Method for Human Eccrine Sweat Gland Isolation from the Scalp by Means of the Micropunch Technique and Vital Dyes.

The isolation of eccrine sweat glands from human skin has always been a difficult task. The human scalp contains thousands of eccrine glands. Recently, the close anatomic relationship of the eccrine gland with the scalp hair follicle has been described. Taking advantage of this anatomic relationship as well as of the availability of follicular units (FUs) obtained in hair transplant procedures, we describe here a simple and efficient method to isolate eccrine sweat glands from the human scalp. This method is identical to the micropunch hair graft harvesting method known as follicular unit excision (FUE), used in modern hair transplantation. Once the FU has been extracted, it needs to be stained with methylene blue or neutral red in order to make the sweat gland visible for stereoscopic microdissection. Only the secretory (coiled) portion of the sweat gland can be obtained with this method. The efficiency of this isolation method should encourage further research into human eccrine sweat glands and opens possibilities for new translational applications.

Eccrine sweat glands associate with the human hair follicle within a defined compartment of dermal white adipose tissue.

BACKGROUND: Eccrine sweat glands (ESGs) are critical for thermoregulation and are involved in wound healing. ESGs have traditionally been considered as separate skin appendages without connection to the pilosebaceous unit (PSU). However, recent preliminary evidence has encouraged the hypothesis that the PSU and ESG are more interconnected than previously thought. OBJECTIVES: To re-evaluate the morphology of human skin adnexa with an integrated three-dimensional (3D) perspective in order to explore the possible interconnections that the PSU and the ESG may form. METHODS: A systematic 3D reconstruction method of skin sections, direct visualization of human scalp follicular unit transplant grafts and a scalp strip ex vivo were used to validate and further explore the hypothesis. RESULTS: We demonstrate that the coiled portion of most ESGs is morphologically integrated into the PSU of human scalp skin and forms a structural unit that is embedded into a specific, hair follicle-associated region of dermal white adipose tissue (dWAT). This newly recognized unit is easily accessible and experimentally tractable by organ culture of follicular units and can be visualized intravitally. CONCLUSIONS: We propose a model of functional human skin anatomy in which ESGs are closely associated with the PSU and the dWAT to form a common homeostatic tissue environment, which may best be encapsulated in the term 'adnexal skin unit'. The challenge now is to dissect how each component of this superstructure of human skin functionally cooperates with and influences the other under physiological conditions, during regeneration and repair and in selected skin diseases.

An efficient method for eccrine gland isolation from human scalp.

We describe a simple and efficient method to isolate eccrine sweat glands from the human scalp. This method is inspired by the hair graft harvesting method used in hair transplantation. Based on the recently described anatomical relationship between the scalp hair follicle and the eccrine gland, we have found that scalp follicular unit grafts are an excellent eccrine gland isolation source, especially for the coiled component. In order to make the gland visible for stereoscopic microdissection, the follicular units need to be previously stained with a vital dye like methylene blue or neutral red. The simplicity and efficiency of this isolation method should encourage further research into human eccrine sweat gland function which has always been hindered by the difficulty of gland isolation.

Histological, chemical and behavioural evidence of pedal communication in brown bears.

Most mammals rely upon scent for intraspecific communication. As most bear species have large home ranges and are non-territorial, scent deposit while walking could be an effective way to communicate with conspecifics. Here, we investigate the existence of pedal glands in brown bears and their role in chemical communication from a histological, biochemical and behavioural perspective. We found eccrine glands in footpads, and prominent apocrine and sebaceous glands in the interdigital, metacarpal and metatarsal skin sections. Pedal scent contained 26 compounds including carboxylic acids, important constituents of mammalian secretions. Six of these compounds were exclusive for males. Finally, we describe a specific marking gait recorded in the field, mostly performed by males. Our study supports the existence of chemical communication through pedal marking in brown bears and suggests sex-coding potential of pedal scent.

Is the eccrine gland an integral, functionally important component of the human scalp pilosebaceous unit?

The pilosebaceous unit (PSU) and the eccrine sweat gland (ESG) are classically described as completely independent skin appendages. However, careful inspection of scalp follicular units reveals that the secretory segment of the ESG spatially approximates the hair follicle in a position below the sebaceous gland and the insertion of the arrector pili muscle. Therefore, we propose here that, contrary to conventional wisdom, the PSU and the ESG should not be viewed in isolation, and may form instead, along with the arrector pili muscle and the apocrine gland (where present),one functional unit. For this, we suggest the more inclusive term of 'Hair Cluster' (HC). If confirmed, e.g. by 3D imaging techniques, the novel concept of a functional HC, whose individual components may communicate via secreted molecules and may share selected progenitor cell populations for HC repair/regeneration, has major physiological and pathological implications, which are briefly discussed.

Eccrine sweat gland development and sweat secretion.

Eccrine sweat glands help to maintain homoeostasis, primarily by stabilizing body temperature. Derived from embryonic ectoderm, millions of eccrine glands are distributed across human skin and secrete litres of sweat per day. Their easy accessibility has facilitated the start of analyses of their development and function. Mouse genetic models find sweat gland development regulated sequentially by Wnt, Eda and Shh pathways, although precise subpathways and additional regulators require further elucidation. Mature glands have two secretory cell types, clear and dark cells, whose comparative development and functional interactions remain largely unknown. Clear cells have long been known as the major secretory cells, but recent studies suggest that dark cells are also indispensable for sweat secretion. Dark cell-specific Foxa1 expression was shown to regulate a Ca(2+) -dependent Best2 anion channel that is the candidate driver for the required ion currents. Overall, it was shown that cholinergic impulses trigger sweat secretion in mature glands through second messengers - for example InsP3 and Ca(2+) - and downstream ion channels/transporters in the framework of a Na(+) -K(+) -Cl(-) cotransporter model. Notably, the microenvironment surrounding secretory cells, including acid-base balance, was implicated to be important for proper sweat secretion, which requires further clarification. Furthermore, multiple ion channels have been shown to be expressed in clear and dark cells, but the degree to which various ion channels function redundantly or indispensably also remains to be determined.

Evaluation of nerves in Mohs micrographic surgery: histologic mimickers of perineural invasion and nervous tissue on frozen section.

BACKGROUND: Perineural invasion (PNI) is an important histologic finding and may be a negative prognostic factor for squamous cell carcinoma (SCC). It may be associated with more-aggressive tumor behavior. Mohs surgeons encounter microscopic PNI regularly and must be able to diagnose it accurately to guide care decisions. OBJECTIVE: To describe benign histologic mimickers of PNI and neural structures in SCC commonly encountered on frozen, hematoxylin and eosin-stained sections and to review how to differentiate them from PNI. METHODS AND MATERIALS: Review of the literature regarding histologic mimickers of PNI and additional contributions to frozen section PNI and nerve tissue mimickers. RESULTS: We describe benign findings, including arrector pili muscles, eccrine muscles, vessels, granulomatous inflammation, and eddies of SCC, that may each be mistaken for nerves or PNI. We discuss the ways in which they may be distinguished on frozen sections and review other commonly encountered entities that resemble PNI. CONCLUSION: Perineural inflammation and peritumoral fibrosis are common mimickers of PNI on frozen section, although other mimickers exist on permanent sections. Normal structures may appear "neural" by way of frozen tissue orientation, processing, or inflammation and thus must be differentiated from nerve tissue and PNI during Mohs surgery.

Basic histological structure and functions of facial skin.

The skin and its appendages that derive from the epidermis (hair follicles, sweat glands, sebaceous glands, nails, and mammary glands) establish the integumentary system. Histologically, skin has two main layers-the epidermis and the dermis-with a subcutaneous fascia called the hypodermis, which lies deep in the dermis. The epidermis is formed of four to five layers of cells made mostly out of keratinocytes, along with three other different and less abundant cells. The dermis underlies the epidermis. The hypodermis is a looser connective tissue that is located beneath the dermis. It blends to the dermis with an unclear boundary.

Immunolocalization of aquaporin-5 in normal human skin and hypohidrotic skin diseases.

Aquaporin (AQP)-5 has been shown to be expressed in the secretory parts of mouse, rat and horse sweat glands. However, the precise localization of AQP-5 in normal and diseased human skin has not been fully determined. The aim of the present study was to further clarify the immunolocalization of AQP-5 in normal human skin and hypohidrotic skin diseases. Normal human scalp skin and biopsies from skin affected by hypohidrotic diseases were analyzed for AQP-5 and/or dermcidin expression by immunohistochemistry, immunofluorescence and/or immunoelectronmicroscopy. AQP-5 was expressed on the apical and basolateral plasma membranes of the clear cells in eccrine sweat coils, but not in ductal components or apocrine glands. Numbers of AQP-5-positive coils in the secretory part of eccrine sweat glands were decreased in Sjögren's syndrome, but not in skin affected by idiopathic segmental anhidrosis or idiopathic pure sudomotor failure. AQP-5 was mostly localized to the plasma membranes of clear cells in the secretory coils of eccrine sweat glands, suggesting that it plays a role in producing the primary sweat fluid.

Development, structure, and keratin expression in C57BL/6J mouse eccrine glands.

Eccrine sweat glands in the mouse are found only on the footpads and, when mature, resemble human eccrine glands. Eccrine gland anlagen were first apparent at 16.5 days postconception (DPC) in mouse embryos as small accumulations of cells in the mesenchymal tissue beneath the developing epidermis resembling hair follicle placodes. These cells extended into the dermis where significant cell organization, duct development, and evidence of the acrosyringium were observed in 6- to 7-postpartum day (PPD) mice. Mouse-specific keratin 1 (K1) and 10 (K10) expression was confined to the strata spinosum and granulosum. In 16.5 and 18.5 DPC embryos, K14 and K17 were both expressed in the stratum basale and diffusely in the gland anlagen. K5 expression closely mimicked K17 throughout gland development. K6 expression was not observed in the developing glands of the embryo but was apparent in the luminal cell layer of the duct by 6 to 7 PPD. By 21 PPD, the gland apertures appeared as depressions in the surface surrounded by cornified squames, and the footpad surface lacked the organized ridge and crease system seen in human fingers. These data serve as a valuable reference for investigators who use genetically engineered mice for skin research.

The secretory clear cell of the eccrine sweat gland as the probable source of excess sweat production in hyperhidrosis.

Primary hyperhidrosis is characterized by excessive sweating in palmar, plantar and axillary body regions. Gland hypertrophy and the existence of a third type of sweat gland, the apoeccrine gland, with high fluid transporting capabilities have been suggested as possible causes. This study investigated whether sweat glands were hypertrophied in axillary hyperhidrotic patients and if mechanisms associated with fluid transport were found in all types of axillary sweat glands. The occurrence of apoeccrine sweat glands was also investigated. Axillary skin biopsies from control and hyperhidrosis patients were examined using immunohistochemistry, image analysis and immunofluorescence microscopy. Results showed that glands were not hypertrophied and that only the clear cells in the eccrine glands expressed proteins associated with fluid transport. There was no evidence of the presence of apoeccrine glands in the tissues investigated. Preliminary findings suggest the eccrine gland secretory clear cell as the main source of fluid transport in hyperhidrosis.

A reappraisal of eyelid eccrine and apocrine hidrocystomas: microanatomic and immunohistochemical studies of 40 lesions.

PURPOSE: To establish reliable criteria for diagnosing eyelid eccrine and apocrine hidrocystomas. DESIGN: Retrospective clinicopathologic and immunohistochemical study. METHODS: Twenty-two specimens of normal portions of eyelids were evaluated to establish the distribution and microanatomy of eccrine and apocrine glands. Immunostaining for cytokeratin 7 (CK7), gross cystic disease fluid protein-15 (GCDFP-15), alpha-smooth muscle actin (α-SMA), epithelial membrane antigen (EMA), and carcinoembryonic antigen (CEA) was performed on these tissues and on 40 lesions in 33 patients diagnosed with eccrine or apocrine hidrocystomas by unaided light microscopy. RESULTS: Eccrine glands were not present in the eyelid margins, the lower half of the upper eyelid pretarsal skin, or the pretarsal lower eyelid skin. Apocrine glands were restricted to the eyelid margins and canthi where the cysts were located. GCDFP-15, CK7, and α-SMA immunoreacted with the eccrine secretory coils but not their ducts; apocrine gland secretory spirals also stained positively for these markers throughout their extended courses, but not their short terminal ducts. Positivity was found in 37 of 40 hidrocystomas for α-SMA and 19 for GCDFP-15; lesions tested for CK7 displayed positivity. CONCLUSIONS: Alpha-SMA-, CK7-, and/or GCDFP-15-positive apocrine hidrocystomas were the only type discovered in this series and arose from glandular secretory spirals within the marginal, perimarginal, or canthal skin. Three lesions did not stain for α-SMA, initially suggesting an absent myoepithelium and therefore an eccrine ductal origin; they manifested CK7 positivity, however, another characteristic of the apocrine secretory spiral but not ducts. Our findings disprove the contention that eccrine predominate over apocrine hidrocystomas in the eyelids.

SIBLING expression patterns in duct epithelia reflect the degree of metabolic activity.

The SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family of secreted glycophosphoproteins includes bone sialoprotein (BSP), dentin matrix protein-1 (DMP1), dentin sialophosphoprotein (DSPP), osteopontin (OPN), and matrix extracellular phosphoglycoprotein (MEPE). For many years, they were thought in normal adults to essentially be limited to metabolically active mesenchymal cells that assembled the mineralized matrices of bones and teeth. Over the last decade they have also been upregulated in a variety of tumors. Three of these proteins (BSP, OPN, and DMP1) have been shown to interact with three matrix metalloproteinases (MMP-2, MMP-3, and MMP-9, respectively). Recently, all five SIBLINGs and their MMP partners when known were observed in specific elements of normal ductal epithelia in salivary gland and kidney. We have hypothesized that the SIBLINGs and their MMP partners may be expressed in ductal cells with high metabolic activity. In this paper, we show that all the SIBLINGs (except MEPE) and their MMP partners are expressed in the metabolically active epithelia of human eccrine sweat gland duct but not in the more passive ductal cells of the macaque (monkey) lacrimal gland. It is hypothesized that MEPE expression may be limited to cells involved in active phosphate transport. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Immunohistochemical differentiation and localization analysis of sweat glands in the adult human axilla.

BACKGROUND: The classic concept of axillary glands differentiates between eccrine glands, producing abundant clear, nonodorous sweat; and apocrine glands, excreting small amounts of turbid, odorous milky sweat. A third type of sweat glands, the "apoeccrine" glands, were recently identified. To define the different types of sweat glands and their location and number, the authors carried out a prospective histologic study on adult human axillary skin, including various immunohistochemical markers. METHODS: Forty-three consecutive Caucasian, subjectively normhidrotic patients, who underwent a surgical procedure in the axilla unrelated to the axillary glands, were included in the study. For verification of normhidrosis, the gravimetric test was carried out by measuring the amount of sweat secretion per minute. Then, a 1 x 1-cm measuring piece of skin and subcutaneous tissue was excised in the apex of the axilla, divided into three samples--altogether, 129 samples--and processed for histologic examination. RESULTS: In the dermis, the authors found only very few eccrine (average, 0.3 gland/cm in only 12 percent of all patients) and apocrine glands (average, 0.1 gland/cm in only 4.7 percent of patients), and no apoeccrine glands in any patient. In the subcutaneous tissue, the mean number of glands per centimeter squared was 10 for the eccrine glands, nine for the apocrine glands, and six for the apoeccrine glands. CONCLUSIONS: In the authors' Caucasian subjects, all or most of the sweat glands were found in the subcutaneous tissue near the border to the dermis and not in the dermis. For extremely hyperfunctioning sweat glands, the authors recommend less radical surgical methods, with the preservation of skin, based on the knowledge that most glands are localized in the subcutaneous tissue.

Morphology and glycoconjugate histochemistry of the eccrine glands in the snout skin of the North American raccoon (Procyon lotor).

The eccrine nasolabial glands were found in the hypodermis of the nasal plane in the North American raccoon (Procyon lotor). In addition to light and electron microscopic observations, the distribution and selectivity of complex glycoconjugates in the eccrine tubular glands of the raccoon snout skin were studied using various histochemical methods, particularly lectin staining. The secretory epithelium and the luminal secretions exhibited high amounts of glycoconjugates with various saccharide residues (alpha-D: -mannose, alpha-L: -fucose, beta-D: -galactose, beta-N-acetyl-D: -glucosamine, sialic acid). The excretory duct cells also showed positive reactions with most of the histochemical methods applied. The results are discussed with regard to possible functions of the glandular secretions. The complex glycoconjugates that are produced by the eccrine nasolabial glands may be related to moistening of the skin surface as well as protecting the epidermis against physical damage or microbial contamination. This is the first report on the glands in the snout skin of carnivores.

Structure and function of human sweat glands studied with histochemistry and cytochemistry.

The basic structure and the physiological function of human sweat glands were reviewed. Histochemical and cytochemical techniques greatly contributed the elucidation of the ionic mechanism of sweat secretion. X-ray microanalysis using freeze-dried cryosections clarified the level of Na, K, and Cl in each secretory cell of the human sweat gland. Enzyme cytochemistry, immunohistochemistry and autoradiography elucidated the localization of Na,K-ATPase. These data supported the idea that human eccrine sweat is produced by the model of N-K-2Cl cotransport. Cationic colloidal gold localizes anionic sites on histological sections. Human eccrine and apocrine sweat glands showed completely different localization and enzyme sensitivity of anionic sites studied with cationic gold. Human sweat glands have many immunohistochemical markers. Some of them are specific to apocrine sweat glands, although many of them stain both eccrine and apocrine sweat glands. Histochemical techniques, especially immunohistochemistry using a confocal laser scanning microscope and in situ hybridization, will further clarify the relationship of the structure and function in human sweat glands.

[Morphology of sweat glands]. / Morphologie des glandes sudorales.

There are two types of sweat glands: eccrine glands, which do not show cytological changes during secretion and apocrine glands, characterised by decapitation secretion, in which part of the cell is pinched off and released into the lumen. Eccrine glands play a major role in thermoregulation and electrolyte balance. They are present everywhere in the human skin and are composed of a secretory portion, an intradermal duct and an upper intraepidermal part, called acrosyringium. The acrosyringium has a unique symmetrical and helicoidal course, which length is correlated to the thickness of the epidermis. Apocrine glands are located only on genital, axillary and mammary areas, where they are always connected to a hair follicle. Their exact role in humans is unknown. A third type of intermediate sweat glands, the apoeccrine glands, was recently described in axillary areas. Sweat glands can be involved in various inflammatory processes and can lead to a large range of both benign and malignant tumors.

Characterization of interdigital glands in the Asian elephant (Elephas maximus).

In the Asian elephant, wetness akin to perspiration is commonly observed on the cuticles and interdigital areas of the feet; this observation has lead to speculation regarding the existence of an interdigital gland. Our goal was to search for interdigital glands and characterise them morphologically, histochemically, and immunohistochemically. Necropsy samples of interdigital areas from two Asian elephants were obtained. Multiple sections were fixed and processed routinely, then stained with hematoxylin/eosin and differential mucin stains. Immunohistochemistry was also performed for cytokeratins 8 and 10. Interdigital glands resembling human eccrine glands were detected deep within the reticular dermis. Histochemical staining indicated neutral mucopolysaccharides and nonsulphated acid mucopolysaccharides in glandular secretions, and the glandular epithelium also showed immunoreactivity to cytokeratins 8 and 10. Both the histochemical and immunohistochemical staining patterns are analogous to human eccrine structures. This study shows with certainty that Asian elephants possess sweat glands as they are defined histologically.