Hair growth disorders often carry a major psychological burden. Therefore, more effective human hair growth–modulatory agents urgently need to be developed. Here, we used the hypertrichosis-inducing immunosuppressant, Cyclosporine A (CsA), as a lead compound to identify new hair growth–promoting molecular targets. Through microarray analysis we identified the Wnt inhibitor, secreted frizzled related protein 1 (SFRP1), as being down-regulated in the dermal papilla (DP) of CsA-treated human scalp hair follicles (HFs) ex vivo. Therefore, we further investigated the function of SFRP1 using a pharmacological approach and found that SFRP1 regulates intrafollicular canonical Wnt/β-catenin activity through inhibition of Wnt ligands in the human hair bulb. Conversely, inhibiting SFRP1 activity through the SFRP1 antagonist, WAY-316606, enhanced hair shaft production, hair shaft keratin expression, and inhibited spontaneous HF regression (catagen) ex vivo. Collectively, these data (a) identify Wnt signalling as a novel, non–immune-inhibitory CsA target; (b) introduce SFRP1 as a physiologically important regulator of canonical β-catenin activity in a human (mini-)organ; and (c) demonstrate WAY-316606 to be a promising new promoter of human hair growth. Since inhibiting SFRP1 only facilitates Wnt signalling through ligands that are already present, this ‘ligand-limited’ therapeutic strategy for promoting human hair growth may circumvent potential oncological risks associated with chronic Wnt over-activation.

Abstract:The cell cycle is of major importance to human hair follicle (HF) biology. Not only is continuously active cell cycling required to facilitate healthy hair growth in anagen VI HFs, but perturbations in the cell cycle are likely to be of significance in HF pathology (i.e. in scarring, non-scarring, chemotherapy-induced and androgenic alopecias). However, cell cycle dynamics of the human hair follicle (HF) are poorly understood in contrast to what is known in mouse. The current Methods Review aims at helping to close this gap by presenting a primer that introduces immunohistological/immunofluorescent techniques to study the cell cycle in the human HF. Moreover, this primer encourages the exploitation of the human HF as a powerful and clinically relevant tool to investigate mammalian cell cycle biology in situ. To achieve this, we describe methods to study markers of general 'proliferation' (nuclei count, Ki-67 expression), apoptosis (terminal deoxynucleotidyl transferase dUTP nick-end labelling, cleaved caspase 3), mitosis (phospho-histone H3, 'pS780'), DNA synthesis (5-ethynyl-2 0 -deoxyuridine) and cell cycle regulation (cyclins) in the human HF. In addition, we provide specific examples of dual immunolabelling for instructive cell cycle analyses and for investigating the cell cycle behaviour of specific HF keratinocyte subpopulations, such as keratin 15+ stem/ progenitor cells.

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Summary Background The signals that induce anagen (growth) in ‘quiescent’ human telogen hair follicles (HFs) are as yet unknown. Their identification promises better targeted therapeutic hair growth interventions. Objectives Recognizing the central role of Wnt signalling in hair biology, the aim was to delineate the differential expression of key agonists, antagonists and target genes of this pathway during the telogen‐to‐anagen transformation of human scalp HFs. Methods This differential expression was studied by in situ hybridization in human telogen and early‐anagen scalp HF sections. Results On anagen induction, gene expression of the Wnt ligands WNT3, WNT4 and WNT10B, the Wnt ligand secretion regulator WLS, and the Wnt target genes AXIN2 and LEF1, is significantly increased within the secondary hair germ and the dermal papilla. Conversely, expression of the secreted Wnt inhibitor SFRP1 (secreted frizzled‐related protein 1) is reduced. Human epithelial HF stem cells upregulate WNT4 and WNT10A expression, suggesting that these Wnt agonists are important for stem cell activation. Conclusions We provide the first evidence that key changes in Wnt signalling that drive murine anagen induction also occur in human scalp HFs, yet with notable differences. This provides a rational basis for Wnt‐targeting therapeutic interventions to manipulate human hair growth disorders. What's already known about this topic? Upregulation of Wnt agonists and downregulation of Wnt antagonists in the secondary hair germ and/or dermal papilla drives hair growth (anagen) induction in mice. Autocrine Wnt signalling in murine epithelial hair follicle stem cells is required to maintain their stem cell function. Reduction of Wnt ligands or increased expression of Wnt antagonists induces dysregulation of the murine hair follicle cycle and causes alopecia. What does this study add? This study demonstrates for the first time that key Wnt pathway regulatory agonists, antagonists and target genes, are expressed in the human telogen‐to‐early‐anagen transformation. On human anagen induction the Wnt ligands WNT3, WNT4 and WNT10B are increased in the regenerating epithelium, whereas the Wnt antagonist, SFRP1 (secreted frizzled‐related protein 1), is reduced. Human anagen induction has fundamental differences in the expression of Wnt ligands compared with the murine system. What is the translational message? Regulation of these Wnt ligands permits targeted therapeutic interventions in human hair growth disorders and informs development of new drugs that promote or suppress anagen induction.

Objectives. Solar ultraviolet radiation (UVR) has major adverse effects on human health. While the mechanisms responsible for induction of UVR-induced inflammation are well-documented, the mediation of its resolution and longer-term adaptive homeostasis is unknown. Therefore, we examined the skin immune and lipid profile over time following UVR inflammation. Methods. To investigate the self-resolving events of UVR inflammation in vivo, human skin was exposed to a single pro-inflammatory dose of UVR. Skin biopsies and suction blister fluid were taken at intervals up to 2 weeks post-UVR. The immune infiltrate was quantified by immunohistochemistry, and lipid mediators were profiled by liquid chromatography/mass spectrometry. Results. We identified that cellular resolution events including switching of macrophage phenotype apply to human sunburn. However, UVR-induced inflammation in humans involves a post-resolution phase that differs from other experimental models. We demonstrate that 2 weeks after the initiating UVR stimulus, there is considerable immune activity with CD8 + GATA3 + T cells maintained in human skin. Our results challenge the dogma of CD4 + FOXP3 + T cells being the main effector CD4 + T-cell population following UVR, with CD4 + GATA3 + T cells the dominant phenotype. Furthermore, lipid mediators are elevated 14 days post-UVR, demonstrating the skin lipid microenvironment does not revert to the tissue setting occurring prior to UVR exposure. Conclusion. We have identified for the first time that CD4 + GATA3 + and CD8 + GATA3 + T-cell subpopulations are recruited to UVR-inflamed human skin, demonstrating discrepancies between the adaptive UVR response in mice and humans. Future strategies to abrogate UVR effects may target these T-cell subpopulations and also the persistent alteration of the lipid microenvironment post-UVR.

Solar ultraviolet radiation (UVR) is a major source of skin damage, resulting in inflammation, premature ageing and cancer. While several UVR-induced changes, including extracellular matrix reorganisation and epidermal DNA damage, have been documented, the role of different fibroblast lineages and their communication with immune cells has not been explored. We show that acute and chronic UVR exposure led to selective loss of fibroblasts from the upper dermis in human and mouse skin. Lineage tracing and in vivo live imaging revealed that repair following acute UVR is predominantly mediated by papillary fibroblast proliferation and fibroblast reorganisation occurs with minimal migration. In contrast, chronic UVR exposure led to a permanent loss of papillary fibroblasts, with expansion of fibroblast membrane protrusions partially compensating for the reduction in cell number. Although UVR strongly activated Wnt-signalling in skin, stimulation of fibroblast proliferation by epidermal b-catenin stabilisation did not enhance papillary dermis repair. Acute UVR triggered an infiltrate of neutrophils and T cell subpopulations and increased pro-inflammatory prostaglandin signalling in skin. Depletion of CD4 and CD8 positive cells resulted in increased papillary fibroblast depletion, which correlated with an increase in DNA damage, pro-inflammatory prostaglandins and reduction in fibroblast proliferation. Conversely, topical COX-2 inhibition prevented fibroblast depletion and neutrophil infiltration after UVR. We conclude that loss of papillary fibroblasts is primarily induced by a deregulated inflammatory response, with infiltrating T cells supporting fibroblast survival upon UVR-induced environmental stress.

Prevalence, correlates and clinical usefulness of antibodies to RNA polymerase III in systemic sclerosis: a cross-sectional analysis of data from an Australian cohort.

Summary Individual hairs grow from follicles which go through a cycle of different stages. During ‘anagen’ the hair is actively growing, in ‘catagen’ the follicle shrinks, while ‘telogen’ is the resting phase when the hair sheds before the next anagen. Abnormal hair growth usually reflects an abnormal hair cycle. For example, failure to re‐enter anagen from telogen, or short duration of anagen, cause poor hair growth, while excessive switching from telogen back to anagen causes excessive hair. If we could understand what controls these stages, it might be possible to develop effective treatments. Previously, scientists have managed to grow individual human anagen hair follicles in the laboratory but could only study the switch from anagen to catagen. The authors of this latest study, from the UK, Spain, Germany and the USA, managed for the first time to isolate human telogen and early anagen hairs. They used scalp samples from five men undergoing hair transplantation and dissected out the relevant hairs under the microscope. Using specific antibodies (a type of protein in the body) to examine telogen follicles they discovered that a group of genes called the WNT pathway induce anagen by prompting certain cells in the hair germ (part of the follicle) to multiply. By studying a whole range of proteins that switch WNT processes on or off they were able to build up a picture of events occurring at the start of anagen which will help future scientists to develop targeted treatments for hair disorders. This is a summary of the study: Deciphering the molecular morphology of the human hair cycle: Wnt signalling during the telogen–anagen transformation.