Adult Human Scalp Research Articles

550 Charting the human hair follicle microbiome: Composition, distribution, and functional impact of the bacterial metabolite, butyrate

Human hair follicles (HFs) harbor rich microbial communities, while dysbiosis of the HF microbiome is associated with hair diseases. Yet, the composition, distribution, and physiological functions of HF commensals for human HF growth, immunity, pigmentation and/or metabolism remain poorly explored. As a first step towards clarifying these items, healthy adult human scalp HFs were laser-capture-microdissected to extract DNA from defined HF compartments for metagenomic sequencing. Besides all known main human HF microbiota (e.g., Staphylococcus, Cutibacterium and Corynebacterium), new human HF-associated microbiota were identified, amongst them some extremophiles within the bulb region, supportive of a more selective and challenging environment.

Hair Follicle and Sebaceous Gland De Novo Regeneration With Cultured Epidermal Stem Cells and Skin-Derived Precursors.

In postpartum humans, skin appendages lost in injury are not regenerated, despite the considerable achievement made in skin bioengineering. In this study, transplantation of a combination of culture-expanded epidermal stem cells and skin-derived progenitors from mice and adult humans led to de novo regeneration of functional hair follicles and sebaceous glands. The data provide transferable knowledge for the development of novel bioengineered skin substitutes with epidermal appendage regeneration capacity.

Quantitative investigation of the effect of the extra-cerebral vasculature in diffuse optical imaging: a simulation study

Diffuse optical imaging (DOI) is a non invasive technique allowing the recovery of hemodynamic changes in the brain. Due to the diffusive nature of photon propagation in turbid media and the fact that cerebral tissues are located around 1.5 cm under the adult human scalp, DOI measurements are subject to partial volume errors. DOI measurements are also sensitive to large pial vessels because oxygenated and deoxygenated hemoglobin are the dominant chromophores in the near infrared window. In this study, the effect of the extra-cerebral vasculature in proximity of the sagittal sinus was investigated for its impact on DOI measurements simulated over the human adult visual cortex. Numerical Monte Carlo simulations were performed on two specific models of the human head derived from magnetic resonance imaging (MRI) scans. The first model included the extra-cerebral vasculature in which constant hemoglobin concentrations were assumed while the second did not. The screening effect of the vasculature was quantified by comparing recovered hemoglobin changes from each model for different optical arrays and regions of activation. A correction factor accounting for the difference between the recovered and the simulated hemoglobin changes was computed in each case. The results show that changes in hemoglobin concentration are better estimated when the extra-cerebral vasculature is modeled and the correction factors obtained in this case were at least 1.4-fold lower. The effect of the vasculature was also examined in a high-density diffuse optical tomography configuration. In this case, the difference between changes in hemoglobin concentration recovered with each model was reduced down to 10%.

Endocrine controls of primary adult human stem cell biology: Thyroid hormones stimulate keratin 15 expression, apoptosis, and differentiation in human hair follicle epithelial stem cells in situ and in vitro

Here we demonstrate that physiological concentrations of the thyroid hormones T3 and T4 enhance the KERATIN 15 promoter activity and expression in epithelial stem cells of adult human scalp hair follicles in situ and in vitro. Additionally, T3 and T4 stimulate expression of the immuno-inhibitory surface molecule CD200 . Subsequently, T3 and T4 induce apoptosis and differentiation and inhibit clonal growth of these progenitor cells in vitro. These data suggest that human hair follicle bulge-derived epithelial stem cells underlie profound, previously unknown hormonal regulation by thyroid hormones, and show that primary human keratin 15-GFP+ progenitor cells can be exploited to further elucidate fundamental endocrine controls of human epithelial stem cells.

An improved, standardised protocol for the isolation, enrichment and targeted neural differentiation of Nestin+ progenitors from adult human dermis

Human skin-derived Nestin+ cells serve as a convenient source for autologous, adult, pluripotent progenitor cells that offer new therapeutic possibilities in cell-based regenerative medicine. However, the isolation of human Nestin+ cells has tended to be of very low efficiency and to produce highly variable cell yields. Here we report a standardised protocol that facilitates the isolation and enrichment of Nestin+ progenitor cells from enzymatically digested adult human scalp dermis. The use of distinct media like Dulbecco's modified Eagle medium supplemented with foetal bovine serum or, alternatively, serum-free, supplemented neural stem cell medium greatly affected cell morphology, proliferation and differentiation (e.g. towards a neural versus mesenchymal phenotype). Finally, Nestin+ cells were isolated from a heterogeneous dermis-derived progenitor cell population, which proliferates within clones or floating microspheres under defined serum-free culture conditions. Supplementation of the medium with epidermal growth factor and basic fibroblast growth factor as well as coating with fibronectin allowed the highest enrichment level of Nestin+ progenitors and differentiation towards neural fate. These methodological advances should greatly facilitate the isolation, culture and targeted differentiation of primary, adult human scalp skin dermis-derived Nestin+ cells.

Nonviral in Situ Green Fluorescent Protein Labeling and Culture of Primary, Adult Human Hair Follicle Epithelial Progenitor Cells

In this article we show that cloning of the human K15 promoter before a green fluorescence protein (GFP)/geneticin-resistance cassette and transfection of microdissected, organ-cultured adult human scalp hair follicles generates specific K15 promoter-driven GFP expression in their stem cell-rich bulge region. K15-GFP+ cells can be visualized in situ by GFP fluorescence and 2-photon laser scanning microscopy. Vital K15-GFP+ progenitor cells can then be selected by using the criteria of their green fluorescence, adhesion to collagen type IV and fibronectin, and geneticin resistance. Propagated K15-GFP+ cells express epithelial progenitor markers, show the expected differential gene expression profile of human bulge epithelium, and form holoclones. This application of nonretroviral, K15 promoter-driven, GFP labeling to adult human hair follicles facilitates the characterization and manipulation of human epithelial stem cells, both in situ and in vitro, and should be transferable to other complex human tissues.

Management of primary cicatricial alopecias: options for treatment

Primary cicatricial alopecias (PCAs) are a poorly understood group of disorders that result in permanent hair loss. Clinically, they are characterized not only by permanent loss of hair shafts but also of visible follicular ostia along with other visible changes in skin surface morphology, while their histopathological hallmark usually (although not always) is the replacement of follicular structures with scar-like fibrous tissue. As hair follicle neogenesis in adult human scalp skin is not yet a readily available treatment option for patients with cicatricial alopecias, the aim of treatment, currently, remains to reduce symptoms and to slow or stop PCA progression, namely the scarring process. Early treatment is the key to minimizing the extent of permanent alopecia. However, inconsistent terminology, poorly defined clinical end-points and a lack of good quality clinical trials have long made management of these conditions very challenging. As one important step towards improving the management of this under-investigated and under-serviced group of dermatoses, the current review presents evidence-based guidance for treatment, with identification of the strength of evidence, and a brief overview of clinical features of each condition. Wherever only insufficient evidence-based advice on PCA management can be given at present, this is indicated so as to highlight important gaps in our clinical knowledge that call for concerted efforts to close these in the near future.

Expression of the heat shock protein-27 in the adult human scalp skin and hair follicle: Hair cycle–dependent changes

Heat shock protein (HSP) is a molecular chaperone involved in protein folding, assembly, and transport and in the regulation of cell growth and differentiation. HSP27 protein is expressed in murine hair follicle (HF) and in human skin during fetal development. In this investigation we hypothesized that HSP27 protein is expressed in the human scalp skin and its expression in HF changes with the transitions form anagen --> catagen --> telogen stages. To test this hypothesis, the immunoreactivity of HSP27 protein was examined in human scalp skin by immunofluorescent method. A total of 50 normal human scalp skin biopsy specimens were examined (healthy women, age 53-57 years). In each case, 50 HF were analyzed (35, 10, and 5 follicles in anagen, catagen, and telogen, respectively). HSP27 protein expression was prominent in human scalp anagen, and weak in both catagen and telogen HFs. Within HF, HSP27 protein immunoreactivity was prominent in the outer root sheath, inner root sheath, precorteocytes, and corteocytes of the hair shaft. In addition, HSP27 protein expression was prominent in the epidermis, sebaceous glands, sweat glands, and arrector pili muscles. Only some types of heat shock proteins are known to date. Also, our knowledge about the exact molecular mechanisms involved in the interactions among these protein and other molecular chaperones is still incomplete. Our investigation reports, for the first time, the expression patterns of HSP27 in human scalp skin and HF. The differential expression of HSP27 during HF cycling suggests its possible roles in human HF biology.

Isolation of multipotent adult stem cells from the dermis of mammalian skin.

We describe here the isolation of stem cells from juvenile and adult rodent skin. These cells derive from the dermis, and clones of individual cells can proliferate and differentiate in culture to produce neurons, glia, smooth muscle cells and adipocytes. Similar precursors that produce neuron-specific proteins upon differentiation can be isolated from adult human scalp. Because these cells (termed SKPs for skin-derived precursors) generate both neural and mesodermal progeny, we propose that they represent a novel multipotent adult stem cell and suggest that skin may provide an accessible, autologous source of stem cells for transplantation.

Three-dimensional demonstration of melanocyte distribution of human hair follicles: special reference to the bulge area.

Melanocytes of human hair follicles were histochemically and immunohistochemically examined in two and three dimensions. EDTA-treated extracted anagen vellus and intermediate hair follicles showed that monoclonal murine antibody (MoAb) NKI/ beteb-reactive melanocytes were distributed from the infundibulum to the bulb. Melanocytes of the infundibulum and bulb were larger and more strongly stained with MoAb NKI/beteb than those of the middle portion below the sebaceous gland. Latter melanocytes showed less dendricity. Dendritic melanocytes were exclusively observed in the bulb as well as the bulge area of vellus and intermediate hair follicles, where they were variably melanized. In longitudinal and transverse sections of adult human scalp some keratinocytes of the outer root sheath of the bulge area were melanized compared to other parts. This phenomenon was independent of the hair cycle. These findings may be characteristic of bulge melanocytes and/or keratinocytes.

Scanning electron microscopic observations of extracted terminal hair follicles of the adult human scalp and eyebrow with special references to the bulge area.

Scanning electron microscopic studies of human terminal hair follicles of the scalp and eyebrow have previously been limited to the hair shaft. In this study we investigated EDTA-treated extracted whole hair follicles in which most of the basal cell surface of the outer root sheath was well preserved. In the bulge area of scalp follicles there were many knob-like or villous projections. These were located in some specimens on one side of the follicle, while in others they were located around the entire circumference of the follicle. These projections were thought to represent the anchoring points of the branched follicular end of the arrector muscles. Ring-like elevations with groove-like depressions above and below were also observed surrounding the entire follicle. These were thought to represent the track of circumfollicular arrector muscles which depressed the outer root sheath when they repeatedly contracted. Most anagen eyebrow follicles showed morphological variations in the bulge area such as lattice-window-like structures and undulation patterns. In telogen follicles, the bulge became indistinguishable from the clubbed end. The lower end of these telogen follicles showed irregularly shaped bulge areas, but did not show lattice-window-like structures or undulation patterns as observed in anagen follicles. Interestingly, a hole was found in some bulge areas of both anagen and telogen follicles. Serial vertical sections of follicles revealed invaginated areas, which seemed to correspond to the openings seen in whole mounts. In vertical sections of eyebrow follicles some keratinocytes of the outer root sheaths of the bulge area were seen to be melanized to various extents. This phenomen was independent of hair cycle phase.

Merkel Cells of the Terminal Hair Follicle of the Adult Human Scalp

Human scalp skins were treated with 20 mM ethylenediaminetetraacetic acid and terminal hair follicles were extracted with the epidermis. Some terminal hair follicles were morphologically preserved well and provided opportunity to examine three-dimensional distribution of CAM5.2 (K8, 52.5 kD) reactive Merkel cells. In anagen terminal hair of the scalp numerous immunoreactive Merkel cells were distributed in the presumptive bulge area. Distinct swelling as in the bulge of human vellus hair was usually absent; however, in rare instances anagen terminal hair demonstrated unilateral prominent swelling with dense aggregation of Merkel cells. In telogen hair the bulge becomes indistinguishable from the regressed end of the club hair follicle but Merkel cells continued to be abundant. We found morphologic variation of the bulge such as formation of knoblike swellings and villous projections. Interestingly, Merkel cells were also located in these structures. Palisading stockade-like nerve endings were observed surrounding the follicular epithelium at the sebaceous gland level. Merkel cells were sparse in this follicular segment. Variable number of Merkel cells were also scattered in the infundibulum of terminal hair in no association with peripheral nerves.