Extracellular matrix remodelling in dental pulp tissue of carious human teeth through the prism of single-cell RNA sequencing.

Carious lesions are bacteria-caused destructions of the mineralised dental tissues, marked by the simultaneous activation of immune responses and regenerative events within the soft dental pulp tissue. While major molecular players in tooth decay have been uncovered during the past years, a detailed map of the molecular and cellular landscape of the diseased pulp is still missing. In this study we used single-cell RNA sequencing analysis, supplemented with immunostaining, to generate a comprehensive single-cell atlas of the pulp of carious human teeth. Our data demonstrated modifications in the various cell clusters within the pulp of carious teeth, such as immune cells, mesenchymal stem cells (MSC) and fibroblasts, when compared to the pulp of healthy human teeth. Active immune response in the carious pulp tissue is accompanied by specific changes in the fibroblast and MSC clusters. These changes include the upregulation of genes encoding extracellular matrix (ECM) components, including COL1A1 and Fibronectin (FN1), and the enrichment of the fibroblast cluster with myofibroblasts. The incremental changes in the ECM composition of carious pulp tissues were further confirmed by immunostaining analyses. Assessment of the Fibronectin fibres under mechanical strain conditions showed a significant tension reduction in carious pulp tissues, compared to the healthy ones. The present data demonstrate molecular, cellular and biomechanical alterations in the pulp of human carious teeth, indicative of extensive ECM remodelling, reminiscent of fibrosis observed in other organs. This comprehensive atlas of carious human teeth can facilitate future studies of dental pathologies and enable comparative analyses across diseased organs.

The genetic aspects of hidradenitis suppurativa.

Genetic aspects have a substantial role in hidradenitis suppurativa (HS) pathogenesis. A positive family history of HS occurs in about one-third of HS cases and is significantly higher in patients with early onset of the disease. Recent twin studies have shown a high heritability in HS, fortifying the importance of genetic factors in disease pathogenesis. Based on existing knowledge on the genomics of HS, the disease can be categorized as familial HS, sporadic, syndromic HS, and "HS plus" associated with other syndromes. In familial HS, autosomal dominant transmission is proposed, and monogenic inheritance is rare. This monogenic trait is related to mutations of γ-secretase component genes and Notch signaling or defects in inflammasome function. With newly discovered gene mutations, such as those related to innate and adaptive immunity, skin microbiome, inflammasome, epidermal homeostasis, and keratinization pathway, we can define HS as a polygenic, multifactorial, autoinflammatory disease. To fully elucidate the genetic aspects of HS, we need extensive, long-term global collaborations.

Nogo-A Regulates the Fate of Human Dental Pulp Stem Cells toward Osteogenic, Adipogenic, and Neurogenic Differentiation.

Human teeth are highly innervated organs that contain a variety of mesenchymal stem cell populations that could be used for cell-based regenerative therapies. Specific molecules are often used in these treatments to favorably modulate the function and fate of stem cells. Nogo-A, a key regulator of neuronal growth and differentiation, is already used in clinical tissue regeneration trials. While the functions of Nogo-A in neuronal tissues are extensively explored, its role in teeth still remains unknown. In this work, we first immunohistochemically analyzed the distribution of Nogo-A protein in the dental pulp of human teeth. Nogo-A is localized in a variety of cellular and structural components of the dental pulp, including odontoblasts, fibroblasts, neurons and vessels. We also cross-examined Nogo expression in the various pulp cell clusters in a single cell RNA sequencing dataset of human dental pulp, which showed high levels of expression in all cell clusters, including that of stem cells. We then assessed the role of Nogo-A on the fate of human dental pulp stem cells and their differentiation capacity in vitro. Using immunostaining, Alizarin Red S, Nile Red and Oil Red O staining we showed that Nogo-A delayed the differentiation of cultured dental pulp stem cells toward the osteogenic, adipogenic and neurogenic lineages, while addition of the blocking anti-Nogo-A antibody had opposite effects. These results were further confirmed by qRT-PCR, which demonstrated overexpression of genes involved in osteogenic (RUNX2, ALP, SP7/OSX), adipogenic (PPAR-γ2, LPL) and neurogenic (DCX, TUBB3, NEFL) differentiation in the presence of the anti-Nogo-A antibody. Conversely, the osteogenic and adipogenic genes were downregulated by Nogo-A. Taken together, our results show that the functions of Nogo-A are not restricted to neuronal cells but are extended to other cell populations, including dental pulp stem cells. We show that Nogo-A regulates their fates toward osteogenic, adipogenic and neurogenic differentiation, thus indicating its potential use in clinics.

Adam10-dependent Notch signaling establishes dental epithelial cell boundaries required for enamel formation.

The disintegrin and metalloproteinase Adam10 is a membrane-bound sheddase that regulates Notch signaling and ensures epidermal integrity. To address the function of Adam10 in the continuously growing incisors, we used Keratin14 Cre/+;Adam10 fl/fl transgenic mice, in which Adam10 is conditionally deleted in the dental epithelium. Keratin14 Cre/+;Adam10 fl/fl mice exhibited severe abnormalities, including defective enamel formation reminiscent of human enamel pathologies. Histological analyses of mutant incisors revealed absence of stratum intermedium, and severe disorganization of enamel-secreting ameloblasts. In situ hybridization and immunostaining analyses in the Keratin14 Cre/+;Adam10 fl/fl incisors showed strong Notch1 downregulation in dental epithelium and ectopic distribution of enamel-specific molecules, including ameloblastin and amelogenin. Lineage tracing studies using Notch1 CreERT2 ;R26 mT/mG mice demonstrated that loss of the stratum intermedium cells was due to their fate switch toward the ameloblast lineage. Overall, our data reveal that in the continuously growing incisors the Adam10/Notch axis controls dental epithelial cell boundaries, cell fate switch and proper enamel formation.

Ptch2 is a Potential Regulator of Mesenchymal Stem Cells.

Ptch receptors 1 and 2 mediate Hedgehog signaling pivotal for organ development and homeostasis. In contrast to embryonic lethal Ptch1 -/- phenotype, Ptch2 -/- mice display no effect on gross phenotype. In this brief report, we provide evidence of changes in the putative incisor mesenchymal stem cell (MSC) niches that contribute to accelerated incisor growth, as well as intriguing changes in the bones and skin which suggest a role for Ptch2 in the regulation of MSCs and their regenerative potential. We employed histological, immunostaining, and computed tomography (µCT) analyses to analyze morphological differences between Ptch2 -/- and wild-type incisors, long bones, and skins. In vitro CFU and differentiation assays were used to demonstrate the MSC content and differentiation potential of Ptch2 -/- bone marrow stromal cells. Wound healing assay was performed in vivo and in vitro on 8-week-old mice to assess the effect of Ptch2 on the wound closure. Loss of Ptch2 causes increases in the number of putative MSCs in the continuously growing incisor, associated with increased vascularization observed in the tooth mesenchyme and the neurovascular bundle. Increased length and volume of Ptch2 -/- bones is linked with the increased number and augmented in vitro differentiation potential of MSCs in the bone marrow. Dynamic changes in the Ptch2 -/- skin thickness relate to changes in the mesenchymal compartment and impact the wound closure potential. The effects of Ptch2 abrogation on the postnatal MSCs suggest a crucial role for Ptch2 in Hedgehog signaling regulation of the organ regenerative potential.

Dermoscopy of Zosteriform and Swirling Pattern Type 1 Segmental Darier Disease.

Dear Editor, Segmental Darier disease (DD) is a rare disease with around 40 described English literature cases. It is hypothesized that one of the causes of the disease is a post-zygotic somatic mutation for the calcium ATPase pump, only present in lesional skin. There are two types of segmental DD: type 1, where lesions follow Blaschko's lines unilaterally, and type 2, characterized by focal areas of increased severity in patients with generalized DD (1). Type 1 segmental DD is not easily diagnosed due to the lack of positive family history, the late onset of the disease in the third or fourth decade of life, and lack of DD-associated features. The differential diagnosis of type 1 segmental DD includes acquired papular dermatoses distributed in linear or zosteriform fashion, such as lichen planus, psoriasis, lichen striatus, or linear porokeratosis (2). We report two cases of segmental DD, of which the first case was a 43-year-old woman who presented with pruritic skin changes five years in duration and a history of seasonal aggravation. On examination, light brownish to reddish keratotic small papules were observed on the left abdomen and inframammary area, arranged in a swirling pattern (Figure 1, a). Dermoscopy showed polygonal or roundish yellowish/brown areas surrounded with whitish structureless areas (Figure 1, b). The histopathological correlations for dermoscopic brownish polygonal or round areas are hyperkeratosis, parakeratosis, and dyskeratotic keratinocytes, which were present in the biopsy specimen (Figure 1, c). The patient was prescribed 0.1% tretinoin gel, which led to marked improvement (Figure 1, d). The second case was a 62-year-old woman who presented with a flare of small red-brown papules, eroded papules, and some yellowish crusts arranged in a zosteriform pattern on the right side of the upper abdomen (Figure 2, a). Dermoscopy showed polygonal, roundish, yellowish areas surrounded with whitish and reddish structureless areas (Figure 2, b). Histopathology mainly revealed compact orthokeratosis and small foci of parakeratosis, marked granular layer with dyskeratotic keratinocytes, and foci of suprabasal acantholysis consistent with the diagnosis of DD (Figure 2, d, d). The patient was prescribed topical steroid cream and 0.1% adapalene cream, which also led to improvement. In both of our cases, a final diagnosis of type 1 segmental DD was established based on clinico-histopathologic correlation, since acantholytic dyskeratotic epidermal nevus could not have been ruled out only based on the histopathology report as it is clinically and histologically indistinguishable from segmental DD. However, the late age of onset and aggravation resulting from external factors such as heat, sunlight, and sweat supported the diagnosis of segmental DD. Although the final diagnosis of type 1 segmental DD is typically established based on clinico-histopathological correlation, we find dermoscopy particularly useful in aiding the diagnosis by eliminating differential diagnoses and being aware of their well-known dermoscopic patterns.

Pyogenic Granuloma of the Proximal Part of a Nail Unit in a Child.

Dear Editor, We present a case of proximal pyogenic granuloma in 4-year-old child. The patient presented to our Department due to a fast-growing lesion on the proximal part of the nail unit. The lesion had appeared over several weeks, and it was extremely painful for the child. On the day of the 1st visit, the lesion was not bleeding but was very painful during examination and photo-documentation. Clinically, it presented as an exogenous tumoral lesion of the proximal 1/3 of the nail, partially exulcerated with one part exhibiting coagulated hemorrhage and with uneven coloration (Figure 1). The lesion was not sharply demarcated. Dermoscopically, the majority of the lesion presented an unspecific dermoscopic structure, orange background color, and matched the criteria for a vascular lesion: few unspecific vessels and hemorrhage. The "sticky fiber" sign was also present (Figure 2). Since the lesion was fast-growing and due to the unspecific dermoscopic appearance, the child was referred to a pediatric surgeon and a complete excisional biopsy of the lesion was performed. The dermoscopy of pyogenic granuloma has been already described (1). The histology report confirmed pyogenic granuloma. Pyogenic granulomas of the nail unit are not a common finding, but our case confirms that even this location can be site of this type of benign lesion. It more commonly found in the periungual region and can be expected due to adverse effects of different kinds of systemic therapies. However, due to differential diagnosis that includes different types of tumors occurring at the nail unit, most importantly amelanotic melanoma and SCC, it is suggested to excise or take a biopsy of this type of lesion to be able to exclude aggressive tumor types, which are very rare but not impossible the in pediatric population (2). In cases of unquestionable diagnosis, several local treatments are available. Since the lesion presented a destructive nature in our case, we decided to perform excisional biopsy followed by histology, which in our case was both a diagnostic and therapeutic procedure.

Use of Trowell-Type Organ Culture to Study Regulation of Dental Stem Cells.

Organ development, function, and regeneration depend on stem cells, which reside within discrete anatomical spaces called stem cell niches. The continuously growing mouse incisor provides an excellent model to study tissue-specific stem cells. The epithelial tissue-specific stem cells of the incisor are located at the proximal end of the tooth in a niche called the cervical loop. They provide a continuous influx of cells to counterbalance the constant abrasion of the self-sharpening tip of the tooth. Presented here is a detailed protocol for the isolation and culture of the proximal end of the mouse incisor that houses stem cells and their niche. This is a modified Trowell-type organ culture protocol that enables in vitro culture of tissue pieces (explants), as well as the thick tissue slices at the liquid/air interface on a filter supported by a metal grid. The organ culture protocol described here enables tissue manipulations not feasible in vivo, and when combined with the use of a fluorescent reporter(s), it provides a platform for the identification and tracking of discrete cell populations in live tissues over time, including stem cells. Various regulatory molecules and pharmacological compounds can be tested in this system for their effect on stem cells and their niches. This ultimately provides a valuable tool to study stem cell regulation and maintenance.

Dental cell type atlas reveals stem and differentiated cell types in mouse and human teeth.

Understanding cell types and mechanisms of dental growth is essential for reconstruction and engineering of teeth. Therefore, we investigated cellular composition of growing and non-growing mouse and human teeth. As a result, we report an unappreciated cellular complexity of the continuously-growing mouse incisor, which suggests a coherent model of cell dynamics enabling unarrested growth. This model relies on spatially-restricted stem, progenitor and differentiated populations in the epithelial and mesenchymal compartments underlying the coordinated expansion of two major branches of pulpal cells and diverse epithelial subtypes. Further comparisons of human and mouse teeth yield both parallelisms and differences in tissue heterogeneity and highlight the specifics behind growing and non-growing modes. Despite being similar at a coarse level, mouse and human teeth reveal molecular differences and species-specific cell subtypes suggesting possible evolutionary divergence. Overall, here we provide an atlas of human and mouse teeth with a focus on growth and differentiation.

Understanding the Relationship Between Smoking and Hidradenitis Suppurativa.

Hidradenitis suppurativa (HS) is a chronic skin disease affecting hair follicles in intertriginous areas, characterized by deep, recurrent, painful nodules and abscesses, fistulae, sinus tracts, and scarring. With a prevalence of 1-4%, HS is not an uncommon disease. Several risk factors have been linked with the development of HS, such as genetic predisposition, smoking, and obesity, leading to the hypothesis that HS develops as a result of environmental triggers in a genetically susceptible individual. Smoking has been recognized as one of the environmental factors with the most impact on HS. This review aims to provide a comprehensive and holistic view on how smoking habits affect the incidence, severity, treatment, and pathophysiology of HS. A growing body of published literature has reported the association between smoking and HS, despite limitations in proving the causal relationship due to the retrospective design of the available studies. There is a consensus that patients with HS who are active smokers have a higher number of affected body areas than patients with HS who do not smoke or have stopped smoking. Similarly, it is recommended for patients with HS to discontinue tobacco use because of its association with weaker treatment response. Studies on the pathophysiological mechanism of smoking on the skin show that tobacco smoke with many of its chemicals as well as nicotine promote the proinflammatory cytokines found in HS lesions, activate the nicotinic acetylcholine (nAChRs) and aryl hydrocarbon receptors (AHRs), and further suppress Notch signaling pathway.

The association between clinical and laboratory findings of bullous pemphigoid and dipeptidyl peptidase-4 inhibitors in the elderly: a retrospective study.

AIM: To evaluate the association between the use of dipeptidyl peptidase-4 inhibitors (DPP4I) and clinical and laboratory findings of bullous pemphigoid (BP) in patients treated at the European Reference Network - Skin Reference Centre in Croatia. METHODS: This retrospective study enrolled 82 patients treated for BP at the Department of Dermatovenereology, University Hospital Center Zagreb from January 2015 to December 2019. Clinical features of BP, presence of comorbidities, and laboratory findings of anti-BP antibodies and eosinophilia were analyzed in three groups of BP patients: 1) diabetes mellitus (DM) type II patients treated with DPP4I, 2) DM type II patients not treated with DPP4I, and 3) non-DM type II patients. RESULTS: The average age and anti-BP180 titer were similar in all three groups. DPP4I group had a slightly lower eosinophil level in both peripheral blood (4.89%) and biopsy specimens (87.5%), but the difference was not significant. The prevalence of inflammatory BP in DPP4I group was 76.5%. DPP4I group had significantly higher percentage of patients with chronic renal failure and dementia (52.9% and 11.8%, respectively) compared with non-DPP4I DM (14.3% and 0%, respectively) and non-DM type II patients (15.7% and 0%, respectively). CONCLUSION: BP patients treated with DPP4I and those not treated with DPP4Is did not significantly differ in laboratory findings. However, DPP4I treatment was associated with an inflammatory subtype of BP and a higher prevalence of dementia and chronic renal failure. These findings warrant further research into the association of BP and DM with dementia and chronic renal failure.

Novel strategies for expansion of tooth epithelial stem cells and ameloblast generation.

Enamel is secreted by ameloblasts derived from tooth epithelial stem cells (SCs). Humans cannot repair or regenerate enamel, due to early loss of tooth epithelial SCs. Contrarily in the mouse incisors, epithelial SCs are maintained throughout life and endlessly generate ameloblasts, and thus enamel. Here we isolated Sox2-GFP+ tooth epithelial SCs which generated highly cellular spheres following a novel in vitro strategy. This system enabled analysis of SC regulation by various signaling molecules, and supported the stimulatory and inhibitory roles of Shh and Bmp, respectively; providing better insight into the heterogeneity of the SCs. Further, we generated a novel mouse reporter, Enamelin-tdTomato for identification of ameloblasts in live tissues and cells, and used it to demonstrate presence of ameloblasts in the new 3D co-culture system of dental SCs. Collectively, our results provide means of generating 3D tooth epithelium from adult SCs which can be utilized toward future generation of enamel.

Altered Levels of Sphingosine, Sphinganine and Their Ceramides in Atopic Dermatitis Are Related to Skin Barrier Function, Disease Severity and Local Cytokine Milieu.

Dysfunctional skin barrier plays a key role in the pathophysiology of atopic dermatitis (AD), a common inflammatory skin disease. Altered composition of ceramides is regarded as a major cause of skin barrier dysfunction, however it is not clear whether these changes are intrinsic or initiated by inflammation and aberrant immune response in AD. This study investigated the levels of free sphingoid bases (SBs) sphingosine and sphinganine and their ceramides and glucosylceramide in the stratum corneum (SC) and related them to skin barrier function, disease severity and local cytokine milieu. Ceramides were measured in healthy skin, and lesional and non-lesional skin of AD patients by a novel method based on deacylation of ceramides which were subsequently determined as corresponding sphingoid bases by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The cytokine levels were determined by multiplex immunoassay. Atopic skin showed increased levels of most investigated markers, predominantly in lesional skin. The largest difference in respect to healthy skin was found for glucosylceramide with respective median values of 0.23 (IQR 0.18-0.61), 0.56 (IQR 0.32-0.76) and 19.32 (IQR 7.86-27.62) pmol/g protein for healthy, non-lesional and lesional skin. The levels of investigated ceramide markers were correlated with disease severity (scoring atopic dermatitis, SCORAD) and skin barrier function (trans-epidermal water loss, TEWL) and furthermore with cytokines involved in innate, Th-1, and Th-2 immune response. Interestingly, the strongest association with SCORAD was found for sphinganine/sphingosine ratio (r = -0.69, p < 0.001; non-lesional skin), emphasizing the importance of SBs in AD. The highest correlation with TEWL was found for glucosylceramide (r2 = 0.60, p < 0.001), which was investigated for the first time in AD. Findings that the changes in SBs and ceramide levels were predominant in lesional skin and their association with disease severity and cytokine levels suggest an immune-system driven effect. a novel analysis method demonstrates a robust and simple approach that might facilitate wider use of lipid biomarkers in the clinics e.g., to monitor (immune) therapy or dissect disease endotypes.

Omega-3 Versus Omega-6 Polyunsaturated Fatty Acids in the Prevention and Treatment of Inflammatory Skin Diseases.

Omega-3 (ω-3) and omega-6 (ω-6) polyunsaturated fatty acids (PUFAs) are nowadays desirable components of oils with special dietary and functional properties. Their therapeutic and health-promoting effects have already been established in various chronic inflammatory and autoimmune diseases through various mechanisms, including modifications in cell membrane lipid composition, gene expression, cellular metabolism, and signal transduction. The application of ω-3 and ω-6 PUFAs in most common skin diseases has been examined in numerous studies, but their results and conclusions were mostly opposing and inconclusive. It seems that combined ω-6, gamma-linolenic acid (GLA), and ω-3 long-chain PUFAs supplementation exhibits the highest potential in diminishing inflammatory processes, which could be beneficial for the management of inflammatory skin diseases, such as atopic dermatitis, psoriasis, and acne. Due to significant population and individually-based genetic variations that impact PUFAs metabolism and associated metabolites, gene expression, and subsequent inflammatory responses, at this point, we could not recommend strict dietary and supplementation strategies for disease prevention and treatment that will be appropriate for all. Well-balanced nutrition and additional anti-inflammatory PUFA-based supplementation should be encouraged in a targeted manner for individuals in need to provide better management of skin diseases but, most importantly, to maintain and improve overall skin health.

Pivotal Role of Tenascin-W (-N) in Postnatal Incisor Growth and Periodontal Ligament Remodeling.

The continuously growing mouse incisor provides a fascinating model for studying stem cell regulation and organ renewal. In the incisor, epithelial and mesenchymal stem cells assure lifelong tooth growth. The epithelial stem cells reside in a niche known as the cervical loop. Mesenchymal stem cells are located in the nearby apical neurovascular bundle and in the neural plexus. So far, little is known about extracellular cues that are controlling incisor stem cell renewal and guidance. The extracellular matrix protein tenascin-W, also known as tenascin-N (TNN), is expressed in the mesenchyme of the pulp and of the periodontal ligament of the incisor, and is closely associated with collagen 3 fibers. Here, we report for the first time the phenotype of tenascin-W/TNN deficient mice, which in a C57BL/6N background exhibit a reduced body weight and lifespan. We found major defects in the alveolar bone and periodontal ligament of the growing rodent incisors, whereas molars were not affected. The alveolar bone around the incisor was replaced by a dense scar-like connective tissue, enriched with newly formed nerve fibers likely leading to periodontal pain, less food intake and reduced body weight. Using soft food to reduce mechanical load on the incisor partially rescued the phenotype. In situ hybridization and Gli1 reporter mouse experiments revealed decreased hedgehog signaling in the incisor mesenchymal stem cell compartment, which coordinates the development of mesenchymal stem cell niche. These results indicate that TNN deficiency in mice affects periodontal remodeling and increases nerve fiber branching. Through periodontal pain the food intake is reduced and the incisor renewal and the neurovascular sonic hedgehog secretion rate are reduced. In conclusion, tenascin-W/TNN seems to have a primary function in rapid periodontal tissue remodeling and a secondary function in mechanosensation.

The Role of the Skin Barrier in Periorificial Dermatitis.

Periorificial dermatitis, mostly known as perioral dermatitis, is a benign inflammatory facial dermatosis which can be a severe burden and even disfiguring and psychologically disturbing. The disease still presents a challenge for physicians when it comes to etiology and appropriate therapy. Although a variety of extrinsic and intrinsic factors have been proposed as etiopathogenetic factors, none of these fully explain complex pathogenesis of the disease. There is more evidence that supports beliefs that the epidermal barrier dysfunction is an underlying main pathogenic factor that contributes to persistent cutaneous inflammation in typical facial localizations. Patients with periorificial dermatitis are considered hyper-reactors who have impaired essential function of the skin barrier, especially the skin barrier of the perioral region, characterized by thin permeable stratum corneum and imbalance of intercellular lipids, which makes them more susceptible to various internal and external irritants that contribute to the development of the disease. The verification of this connection reinforces the need for clinicians to address this issue when approaching their patients and formulating the best treatment plan. Treatment should emphasize repairing the impaired skin barrier function to minimize associated skin inflammation and sensitivity, which results in resolution of the objective and subjective symptoms.

Occupational Airborne Contact Dermatitis Caused by Omeprazole.

Airborne contact dermatitis (ACD) is a frequent condition, and there has been increasing recognition of the occupational origin of airborne contact dermatitis. ACD caused by drugs is often occupation-related and occurs mainly in healthcare workers who use the drugs for therapeutic aims and employees of pharmaceutical industries involved in the production of the drugs (1). Omeprazole (OM) is a proton pump inhibitor from the benzimidazole group used for treatment of gastric acid-related disorders (2). A 52-years-old female chemist had been working in a pharmaceutical company for 20 years. When working in the laboratory, she wore protective latex-free gloves, a mask, and glasses. Skin lesions started 6 months after she had started working in an analytic laboratory with omeprazole and azithromycin. Whenever omeprazole was being manufactured, the patient presented with eczema with scaling on the eyelids, face, and neck, with the hands subsequently being affected as well. The patient's skin lesions cleared during holidays and sick leave and worsened when she was working in omeprazole production. Topical corticosteroids were applied, which resulted in temporally regression of skin symptoms. We performed patch tests with the baseline series (Chemotechnique Diagnostics, Vellinge, Sweden, and Imunoloski zavod, Zagreb, Croatia) to materials in the patient's workplace and a lymphocyte transformation test (LTT) to omeprazole. All tests were negative, except the patch test to OM which showed a positive reaction (+) to 0.1% OM in saline solution on day (D) 2 and D3 and positive reaction (+) to 0.5% OM in saline solution on D2 and ++ on D3 (Figure 1). Hausen et al. performed experimental animal studies in which they concluded that OM and other proton pump inhibitors constitute a high-sensitizing-potential group (3). However, when administrated, orally or parenterally, the frequency of contact sensitization was low (3). Although direct contact with the skin was not always present, distribution of the dust containing OM through the air and deposition on exposed areas may result in ACD. The first two occupational cases of ACD caused by OM among pharmaceutical workers were reported in 1986 (4). Since then, ACD caused by OM in an occupational setting has been reported occasionally (2,4-6). Other proton pump inhibitors such as lansoprazole and pantoprazole have less pronounced potential to cause ACD (7,8). Ghatan et al. conducted a study in 2014 in an occupational setting with 97 workers and reported 31 positive LTT tests and 28 positive patch tests; these results confirm a high risk of sensitization to OM from occupational exposure (6). Although direct contact with the skin is not always present, it is important to bear in mind that distribution of dust containing OM through the air and deposition on exposed areas may result in ACD.

Do We Utilize Our Knowledge of the Skin Protective Effects of Carotenoids Enough?

Due to their potential health-promoting effects, carotenoids have drawn both scientific and public attention in recent years. The primary source of carotenoids in the human skin is diet, mainly fruits, vegetables, and marine product, but they may originate from supplementation and topical application, too. In the skin, they accumulate mostly in the epidermis and act as a protective barrier to various environmental influences. Namely, the skin is exposed to numerous environmental factors, including ultraviolet radiation (UVR), air pollution, and smoking, that cause oxidative stress within the skin with consequent premature (extrinsic) aging. UVR, as the most prominent environmental factor, may cause additional detrimental skin effects, such as sunburn, DNA damage, and skin cancer. Therefore, photoprotection is the first line intervention in the prevention of premature aging and skin cancer. Numerous studies have demonstrated that carotenoids, particularly ß-carotene, lycopene, lutein, and astaxanthin, have photoprotective effects, not only through direct light-absorbing properties, but also through their antioxidant effects (scavenging reactive oxygen species), as well as by regulation of UV light-induced gene expression, modulation of stress-dependent signaling, and/or suppression of cellular and tissue responses like inflammation. Interventional studies in humans with carotenoid-rich diet have shown its photoprotective effects on the skin (mostly by decreasing the sensitivity to UVR-induced erythema) and its beneficial effects in prevention and improvement of skin aging (improved skin elasticity and hydration, skin texture, wrinkles, and age spots). Furthermore, carotenoids may be helpful in the prevention and treatment of some photodermatoses, including erythropoietic protoporphyria (EPP), porphyria cutanea tarda (PCT) and polymorphous light eruption (PMLE). Although UVR is recognized as the main etiopathogenetic factor in the development of non-melanoma skin cancer (NMSC) and melanoma, and the photoprotective effects of carotenoids are certain, available studies still could not undoubtedly confirm the protective role of carotenoids in skin photocarcinogenesis.

Hyperpigmented Mycosis Fungoides - A Rare Entity.

Dear Editor, A 67-year-old man of Kosovar-Albanian ethnic origin (skin phenotype IV) presented to our dermatology clinic with generalized hyperpigmented patches and plaques all over the body, so-called melanoerythroderma (Figure 1). The lesions, which first appeared nearly six years ago, developed gradually; they were diagnosed as mycosis fungoides (MF), and were subsequently treated only with topical corticosteroids. We performed further examinations upon admission to our department. Relevant laboratory parameters - blood cell count, LDH, urinalysis, and serum chemistry - were within normal limits. Endocrinological examination excluded Addison disease, and the patient was not receiving any drugs that could cause skin hyperpigmentation. Chest-abdomen-pelvis computed tomography (CT) scan and sternal puncture were normal. Flow cytometric immunophenotyping revealed less than 5% aberrant T-cells. Histopathology and immunohistochemistry of skin specimens revealed lichenoid infiltration of small- to medium-sized atypical T-lymphocytes within the upper dermis, epidermotropic lymphocytes with several Pautrier's microabscesses (Darier's nests), pigment incontinence, abundant melanophages in the papillary dermis (Figure 2, a, b), and the T-cell CD4+CD7-CD8+ phenotype (Figure 2, c, d). Based on the clinical picture, histopathology, and immunohistochemistry the diagnosis of hyperpigmented mycosis fungoides (MF) stage IIIA (T4N0M0B0) was established. Skin-oriented therapy (retinoids-PUVA) resulted in slight improvement. Hyperpigmented MF is a rare, uncommon, clinical variant of MF, with a predilection for dark-skinned people (1). Only a few cases of hyperpigmented MF have been reported so far, and our case being one of them (2-5). Hyperpigmented patches or/and plaques dominate the clinical picture. Hyperpigmented MF is characterized by a predominantly CD8+ epidermotropic T-cell phenotype, although different phenotypes have been reported (CD4+ or CD4-CD8-) (2). Histopathologically, interface changes, pigment incontinence and melanophages are usually found in addition to the classical findings of early MF (1). The exact mechanism of hyperpigmentation is not well understood. Hyperpigmented MF had an indolent course in most reported cases, and skin-directed therapy is therefore the treatment of choice. Although MF and its hyperpigmented variant is a lymphoma of low-grade malignancy, large-cell transformation (CD30+) of hyperpigmented MF can occur (1). These rare cases of special clinical MF variants are extremely valuable and can help us investigate and understand the pathophysiology of the disease. Treatment and close follow-up is mandatory in the hyperpigmented variant of MF.

Functionally Distinctive Ptch Receptors Establish Multimodal Hedgehog Signaling in the Tooth Epithelial Stem Cell Niche.

Continuous growth of the mouse incisor teeth is due to the life-long maintenance of epithelial stem cells (SCs) in their niche called cervical loop (CL). Several signaling factors regulate SC maintenance and/or their differentiation to achieve organ homeostasis. Previous studies indicated that Hedgehog signaling is crucial for both the maintenance of the SCs in the niche, as well as for their differentiation. How Hedgehog signaling regulates these two opposing cellular behaviors within the confinement of the CL remains elusive. In this study, we used in vitro organ and cell cultures to pharmacologically attenuate Hedgehog signaling. We analyzed expression of various genes expressed in the SC niche to determine the effect of altered Hedgehog signaling on the cellular hierarchy within the niche. These genes include markers of SCs (Sox2 and Lgr5) and transit-amplifying cells (P-cadherin, Sonic Hedgehog, and Yap). Our results show that Hedgehog signaling is a critical survival factor for SCs in the niche, and that the architecture and the diversity of the SC niche are regulated by multiple Hedgehog ligands. We demonstrated the presence of an additional Hedgehog ligand, nerve-derived Desert Hedgehog, secreted in the proximity of the CL. In addition, we provide evidence that Hedgehog receptors Ptch1 and Ptch2 elicit independent responses, which enable multimodal Hedgehog signaling to simultaneously regulate SC maintenance and differentiation. Our study indicates that the cellular hierarchy in the continuously growing incisor is a result of complex interplay of two Hedgehog ligands with functionally distinct Ptch receptors. Stem Cells 2019;37:1238-1248.