Transepidermal UV radiation of scalp skin ex vivo induces hair follicle damage that is alleviated by the topical treatment with caffeine.

OBJECTIVES: Although the effect of ultraviolet radiation (UVR) on human skin has been extensively studied, very little is known on how UVR impacts on hair follicle (HF) homeostasis. Here, we investigated how solar spectrum UVR that hits the human skin surface impacts on HF biology, and whether any detrimental effects can be mitigated by a widely used cosmetic and nutraceutical ingredient, caffeine. METHODS: Human scalp skin with terminal HFs was irradiated transepidermally ex vivo using either 10 J/cm2 UVA (340-440 nm) + 20 mJ/cm2 UVB (290-320 nm) (low dose) or 50 J/cm2 UVA + 50 mJ/cm2 UVB (high dose) and organ-cultured under serum-free conditions for 1 or 3 days. 0.1% caffeine (5.15 mmol/L) was topically applied for 3 days prior to UV exposure with 40 J/cm2 UVA + 40 mJ/cm2 UVB and for 3 days after UVR. The effects on various toxicity and vitality read-out parameters were measured in defined skin and HF compartments. RESULTS: Consistent with previous results, transepidermal UVR exerted skin cytotoxicity and epidermal damage. Treatment with high and/or low UVA+UVB doses also induced oxidative DNA damage and cytotoxicity in human HFs. In addition, it decreased proliferation and promoted apoptosis of HF outer root sheath (ORS) and hair matrix (HM) keratinocytes, stimulated catagen development, differentially regulated the expression of HF growth factors, and induced perifollicular mast cell degranulation. UVR-mediated HF damage was more severe after irradiation with high UVR dose and reached also proximal HF compartments. The topical application of 0.1% caffeine did not induce skin or HF cytotoxicity and stimulated the expression of IGF-1 in the proximal HF ORS. However, it promoted keratinocyte apoptosis in selected HF compartments. Moreover, caffeine provided protection towards UVR-mediated HF cytotoxicity and dystrophy, keratinocyte apoptosis, and tendential up-regulation of the catagen-promoting growth factor. CONCLUSION: Our study highlights the clinical relevance of our scalp UV irradiation ex vivo assay and provides the first evidence that transepidermal UV radiation negatively affects important human HF functions. This suggests that it is a sensible prophylactic strategy to integrate agents such as caffeine that can act as HF photoprotectants into sun-protective cosmeceutical and nutraceutical formulations.

OBJECTIFS: Alors que l'effet de rayons ultraviolets (RUV) sur la peau humaine a été largement étudié, on sait très peu de choses de l'impact des UV sur l'homéostasie du follicule pileux (FP). Ici, nous avons étudié l'effet du spectre des RUV solaires qui atteignent la surface de la peau humaine sur la biologie du FP, et si tout effet nocif peut être atténué par de la caféine, un ingrédient cosmétique et neutraceutique largement utilisé. MÉTHODES: Une peau de cuir chevelu humain avec ses FP terminaux a été irradiée ex vivo via l'épiderme soit par 10 J/cm2 d'UVA (340-440 nm) + 20 mJ/cm2 d'UVB (290-320 nm) (dose faible) soit par 50 J/cm2 d'UVA + 50 mJ/cm2 d'UVB (dose élevée) et placée en culture sans sérum pendant 1 ou 3 jours. 0,1% (5,15 mM) de caféine a été appliquée par voie topique pendant 3 jours avant l'exposition aux UV à raison de 40 J/cm2 d'UVA + 40 mJ/cm2 UVB et pendant 3 jours après l'exposition aux RUV. Les effets sur divers paramètres de toxicité et de vitalité ont été mesurés au niveau de compartiments définis de la peau et des FP. RÉSULTATS: Cohérent avec les résultats précédents, les RUV transépidermique ont exercé une cytotoxicité au niveau de la peau et des lésions épidermiques. Le traitement par des doses élevées et/ou faibles d'UVA+UVB a également induit des lésions oxydatives de l'ADN et une cytotoxicité au niveau des FP humains. En outre, il a diminué la prolifération et favorisé l'apoptose de la gaine externe de la racine (ORS) du FP et des kératinocytes de la matrice des cheveux (MC), a stimulé le développement de la phase catagène, a régulé de manière différentielle l'expression des facteurs de croissance des FP, et induit une dégranulation périfolliculaire des mastocytes. Les lésions du FP médiées par les RUV étaient plus graves après une irradiation par dose élevée de RUV et atteignaient également les compartiments proximaux du FP. L'application topique de 0,1 % de caféine n'a pas induit de cytotoxicité de la peau ou du FP et a stimulé l'expression d'IGF-1 dans la partie proximale de l'ORS du FP. Cependant, elle a promu l'apoptose des kératinocytes dans certains compartiments de FP. En outre, la caféine a fourni une protection des FP contre la cytotoxicité et la dystrophie médiées par les RUV, l'apoptose des kératinocytes et une régulation à tendance positive de l'effet catagène induit par le facteur de croissance. CONCLUSION: Notre étude souligne la pertinence clinique de notre dosage d'irradiation UV ex vivo du cuir chevelu et fournit la première preuve que le rayonnement UV transépidermique affecte négativement d'importantes fonctions du FP chez l'homme. Cela suggère que l'intégration d'agents photoprotecteurs des FP tels que la caféine dans les formulations cosmétiques et nutraceutiques des écrans solaires pourrait constituer une stratégie prophylactique sensée.

Nestin+ progenitor cells isolated from adult human sweat gland stroma promote reepithelialisation and may stimulate angiogenesis in wounded human skin ex vivo.

The combination of an aging population and an increasing prevalence of diseases associated with impaired-wound healing, including obesity, peripheral vascular disease and diabetes, is likely to result in a dramatic increase in the incidence and prevalence of chronic skin wounds. Indeed, systemic reviews are now not only trying to establish both the prevalence and the often under-estimated socio-economic costs of chronic skin wounds, but most importantly are addressing the impact that chronic wounds have on quality of life. Given the clear need for novel approaches to the management of chronic skin ulceration, ideally developed and tested in the human system in a manner that can be rapidly translated into clinical practice, we examined the effects of multipotent primary human nestin+ progenitor cells on human wound healing in an ex vivo model. Human sweat gland-derived nestin+ cells demonstrated the capacity to significantly promote two key wound healing parameters, i.e., both reepithelialisation and angiogenesis in experimentally wounded, organ-cultured human skin. The current data further support the use of full-thickness human skin wound-healing models ex vivo to pre-clinically test wound healing-promoting candidate agents. Whilst larger studies are required to substantiate a firm "proof-of-concept," our preliminary studies encourage further efforts to systemically determine the potential of cell-based regenerative medicine strategies in general, and the use of skin appendage-associated human nestin+ cells in particular, as novel treatment strategies for chronic skin ulceration.

Olfactory receptor OR2AT4 regulates human hair growth.

Olfactory receptors are expressed by different cell types throughout the body and regulate physiological cell functions beyond olfaction. In particular, the olfactory receptor OR2AT4 has been shown to stimulate keratinocyte proliferation in the skin. Here, we show that the epithelium of human hair follicles, particularly the outer root sheath, expresses OR2AT4, and that specific stimulation of OR2AT4 by a synthetic sandalwood odorant (Sandalore®) prolongs human hair growth ex vivo by decreasing apoptosis and increasing production of the anagen-prolonging growth factor IGF-1. In contrast, co-administration of the specific OR2AT4 antagonist Phenirat® and silencing of OR2AT4 inhibit hair growth. Together, our study identifies that human hair follicles can engage in olfactory receptor-dependent chemosensation and require OR2AT4-mediated signaling to sustain their growth, suggesting that olfactory receptors may serve as a target in hair loss therapy.

Splice variants of the endonucleases XPF and XPG contain residual DNA repair capabilities and could be a valuable tool for personalized medicine.

The two endonucleases XPF and XPG are essentially involved in nucleotide excision repair (NER) and interstrand crosslink (ICL) repair. Defects in these two proteins result in severe diseases like xeroderma pigmentosum (XP). We applied our newly CRISPR/Cas9 generated human XPF knockout cell line with complete loss of XPF and primary fibroblasts from an XP-G patient (XP20BE) to analyze until now uncharacterized spontaneous mRNA splice variants of these two endonucleases. Functional analyses of these variants were performed using luciferase-based reporter gene assays. Two XPF and XPG splice variants with residual repair capabilities in NER, as well as ICL repair could be identified. Almost all variants are severely C-terminally truncated and lack important protein-protein interaction domains. Interestingly, XPF-202, differing to XPF-003 in the first 12 amino acids only, had no repair capability at all, suggesting an important role of this region during DNA repair, potentially concerning protein-protein interaction. We also identified splice variants of XPF and XPG exerting inhibitory effects on NER. Moreover, we showed that the XPF and XPG splice variants presented with different inter-individual expression patterns in healthy donors, as well as in various tissues. With regard to their residual repair capability and dominant-negative effects, functionally relevant spontaneous XPF and XPG splice variants present promising prognostic marker candidates for individual cancer risk, disease outcome, or therapeutic success. This merits further investigations, large association studies, and translational research within clinical trials in the future.

Photocarcinogenesis and Skin Cancer Prevention Strategies: An Update.

UV radiation is acknowledged as the primary cause of photocarcinogenesis and therefore contributes to the development of skin cancer entities such as squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and melanoma. Typical DNA photoproducts and indirect DNA damage caused by reactive oxygen species are the result of UV radiation. UV-induced DNA damage is repaired by nucleotide excision repair, which consequently counteracts the development of mutations and skin carcinogenesis. Tumour-suppressor genes are inactivated by mutation and growth-promoting pathways are activated leading to disruption of cell-cycle progression. Depending on the skin cancer entity, some genes are more frequently affected than others. In BCC mutations in Patched or Smoothened are common and affect the Sonic hedgehog pathway. In SCC, cell regulator protein p53 (TP53) mutations are prevalent, as well as mutations of the epidermal growth factor receptor (EGFR), cyclin-dependent kinase 2A (CDKN2A), Rat sarcoma (RAS), or the tyrosine kinase Fyn (FYN). UV-induced mutations in TP53 and CDKN2A are frequent in melanoma. UV-induced inflammatory processes also facilitate photocarcinogenesis. Recent studies showed a connection between photocarcinogenesis and citrus consumption, phytochemicals, alcohol consumption, hormone replacement therapy, as well as oral contraceptive use. Preventative measures include adequate use of sun protection and skin cancer screening at regular intervals, as well as the use of chemopreventative agents.

Xeroderma Pigmentosum - Facts and Perspectives.

Ultraviolet (UV)-induced DNA lesions are almost exclusively removed by the nucleotide excision repair (NER) pathway, which is essential for prevention of skin cancer development. Patients with xeroderma pigmentosum (XP) are extremely sun sensitive due to a genetic defect in components of the NER cascade. They present with first signs of premature skin aging at an early age, with a considerably increased risk of developing UV-induced skin cancer. XP belongs to the group of DNA repair defective disorders that are mainly diagnosed in the clinic and in hindsight confirmed at the molecular level. Unfortunately, there are no causative treatment options for this rare, autosomal-recessive disorder, emphasizing the importance of an early diagnosis. Subsequently, UV-protective measures such as the reduction of exposure to environmental UV and regular skin cancer screenings should be undertaken to substantially improve prognosis as well as the disease course.

Research on genodermatoses using novel genome-editing tools.

Genodermatoses comprise a clinically heterogeneous group of mostly devastating disorders affecting the skin. To date, treatment options have in general been limited to symptom relief. However, the recent technical evolution in genome editing has ushered in a new era in the development of causal therapies for rare monogenetic diseases such as genodermatoses. The present review revisits the advantages and drawbacks of engineered nuclease tools currently available: zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), meganucleases, and - the most innovative - clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) nuclease 9 (CRISPR/Cas9) system. A mechanistic overview of the different modes of action of these programmable nucleases as well as their significance for causal therapy of genodermatoses is presented. Remaining limitations and challenges such as efficient delivery and off-target activity are critically discussed, highlighting both the past and future of gene therapy in dermatology.

XPF knockout via CRISPR/Cas9 reveals that ERCC1 is retained in the cytoplasm without its heterodimer partner XPF.

The XPF/ERCC1 heterodimeric complex is essentially involved in nucleotide excision repair (NER), interstrand crosslink (ICL), and double-strand break repair. Defects in XPF lead to severe diseases like xeroderma pigmentosum (XP). Up until now, XP-F patient cells have been utilized for functional analyses. Due to the multiple roles of the XPF/ERCC1 complex, these patient cells retain at least one full-length allele and residual repair capabilities. Despite the essential function of the XPF/ERCC1 complex for the human organism, we successfully generated a viable immortalised human XPF knockout cell line with complete loss of XPF using the CRISPR/Cas9 technique in fetal lung fibroblasts (MRC5Vi cells). These cells showed a markedly increased sensitivity to UVC, cisplatin, and psoralen activated by UVA as well as reduced repair capabilities for NER and ICL repair as assessed by reporter gene assays. Using the newly generated knockout cells, we could show that human XPF is markedly involved in homologous recombination repair (HRR) but dispensable for non-homologous end-joining (NHEJ). Notably, ERCC1 was not detectable in the nucleus of the XPF knockout cells indicating the necessity of a functional XPF/ERCC1 heterodimer to allow ERCC1 to enter the nucleus. Overexpression of wild-type XPF could reverse this effect as well as the repair deficiencies.

Identification and Functional Testing of ERCC2 Mutations in a Multi-national Cohort of Patients with Familial Breast- and Ovarian Cancer.

The increasing application of gene panels for familial cancer susceptibility disorders will probably lead to an increased proposal of susceptibility gene candidates. Using ERCC2 DNA repair gene as an example, we show that proof of a possible role in cancer susceptibility requires a detailed dissection and characterization of the underlying mutations for genes with diverse cellular functions (in this case mainly DNA repair and basic cellular transcription). In case of ERCC2, panel sequencing of 1345 index cases from 587 German, 405 Lithuanian and 353 Czech families with breast and ovarian cancer (BC/OC) predisposition revealed 25 mutations (3 frameshift, 2 splice-affecting, 20 missense), all absent or very rare in the ExAC database. While 16 mutations were unique, 9 mutations showed up repeatedly with population-specific appearance. Ten out of eleven mutations that were tested exemplarily in cell-based functional assays exert diminished excision repair efficiency and/or decreased transcriptional activation capability. In order to provide evidence for BC/OC predisposition, we performed familial segregation analyses and screened ethnically matching controls. However, unlike the recently published RECQL example, none of our recurrent ERCC2 mutations showed convincing co-segregation with BC/OC or significant overrepresentation in the BC/OC cohort. Interestingly, we detected that some deleterious founder mutations had an unexpectedly high frequency of > 1% in the corresponding populations, suggesting that either homozygous carriers are not clinically recognized or homozygosity for these mutations is embryonically lethal. In conclusion, we provide a useful resource on the mutational landscape of ERCC2 mutations in hereditary BC/OC patients and, as our key finding, we demonstrate the complexity of correct interpretation for the discovery of "bonafide" breast cancer susceptibility genes.

A unique chromosomal in-frame deletion identified among seven XP-C patients.

BACKGROUND: The nucleotide excision repair (NER) pathway, defective in xeroderma pigmentosum (XP) patients, removes DNA photolesions in order to prevent carcinogenesis. Complementation group C (XP-C) is the most frequent group of XP patients worldwide. METHODS: We analyzed seven XP-C patients clinically and molecular-genetically applying: post-UV cell survival (MTT-assay), quantitative Real-time PCR, sequencing on chromosomal as well as cDNA level, and in silico interpretation of sequencing data. RESULTS: All cases displayed diminished post-UV cell survival as well as reduced XPC mRNA levels. Five homozygous and two heterozygous disease causing mutations were identified. A large chromosomal deletion of ~5.8 kb identified in XP174MA leads to an unique in frame deletion of XPC exon 2 and exon 3. In silico analysis revealed the deletion of 102 amino acids in the N-terminal part of XPC while leaving the C-terminal domain intact. The novel c.361delA mutation in XP168MA leads to a frameshift in exon 3 resulting in a premature stop codon 27 codons downstream of the deleted adenine. CONCLUSION: Our analysis confirms that XP-C patients without increased sun sensitivity develop non-melanoma skin cancers earlier than sun-sensitive XP-C patients. Reduced cellular mRNA levels are characteristic for XP complementation group C and qRT-PCR represents a rapid diagnostic tool.

Photocarcinogenesis and Skin Cancer Prevention Strategies.

In this review the basic principles of UV-induced carcinogenesis are summarized and the state of the art diagnosis and therapeutic strategies are discussed. The prevalent keratinocyte-derived neoplasms of the skin are basal cell and squamous cell carcinomas. Cutaneous melanoma is less frequent but associated with high mortality. Common risk factors for all three tumor entities include sun exposure and DNA-repair deficiencies. Photocarcinogenesis follows a multistep model of cancer development in which ultraviolet-induced DNA damage leads to mutations resulting in activation of oncogenes or silencing of tumor-suppressor genes. This ends in a cellular mutator phenotype even more prone to mutation acquisition. DNA repair, especially the nucleotide excision repair (NER) pathway, counteracts mutation formation and skin cancer development. This is vividly demonstrated by the NER-defective disorder xeroderma pigmentosum. Primary skin cancer preventative strategies, therefore, include reduction of DNA photodamage by protection from the sun. Secondary preventative strategies include skin cancer screening. This implies standard examination techniques with the naked eye, an epiluminescence microscope, or digital epiluminescence microscopy. More advanced techniques include confocal laser scan microscopy.

Xeroderma pigmentosum: diagnostic procedures, interdisciplinary patient care, and novel therapeutic approaches.

Xeroderma pigmentosum (XP) is an autosomal recessive disease, caused by a gene defect in the nucleotide-excision-repair (NER) pathway or in translesional DNA synthesis. At the age of eight, patients already develop their first skin cancers due to this DNA repair defect. In contrast, in the Caucasian population the first tumor formation in UV exposed skin regions occurs at a mean age of 60. The clinical picture among patients suffering from XP is highly diverse and includes signs of accelerated skin aging, and UV-induced skin cancers, as well as ophthalmologic and neurological symptoms. Patients should therefore receive interdisciplinary care. This includes dermatologists, ophthalmologists, ENT specialists, neurologists, and human geneticists. Patients with XP are clinically diagnosed, but this may be supported by molecular-genetic and functional analyses. These analyses allow pinpointing the exact disease-causing gene defect (complementation group assignment, detection of the type and location of the mutation within the gene). The resulting information is already relevant to predict the course of disease and symptoms and probably will be utilized for individualized therapeutic approaches in the future. Recently, enhanced repair of UV photolesions in xeroderma pigmentosum group C cells induced by translational readthrough of premature termination codons by certain antibiotics could be demonstrated.

Increased number of Langerhans cells in the epidermis of diabetic foot ulcers correlates with healing outcome.

Langerhans cells (LCs) are a specialized subset of epidermal dendritic cells. They represent one of the first cells of immunologic barrier and play an important role during the inflammatory phase of acute wound healing. Despite considerable progress in our understanding of the immunopathology of diabetes mellitus and its associated comorbidities such as diabetic foot ulcers (DFUs), considerable gaps in our knowledge exist. In this study, we utilized the human ex vivo wound model and confirmed the increased epidermal LCs at wound edges during early phases of wound healing. Next, we aimed to determine differences in quantity of LCs between normal human and diabetic foot skin and to learn if the presence of LCs correlates with the healing outcome in DFUs. We utilized immunofluorescence to detect CD207+ LCs in specimens from normal and diabetic foot skin and DFU wound edges. Specimens from DFUs were collected at the initial visit and 4 weeks later at the time when the healing outcome was determined. DFUs that decreased in size by >50 % were considered to be healing, while DFUs with a size reduction of <50 % were considered non-healing. Quantitative assessment of LCs showed a higher number of LCs in healing when compared to non-healing DFU's. Our findings provide evidence that LCs are present in higher number in diabetic feet than normal foot skin. Healing DFUs show a higher number of LCs compared to non-healing DFUs. These findings indicate that the epidermal immune barrier plays an important role in the DFU healing outcome and may offer new therapeutic avenues targeting LC in non-healing DFUs.