neogenesis (HFN) occurs after large skin excisions in mice, serving as a rare regenerative model in mammalian wound healing. Wound healing typically results in fibrosis in mice and humans. We previously showed that small skin excisions in mice result in scarring devoid of HFN, displaying features of nonregenerative healing, and hedgehog (Hh) activation in the dermis of such wounds can induce HFN. In this study, we sought to verify the role of dermal Wnt/ß-catenin signaling in HFN because this pathway is essential for hair follicle development but is also paradoxically well-characterized in fibrosis of adult wounds. By deletion of ß-catenin in large wound myofibroblasts, we show that Wnt/ß-catenin signaling is required for endogenous mechanisms of HFN. By utilizing a combined mouse model that simultaneously induces deletion of ß-catenin and constitutive activation of Smoothened in myofibroblasts, we also found that ß-catenin is required for Hh-driven dermal papilla formation. Transcriptome analysis confirms that Wnt/ß-catenin and Hh pathways are activated in dermal papilla cells. Our results indicate that Wnt-active fibrotic status may also create a permissive state for the regenerative function of Hh, suggesting that activation of both Wnt and Hh pathways in skin wound fibroblasts must be ensured in future strategies to promote HFN.

The evolving mechanical response of curly hair fibres subject to fatigue testing.

Cyclic testing of human hair reveals important details about the behaviour of fibres over many cycles of loading. Phenomena which are observed under static tensile tests give important clues about the form and behaviour of hair fibres, but these do not necessarily remain constant on the inevitable march to failure. In previous work, we demonstrated that curly fibres exhibited a toe-region during tensile tests. The form of curly fibres could be altered by mechanical manipulation but the curl could be recovered upon immersion in water. In this study, where straight and curly fibres are subject to cyclic loading, this characteristic toe-region was shown to be present in the first cycle of loading (for curly fibres). As the number of cycles increased (and the curly fibres progressively became straighter), the stress-strain response of curly fibres started to resemble that of straight fibres. This observation supports our previous hypothesis, which states that the toe-region can be attributed to the presence of a hydrogen bonding mechanism, which is present in curly fibres only, and can be altered by mechanical force. Interestingly, the alteration in load-bearing pattern in curly fibres did not necessarily translate to increased endurance, demonstrating that the relationship between fatigue and strength is a complex one in hair fibres.

The what, why and how of curly hair: a review.

An attempt to understand and explain a peculiarity that was observed for curly fibres during experimentation revealed disparate literature reporting on several key issues. The phenotypical nature of curly fibres is only accurately understood within the larger scope of hair fibres, which are highly complex biological structures. A brief literature search produced thousands of research items. Besides the large amount of information on the topic, there was also great variability in research focus. From our review, it appeared that the complexity of hair biology, combined with the variety of research subtopics, often results in uncertainty when relating different aspects of investigation. During the literature investigation, we systematically categorized elements of curly hair research into three basic topics: essentially asking why fibres curl, what the curly fibre looks like and how the curly fibre behaves. These categories were subsequently formalized into a curvature fibre model that is composed of successive but distinctive tiers comprising the elements in curly hair research. The purpose of this paper is twofold: namely to present (i) a literature review that explores the different aspects of curly human scalp hair and (ii) the curvature fibre model as a systemized approach to investigating curly hair.

Hair Biology: Growth and Pigmentation.

Healthy hair is vital to identity. Understanding the intricate anatomy and physiology of hair provides insight into the aging process and the eventual loss of either hair pigmentation or hair shafts. Several biologics are available that have enabled altering or slowing the aging process of hair, but, unfortunately, no agent exists that can reverse the natural course. The commonly used biologics are discussed.

Effects of all-trans retinoic acid on goat dermal papilla cells cultured in vitro

Background: All-trans retinoic acid (ATRA), a vitamin A-derived active metabolite, exerts important functions in hair biology. Previous studies indicated that excess ATRA hampered hair follicle morphogenesis and cyclic regeneration in adulthood, but other studies stated that ATRA promoted hair growth. Dermal papilla (DP), a cluster of specialized fibroblasts, plays pivotal roles in controlling development and regeneration of hair follicle. Several lines of evidence indicated that DP might be the target cells of ATRA in the hair follicle. To confirm this hypothesis, the present study was performed to explore the biological effects of ATRA on goat dermal papilla cells (DPCs) and clarify the roles of ATRA in hair biology. Results: Our experimental results indicated that key signaling transducers of ATRA were dynamically expressed in distinct stages of goat cashmere growth cycle, and high-dose ATRA treatment (10-5 M) significantly impaired the viability of goat DPCs and lowered the ratio of proliferating cells. Otherwise, goat DPCs were stimulated to enter apoptosis and their cell cycle progression was severely blocked by ATRA. Moreover, the expression of fibroblast growth factor 7 (Fgf7), one of the potent hair growth stimulators secreted by DPCs, was transcriptionally repressed following ATRA treatment. Conclusion: DPCs are the targets of ATRA in the hair follicle, and ATRA negatively regulates hair growth by the targeted suppression of cell viability and growth factor expression of goat DPCs. Through these observations, we offer a new mechanistic insight into the roles of ATRA in hair biology.