Foxc1 Ablated Mice Are Anhidrotic and Recapitulate Features of Human Miliaria Sweat Retention Disorder.

Sweat glands are critical for thermoregulation. The single tubular structure of sweat glands has a lower secretory portion and an upper reabsorptive duct leading to the secretory pore in the skin. Genes that determine sweat gland structure and function are largely unidentified. Here we report that a Fox family transcription factor, Foxc1, is obligate for appreciable sweat duct activity in mice. When Foxc1 was specifically ablated in skin, sweat glands appeared mature, but the mice were severely hypohidrotic. Morphologic analysis revealed that sweat ducts were blocked by hyperkeratotic or parakeratotic plugs. Consequently, lumens in ducts and secretory portions were dilated, and blisters and papules formed on the skin surface in the knockout mice. The phenotype was strikingly similar to the human sweat retention disorder miliaria. We further show that Foxc1 deficiency ectopically induces the expression of keratinocyte terminal differentiation markers in the duct luminal cells, which most likely contribute to keratotic plug formation. Among those differentiation markers, we show that Sprr2a transcription is directly repressed by overexpressed Foxc1 in keratinocytes. In summary, Foxc1 regulates sweat duct luminal cell differentiation, and mutant mice mimic miliaria and provide a possible animal model for its study.

Sweat, the driving force behind normal skin: an emerging perspective on functional biology and regulatory mechanisms.

The various symptoms associated with excessive or insufficient perspiration can significantly reduce a patient's quality of life. If a versatile and minimally invasive method could be established for returning sweat activity to normalcy, there is no question that it could be used in the treatment of many diseases that are believed to involve perspiration. For this reason, based on an understanding of the sweat-gland control function and sweat activity, it was necessary to conduct a comprehensive search for the factors that control sweating, such as the central and peripheral nerves that control sweat-gland function, the microenvironment surrounding the sweat glands, and lifestyle. We focused on the mechanism by which atopic dermatitis leads to hypohidrosis and confirmed that histamine inhibits acetylcholinergic sweating. Acetylcholine promotes the phosphorylation of glycogen synthesis kinase 3ß (GSK3ß) in the sweat-gland secretory cells and leads to sensible perspiration. By suppressing the phosphorylation of GSK3ß, histamine inhibits the movement of sweat from the sweat-gland secretory cells through the sweat ducts, which could presumably be demonstrated by dynamic observations of the sweat glands using two-photon microscopy. It is expected that the discovery of new factors that control sweat-gland function can contribute to the treatment of diseases associated with dyshidrosis.

Involvement of Wnt, Eda and Shh at defined stages of sweat gland development.

To maintain body temperature, sweat glands develop from embryonic ectoderm by a poorly defined mechanism. We demonstrate a temporal cascade of regulation during mouse sweat gland formation. Sweat gland induction failed completely when canonical Wnt signaling was blocked in skin epithelium, and was accompanied by sharp downregulation of downstream Wnt, Eda and Shh pathway genes. The Wnt antagonist Dkk4 appeared to inhibit this induction: Dkk4 was sharply downregulated in ß-catenin-ablated mice, indicating that it is induced by Wnt/ß-catenin; however, its overexpression repressed Wnt target genes and significantly reduced gland numbers. Eda signaling succeeded Wnt. Wnt signaling was still active and nascent sweat gland pre-germs were still seen in Eda-null mice, but the pre-germs failed to develop further and the downstream Shh pathway was not activated. When Wnt and Eda were intact but Shh was ablated, germ induction and subsequent duct formation occurred normally, but the final stage of secretory coil formation failed. Thus, sweat gland development shows a relay of regulatory steps initiated by Wnt/ß-catenin - itself modulated by Dkk4 - with subsequent participation of Eda and Shh pathways.

Expression of caspase-14 and keratin-19 in the human epidermis and appendages during fetal skin development.

Caspase-14 is a seemingly non-apoptotic caspase involved in keratinocyte differentiation and cornification of the skin. Keratin-19 is an epithelial marker and a potential marker of epidermal stem cells that is expressed during human fetal skin development. We examined the immunohistochemical expression of caspase-14 in relation to CK-19 in the human fetal skin during development and perinatally, to assess their role in human skin maturation. Skin samples were received at autopsy. In the fetal epidermis, caspase-14 was predominantly expressed in the more differentiated layers, gradually disappearing from the basal layer toward term. By contrast, keratin-19 expression gradually decreased with epidermal maturation through gestation (rho = -0.949; p = 0.0001) and was a marker of the germinative layers. Keratin-19 was preserved in scarce basal cell nests at term and postnatally. Caspase-14 and keratin-19 were inversely expressed in the differentiating epidermal layers through gestation (p < 0.0001). Concerning the appendages, in hair follicles and sebaceous glands, caspase-14 located preferentially in the more differentiated layers of the inner root sheath, whereas keratin-19 was expressed in the outer sheath. Eccrine sweat glands showed a variable pattern of caspase-14 and keratin-19 expression. In conclusion, caspase-14 emerged as a marker of human skin differentiation during development, while keratin-19 marked the germinative epithelial layers in the fetal epidermis and appendages and possibly the nests of epidermal stem cells.

Identification of stem cell populations in sweat glands and ducts reveals roles in homeostasis and wound repair.

Sweat glands are abundant in the body and essential for thermoregulation. Like mammary glands, they originate from epidermal progenitors. However, they display few signs of cellular turnover, and whether they have stem cells and tissue-regenerative capacity remains largely unexplored. Using lineage tracing, we here identify in sweat ducts multipotent progenitors that transition to unipotency after developing the sweat gland. In characterizing four adult stem cell populations of glandular skin, we show that they display distinct regenerative capabilities and remain unipotent when healing epidermal, myoepithelial-specific, and lumenal-specific injuries. We devise purification schemes and isolate and transcriptionally profile progenitors. Exploiting molecular differences between sweat and mammary glands, we show that only some progenitors regain multipotency to produce de novo ductal and glandular structures, but that these can retain their identity even within certain foreign microenvironments. Our findings provide insight into glandular stem cells and a framework for the further study of sweat gland biology.

Fibroepithelioma of Pinkus is a true basal cell carcinoma developing in association with a newly identified tumour-specific type of epidermal hyperplasia.

BACKGROUND: Fibroepithelioma of Pinkus (FEP) has long been viewed as a subtype of basal cell carcinoma (BCC). Recently, however, the proposal has been made that FEP represents a fenestrated trichoblastoma/trichoepithelioma. One of the main arguments is the presence of Merkel cells in FEP, which typically do not occur in BCC. OBJECTIVES: As the new stem cell marker, PHLDA1 (TDAG51), labels trichoepithelioma but not BCC, our aim was to characterize its staining pattern in FEP. Because adnexal tumours have been viewed as recapitulating embryogenesis, we also examined PHLDA1 immunoreactivity in the skin of human embryos and fetuses. METHODS: We studied immunohistochemically PHLDA1 staining in 31 FEPs, 14 BCCs and 16 trichoepitheliomas and compared this with its staining pattern in embryonic skin and with the distribution of Merkel cells. RESULTS: In FEP, PHLDA1 labels the anastomosing network of thin cellular strands but not the basaloid nubbins. During embryogenesis, PHLDA1 stains the basal cell layer of the epidermis, as long as adnexal structures develop. Immunoreactivity for PHLDA1 correlates positively with the presence of Merkel cells. CONCLUSIONS: We propose that the thin anastomosing network of PHLDA1-positive cells represents a type of epidermal hyperplasia specific to FEP. The multifocal BCCs that are PHLDA1-negative develop from this network which becomes incorporated into the tumour. Viewing the anastomosing network as a tumour-specific form of epidermal hyperplasia explains the hitherto enigmatic presence of Merkel cells in FEP.

Ectodysplasin signaling in cutaneous appendage development: dose, duration, and diversity.

The development of several types of skin appendages is guided by prenatal ectodysplasin signaling. In this issue, Cui et al. report on the dose and duration of ectodysplasin signaling required for the maintenance and morphogenesis of different types of appendages. They report that achievement of an intimate arrangement between epithelial and mesenchymal cell populations correlates with the acquisition of autonomy from ectodysplasin stimulation.

Requirement for Shh and Fox family genes at different stages in sweat gland development.

Sweat glands play a fundamental role in thermal regulation in man, but the molecular mechanism of their development remains unknown. To initiate analyses, we compared the model of Eda mutant Tabby mice, in which sweat glands were not formed, with wild-type (WT) mice. We inferred developmental stages and critical genes based on observations at seven time points spanning embryonic, postnatal and adult life. In WT footpads, sweat gland germs were detected at E17.5. The coiling of secretory portions started at postnatal day 1 (P1), and sweat gland formation was essentially completed by P5. Consistent with a controlled morphological progression, expression profiling revealed stage-specific gene expression changes. Similar to the development of hair follicles-the other major skin appendage controlled by EDA-sweat gland induction and initial progression were accompanied by Eda-dependent up-regulation of the Shh pathway. During the further development of sweat gland secretory portions, Foxa1 and Foxi1, not at all expressed in hair follicles, were progressively up-regulated in WT but not in Tabby footpads. Upon completion of WT development, Shh declined to Tabby levels, but Fox family genes remained at elevated levels in mature sweat glands. The results provide a framework for the further analysis of phased down-stream regulation of gene action, possibly by a signaling cascade, in response to Eda.

Analysis of the temporal requirement for eda in hair and sweat gland development.

EDA signaling is important in skin appendage initiation. Its possible involvement in appendage subtype determination and postinduction stage appendage development, however, has not been studied systematically. To address these issues we manipulated Eda-A1 transgene expression in a tetracycline-regulated conditional mouse model, where the transgene is the only source of active ectodysplasin (Eda). We find that Eda-A1 restores sweat glands and all hair subtypes in Tabby, but each requires its action at an idiosyncratic time of development: by E17 for guard, by E19 for awl, and starting at E18 for zigzag/auchen hair. Guard and awl hairs were indistinguishable from their wild-type counterparts; but restored zigzag and auchen hairs, although recognizable, were somewhat smaller and lacked characteristic bends. Notably, secondary hair follicle formation of awl, auchen, and zigzag hairs required higher Eda-A1 expression level than did guard hair or sweat glands. Furthermore, Eda-A1 expression is required until the early dermal papilla stage for guard hair germs to make follicles, but is dispensable for their maturation. Similarly, sweat gland pegs require Eda-A1 at an early stage to form mature glands. Thus we infer that EDA signaling is needed for the determination and development of various skin appendages at spatiotemporally restricted intervals.

Naegeli-Franceschetti-Jadassohn syndrome and dermatopathia pigmentosa reticularis: two allelic ectodermal dysplasias caused by dominant mutations in KRT14.

Naegeli-Franceschetti-Jadassohn syndrome (NFJS) and dermatopathia pigmentosa reticularis (DPR) are two closely related autosomal dominant ectodermal dysplasia syndromes that clinically share complete absence of dermatoglyphics (fingerprint lines), a reticulate pattern of skin hyperpigmentation, thickening of the palms and soles (palmoplantar keratoderma), abnormal sweating, and other subtle developmental anomalies of the teeth, hair, and skin. To decipher the molecular basis of these disorders, we studied one family with DPR and four families with NFJS. We initially reassessed linkage of NFJS/DPR to a previously established locus on 17q11.2-q21. Combined multipoint analysis generated a maximal LOD score of 8.3 at marker D17S800 at a recombination fraction of 0. The disease interval was found to harbor 230 genes, including a large cluster of keratin genes. Heterozygous nonsense or frameshift mutations in KRT14 were found to segregate with the disease trait in all five families. In contrast with KRT14 mutations affecting the central alpha -helical rod domain of keratin 14, which are known to cause epidermolysis bullosa simplex, NFJS/DPR-associated mutations were found in a region of the gene encoding the nonhelical head (E1/V1) domain and are predicted to result in very early termination of translation. These data suggest that KRT14 plays an important role during ontogenesis of dermatoglyphics and sweat glands. Among other functions, the N-terminal part of keratin molecules has been shown to confer protection against proapoptotic signals. Ultrastructural examination of patient skin biopsy specimens provided evidence for increased apoptotic activity in the basal cell layer where KRT14 is expressed, suggesting that apoptosis is an important mechanism in the pathogenesis of NFJS/DPR.

Target-dependent specification of the neurotransmitter phenotype: cholinergic differentiation of sympathetic neurons is mediated in vivo by gp 130 signaling.

Sympathetic neurons are generated through a succession of differentiation steps that initially lead to noradrenergic neurons innervating different peripheral target tissues. Specific targets, like sweat glands in rodent footpads, induce a change from noradrenergic to cholinergic transmitter phenotype. Here, we show that cytokines acting through the gp 130 receptor are present in sweat glands. Selective elimination of the gp 130 receptor in sympathetic neurons prevents the acquisition of cholinergic and peptidergic features (VAChT, ChT1, VIP) without affecting other properties of sweat gland innervation. The vast majority of cholinergic neurons in the stellate ganglion, generated postnatally, are absent in gp 130-deficient mice. These results demonstrate an essential role of gp 130-signaling in the target-dependent specification of the cholinergic neurotransmitter phenotype.

Epidermal stem cells are the source of sweat glands in human fetal skin: evidence of synergetic development of stem cells, sweat glands, growth factors, and matrix metalloproteinases.

The development of sweat glands is a complex biological process, and the extent of cellular trafficking between epidermal stem cells and the development of sweat glands is uncertain. Therefore, we studied the synergetic development effects of stem cells, sweat glands, growth factors, and matrix metalloproteinases (MMPs) in human skin. Human fetal skin was obtained from spontaneously aborted fetuses at 11-31 weeks of gestation. Paraffin sections were cut and stained with hematoxylin and eosin or immunostained with antibodies against beta(1) integrin, keratin (K)-19 and K7, MMP-2 and -7, and epidermal growth factor. In situ hybridization was used along with semiquantitative analysis of the positive expression of these proteins to analyze for mRNA expression of MMP-2 and -7. Histological studies revealed the fetal epidermis began to form a primary epidermal ridge at gestational age 13-14 weeks and these primordial basal cells became tightly packed to take the form of multiple hillocks between 14 and 16 weeks. Furthermore, these cells gave rise to chord-like columnar buds in the embryonic epidermis, and these buds gradually migrated downward into the dermis to form juvenile sweat glands at 18-20 weeks. Mature sweat glands were found in the fetal epidermis at the end of 24 weeks. beta(1) integrin and K19 immunoreactivities were first detected in those cells that gathered together to form primary epidermal ridges, including sweat gland cords, buds, and immature sweat gland cells. The positive immunostaining for K7 appeared in early sweat gland buds at 14-16 weeks, and from then on K7 was concentrated in developing sweat gland cords or cells. At 14-16 weeks, positive epidermal growth factor, MMP-2, and MMP-7 expression was first observed weakly in developing sweat gland buds. The immunoreactivity of these proteins was then gradually increased in the developing sweat gland buds and extracellular stroma from 14 to 20 weeks. The intensity of the positive signal peaked at 20-22 weeks of gestational age. After that, the intensity of immunostaining for MMP-2 and MMP-7 proteins was gradually weakened. However, the expression of epidermal growth factor did not show an apparent decrease. These results suggest that epidermal stem cells are the source of sweat glands. Epidermal growth factor is one of the main inducers in the development and maturity of sweat gland buds or cells and the local activated MMPs may play an important role in cleaving the major matrix components in the basement membrane.

Fine needle aspiration cytology of breast cylindroma in a woman with familial cylindromatosis: a case report.

BACKGROUND: That sweat gland type tumors occur occasionally in the breast is not surprising, as the breast and cutaneous sweat glands are embryologically related. Cylindromas present most commonly as solitary and sporadic dermal nodules on the face and scalp. Cases of multiple cylindromas are dominantly inherited, and the neoplasms are referred to as "turban tumors" when multiple lesions cover the scalp. Primary cylindroma of the breast has been reported once in the past. To the best of our knowledge, the fine needle aspiration cytology of primary breast cylindroma and its occurrence in the setting of familial cylindromatosis have not previously been reported. CASE: A 59-year-old woman presented with an ill-defined left breast mass. She had a personal and family history of dermal cylindromas on the head and face. Fine needle aspiration cytology demonstrated small, uniform cells with oval nuclei and finely granular cytoplasm, with some cells arranged around conspicuous cylinders of dense, acellular material. Excisional biopsy was recommended to exclude adenoid cystic carcinoma. Tissue biopsy revealed a benign cylindroma arising in breast parenchyma. CONCLUSION: Fine needle aspiration cytology of cylindroma very closely mimics that of adenoid cystic carcinoma. Although extremely rare, primary breast cylindroma is another entity to be included in the cytologic differential diagnosis of bland, basaloid cells associated with globular, extracellular material, a finding most commonly associated with adenoid cystic carcinoma.

Keratin 16 expression defines a subset of epithelial cells during skin morphogenesis and the hair cycle.

The morphogenesis of skin epithelia and adult hair follicle cycling both require integrated signaling between the epithelium and underlying mesenchyme. Because of their unique regulation, keratin intermediate filaments represent useful markers for the analysis of determination and differentiation processes in complex epithelia, such as the skin. In this study, we analyzed the distribution of mouse type I keratin 16 during skin morphogenesis, in the adult hair cycle, and in challenged epidermis. In mature hair follicles, we find keratin 16 along with its type II keratin partner keratin 6 in the companion layer of the outer root sheath during anagen and in the club hair sheath during catagen and telogen. During embryonic development, the distribution of keratin 16 is uncoupled from its presumed polymerization partner, keratin 6. Keratin 16 initially localizes within early hair germs, but rapidly shifts to a subset of cells at the interface of basal and suprabasal cells above and around the hair germ. The presence of keratin 16 at the transition between mitotically active and differentiating cells is recapitulated in primary keratinocytes cultured in vitro and in phorbol 12-myristate 13-acetate-treated back skin in vivo. We propose that keratin 16 marks cells in an intermediate state of cellular properties in which keratinocytes retain the flexibility required for activities such as cell migration and even mitosis but are resilient enough to provide the structural integrity required of the early suprabasal layers in the context of development, adult hair cycling, and wound repair.

The interaction between epidermal growth factor and matrix metalloproteinases induces the development of sweat glands in human fetal skin.

BACKGROUND: The development of sweat glands is a very complicated biological process involving many factors. In this study, we explore the interrelationship among epidermal growth factor (EGF), matrix metalloproteinase 2 (MMP-2), matrix metalloproteinase 7 (MMP-7), and the development of sweat glands in human embryos. Furthermore, we hope to elucidate the mechanism(s) underlying the induction of epidermal stem cells into sweat gland cells. MATERIALS AND METHODS: Skin biopsies of human embryos obtained from spontaneous abortions at different gestational ages from 11 to 31 weeks were used in this study. The dynamic expression of EGF, MMP-2, MMP-7, and keratin-7 (K7) in developing sweat gland cells or extracellular stroma surrounding the sweat gland cells was examined with SP immunohistochemical methods. The localization of the cellular sources of MMP-2 and MMP-7 was examined with in situ hybridization. RESULTS: At 14-20 weeks of gestation, a gradual increase in EGF immunoreactivity was observed not only in developing sweat gland buds but also in extracellular stroma surrounding the buds, and the expression intensity of EGF peaked at 20-22 weeks of gestational age. All mRNA-positive buds or cells in developing sweat glands contained corresponding immunoreactive proteins. Positive immunostaining for K7 appeared in early sweat gland buds at 14-16 weeks of gestation, and from then on, the positive signal of K7 was concentrated in developing sweat gland cords or cells. CONCLUSIONS: The morphogenesis of sweat glands in human fetal skin begins at 14-16 weeks of gestational age, and is essentially complete by 24 weeks. There is a close relationship among EGF, extracellular matrix remodeling, and morphogenesis of the sweat glands. EGF is one of the inducers in the development and maturity of sweat gland buds or cells.

[Study on the relationship between epidermal stem cells and the developing process of sweat gland in human fetal skin].

OBJECTIVE: To explore the relationship between epidermal stem cells and the developing process of sweat gland in human fetal skin, so as to obtain a hint for future induction of epidermal stem cells to differentiate into sweat gland cells. METHODS: Total layer of human skin from the back of fetus at gestational ages from 11 to 31 weeks, obtained from spontaneous abortion was routinely examined. The expressions of beta1 integrin and keratin 19 in sweat gland cords or buds and mature sweat gland cells were dynamically observed with SP immunohistochemical technique. The development and maturation of sweat gland were identified by the positive staining of keratin 8 with immunohistochemistry. RESULTS: It was revealed by histologic observation that basal layer cells of the primary epidermal ridge exhibited focal aggregation and formed hillocks at 16 gestational weeks. The hillocks of cells then migrated downward as cords into the dermis during 18 - 20 gestational weeks. Then, the end part of the cell cord developed into a round lump of twining cords assuming the mature sweat gland. The expressions of beta1 integrin and keratin 19 were found not only in sweat gland cords and buds but also in the mature cells and lasted throughout the total period of sweat gland development. The expression of keratin 8 in sweat gland buds started since 14 - 16 gestational weeks and maintained thereafter. CONCLUSION: The sweat gland started to develop during 14 - 16 gestational weeks and matured at 24 weeks. During the development process of sweat gland, epidermal stem cells were considered to be the key source.