Hair keratin pattern in human hair follicles grown in vitro

Incorporation of hair follicles in 3D bioprinted models of human skin

Current approaches fail to adequately introduce complex adnexal structures such as hair follicles within tissue engineered models of skin. Here, we report on the use of 3D bioprinting to incorporate these structures in engineered skin tissues. Spheroids, induced by printing dermal papilla cells (DPCs) and human umbilical vein cells (HUVECs), were precisely printed within a pregelled dermal layer containing fibroblasts. The resulting tissue developed hair follicle-like structures upon maturation, supported by migration of keratinocytes and melanocytes, and their morphology and composition grossly mimicked that of the native skin tissue. Reconstructed skin models with increased complexity that better mimic native adnexal structures can have a substantial impact on regenerative medicine as grafts and efficacy models to test the safety of chemical compounds.

How different is human hair? A critical appraisal of the reported differences in global hair fibre characteristics and properties towards defining a more relevant framework for hair type classification

This review critically appraises the reported differences in human hair fibre within three related domains of research: hair classification approaches, fibre characteristics and properties. The most common hair classification approach is based on geo-racial origin, defining three main groups: African, Asian and Caucasian hair. This classification does not account sufficiently for the worldwide hair diversity and intergroups variability in curl, shape, size and colour. A global classification into eight curl types has been proposed but may be too complex for reproducibility. Beyond that, hair cross-sectional shape and area have been found to have an inverse relation to curl: straighter fibres are circular with larger cross-sectional area, whilst the curlier fibres are elliptical with smaller cross-sectional area. These geometrical differences have been associated with bilateral vs homogenous distribution of cortical cell in curly vs straight hair respectively. However, there is no sufficient data demonstrating significant differences in hair amino composition, but proteomic studies are reporting associations of some proteins with curly hair. Eumelanin's relative abundance has been reported in all hair colours except for red hair which has a high pheomelanin content. Higher tensile and fatigue strength of straight hair are reported, however, curly hair fragility is attributed to knotting, and crack and flow formations rather than the structural variations. African hair has been found to have the highest level of lipids, whilst the water sorption of Caucasian hair is the highest, and that of Asian hair the lowest. Not all comparative studies clearly report their hair sampling approaches. Therefore, to strengthen the robustness of comparative studies and to facilitate cross-study data comparisons, it is recommended that the following hair defining characteristics are reported in studies: hair cross sectional diameter/area, curl type, hair assembly colour, as well as where possible donor data (age/gender) and sample pooling approach.

Talquetamab, a T-Cell-Redirecting GPRC5D Bispecific Antibody for Multiple Myeloma

BACKGROUND

G protein-coupled receptor, family C, group 5, member D (GPRC5D) is an orphan receptor expressed in malignant plasma cells. Talquetamab, a bispecific antibody against CD3 and GPRC5D, redirects T cells to mediate killing of GPRC5D-expressing myeloma cells.

METHODS

In a phase 1 study, we evaluated talquetamab administered intravenously weekly or every other week (in doses from 0.5 to 180 μg per kilogram of body weight) or subcutaneously weekly, every other week, or monthly (5 to 1600 μg per kilogram) in patients who had heavily pretreated relapsed or refractory multiple myeloma that had progressed with established therapies (a median of six previous lines of therapy) or who could not receive these therapies without unacceptable side effects. The primary end points - the frequency and type of dose-limiting toxic effects (study part 1 only), adverse events, and laboratory abnormalities - were assessed in order to select the recommended doses for a phase 2 study.

RESULTS

At the data-cutoff date, 232 patients had received talquetamab (102 intravenously and 130 subcutaneously). At the two subcutaneous doses recommended for a phase 2 study (405 μg per kilogram weekly [30 patients] and 800 μg per kilogram every other week [44 patients]), common adverse events were cytokine release syndrome (in 77% and 80% of the patients, respectively), skin-related events (in 67% and 70%), and dysgeusia (in 63% and 57%); all but one cytokine release syndrome event were of grade 1 or 2. One dose-limiting toxic effect of grade 3 rash was reported in a patient who had received talquetamab at the 800-μg dose level. At median follow-ups of 11.7 months (in patients who had received talquetamab at the 405-μg dose level) and 4.2 months (in those who had received it at the 800-μg dose level), the percentages of patients with a response were 70% (95% confidence interval [CI], 51 to 85) and 64% (95% CI, 48 to 78), respectively. The median duration of response was 10.2 months and 7.8 months, respectively.

CONCLUSIONS

Cytokine release syndrome, skin-related events, and dysgeusia were common with talquetamab treatment but were primarily low-grade. Talquetamab induced a substantial response among patients with heavily pretreated relapsed or refractory multiple myeloma. (Funded by Janssen Research and Development; MonumenTAL-1 ClinicalTrials.gov number, NCT03399799.).

Hair Growth Promoting Effect of 4HGF Encapsulated with PGA Nanoparticles (PGA-4HGF) by β-Catenin Activation and Its Related Cell Cycle Molecules

Poly-γ-glutamic acid (γ-PGA)-based nanoparticles draw remarkable attention as drug delivery agents due to their controlled release characteristics, low toxicity, and biocompatibility. 4HGF is an herbal mixture of Phellinus linteus grown on germinated brown rice, Cordyceps militaris grown on germinated soybeans, Polygonum multiflorum, Ficus carica, and Cocos nucifera oil. Here, we encapsulated 4HGF within PGA-based hydrogel nanoparticles, prepared by simple ionic gelation with chitosan, to facilitate its penetration into hair follicles (HFs). In this study, we report the hair promoting activity of 4HGF encapsulated with PGA nanoparticles (PGA-4HGF) and their mechanism, compared to 4HGF alone. The average size of spherical nanoparticles was ~400 nm in diameter. Continuous release of PGA-4HGF was observed in a simulated physiological condition. As expected, PGA-4HGF treatment increased hair length, induced earlier anagen initiation, and elongated the duration of the anagen phase in C57BL/6N mice, compared with free 4HGF treatment. PGA-4HGF significantly increased dermal papilla cell proliferation and induced cell cycle progression. PGA-4HGF also significantly increased the total amount of β-catenin protein expression, a stimulator of the anagen phase, through induction of cyclinD1 and CDK4 protein levels, compared to free 4HGF treatment. Our findings underscore the potential of PGA nanocapsules to efficiently deliver 4HGF into HFs, hence promoting hair-growth. Therefore, PGA-4HGF nanoparticles may be promising therapeutic agents for hair growth disorders.

The biology and genetics of curly hair

Hair fibres show wide diversity across and within all human populations, suggesting that hair fibre form and colour have been subject to much adaptive pressure over thousands of years. All human hair fibres typically have the same basic structure. However, the three-dimensional shape of the entire fibre varies considerably depending on ethnicity and geography, with examples from very straight hair with no rotational turn about the long axis, to the tightly sprung coils of African races. The creation of the highly complex biomaterials in hair follicle and how these confer mechanical functions on the fibre so formed is a topic that remains relatively unexplained thus far. We review the current understanding on how hair fibres are formed into a nonlinear coiled form and which genetic and biological factors are thought to be responsible for hair shape. We report on a new GWAS comparing low and high curl individuals in South Africa, revealing strong links to polymorphic variation in trichohyalin, a copper transporter protein CUTC and the inner root sheath component keratin 74. This builds onto the growing knowledge base describing the control of curly hair formation.

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

The complex mechanical properties of biomaterials such as hair, horn, skin, or bone are determined by the architecture of the underlying fibrous bionetworks. Although much is known about the influence of the cytoskeleton on the mechanics of isolated cells, this has been less studied in tridimensional tissues. We used the hair follicle as a model to link changes in the keratin network composition and architecture to the mechanical properties of the nascent hair. We show using atomic force microscopy that the soft keratinocyte matrix at the base of the follicle stiffens by a factor of ∼360, from 30 kPa to 11 MPa along the first millimeter of the follicle. The early mechanical stiffening is concomitant to an increase in diameter of the keratin macrofibrils, their continuous compaction, and increasingly parallel orientation. The related stiffening of the material follows a power law, typical of the mechanics of nonthermal bending-dominated fiber networks. In addition, we used X-ray diffraction to monitor changes in the (supra)molecular organization within the keratin fibers. At later keratinization stages, the inner mechanical properties of the macrofibrils dominate the stiffening due to the progressive setting up of the cystine network. Our findings corroborate existing models on the sequence of biological and structural events during hair keratinization.

Testosterone regulates keratin 33B expression in rat penis growth through androgen receptor signaling

Androgen therapy is the mainstay of treatment for the hypogonadotropic hypogonadal micropenis because it obviously enhances penis growth in prepubescent microphallic patients. However, the molecular mechanisms of androgen treatment leading to penis growth are still largely unknown. To clarify this well-known phenomenon, we successfully generated a castrated male Sprague Dawley rat model at puberty followed by testosterone administration. Interestingly, compared with the control group, testosterone treatment stimulated a dose-dependent increase of penis weight, length, and width in castrated rats accompanied with a dramatic recovery of the pathological changes of the penis. Mechanistically, testosterone administration substantially increased the expression of androgen receptor (AR) protein. Increased AR protein in the penis could subsequently initiate transcription of its target genes, including keratin 33B (Krt33b). Importantly, we demonstrated that KRT33B is generally expressed in the rat penis and that most KRT33B expression is cytoplasmic. Furthermore, AR could directly modulate its expression by binding to a putative androgen response element sequence of the Krt33b promoter. Overall, this study reveals a novel mechanism facilitating penis growth after testosterone treatment in precastrated prepubescent animals, in which androgen enhances the expression of AR protein as well as its target genes, such as Krt33b.

Cornus officinalis Methanol Extract Upregulates Melanogenesis in Melan-a Cells

Cornus officinalis is widely distributed in Korea, and its fruit has been used to make as herbal drug for traditional medicine in Korea, Japan, and China because of its tonic, analgesic, and diuretic properties. However, the effects of C. officinalis methanol extract (COME) on melanogenesis remain poorly understood. We evaluated the melanogenic capability of COME in melan-a cells, which are immortalized mouse melanocytes. COME increased melanin synthesis in a dose-dependent manner. Treatment with 12.5 μg/mL of COME significantly increased melanin content by 36.1% (p < 0.001) to a level even higher than that (31.6%) of 3-isobutyl-1-methyl-xanthine, a well-known pigmentation agent. COME also upregulated tyrosinase activity and its messenger RNA and protein expression. In addition, COME upregulated the expression of tyrosinase-related proteins 1 and 2 and microphthalmia-associated transcription factor-M messenger RNA expression. These results imply that COME may be appropriate for development as a natural product to treat hair graying.

Hair curvature: a natural dialectic and review

Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways, and others, can explain many alternatives and specific variations of hair bending phenotypes. Mechanisms for hair papilla budding or its division by bisection or fission can explain MPC formation. Epithelial-to-mesenchymal (EMT) and mesenchymal-to-epithelial (MET) transitions, acting in collaboration with epithelial-mesenchymal communications are also considered as mechanisms affecting hair growth and its bending and twisting. These may be treated as sub-mechanisms of an overall development from neural-crest stem cell (NCSC) lineages to differentiated hair follicle (HF) cell types, thus providing a unified framework for hair growth and development.

The cycling hair follicle as an ideal systems biology research model

In the postgenomic era, systems biology has rapidly emerged as an exciting field predicted to enhance the molecular understanding of complex biological systems by the use of quantitative experimental and mathematical approaches. Systems biology studies how the components of a biological system (e.g. genes, transcripts, proteins, metabolites) interact to bring about defined biological function or dysfunction. Living systems may be divided into five dimensions of complexity: (i) molecular; (ii) structural; (iii) temporal; (iv) abstraction and emergence; and (v) algorithmic. Understanding the details of these dimensions in living systems is the challenge that systems biology aims to address. Here, we argue that the hair follicle (HF), one of the signature features of mammals, is a perfect and clinically relevant model for systems biology research. The HF represents a stem cell-rich, essentially autonomous mini-organ, whose cyclic transformations follow a hypothetical intrafollicular "hair cycle clock" (HCC). This prototypic neuroectodermal-mesodermal interaction system, at the cross-roads of systems and chronobiology, encompasses various levels of complexity as it is subject to both intrafollicular and extrafollicular inputs (e.g. intracutaneous timing mechanisms with neural and systemic stimuli). Exploring how the cycling HF addresses the five dimensions of living systems, we argue that a systems biology approach to the study of hair growth and cycling, in man and mice, has great translational medicine potential. Namely, the easily accessible human HF invites preclinical and clinical testing of novel hypotheses generated with this approach.

Evaluation of cytotoxic properties of organometallic ferrocifens on melanocytes, primary and metastatic melanoma cell lines

Malignant melanoma is one of the most severe forms of skin cancer, and chemotherapeutic agents currently in use are poorly effective in curing the disease. Here we describe the properties of two organometallic ferrocenyl derivatives, ferrocifen (Fc-OH-Tam) and ferrociphenol (Fc-diOH) that show a specific antiproliferative effect on melanoma cells. After a short incubation period, Fc-OH-Tam is highly cytotoxic on melanoma cells but less toxic on melanocytes. Fc-diOH is slightly toxic at a high concentration but no discrepancy is observed between malignant and normal cells. After a long incubation time the latter is highly toxic for malignant cells but not for normal cells while the former was very highly toxic for primary malignant cells and significantly less toxic for normal cells. We also found that oxidative stress is not implicated in the mechanism of cytotoxicity, since both derivatives neither induce reactive oxygen species (ROS) level in melanocytes nor in melanoma cells. Finally, investigation on hair follicle growth revealed that the two organometallic derivatives induced an irreversible ejection of the hair shaft, thus predicting a potential hair loss side effect if used as a chemotherapeutic treatment.

Heparanase 1: a key participant of inner root sheath differentiation program and hair follicle homeostasis

Heparanase is a heparan sulphate endo-glycosidase which was previously detected in the outer root sheath of murine hair follicles. Heparanase overexpression was reported to improve mouse hair (re)growth. In this study, we investigated its involvement in human hair biology. Immunofluorescence detection was used to explore heparanase distribution in both anagen and catagen hair follicles. Heparanase functionality was assessed in in vitro cultured hair follicles, in the presence of a heparanase activity inhibitor. Our results showed that heparanase expression was (i) primarily located in the inner root sheath (IRS) of human hair follicle, and there (ii) restricted to anagen phase. Furthermore, inhibition of heparanase in in vitro cultured hair follicles induced a catagen-like process. Hair shaft retreat upward was accompanied by a decrease in Ki67-positive cells, the formation of an epithelial strand as evidenced by K14 keratin expression, and the loss of IRS as assessed by transglutaminase 1 and desmoglein labelling. IRS distribution of heparanase and the induction of catagen-like involution of hair follicles when a potent heparanase inhibitor is added suggest that heparanase is a key actor of IRS differentiation and hair homeostasis.

The effect of tripeptide-copper complex on human hair growth in vitro

The tripeptide-copper complex, described as a growth factor for various kinds of differentiated cells, stimulates the proliferation of dermal fibroblasts and elevates the production of vascular endothelial growth factor, but decreased the secretion of transforming growth factor-beta1 by dermal fibroblasts. Dermal papilla cells (DPCs) are specialized fibroblasts, which are important in the morphogenesis and growth of hair follicles. In the present study, the effects of L-alanyl-L-histidyl-L-lysine-Cu2+ (AHK-Cu) on human hair growth ex vivo and cultured dermal papilla cells were evaluated. AHK-Cu (10(-12) - 10(-9) M) stimulated the elongation of human hair follicles ex vivo and the proliferation of DPCs in vitro. Annexin V-fluorescein isothiocyanate/propidium iodide labeling and flow cytometric analysis showed that 10(-9) M AHK-Cu reduced the number of apoptotic DPCs, but this decrease was not statistically significant. The ratio of Bcl-2/Bax was elevated, and the levels of the cleaved forms of caspase-3 and PARP were reduced by treatment with 10(-9) M AHK-Cu. The present study proposed that AHK-Cu promotes the growth of human hair follicles, and this stimulatory effect may occur due to stimulation of the proliferation and the preclusion of the apoptosis of DPCs.

[The life of human hair follicle revealed]

The human hair follicle is a unique appendage which results from epithelio-mesenchymal interactions initiated around the 3rd month of development. This appendage has a very complex structure, with a dermal compartment and an epithelial compartment. The dermal compartment comprises the connective tissue sheath and the dermal papilla, both of which are irrigated by microvessels. The epithelial compartment is made of highly replicating matrix cells giving rise to three concentrical domains, namely the outer root sheath, the inner root sheath and the hair shaft. The pigmentation unit, responsible for hair color, is made of fully active melanocytes located on top of the dermal papilla. Altogether a hair follicle contains more than 20 different cell types, engaged in different differentiation pathways and/or interacting with each other. This complex appendage has a unique behavior in mammals since, after a hair production phase, it involutes in place before entering a resting phase after which it renews itself under a cyclical but stochastic way, out of a double reservoir of pluripotent stem cells able to also regenerate epidermis. For yet unknown reasons, this well ordered process can be disturbed, provoking alopecia. The pigmentation unit also renews itself under a cyclical way, out of a melanocyte progenitor reservoir which progressively declines with time, provoking the hair whitening process. Finally, the shape of the hair shaft is programmed from the bulb. What makes this appendage unique and fascinating is its high degree of autonomy, its incredibly complex though stable structure, the number of different cell types interacting under an equilibrated way and its potential of regeneration. It represents a true paradigm of tissue homeostasis, exemplifying in a small living cylinder all the fundamental laws of cell-cell and tissue interactions. This life is revealed in this short synthesis.

Novel Application of Layered Expression Scanning for Proteomic Profiling of Plucked Hair Follicles

BACKGROUND

There is a need for a technology that can quantitatively assay multiple proteins from a single hair follicle while preserving the morphology of the follicle. For proteomic profiling, the technology should be less labor intensive, with a higher throughput, more quantitative and more reproducible than immunohistochemistry.

OBJECTIVE

To test the ability of a novel method, layered expression scanning of hair (LES-hair) to detect the levels and localization of proteins in plucked hair follicles.

METHODS

LES-hair was used to assay proteins in the plucked hair follicle.

RESULTS

LES-hair detected differential expression of proteins within discrete regions of the plucked hair follicle. These proteins included cleaved caspase 3, Ki-67 and the phosphorylated forms of c-Kit, epidermal growth factor receptor and vascular endothelial growth factor receptor.

CONCLUSION

LES-hair provides a research tool for studying the basic biology of plucked hair follicles and has potential clinical applications such as monitoring treatment of alopecia or using plucked hair follicles as a surrogate tissue to monitor pharmacodynamic effects of targeted cancer therapies.

Human hair shape is programmed from the bulb

BACKGROUND

Few biological data on curly hair follicles have been reported in the literature.

OBJECTIVES

To investigate the growth and morphology of curly hair follicles.

METHODS

Follicles were dissected from scalp skin samples from African, Guyanese and caucasian volunteers and were observed macroscopically, in culture in William's E medium, and by immunohistochemistry.

RESULTS

Macroscopic study of scalp biopsies obtained from African volunteers showed that the dermal implantation of follicles was curved with a retrocurvature at the level of the bulb, as opposed to a straight shape in caucasian follicles. The bulb itself was bent, in the shape of a golf club, while both the outer root sheath (ORS) and the connective tissue sheath were dissymmetrical along the follicle. In vitro growth of curly hair follicles was slightly slower than that of caucasian follicles but, more importantly, the curvature was maintained in the hair shaft produced in vitro. As shown by immunohistochemistry, the proliferative matrix compartment of curly hair follicles was asymmetrical, Ki-67-labelled cells being more numerous on the convex side and extending above the Auber line. On the convex part of the follicle, the ORS was thinner and the differentiation programmes of the inner root sheath and hair shaft were delayed. Furthermore, some ORS cells expressed alpha-smooth muscle actin protein on the concave side of the curvature, reflecting a mechanical stress.

CONCLUSIONS

Hair curliness is programmed from the bulb and is linked to asymmetry in differentiation programmes.

Evo-Devo of amniote integuments and appendages

Integuments form the boundary between an organism and the environment. The evolution of novel developmental mechanisms in integuments and appendages allows animals to live in diverse ecological environments. Here we focus on amniotes. The major achievement for reptile skin is an adaptation to the land with the formation of a successful barrier. The stratum corneum enables this barrier to prevent water loss from the skin and allowed amphibian / reptile ancestors to go onto the land. Overlapping scales and production of beta-keratins provide strong protection. Epidermal invagination led to the formation of avian feather and mammalian hair follicles in the dermis. Both adopted a proximal - distal growth mode which maintains endothermy. Feathers form hierarchical branches which produce the vane that makes flight possible. Recent discoveries of feathered dinosaurs in China inspire new thinking on the origin of feathers. In the laboratory, epithelial - mesenchymal recombinations and molecular mis-expressions were carried out to test the plasticity of epithelial organ formation. We review the work on the transformation of scales into feathers, conversion between barbs and rachis and the production of "chicken teeth". In mammals, tilting the balance of the BMP pathway in K14 noggin transgenic mice alters the number, size and phenotypes of different ectodermal organs, making investigators rethink the distinction between morpho-regulation and pathological changes. Models on the evolution of feathers and hairs from reptile integuments are discussed. A hypothetical Evo-Devo space where diverse integument appendages can be placed according to complex phenotypes and novel developmental mechanisms is presented.