Human Hair Cuticle Research Articles

Human hair keratin responds to oxidative stress via reactive sulfur and supersulfides

Keratin is a central component of human hair proteins, which explicitly possesses many cysteine residues (Cys-SH). For a long time, these Cys-SH residues were believed to contribute to human hair strength by forming intra- and inter-molecular disulfide bond crosslinks. However, we detected that many polysulfide bonds (R-SS(n)H or R-SS(n)S-R') exist in keratin. Polysulfide is one of the reactive sulfur and supersulfides, similar to cysteine persulfide (Cys-SSH), that regulates oxidative stress and redox signaling. In the present study, we elucidated the distribution of polysulfide in human hair and the reaction of polysulfide to various oxidative stress, such as heat shock and ultraviolet radiation. The decrease of the polysulfides in hair leads to the loss of antioxidant activity. Additionally, we demonstrated the effect of sulfur supplementation on human hair strength and hair cuticle structure. All types of oxidative stresses decreased the polysulfide in human hair, and hair polysulfide positively correlated with human hair strength. Intriguingly, sulfur supplementation improved human hair strength and the structure of hair cuticles. In conclusion, polysulfide in human hair keratin contributes to hair strength and antioxidant activity against oxidative stresses such as ultraviolet radiation and maintains hair homeostasis.

Facile and Efficient Enzymatic Methods for Harvesting or Removal of Cuticle Cells from Human Hair Shafts

ABSTRACT Human hair fibers are structurally organized as a cortex protected by an outer scaly sheath (cuticle). Developing methods to isolate these two compartments will help to elucidate their roles in hair biology and develop potential applications. Herein, we developed enzymatic methods for human hair cuticle cell harvesting or removal. After a single treatment with esperase for three days, cuticle cells were released from hair shafts and effectively harvested by a series of filtration, centrifugation, and resuspension steps. Separately, combining L-cysteine and either esperase or savinase could remove the entire cuticle layer to obtain descaled hair fibers. The physical and chemical structures, and performance of the isolated cuticle cells and descaled hair samples were characterized using electron microscopy, FTIR, solid state 13C NMR, TGA, and DSC. Results show that the harvested cuticle cells contain mainly β-sheets and random coil structures, while descaled hair samples contain more α-helical structures. Harvested cuticle cells have greater thermal stability than the descaled hair samples below 260°C. The enzymatic methods developed in this study are convenient and easily controlled. They are effective not just for cuticle cell harvesting but also for surface modification and structure disintegration of hair fibers.

Cuticle – Designed by nature for the sake of the hair

The cuticle of human hair has been examined, via a range of analytical methods, in order to reveal previously unknown information about its structure and to deepen understanding of its contribution to fibre properties. Cross-sections of hair fibre have been examined with X-ray microdiffraction oriented perpendicular to the surface of the cross-sections. AFM investigations were carried out for further investigating and deciphering the structure of the cuticle. Moisture sorption analytics of cuticle separated from fibre and mechanical tests of decuticled fibres against virgin fibres were used for understanding the role of the cuticle in the economy of hair fibre. Previously unknown swelling behaviour of the hair cuticle during moisture sorption has been revealed, as has an increased significance of the cuticle's role in moisture management at higher values of relative humidity. Through AFM investigation, the reaction of hair cuticles with chlorine water has further strengthened the idea that the Allwörden membrane does not exist, and is actually an artefact of the delamination of the A-layer and exocuticle from the underlying endocuticle. Using decuticled fibres for stress-strain tests, and by comparing the results with those of virgin fibres, the effect of the cuticle on the post-yield area of the hair fibre stress-strain diagram has also been demonstrated. Finally, X-ray microdiffraction and AFM investigations suggest that the cuticle possesses a small-scale ordered structure, based on possibly not fully crystalline and irregularly arranged α-helices oriented almost perpendicular to the growth axis of the fibre and enhancing the general description of cuticle as the protective layer of the fibre. The role of the cuticle for the hair fibre is more complex than previously thought. The cuticle is demonstrated not only to possess a hidden rod-matrix structure, that supports its protective nature, but also to play specific roles in the fibre's response to moisture, and in fibre mechanical behaviour.

Nanoscale Molecular Characterization of Hair Cuticle Cells Using Integrated Atomic Force Microscopy-Infrared Laser Spectroscopy.

The hair cuticle provides significant protection from external sources, as well as giving rise to many of its bulk properties, e.g., friction, shine, etc. that are important in many industries. In this work, atomic force microscopy-infrared spectroscopy (AFM-IR) has been used to investigate the nanometer-scale topography and chemical structure of human hair cuticles in two spectral regions. AFM-IR combines atomic force microscopy with a tunable infrared laser and circumvents the diffraction limit that has impaired traditional infrared spectroscopy, facilitating surface-selective spectroscopy at ultra-spatial resolution. This high resolution was exploited to probe the protein secondary structures and lipid content, as well as specific amino acid residues, e.g., cystine, within individual cuticle cells. Characterization across the top of individual cells showed large inhomogeneity in protein and lipid contributions that suggested significant changes to physical properties on approaching the hair edge. Additionally, the exposed layered sub-structure of individual cuticle cells allowed their chemical compositions to be assessed. The variation of protein, lipid, and cystine composition in the observed layers, as well as the measured dimensions of each, correspond closely to that of the epicuticle, A-layer, exocuticle, and endocuticle layers of the cuticle cell sub-structure, confirming previous findings, and demonstrate the potential of AFM-IR for nanoscale chemical characterization within biological substrates.

On the Strength of Hair across Species

Summary The hair of mammals varies in diameter across species from ∼60 μm in humans to over ∼400 μm in giraffes and elephants. Here, we establish that the tensile strength of hair generally decreases with increasing diameter. Although there is a commonality in the morphology of the hair in such differing species as they all possess a cortex surrounded by cuticles, there are also significant differences in the hierarchical structure that contribute to the observed differences in strength. In this work, the internal structure of the hair from different species is examined, with some unique peculiarities in javelina and capybara hair uncovered. The dimensional dependence of hair strength is compared using Weibull predictions. The good correlation of the strength of hair using such Weibull analysis suggests that the failure strength is dictated by the probability distribution of flaws within the cortex.

Evolution of S100A3 and PAD3, two important genes for mammalian hair

Hair is one of the defining characteristics of mammals. The hair shaft has a two-layer structure comprising the cortex, which is the inner layer and is composed of cortical cells, and the cuticle, which is the outermost layer. S100 calcium-binding protein A3 (S100A3) is expressed at high levels in the human hair cuticle. Arginine 51 of S100A3 protein is citrullinated specifically by peptidylarginine deiminase 3 (PAD3), and this citrullination is related to maturation of the cuticle. However, the detailed evolutionary processes of S100A3 and PAD3 during mammalian evolution are unknown. Here, we show that nonsynonymous changes in S100A3 accelerated in the common ancestral branch of mammals, probably as a result of positive selection that returned after the acquisition of hair cuticle–specific function in mammals. Later, pseudogenisation or nonfunctionalisation of S100A3 and PAD3 occurred in some species, such as the cetaceans. Our results show that positive selection and relaxation of the functional constraints of genes played important roles in the evolution of mammalian hair.

Hair Loss Management

95% of hair loss in men is caused by Androgenetic Alopecia. Major causes of hair loss are Stress, Pollution, Lack of nutrition, Illness, Alcohol, Smoking, Effluvium. For hair loss should we take oral drugs or apply topically on hair? It’s a big question for all of us. Before discussion we need to know the Hair Constituents: Human hair consists of approximately 65 % to 95 %protein. Besides cystine, human hair cuticle contains cysteic acid, proline, thereonine, isoleucine, methionine, leucine, tyrosine, phenylalanine in quite high proportion. The remaining constituents are water, lipid, pigment & trace elements that are not free but bound with protein or fatty acids side chain. So…? Consumed food products should contain; PROTEIN, LIPID, WATER and TRACE ELEMENTS. For direct impact on structure, growth and keeping hair shiny and healthy. Standard value proteins containing Sulphur amino acids: Cysteine & Methionine as precursor to keratin hair protein Synthesis are basic element of diet conditioning of hair building.

WITHDRAWN: SEM/SDD-EDS—An analytical tool to identify water borne micro minerals pick up in human scalp hair cuticle due to water quality

Abstract Water borne micro minerals calcium and aluminium pick up in human scalp hair cuticle and its change due to water quality and or the influence of hair care substances were identified using Scanning Electron Microscope/Silicon Drift Detector-Energy Dispersive X-ray spectrometry (SEM/SDD-EDS ) , a non-digestive and a non destructive method. Scalp hair obtained from four male volunteers, two each from urban and rural area respectively were used for this study where water quality supply to homes representing treated and untreated water supply as a reference. Water borne elements calcium and aluminium in the hair cuticle was significant and showed a clear trend among volunteers of urban and rural. Estimated pick up in concentration of calcium and aluminium are ascribed due to untreated ground water used directly in rural homes combined with oxidative damage caused due to periodic application of hair colouring substances and usage of uncontrolled aluminium containing coagulants/flocculants in treated water supply to urban homes respectively. Application of coconut oil on the scalp hair practised by a rural volunteer before hair wash and subsequent SEM/SDD-EDS analysis showed lower calcium pick up. Thus SEM/SDD-EDS is one of the suitable techniques to estimate concentration of water borne minerals in scalp hair cuticle.

A highly resistant structure between cuticle and cortex of human hair.

To clarify the presence and properties of a unique structure which is located between the cuticle and cortex of human hair. Whole hair fibre and longitudinally split hair were used. Treated with a mixture of urea, reductant and alkaline, hair was split at the interface between cuticle and cortex. The residues in the solution were observed by microscope, and the distribution of lipids and protein was determined. From the treated longitudinally split hair, a membrane-like structure which was located at the interface between cuticle and cortex was obtained. This structure showed especially high resistance against chemical treatment and was thought to be the region into which the proximal roots of the cuticle cells are embedded. It was supposed that some steryl glucoside-like lipid, of which the presence in the cuticle and cortex interface was previously reported, is located in this structure. This study proposed the presence of a membrane-like structure, which is highly resistant against chemical treatment, at the region between cuticle and cortex of human hair. This may protect cortex from external stimuli more firmly than the surface part of cuticle.

Morphological degradation of human hair cuticle due to simulated sunlight irradiation and washing

Morphological changes in hair surface are undesirable, since they cause shine loss, roughness increase and split ends. These effects occur more frequently in the cuticle, which is the outermost layer of the hair strand, and thus the most exposed to the environmental damages. Sunlight irradiation contributes significantly to these morphological alterations, which motivates the investigation of this effect on hair degradation. In this work, the influence of irradiation and hand-washing steps on the morphology of pigmented and non-pigmented hair cuticle was investigated using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). To simulate daily conditions, where hair is hand-washed and light exposed, samples of dark brown and gray hair underwent three different conditions: 1) irradiation with a mercury lamp for up to 600h; 2) irradiation with the mercury lamp combined with washes with a sodium lauryl sulphate solution; and 3) only washing. A new preparation procedure was applied for TEM samples to minimize natural variations among different hair strands: a single hair strand was cut into two neighbouring halves and only one of them underwent irradiation and washing. The non-exposed half was used as a control, so that the real effects caused by the controlled irradiation and washing procedures could be highlighted in samples that had very similar morphologies initially. More than 25images/sample were analysed using FESEM (total of 300 images) and ca. 150images/sample were obtained with TEM (total of 900 images). The results presented herein show that the endocuticle and the cell membrane complex (CMC) are the cuticle structures more degraded by irradiation. Photodegradation alone results in fracturing, cavities (Ø≈20–200nm) and cuticle cell lifting, while the washing steps were able to remove cuticle cells (≈1–2 cells removed after 60 washes). Finally, the combined action of irradiation and washing caused the most severe damages, resulting in a more pronounced cuticle extraction (≈1–4 cuticle cells after a 600h irradiation and a 60 times washing). This irradiation dose corresponds to ca. 2months of sunlight exposure (considering 5h/day) in Campinas-SP, Brazil, during the day period of maximum irradiation intensity. The combined action of irradiation and washing can be explained by the creation of fragile photodegraded spots in the endocuticle and in the CMC, where the mechanical stress associated to the washing steps are more prone to induce rupture.

Age-dependent damage of hair cuticle: contribution of S100A3 protein and its citrullination.

There are two types of damage pattern of human hair cuticle: type L, where the cell membrane complex is split and the cuticle lifts up, and type E, where the fragile substructure of the cuticle cell (endocuticle) is broken. In our previous paper, it was reported that the dominant damage pattern shifts from type L to E with the subjects' age around the 40s. Loss of the cuticle due to daily grooming stresses increases with the subjects' age and is related to the level of type E damage. It is supposed that deterioration of endocuticle advances the loss of cuticle. S100A3 protein, located at the endocuticle, was found to be citrullinated and transformed into tetramer to improve its Ca(2+) -binding ability. It is postulated that this biochemical property affects the maturation of cuticle and contributes to its reinforcement. This study aims to elucidate the role that S100A3 plays in age-dependent cuticle damage. Hair fibers collected from Japanese females were evaluated for the content and citrullination rate of S100A3, incidence of type E damage, and resistance of cuticle. In the aged hair, the content of S100A3 was positively correlated with the level of type E damage and low resistance to stress. Hair fibers in which S100A3 is highly citrullinated, however, showed low levels of type E damage and high resistance of cuticle, even in the aged hair as well as at younger ages. S100A3 and its citrullination process are related to rigidity of endocuticle of aged hair.

Age-dependent changes in damage processes of hair cuticle.

Human hair cuticle is always exposed to various stresses and then gradually lost in daily life. There are two typical patterns of cuticle damage: type L, where the cell membrane complex, the structure located between cuticle cells, is split and the cuticle lifts up, and type E, where the fragile substructure of the cuticle cell (endocuticle) is damaged so that its rugged residue is exposed. We previously reported that type L damage preferentially occurs in the case of Japanese females in their 20s to 40s. This study aims to elucidate the age-dependent change of cuticle and its effect on hair properties. Hair fibers collected from Japanese females (ranging from 10 to 70years old) were evaluated in the aspects of inclination for each type of damage, resistance of cuticle against grooming stresses and content of fatty acid 18-MEA on hair surface. It was revealed that the dominant damage pattern shifts from type L to E with aging. Furthermore, the cuticle becomes gradually less resistant to daily grooming stress. The dominance of type E damage accelerates cuticle loss. Reduction of 18-MEA on weathered hair is accelerated with aging on elder hair. It has been reported that various age-dependent changes of whole hair shaft, such as diameter, density, elasticity, etc., occur in the age range of 40s and 50s. In this study, it was revealed that cuticle becomes more fragile and the hair surface properties deteriorate in the same age range.

Topographical and Tribological Characteristics of Asian Human Hair Cuticles

The topography and frictional force of Asian black male and female hair cuticles at different locations are determined using atomic force microscopy (AFM) and friction force microscopy (FFM). The frictional values, mapped for comparison with surface morphology, corresponded qualitatively with the structures’ plane surface characteristics. The results indicate that the hair surface was damaged and modified at different temperatures and heating times. The height of the female hair at a blowing temperature of 60°C after a duration of 2 min between the cuticle edge and cuticle surface was approximately 440–556 nm. The adhesion phenomenon occurs on the hair surface and interface. The cuticles do not vary after the heating; however, the hair damage sustained increases with serious deterioration.

Investigation of dyeing behavior of oxidative dye in fine structures of the human hair cuticle by nanoscale secondary ion mass spectrometry.

In oxidative coloring, the hair cuticle layers are not only the penetration pathway for active ingredients but also one of the most important dyeing regions. The dyeing mechanism of oxidative dyes in fine structures of the cuticle remains unclear. To investigate the dyeing behavior of oxidative dyes in fine structures of the cuticle, hair cross-sections were analyzed by nanoscale secondary ion mass spectrometry (NanoSIMS). The preparation method of hair cross-section for NanoSIMS measurement was improved. Improved hair cross-sections were analyzed using NanoSIMS. The cuticle layer thickness of the hair cross-section could be widened. It was confirmed that (12) C(-) ions were more strongly detected from endocuticle than from other fine structures of cuticle. The NanoSIMS (12) C(-) image and hue saturation intensity (HSI) D(-) /(1) H(-) ratio image of the hair, dyed with deuterium-labeled oxidative dye, indicated that the endocuticle had a higher D(-) /(1) H(-) ratio than the other fine structures of the cuticle. It was substantiated that more colored chromophores were fixated in the endocuticle than in other fine structures of the cuticle. The dyeing behavior of oxidative dyes in fine structures of hair cuticle was substantiated by NanoSIMS analysis using the improved hair cross-section preparation method.

Distribution and localization of hydrophobic and ionic chemical groups at the surface of bleached human hair fibers.

A chemical mapping with high lateral resolution using an atomic force microscope in the pulsed force mode with chemically modified tips, introduced as "dynamic chemical force microscopy" (dCFM), was carried out to investigate the chemical properties of the cuticle of human hair and its changes following an oxidative treatment. Chemically modified atomic force microscopy (AFM) tips, CH3- and NH2-terminated, were applied to achieve a defined chemical contrast (hydrophobic and ionic) in aqueous medium. A comparative Fourier transform infrared spectroscopy-attenuated total reflection identified the dominant chemical groups of the surface vicinity of the hair fiber resulting from the bleaching process. The combined experimental results lead to the conclusion that the hydrophobic top layer is partially removed after bleaching, resulting mostly in hydrophilic SO3(-) end groups at the top of the surface of the hair, with a mean surface density "δ(mean)" of negatively charged groups of approximately 2.2 molecules/nm(2), corresponding to ∼600 μg/m(2) cysteic acid. This indicates that thioester bonds are disrupted and fatty acids are removed as a result of cysteine oxidation. At the molecular level, our results indicate a clustered "self-assembled monolayer" alignment of cysteic acid with a crystal-like structuring, reminiscent of the "fluid mosaic model of cell membranes", with a surface energy of approximately 0.04 N/m. Despite previous extensive works of AFM on human hair, this is, to our knowledge, the first time that the hydrophobic and ionic sites at the top surface of hair have been imaged at the nanoscale with dCFM.

AFM friction and adhesion mapping of the substructures of human hair cuticles

Using atomic force microscopy, values of the microscale friction coefficient, the tip (silicon nitride) - surface adhesion force and the corresponding adhesion energy, for the substructures that constitute the surface of human hair (European brown hair) have been determined from Amonton plots. The values, mapped for comparison with surface topography, corresponded qualitatively with the substructures’ plane surface characteristics. Localised maps and values of the frictional coefficient, extracted avoiding scale edge effects, are likely to inform the formulation of hair-care products and treatments.

Analysis of internal structure changes in black human hair keratin fibers resulting from bleaching treatments using Raman spectroscopy

In order to investigate in detail the internal structure changes in virgin black human hair keratin fibers resulting from bleaching treatments, the structure of cross-sections at various depths of black human hair, which had been impossible due to high melanin grande content, was directly analyzed using Raman spectroscopy. The gauche–gauche–gauche (GGG) content of the SS groups existing from the cuticle region to the center of cortex region of the virgin black human hair remarkably decreased, while the gauche–gauche–trans and trans–gauche–trans contents were not changed by performing the excessive bleaching treatment. In particular, it was found that not only the β-sheet and/or random coil content, but also the α-helix content existing throughout the cortex region of virgin black human hair decreased. In addition, the transmission electron microscope observation shows that the proteins in the cell membrane complex, the cuticle and cortex of the virgin black human hair were remarkably eluted by performing the excessive bleaching treatment. From these experiments, the author concluded that the SS groups, which have a GGG conformation were decomposed and finally converted to cysteic acid, and the α-helix structure of some of the proteins existing in the keratin was changed to the random coil structure, or eluted from the cortex region, thereby leading to the reduction in the protein density of the virgin human hair after the excessive bleaching treatment.

Resistance of human hair cuticle after a shaking process in wet conditions: comparison between Chinese and Caucasian hair

Hair cuticle is the first protection shield of hair against external aggressions such as daily combing or brushing that induce friction, mechanical stress leading to ageing process. The identification of alterations of the hair surface induced by shaking process of various hair fibres, such as virgin and chemically treated Chinese and Caucasian hair, sheds some light on some specific features, e.g. Chinese cuticle is torn out in smaller particles than Caucasian, which seems to be related to geometrical rather than ethnic reasons. The present work also shows that two geometrical parameters of human hair, the inter-scale distance and the scale angle are directly linked to fibre dimensions, regardless of ethnic origin. Representative of hair with an average larger cross-sectional area, Chinese hair shows a slightly smaller inter-scale distance as well as a higher scale angle. On the other hand, Chinese hair cuticle seems to be more sensitive to chemical treatment than Caucasian hair, at least for straightening treatment taken here as an example. Such an approach can be of interest in designing cosmetic products more suited to specific needs of human hair.

Laser capture microscopy in a study of expression of structural proteins in the cuticle cells of human hair

The cuticle of human hair consists of several layers of flat cells that are hardened through their content of cross-linked proteins and protect the hair structure from the environment. Known proteins in the cuticle are the sulphur-rich KAP 5 and KAP10 proteins located in the exocuticle and cross-linked by disulphide bonds. Isopeptide bonds are also present and led to a proposal from amino acid analysis that the surface of cuticle cells also contains keratinocyte cell envelope proteins, loricrin, involucrin and small proline-rich proteins that contribute to the stability of the hair cuticle. Confirmation of that proposal by protein chemical methods is difficult because of the insolubility of the surface membranes. In the previous studies by other authors, involucrin was not detected in the cuticle by in situ hybridization or by immunoelectron microscopy with specific antibodies. An alternative approach was undertaken to determine whether mRNAs encoding keratinocyte envelope proteins are expressed in cuticle cells in the human hair follicle. The study utilized dissection of the cuticle, cortex and inner root sheath layers from follicles by laser capture microscopy. RNA was isolated and subjected to PCR analysis with specific primers to detect expression of mRNAs encoding cell envelope proteins. Their presence in the cuticle was not detected, and it was concluded that the proteins they encode are not produced. The structural consequences including the possibility that KAPs 5 and 10 are the prime components cross-linked by both disulphide and isopeptide bonds are discussed.

Structural analysis of the cell membrane complex in the human hair cuticle using microbeam X‐ray diffraction: relationship with the effects of hair dyeing

This article deals with the structure of the cell membrane complex (CMC) in the human hair cuticle. The microbeam X-ray provided a pattern of small-angle scattering from the CMC in the cuticle with no sample preparations, including slicing and pre-staining of hair. The thickness of the beta- and delta-layers, substructure in CMC, was estimated by analysis of the scattering pattern. We used hair samples extracted with several solvents, and found that solvent extraction changed the thickness of the beta- and delta-layers in a manner dependent on the type of solvent. Extraction of hair with solvent was also shown to have effects on the extent of dyeing. There was a high correlation between the extent of dyeing and the thickness of the delta-layer, i.e., a thin layer tended to show a high amount of dyeing, whereas there was no significant correlation between the thickness of the beta-layer and the extent of dyeing.