RESUMO
The elephant's trunk is multifunctional: It must be flexible to wrap around vegetation, but tough to knock down trees and resist attack. How can one appendage satisfy both constraints? In this combined experimental and theoretical study, we challenged African elephants to reach far-away objects with only horizontal extensions of their trunk. Surprisingly, the trunk does not extend uniformly, but instead exhibits a dorsal "joint" that stretches 15% more than the corresponding ventral section. Using material testing with the skin of a deceased elephant, we show that the asymmetry is due in part to patterns of the skin. The dorsal skin is folded and 15% more pliable than the wrinkled ventral skin. Skin folds protect the dorsal section and stretch to facilitate downward wrapping, the most common gripping style when picking up items. The elephant's skin is also sufficiently stiff to influence its mechanics: At the joint, the skin requires 13 times more energy to stretch than the corresponding length of muscle. The use of wrinkles and folds to modulate stiffness may provide a valuable concept for both biology and soft robotics.
Assuntos
Elefantes , Nariz , Fenômenos Fisiológicos da Pele , Pele , Animais , Elefantes/anatomia & histologia , Elefantes/fisiologia , Nariz/anatomia & histologia , Nariz/fisiologiaRESUMO
Although many clinical variants of Staphylococcus aureus infection are well-recognized, atypical presentations may mimic other conditions. We describe two cases of atypical S. aureus infections in pediatric patients: a S. aureus infection presenting with a vesicopustular rash mimicking varicella zoster virus and a case of multifocal panniculitis. Both of these cases were specifically caused by methicillin-resistant S. aureus (MRSA). Additional cases of atypical S. aureus infections and presenting features from the current literature are also discussed.
RESUMO
Male pattern hair loss (MPHL), also referred to as male androgenetic alopecia (AGA) is the most common type of non-scarring progressive hair loss, with 80% of men suffering from this condition in their lifetime. In MPHL, the hair line recedes to a specific part of the scalp which cannot be accurately predicted. Hair is lost from the front, vertex, and the crown, yet temporal and occipital follicles remain. The visual effect of hair loss is due to hair follicle miniaturisation, where terminal hair follicles become dimensionally smaller. Miniaturisation is also characterised by a shortening of the growth phase of the hair cycle (anagen), and a prolongation of the dormant phase (kenogen). Together, these changes result in the production of thinner and shorter hair fibres, referred to as miniaturised or vellus hairs. It remains unclear why miniaturisation occurs in this specific pattern, with frontal follicles being susceptible while occipital follicles remain in a terminal state. One main factor we believe to be at play, which will be discussed in this viewpoint, is the developmental origin of the skin and hair follicle dermis on different regions of the scalp.
Assuntos
Alopecia , Cabelo , Masculino , Humanos , Alopecia/etiologia , Folículo Piloso , Couro Cabeludo , PeleRESUMO
Skin injuries remain a persistent problem for users of lower-limb prostheses despite sustained progress in prosthesis design. One factor limiting the prevention of skin injuries is that skin on the residual limb is not suited to bear the mechanical loads of ambulation. One part of the body that is suited to this task is the sole of the foot. Here, we propose a novel strategy to actively augment skin's tolerance to load, increasing its resistance to mechanically induced injuries. We hypothesise that the load tolerance of skin can be augmented by autologous transplantation of plantar fibroblasts into the residual limb dermis. We expect that introducing plantar fibroblasts will induce the overlying keratinocytes to express plantar-specific keratins leading to a tougher epidermis. Using a computational finite element model of a weight-bearing residual limb, we estimate that skin deformation (a key driver of pressure ulcer injuries) could be halved by reprogramming skin to a plantar-like phenotype. We believe this strategy could yield new progress in pressure ulcer prevention for amputees, facilitating rehabilitation and improving quality of life for patients.
Assuntos
Amputados/reabilitação , Fibroblastos/transplante , Desenho de Prótese , Pele/lesões , Simulação por Computador , Antepé Humano , HumanosRESUMO
The ability to manipulate the mammalian hair cycle will lead to novel therapies and strategies to combat all forms of alopecia. Thus, in addition to the epithelial-mesenchymal interactions in the hair follicle, niche and microenvironmental signals that accompany the phases of growth, regression and rest need to be scrutinized. Immune cells are well described in skin homeostasis and wound healing and have recently been shown to play an important role in the mammalian hair cycle. In this review, we will summarize our current knowledge of the role of immune cells in hair cycle control and discuss their relevance to human hair cycling disorders. Increased attention to this aspect of the hair cycle will provide new avenues to manipulate hair regeneration in humans and provide better insight into developing better ex vivo models of hair growth.
Assuntos
Cabelo/imunologia , Cabelo/fisiologia , Sistema Imunitário/fisiologia , Alopecia/imunologia , Alopecia/fisiopatologia , Alopecia em Áreas/imunologia , Alopecia em Áreas/fisiopatologia , Animais , Biópsia , Ciclo Celular , Transição Epitelial-Mesenquimal , Folículo Piloso/citologia , Homeostase , Humanos , Camundongos , Pele/imunologia , Fenômenos Fisiológicos da PeleRESUMO
Hair plays a large part in communication and society with its role changing through time and across cultures. Most people do not leave the house before combing their hair or shaving their beard and for many hair loss or irregular hair growth can have a significant impact on their psychological health. Somewhat unsurprisingly, according to GMR Data, today's global hair care industry is worth an estimated $87 Billion, with hair loss estimated at $2.8 Billion. Considering that no current hair loss-related products can completely reverse hair loss, it is reasonable to believe this market could expand significantly with the discovery of a comprehensive therapy. As such, a great deal of research focuses on overcoming hair loss, and in particular, a common form of hair loss known as androgenetic alopecia (AGA) or male pattern baldness. In AGA, hair follicles miniaturise in a large step change from a terminal to a vellus state. Within this viewpoint article, we discuss how influx and efflux of cells into and out from the dermal papilla (DP) can modulate DP size during the hair cycle. As DP size is positively correlated with the size of the hair fibre produced by a follicle, we argue here that therapies for treating AGA should be developed which can alter DP size, rather than just promote hair growth. We also discuss current therapeutics for AGA and emphasise the importance of using the right model systems to analyse miniaturisation.
Assuntos
Alopecia/tratamento farmacológico , Alopecia/patologia , Androgênios/metabolismo , Folículo Piloso/metabolismo , Folículo Piloso/patologia , Alopecia/metabolismo , Animais , Cabelo/crescimento & desenvolvimento , Cabelo/patologia , Folículo Piloso/efeitos dos fármacos , Humanos , Receptores Androgênicos/metabolismo , Fenômenos Fisiológicos da Pele , Testosterona/metabolismoRESUMO
BACKGROUND: The European Chemical Agency (ECHA) definition of prolonged contact was introduced in 2014 and has not been evaluated clinically. OBJECTIVES: To assess whether nickel-sensitized individuals react on patch testing with high nickel-releasing metal discs for short and repetitive periods. MATERIALS AND METHODS: We patch tested 45 nickel-sensitized individuals double-blind with 2 different types of high nickel-releasing discs for 10, 30 and 60 minutes on 3 occasions over a period of 2 weeks, and for 1 longer period. Discs were tested for nickel release. RESULTS: Nickel release from both discs significantly exceeded the 0.5 µg Ni/cm2 /week limit of the EU REACH nickel restriction. However, only 1 individual tested had a largely dose-dependent allergic reaction. CONCLUSIONS: The majority of nickel-allergic subjects did not react to nickel discs after 2 hours or after repetitive exposures of up to 30 minutes on 3 occasions over a period of 2 weeks. The length of time needed to cause nickel allergic contact dermatitis in most nickel-allergic individuals is longer than the ECHA guidance definition. Longer test times are needed to define the time required to cause dermatitis in most nickel-allergic individuals. As a limitation, the test conditions did not adequately assess real-life factors such as friction, which is relevant for some uses of nickel.
Assuntos
Dermatite Alérgica de Contato/diagnóstico , Dermatite Alérgica de Contato/etiologia , Níquel/administração & dosagem , Níquel/efeitos adversos , Adulto , Método Duplo-Cego , União Europeia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes do Emplastro/estatística & dados numéricosRESUMO
The dermal papilla is a cluster of mesenchymal cells located at the base of the hair follicle which have a number of important roles in the regulation of hair growth. As a consequence, in vitro models of these cells are widely used to study the molecular mechanisms which underlie hair follicle induction, growth and maintenance. While dermal papilla from rodent hair follicles can be digested prior to cell isolation, the unique extracellular matrix composition found in human dermal papilla renders enzymes such as trypsin and collagenase insufficient for digestion of the dermal papilla into a single cell suspension. As such, to grow human dermal papilla cells in vitro, the papilla has to first be isolated via a micro-dissection approach from the follicle. In this article we describe the micro-dissection and culture methods, which we use within our laboratory, for the study of human dermal papilla cells.
Assuntos
Técnicas de Cultura de Células/métodos , Separação Celular/métodos , Derme/citologia , Folículo Piloso/citologia , Biópsia , Adesão Celular , Contagem de Células , Células Cultivadas , Matriz Extracelular , Cabelo/crescimento & desenvolvimento , Humanos , Células-Tronco Mesenquimais/citologia , Pele/citologia , Fenômenos Fisiológicos da PeleRESUMO
Mechanisms that regulate the growth of eyelashes have remained obscure. We ascertained two families from Pakistan who presented with familial trichomegaly, or extreme eyelash growth. Using a combination of whole exome sequencing and homozygosity mapping, we identified distinct pathogenic mutations within fibroblast growth factor 5 (FGF5) that underlie the disorder. Subsequent sequencing of this gene in several additional trichomegaly families identified an additional mutation in FGF5. We further demonstrated that hair fibers from forearms of these patients were significantly longer than hairs from control individuals, with an increased proportion in the growth phase, anagen. Using hair follicle organ cultures, we show that FGF5 induces regression of the human hair follicle. We have identified FGF5 as a crucial regulator of hair growth in humans for the first time, to our knowledge, and uncovered a therapeutic target to selectively regulate eyelash growth.
Assuntos
Fator 5 de Crescimento de Fibroblastos/metabolismo , Cabelo/anatomia & histologia , Sequência de Aminoácidos , Éxons/genética , Feminino , Fator 5 de Crescimento de Fibroblastos/química , Fator 5 de Crescimento de Fibroblastos/genética , Cabelo/crescimento & desenvolvimento , Folículo Piloso/metabolismo , Homozigoto , Humanos , Masculino , Dados de Sequência Molecular , Mutação de Sentido Incorreto/genética , Linhagem , Fenótipo , Transporte Proteico , Análise de Sequência de DNARESUMO
BACKGROUND: Healthcare workers (HCWs) are at risk of developing occupational skin disease (OSD). OBJECTIVES: To ascertain the causes of OSD in Australian HCWs in a tertiary referral clinic. METHODS: A retrospective review was performed of patients assessed at the Occupational Dermatology Clinic in Melbourne from 1993 to 2014. RESULTS: Of 685 HCWs assessed in the clinic over a period of 22 years, 555 (81.0%) were diagnosed with OSD. The most common diagnosis was irritant contact dermatitis (ICD) (79.1%), followed by allergic contact dermatitis (ACD) (49.7%). Natural rubber latex allergy was also relatively frequent (13.0%). The major substances causing ACD were rubber glove chemicals (thiuram mix and tetraethylthiuram disulfide), preservatives (formaldehyde, formaldehyde releasers, and isothiazolinones), excipients in hand cleansers, which are hard-to-avoid weak allergens, and antiseptics. ACD caused by commercial hand cleansers occurred more frequently than ACD caused by alcohol-based hand rubs (ABHRs). Occupational ICD was mostly caused by water/wet work and hand cleansers, and environmental irritants such as heat and sweating. CONCLUSIONS: Understanding the causes of OSD in HCWs is important in order to develop strategies for prevention. We suggest that skin care advice should be incorporated into hand hygiene education. The use of ABHRs should be encouraged, weak allergens in skin cleansers should be substituted, and accelerator-free gloves should be recommended for HCWs with OSD.
Assuntos
Dermatite Alérgica de Contato/etiologia , Dermatite Irritante/etiologia , Dermatite Ocupacional/etiologia , Dermatoses da Mão/etiologia , Setor de Assistência à Saúde , Pessoal de Saúde , Hipersensibilidade ao Látex/etiologia , Adolescente , Adulto , Idoso , Alérgenos/efeitos adversos , Anti-Infecciosos Locais/efeitos adversos , Austrália , Dermatite Alérgica de Contato/diagnóstico , Dermatite Irritante/diagnóstico , Dermatite Ocupacional/diagnóstico , Desinfetantes/efeitos adversos , Dissulfiram/efeitos adversos , Feminino , Formaldeído/efeitos adversos , Fungicidas Industriais/efeitos adversos , Luvas Protetoras/efeitos adversos , Dermatoses da Mão/diagnóstico , Humanos , Irritantes/efeitos adversos , Hipersensibilidade ao Látex/diagnóstico , Masculino , Pessoa de Meia-Idade , Testes do Emplastro , Estudos Retrospectivos , Tiram/efeitos adversos , Adulto JovemRESUMO
De novo organ regeneration has been observed in several lower organisms, as well as rodents; however, demonstrating these regenerative properties in human cells and tissues has been challenging. In the hair follicle, rodent hair follicle-derived dermal cells can interact with local epithelia and induce de novo hair follicles in a variety of hairless recipient skin sites. However, multiple attempts to recapitulate this process in humans using human dermal papilla cells in human skin have failed, suggesting that human dermal papilla cells lose key inductive properties upon culture. Here, we performed global gene expression analysis of human dermal papilla cells in culture and discovered very rapid and profound molecular signature changes linking their transition from a 3D to a 2D environment with early loss of their hair-inducing capacity. We demonstrate that the intact dermal papilla transcriptional signature can be partially restored by growth of papilla cells in 3D spheroid cultures. This signature change translates to a partial restoration of inductive capability, and we show that human dermal papilla cells, when grown as spheroids, are capable of inducing de novo hair follicles in human skin.
Assuntos
Microambiente Celular/fisiologia , Derme/citologia , Folículo Piloso/fisiologia , Regeneração/fisiologia , Esferoides Celulares/fisiologia , Técnicas de Cultura de Células , Biologia Computacional , Derme/fisiologia , Imunofluorescência , Perfilação da Expressão Gênica , Folículo Piloso/citologia , Humanos , Análise em Microsséries , Reação em Cadeia da Polimerase em Tempo Real , Biologia de SistemasRESUMO
We report a case of a 50-year-old lady with allergic contact dermatitis to para-phenylenediamine, who in her quest to find a substitute hair dye, subsequently reacted to a number of plant-based hair dyes, including pure henna, black tea and indigo powder respectively. While these substances all contain tannins, testing to possible constituents tannic acid and gallic acid was negative.
Assuntos
Dermatite Alérgica de Contato/etiologia , Tinturas para Cabelo/efeitos adversos , Fenilenodiaminas/efeitos adversos , Dermatoses do Couro Cabeludo/etiologia , Alérgenos , Dermatite Alérgica de Contato/fisiopatologia , Feminino , Humanos , Índigo Carmim/imunologia , Lawsonia (Planta)/imunologia , Pessoa de Meia-Idade , Testes do Emplastro , Prurido/diagnóstico , Prurido/etiologia , Dermatoses do Couro Cabeludo/diagnóstico , Índice de Gravidade de Doença , Chá/imunologiaRESUMO
Hair follicle development is driven by interactions between the epithelium and underlying mesenchyme. These reciprocal interactions are essential for development, as a lack of response from either the mesenchyme or epithelium results in arrested growth. A large body of research has focused on the role of mesenchymal cells during hair follicle development and their inductive properties for hair neogenesis. In this commentary, the role of the epidermis during hair follicle induction will be discussed.
Assuntos
Epiderme/crescimento & desenvolvimento , Cabelo/crescimento & desenvolvimento , Animais , Diferenciação Celular , Células Epidérmicas , Folículo Piloso/citologia , Folículo Piloso/crescimento & desenvolvimento , Humanos , Queratinócitos/citologia , Modelos Biológicos , Técnicas de Cultura de TecidosRESUMO
Fibroblasts in the skin are highly heterogeneous, both in vivo and in vitro. One difference between follicular (dermal papilla fibroblasts [DP]) and interfollicular fibroblasts (papillary fibroblasts [PFi]) in vitro is their ability to differentiate in response to osteogenic media (OM), or mechanical stimulation. Here, we asked whether differences in the ability of DP and PFi to respond to differentiation stimuli are due to differences in chromatin accessibility. We performed chromatin accessibility and transcriptional profiling of DP and PFi in human skin, which arise from a common progenitor during development, yet display distinct characteristics in adult tissue and in vitro. We found that cells cultured in growth media had unique chromatin accessibility profiles; however, these profiles control similar functional networks. Upon introduction of a chemical perturbation (OM) to promote differentiation, we observed a divergence not only in the accessible chromatin signatures but also in the functional networks controlled by these signatures. The biggest divergence between DP and PFi was observed when we applied 2 perturbations to cells: growth in OM and mechanical stimulation (a shock wave [OMSW]). DP readily differentiate into bone in OMSW conditions, while PFi lack differentiation capability in vitro. In the DP we found a number of uniquely accessible promoters that controlled osteogenic interaction networks associated with bone and differentiation functions. Using ATAC-seq and RNA-seq we found that the combination of 2 stimuli (OMSW) could result in significant changes in chromatin accessibility associated with osteogenic differentiation, but only within the DP (capable of osteogenic differentiation). De novo motif analysis identified enrichment of motifs bound by the TEA domain (TEAD) family of transcription factors, and inter-cell comparisons (UpSet analysis) displayed large groups of genes to be unique to single cell types and conditions. Our results suggest that these 2 stimuli (OMSW) elicit cell-specific responses by modifying chromatin accessibility of osteogenic-related gene promoters.