The distribution of sympathetic adrenergic, tyrosine hydroxylase- and neuropeptide Y-immunoreactive nerves in human axillary sweat glands

The innervation of human axillary sweat glands was studied by using the specific SPG (sucrose-potassium phosphate-glyoxylic acid) catecholamine histofluorescence method and the peroxidase-antiperoxidase (PAP) immunocytochemical method. The present results demonstrated that human sweat glands are surrounded by nerves containing a weak tyrosine hydroxylase activity. Nerves showing catecholamine histofluorescence could be visualized around the sweat glands only in the presence of exogenous catecholamine (adrenaline in the local anestheticum). In all tissue specimens studied fluorescent adrenergic nerves could be seen around arteries and arterioles corresponding to the distribution of neuropeptide Y-like immunoreactive nerves.     

Target influences on transmitter choice by sympathetic neurons developing in the anterior chamber of the eye

In contrast to the majority of sympathetic neurons which are noradrenergic, the sympathetic neurons which innervate sweat glands are cholinergic. Previous studies have demonstrated that during development the sweat gland innervation initially contains catecholamines which are lost as cholinergic function appears. The neurotransmitter phenotype of sweat gland neurons further differs from the majority in that they contain vasoactive intestinal peptide (VIP) rather than neuropeptide Y (NPY). In the experiments described here, we addressed the question of whether sympathetic targets influence the neurotransmitter-related properties of the neurons which innervate them; in particular, do sweat glands play a role in reducing the expression of noradrenergic properties and inducing the expression of cholinergic properties and VIP in sympathetic neurons? This was accomplished by cotransplanting to the anterior chamber of the eye of host rats the superior cervical ganglia (SCG) which contains neurons that normally innervate targets other than the sweat glands and differentiate noradrenergically and footpad tissue from neonatal rats. Sweat glands developed in the transplanted footpad tissue and became innervated by the cotransplanted SCG neurons. The transplanted neurons and sweat gland innervation initially exhibited catecholamine histofluorescence which declined with further development in the anterior chamber. After 4 weeks, choline acetyltransferase (ChAT) and VIP immunoreactivities were evident. These observations suggest that as in the neurons which innervate the glands in situ, noradrenergic properties were suppressed and cholinergic function was induced in the neurons which innervated the glands in oculo. To distinguish a specific influence of the sweat glands on transmitter choice, SCG were also cotransplanted with the pineal gland, a normal target of the ganglion. Neurons cotransplanted with the pineal gland continued to exhibit catecholamine histofluorescence and contained NPY immunoreactivity. At least some neurons in SCG/pineal cotransplants, however, developed ChAT immunoreactivity. The target-appropriate expression of catecholamines and peptides in these experiments is consistent with the hypothesis that some transmitter properties are influenced by target tissues. The indiscriminant expression of ChAT, however, suggests that at least in oculo, additional factors can influence transmitter choice.     

Developmental interactions between sweat glands and the sympathetic neurons which innervate them: effects of delayed innervation on neurotransmitter plasticity and gland maturation

The neurotransmitter properties of the sympathetic innervation of sweat glands in rat footpads have previously been shown to undergo a striking change during development. When axons first reach the developing glands, they contain catecholamine histofluorescence and immunoreactivity for catecholamine synthetic enzymes. As the glands and their innervation mature, catecholamines disappear and cholinergic and peptidergic properties appear. Final maturation of the sweat glands, assayed by secretory competence, is correlated temporally with the development of cholinergic function in the innervation. To determine if the neurotransmitter phenotype of sympathetic neurons developing in vivo is plastic, if sympathetic targets can play a role in determining neurotransmitter properties of the neurons which innervate them, and if gland maturation is dependent upon its innervation, the normal developmental interaction between sweat glands and their innervation was disrupted. This was accomplished by a single injection of 6-hydroxy-dopamine (6-OHDA) on Postnatal Day 2. Following this treatment, the arrival of noradrenergic sympathetic axons at the developing glands was delayed 7 to 10 days. Like the gland innervation of normal rats, the axons which innervated the sweat glands of 6-OHDA-treated animals acquired cholinergic function and their expression of endogenous catecholamines declined. The change in neurotransmitter properties, however, occurred later in development than in untreated animals and was not always complete. Even in adult animals, some fibers continued to express endogenous catecholamines and many nerve terminals contained a small proportion of small granular vesicles after permanganate fixation. The gland innervation in the 6-OHDA-treated animals also differed from that of normal rats in that immunoreactivity for VIP was not expressed in the majority of glands. It seems likely that following treatment with 6-OHDA sweat glands were innervated both by neurons that would normally have done so and by neurons that would normally have innervated other, noradrenergic targets in the footpads, such as blood vessels. Contact with sweat glands, therefore, appears to suppress noradrenergic function and induce cholinergic function not only in the neurons which normally innervate the glands but also in neurons which ordinarily innervate other targets. Effects of delayed innervation were also observed on target development. The appearance of sensitivity to cholinergic agonists by the sweat glands was coupled with the onset of cholinergic transmission.(ABSTRACT TRUNCATED AT 400 WORDS)     

The distribution of substance P-, CGRP-, galanin-and ANP-like immunoreactive nerves in human sweat glands

Summary The distribution in immunoreactivities towards atrial natriuretic peptide, calcitonin gene-related peptide, galanin and substance P were demonstrated in human skin at the light and electron microscopic levels. Nerves immunoreactive to the first three of these peptides were found around eccrine sweat glands, whereas only a few positively-labelled nerve fibres could be seen around apocrine glands. At the ultrastructural level, immunoreactivity to the neuropeptides was localized in the large dense-cored vesicles of the nerve terminals. No immunoreactivity to substance P could be detected around sweat glands. In addition to these findings, the four types of immunoreactivity were seen in the thick preterminal nerve bundles.     

Catecholamine-containing nerve terminals of the eccrine sweat glands of macaques

Summary A loose network of catecholamine-containing nerves was demonstrated with a fluorescence histochemical method (Falck-Hillarp) in the coiled portion of eccrine sweat glands in the digital pads of macaques after the injection of nialamide and noradrenaline. In the skin of untreated control animals, fluorescent fibers appear only in some of the glands. A systemic administration of reserpine and a local injection of 6-hydroxydopamine (6-OHDA) or 5-hydroxydopamine (5-OHDA) into the digital pad cause a complete disappearance of fluorescent fibers around the glands and blood vessels. Electron micrographs reveal many unmyelinated varicose axon profiles outside the basement membrane of secretory tubules. Most of these profiles contain many small agranular vesicles and a few large dense-cored vesicles (cholinergic terminal), and some have numerous small granular and a few large densecored vesicles (adrenergic terminal).The local injection of 6-OHDA causes various degenerative changes in the adrenergic terminals but the cholinergic ones and the rest of the cellular structure remain intact. The injection of 5-OHDA induces a significant increase of electron-dense granules in the vesicles of adrenergic terminals.The presence of catecholamine and the effects of 6-OHDA and 5-OHDA in the nerve terminals indicate that the innervation of the eccrine sweat glands of macaques consists of cholinergic as well as adrenergic terminals.Publication No. 783 of the Oregon Regional Primate Research Center supported in part by Public Health Service, National Institutes of Health Grant RR 00163 of the Animal Resources Branch, Division of Research Resources.We acknowledge the excellent assistance of Tsutomu Yoshida, Tsuneka zu Fuse, John Ochsner, and Nickolas Roman.     

Catecholamine- and acetylcholinesterase-containing nerves in human lower respiratory tract

Summary The innervation of human lower respiratory tract was studied with special emphasis on airways with sodium-potassium glyoxylic acid (SPG) and acetylcholinesterase (AChE) methods to demonstrate catecholamine-containing and acetylcholinesterase-containing nerve fibers. AChE-method revealed a rich network of cholinesterase positive nerves both inside the bronchial glands where they run around and between the acini, and the airway smooth muscle from secondary bronchi to terminal bronchioli. No AChE-positive fibers were found in connection with the blood vessels or within the epithelium of bronchi or bonchioli. The AChE-positive nerve fibers in bronchial smooth muscle greatly outnumbered those containing catecholamine. The SPG-method revealed the presence of adrenergic nerves from the level of secondary bronchi to that of terminal bronchioli. These nerve fibers were most abundant in bronchial glands, where their amount was equal and distribution similar to those of AChE-containing nerve fibers. Outside the glands adrenergic fibers were constantly seen in connection with the bronchial blood vessels in connective tissues surrounding bronchi. A few nerve fibers were also present in airway smooth muscle from the secondary bronchi to terminal bronchioli.     

Immunocytochemical demonstration of nerve growth factor and histofluorescence of catecholaminergic nerves in the salivary glands of diabetic mice

Summary Nerve growth factor (NGF) was localized in the submandibular, sublingual, and parotid salivary glands of male and female diabetic mice and their normal littermates by immunoperoxidase staining usingp-phenylenediamine-pyrocatechol as a chromogen for the cytochemical demonstration of peroxidase activity. In the normal male submandibular gland, immunoreactive NGF was localized in the apical regions of granular, intercalated and collecting duct cells, while in the normal female submandibular gland, NGF was present throughout the cytoplasm of granular duct cells. The localization of NGF in the diabetic male and female submandibular glands was similar and resembled that of the normal female. NGF immunoreactivity was also observed in the striated duct cells in the sublingual and parotid glands of all four types of mice.The sympathetic innervation of the submandibular glands of normal and diabetic mice was demonstrated using glyoxylic acid-induced histofluorescence. The pattern of sympathetic innervation and the intensity of catecholamine fluorescence was consistently different in the four types of mice. In the normal male submandibular gland the fluorescence was very intense, particularly in nerves adjacent to the granular ducts. In the normal female submandibular gland, the fluorescence was weak, while in the diabetic male and female the fluorescence was moderate.The correlation between the intensity of the immunocytochemical staining for NGF and the catecholamine fluorescence adjacent to the granular ducts suggests a trophic influence of the NGF-containing granular ducts on their sympathetic innervation.     

A melanocyte–melanoma precursor niche in sweat glands of volar skin

Determination of the niche for early‐stage cancer remains a challenging issue. Melanoma is an aggressive cancer of the melanocyte lineage. Early melanoma cells are often found in the epidermis around sweat ducts of human volar skin, and the skin pigmentation pattern is an early diagnostic sign of acral melanoma. However, the niche for melanoma precursors has not been determined yet. Here, we report that the secretory portion (SP) of eccrine sweat glands provide an anatomical niche for melanocyte–melanoma precursor cells. Using lineage‐tagged H2B‐GFP reporter mice, we found that melanoblasts that colonize sweat glands during development are maintained in an immature, slow‐cycling state but renew themselves in response to genomic stress and provide their differentiating progeny to the epidermis. FISH analysis of human acral melanoma expanding in the epidermis revealed that unpigmented melanoblasts with significant cyclin D1 gene amplification reside deep in the SP of particular sweat gland(s). These findings indicate that sweat glands maintain melanocyte–melanoma precursors in an immature state in the niche and explain the preferential distribution of early melanoma cells around sweat glands in human volar skin.     

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.     

Early increase in CGRP- and VIP-immunoreactive nerves in the skin of streptozotocin-induced diabetic rats.

We have previously shown depletion of nerves and neuropeptides in skin biopsies of diabetic patients, even in the absence of clinical signs and symptoms of sensory and autonomic neuropathy, but were unable to examine the changes occurring at an early stage of the disease. Therefore, the distribution and relative density of peptide-containing nerves was studied in streptozotocin-treated rats in order to assess the progression of neural changes in the initial stages of diabetes. Skin samples dissected from the lip and footpad of diabetic rats, 2, 4, 8 and 12 weeks after streptozotocin injection and age matched controls were sectioned and were immunostained with antisera to the neuropeptides substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY), and to a general neural marker, protein gene product 9.5 (PGP 9.5). No change was apparent in the distribution or relative density of immunoreactive cutaneous nerve fibres 2, 4 and 8 weeks after streptozotocin treatment. By 12 weeks there was a marked increase in the number of CGRP-immunoreactive fibres present in epidermis and dermis, and of VIP-immunoreactive fibres around sweat glands and blood vessels. A parallel increase was seen in nerves displaying PGP 9.5 immunoreactivity. No differences were detected in nerves immunoreactive for either substance P in the epidermis and dermis, and NPY around blood vessels. The alterations in the peptide immunoreactivities may be similar in the initial stages of human diabetes.     

Early increase in CGRP- and VIP-immunoreactive nerves in the skin of streptozotocin-induced diabetic rats

Summary We have previously shown depletion of nerves and neuropeptides in skin biopsies of diabetic patients, even in the absence of clinical signs and symptoms of sensory and autonomic neuropathy, but were unable to examine the changes occurring at an early stage of the disease. Therefore, the distribution and relative density of peptide-containing nerves was studied in streptozotocin-treated rats in order to assess the progression of neural changes in the initial stages of diabetes. Skin samples dissected from the lip and footpad of diabetic rats, 2, 4, 8 and 12 weeks after streptozotocin injection and age matched controls were sectioned and were immunostained with antisera to the neuropeptides substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY), and to a general neural marker, protein gene product 9.5 (PGP 9.5). No change was apparent in the distribution or relative density of immunoreactive cutaneous nerve fibres 2, 4 and 8 weeks after streptozotocin treatment. By 12 weeks there was a marked increase in the number of CGRP-immunoreactive fibres present in epidermis and dermis, and of VIP-immunoreactive fibres around sweat glands and blood vessels. A parallel increase was seen in nerves displaying PGP 9.5 immunoreactivity. No differences were detected in nerves immunoreactive for either substance P in the epidermis and dermis, and NPY around blood vessels. The alterations in the peptide immunoreactivities may be similar in the initial stages of human diabetes.     

Immunohistochemical localization of activated EGF receptor in human eccrine and apocrine sweat glands.

Epidermal growth factor (EGF) is secreted into sweat from secretory cells of human sweat glands. The function of EGF in sweat is poorly understood. The biological function of EGF is exerted by the binding of EGF to the receptor (EGFR) and its activation. Therefore, we immunohistochemically localized the activated form of EGFR in human eccrine and apocrine sweat glands to assess the functional importance of the EGF-EGFR system in human sweat glands. Frozen sections of human skin were stained with a monoclonal antibody (MAb) specific for tyrosine-phosphorylated (activated) EGFR and with an MAb that stains both activated and non-activated EGFR. In the secretory portion of eccrine sweat glands, nuclei of the secretory cells were stained with the anti-activated EGFR MAb. In coiled and straight portions of eccrine sweat ducts, nuclei of luminal and peripheral cells were stained with the antibody specific for activated EGFR. Luminal cell membranes and luminal cytoplasm of inner ductal cells possessed non-activated EGFR. In the secretory portion of apocrine sweat glands, activated EGFRs were present in cytoplasm and nuclei of secretory cells. These data suggest that EGF, already known to be present in the cytoplasm of secretory cells in eccrine and apocrine sweat glands, activates EGFR in the nuclei of secretory cells themselves in an intracrine manner. Because ductal cells do not express EGF, EGF in the sweat secreted from the secretory cells should activate EGFR in the ductal cells in a paracrine manner. (J Histochem Cytochem 49:597-601, 2001)     

Differential expression of dipeptidyl peptidase IV in human versus cynomolgus monkey skin eccrine sweat glands

Dipeptidyl peptidase IV (DPP4) is a peptidase whose inhibition is beneficial in Type II diabetes treatment. Several evidences suggest potential implication of DPP4 in skin disorders such as psoriasis, keloids and fibrotic skin diseases where its inhibition could also be beneficial. DPP4 expression in human skin was described mainly in dermal fibroblasts and a subset of keratinocytes in the basal layer. Of importance in the perspective of preclinical experimentation, DPP4 distribution in skin of non-human primate species has not been documented. This report evidences unexpected differences between a set of human and cynomolgus monkey skin samples revealing a major expression of DPP4 in eccrine sweat glands of cynomolgus monkeys but not in humans. This represents a unique distinctive feature compared to the conserved expression of dipeptidyl peptidases 8 and 9 and potential relevant DPP4 substrates such as neuropeptide Y (NPY) and receptors (NPY-receptor 1 and Neurokinin receptor). Finally the observation that cathepsin D, an unrelated protease, shows the opposite expression compared to DPP4 (present in human but not in cynomolgus monkey eccrine sweat glands) could indicate that human eccrine sweat glands evolved a divergent protease repertoire compared to non-human primates. These unexpected differences in the eccrine sweat glands protease repertoire will need to be confirmed extending the analysis to a major number of donors but could imply possible biochemical divergences, reflecting the functional evolution of the glands and the control of their activity. Our findings also demonstrate that non-human primates studies aiming at understanding DPP4 function in skin biology are not readily translatable to human.     

Adrenergic and cholinergic nerves of bovine,guinea pig and hamster salivary glands

Summary The distribution of formaldehyde-induced fluorescence and acetylcholine-esterase (AChE) activity was histochemically investigated in certain salivary glands of the cow (submandibular gland), guinea pig and hamster (submandibular and sublingual glands). Adrenergic nerves occur around the secretory acini of the bovine, guinea pig and hamster submandibular glands, as well as around those of the hamster sublingual gland. The mucous secretory acini of the guinea pig sublingual gland, however, seem to be devoid of adrenergic nerve supply. Except in the sublingual gland of the hamster, no adrenergic nerves occur in relation to duct cells.The pattern of AChE activity is similar to that of adrenergic nerves. Thus, AChE-positive nerves form a network around secretory acini of all the five glands examined. Furthermore, AChE activity was also observed in nerve fibres in close proximity to striated duct cells.Both adrenergic and AChE-containing fibres were observed around blood vessels of different sizes. Ganglionic cells are occasionally to be seen; they all display AChE-activity. No adrenergic ganglionic cells were observed in any of the glands examined.All glands were also studied in the electron microscope. Interest was focussed on the fine structure of the autonomic nerves with special reference to their contents and type of storage vesicles.The content of noradrenaline was chemically determined in each type of salivary gland studied.This work was supported by grants from the University of Umeå and from the Swedish Society for Medical Research and was also carried out within a research organization supported by the Swedish Medical Research Council (projects B73-04X-712-08C and B73-04X-56-09C). The authors are indebted to Miss Kristina Karlsson and Miss Marianne Borg for valuable technical assistance.     

High endocytotic and lysosomal activities in segments of rat myotubes differentiated in vitro

Summary The entire microvascular architecture in rat foot-pads including that of eccrine sweat glands was studied by scanning electron microscopy using a vascular corrosion-cast replication technique. In the central roofs of the pads, particularly elaborate capillary networks were arranged in rows perpendicular to the long axis of the foot. In the marginal regions of the pads, simple networks of capillaries were arranged in lamellar sheets parallel to the surface of the sole of the foot. Complex spongy networks of vascular trees were observed in the subcutaneous layer of the pads. These vessels were supplied by the pad artery, and then, after forming capillary networks in the roofs of the pads, they drained into the metatarsal vein. Rod-shaped cages of capillaries were observed around the eccrine sweat glands. One descending arteriole, arising from a connecting arteriole, and a few venules were connected with these capillary cages at their upper and lateral sides. Occasional arterio-venous and veno-venous anastomoses were also observed around the eccrine sweat glands. This microvascular architecture may adjust well to the mechanical and physiological conditions encountered in the foot-pads. The relation of the microvascular architecture around the eccrine sweat glands with their development is also discussed.     

Acquisition of cholinergic and peptidergic properties by sympathetic innervation of rat sweat glands requires interaction with normal target

The sweat glands, a target of cholinergic sympathetic neurons, were replaced with parotid gland, a target of noradrenergic sympathetic neurons, in neonatal rats. This transplantation paradigm allowed sympathetic neurons that would normally innervate the sweat glands and develop a cholinergic phenotype to innervate the parotid gland instead. The innervation of the transplanted parotid gland did not develop a cholinergic phenotype, as assessed by choline acetyltransferase activity and acetylcholinesterase immunoreactivity, but continued to express intense catecholamine fluorescence. In addition, immunoreactivity for vasoactive intestinal peptide, normally expressed by the sympathetic innervation of the sweat glands but not the parotid, was observed in only a small percentage of the parotid-associated fibers. These results suggest that cellular interactions between neurons and their targets play an important role in the differentiation of mature neurotransmitter and neuropeptide phenotypes in vivo.     

Cholinergic- rather than adrenergic-induced sweating play a role in developing and developed rat eccrine sweat glands

Both cholinergic and adrenergic stimulation can induce sweat secretion in human eccrine sweat glands, but whether cholinergic and adrenergic stimulation play same roles in rat eccrine sweat glands is still controversial. To explore the innervations, and adrenergic- and cholinergic-induced secretory response in developing and developed rat eccrine sweat glands, rat hind footpads from embryonic day (E) 15.5–20.5, postanal day (P) 1–14, P21 and adult were fixed, embedded, sectioned and subjected to immunofluorescence staining for general fiber marker protein gene product 9.5 (PGP 9.5), adrenergic fiber marker tyrosine hydroxylase (TH) and cholinergic fiber marker vasoactive intestinal peptide (VIP), and cholinergic- and adrenergic-induced sweat secretion was detected at P1–P21 and adult rats by starch-iodine test. The results showed that eccrine sweat gland placodes of SD rats were first appeared at E19.5, and the expression of PGP 9.5 was detected surrounding the sweat gland placodes at E19.5, TH at P7, and VIP at P11. Pilocarpine-induced sweat secretion was first detected at P16 in hind footpads by starch-iodine test. There was no measurable sweating when stimulated by alpha- or beta-adrenergic agonists at all the examined time points. We conclude that rat eccrine sweat glands, just as human eccrine sweat glands, co-express adrenergic and cholinergic fibers, but different from human eccrine sweat glands, cholinergic- rather than adrenergic-induced sweating plays a role in the developing and developed rat eccrine sweat glands.     

Protein gene product 9.5-immunoreactive nerve fibres and cells in human skin

Summary Sections of human skin were processed according to the indirect immunofluorescence technique with a rabbit antiserum against human protein gene product 9.5 (PGP 9.5). Immunoreactivity was detected in intraepidermal and dermal nerve fibres and cells. The intraepidermal nerves were varicose or smooth with different diameters, running as single processes or branched, straight or bent, projecting in various directions and terminating in the stratum basale, spinosum or granulosum. The density of the intraepidermal nerves varied between the different skin areas investigated. PGP 9.5-containing axons of the lower dermis were found in large bundles. They separated into smaller axon bundles within the upper dermis, entering this portion of the skin perpendicular to the surface. Then they branched into fibres mainly arranged parallel to the epidermal-dermal junctional zone. However, the fibres en route to the epidermis traversed the upper dermis more or less perpendicularly. Furthermore, immunoreactive dermal nerve fibres were found in the Meissner corpuscles, the arrector pili muscles, hair follicles, around the eccrine and apocrine sweat glands and around certain blood vessels. Such fibres were also observed around most subcutaneous blood vessels, sometimes heavily innervating these structures. Numerous weakly-to-strongly PGP 9.5-immunoreactive cells were found both in the epidermis and in the dermis.     

An NADH-linked luciferase assay for glycogen: the preparation of glycogen-free, viable human eccrine sweat glands

A glycogen assay based on bacterial NADH luciferase is described. It is free of tissue interference. The detection limit is 0.12 nmol glycogen, and the coefficient of variation is 5.5%. A method of depleting human eccrine sweat glands while retaining their viability is described. This depends on their incubation in 10(-5) M acetylcholine and 1 mM pyruvate. This method may be applicable to other tissues. The evidence for the viability of glycogen-depleted human eccrine sweat glands is reported and includes tissue contents of ATP and the rates of oxidation of glucose, pyruvate, beta-hydroxybutyrate, and palmitate.     

Expression of S100A2 and S100P in human eccrine sweat glands and their application in differentiating secretory coil-like from duct-like structures in the 3D reconstituted eccrine sweat spheroids

Secretory coils and ducts are two components of eccrine sweat glands with different structures and functions. In our previous study, we combined keratins and α-SMA to distinguish between secretory coils and ducts. However, the key deficiency of the method was that none of the antibodies used was specific for ducts. In this study, we first examined the co-localization of K5/K7, α-SMA/K14, K7/S100P and α-SMA/S100A2 by double-immunofluorescence staining to confirm the localization of S100P and S100A2 in native human eccrine sweat glands, and second we identified secretory coil-like and duct-like structures in the 3D reconstituted eccrine sweat gland spheroids by double-immunofluorescence staining for K7/S100P and α-SMA/S100A2. In native human eccrine sweat glands, S100A2 immunoreactivity was confined to the outer layer and S100P to the inner layer of the duct. In 12-week Matrigel plugs containing eccrine sweat gland cells, double-immunofluorescence staining for K7/S100P and α-SMA/S100A2 could easily distinguish duct-like structures from secretory coil-like structures. We conclude that S100A2 and S100P can be used as specific duct markers in eccrine sweat glands, and combined use of S100P or S100A2 with keratins enables easy to distinction between secretory coils and ducts.