Sweat Gland Cells Research Articles

Expression of ODC Antizyme Inhibitor 2 (AZIN2) in Human Secretory Cells and Tissues.

Ornithine decarboxylase (ODC) antizyme inhibitor 2 (AZIN2), originally called ODCp, is a regulator of polyamine synthesis that we originally identified and cloned. High expression of ODCp mRNA was found in brain and testis. We reported that AZIN2 is involved in regulation of cellular vesicle transport and / or secretion, but the ultimate physiological role(s) of AZIN2 is still poorly understood. In this study we used a peptide antibody (K3) to human AZIN2 and by immunohistochemistry mapped its expression in various normal tissues. We found high expression in the nervous system, in type 2 pneumocytes in the lung, in megakaryocytes, in gastric parietal cells co-localized with H,K-ATPase beta subunit, in selected enteroendocrine cells, in acinar cells of sweat glands, in podocytes, in macula densa cells and epithelium of collecting ducts in the kidney. The high expression of AZIN2 in various cells with secretory or vesicle transport activity indicates that the polyamine metabolism regulated by AZIN2 is more significantly involved in these events than previously appreciated.

Shh promotes sweat gland cell maturation in three-dimensional culture.

Sweat gland (SG) cells forming SG tubule-like structures in 3D culture, this is one of the most important methods to identify the biological function of SG cells and stem cells-derived SG-like cells, but also the important way on research of SG regeneration in vitro. In this study, we seeded human fibroblasts and SG cells in gels and used immunohistochemistry to confirm whether SG tubule-like structures formed. Fibroblasts are necessary factor in the process of SG cells maturation and forming SG’s secretory region in 3D culture. Further experimentation revealed that Sonic hedgehog (Shh) was secreted by fibroblasts within the 3D culture. By adding Shh protein to 3D culture, there had more SG tubule-like structures formed. These results suggest that Shh is an important factor during the process of forming SG tubule-like structures in 3D cultures, and adding Shh recommbinant protein could promote SG cell maturation and enhance the efficiency of structure formation.Electronic supplementary materialThe online version of this article (doi:10.1007/s10561-016-9548-7) contains supplementary material, which is available to authorized users.

Changes in keratins and alpha-smooth muscle actin during three-dimensional reconstitution of eccrine sweat glands.

We have examined the changes of keratins and alpha-SMA at various time points in order to investigate the development and differentiation of eccrine sweat gland cells during the course of three-dimensional (3D) reconstitution. Mixtures of eccrine sweat gland cells and Matrigel were injected subcutaneously into the inguinal regions of nude mice. At 1, 2, 4, 6, 8, 14, 21, 28, 35, and 42days post-implantation, Matrigel plugs were removed and immunostained. We found that during 3D reconstitution, keratin and alpha-SMA expression changed in a time-dependent manner. At day 1, all cells stained positively for keratin isoforms K5, K14, and K15, with the staining intensity of K15 being weak and K5 and K14 being strong, but none of the cells displayed K7, K8, or alpha-SMA. As time progressed, spheroid-like structures formed with the inner layer acquiring K7 and K8, but losing K5 and K14 expression, and the outer layer acquiring alpha-SMA expression, but losing K15 expression. K8 expression was first noted at day 14, and K7 and alpha-SMA at day 21. The loss of K15 expression was first noted at day 14, K14 at day 21, and K5 at day 28. At 28, 35, and 42days, the spheroid-like structures could be distinguished, by immunohistochemistry, as having secretory coil-like and coiled duct-like structures. We conclude that the changes in expression of keratins and alpha-SMA in 3D-reconstituted eccrine sweat glands are similar to those of native eccrine sweat glands, indicating that the 3D reconstitution of sweat glands provides an excellent model for studying the development, cytodifferentiation, and regulation of eccrine sweat glands.

New Findings on the Mechanism of Perspiration Including Aquaporin-5 Water Channel.

Aquaporin-5 (AQP5) is a member of the water channel protein family. Although AQP5 has been shown to be present in sweat glands, the presence or absence of regulated intracellular translocation of AQP5 in sweat glands remains to be determined. In this article, recent findings on AQP5 in sweat glands are presented. (1) Immunoreactive AQP5 was detected in the apical membranes and the intercellular canaliculi of secretory coils, and in the basolateral membranes of the clear cells in human eccrine sweat glands. (2) AQP5 rapidly concentrated at the apical membranes during sweating in mouse sweat glands. (3) Treatment of human AQP5-expressing Madin-Darby canine kidney cells with calcium ionophore A23187 resulted in a twofold increase in the AQP5 level in the apical membranes within 5 min. (4) Anoctamin-1, a calcium-activated chloride channel was detected in the apical membranes and it completely colocalized with AQP5 in the apical membranes in mouse sweat glands. AQP5 may be involved in sweating and its translocation may help to increase the water permeability of the apical membranes of sweat glands. AQP5 is a potential target molecule for the design of a sweat-modulating drug.

3D bioprinted extracellular matrix mimics facilitate directed differentiation of epithelial progenitors for sweat gland regeneration

Sweat glands perform a vital thermoregulatory function in mammals. Like other skin appendages, they originate from epidermal progenitors. However, they have low regenerative potential in response to injury, and whether adult epidermal progenitors could be specified to differentiate to a sweat gland cell lineage remains largely unexplored. We used bioprinting technology to create a functional in vitro cell-laden 3D extracellular matrix mimics (3D-ECM) with composite hydrogels based on gelatin and sodium alginate because of chemical and structural similarity to ECM components. To achieve specific cell differentiation, mouse plantar dermis and epidermal growth factor were synchronously incorporated into the 3D-ECM mimics to create an inductive niche for epidermal progenitor cells obtained from mice. The biological 3D construct could maintain cell viability, thereby facilitating cell spreading and matrix formation. In vitro data by immunofluorescence and gene expression assay of key cell-surface markers demonstrated that the bioprinted 3D-ECM could effectively create a restrictive niche for epidermal progenitors that ensures unilateral differentiation into sweat gland cells. Furthermore, direct delivery of bioprinted 3D-ECM into burned paws of mice resulted in functional restoration of sweat glands. This study represents the rational design to enhance the specific differentiation of epidermal lineages using 3D bioprinting and may have clinical and translational implications in regenerating sweat glands. Statement of SignificanceSweat gland regeneration after injury is of clinical importance but remains largely unsolved because of low regenerative potential and lack of a definite niche. Some studies have shown sweat gland regeneration with gene-based interventions or cell-based induction via embryonic components, but translation to clinic is challenging. The novelty and significance of the work lies in the fact that we design a 3D bioprinted extracellular matrix that provides the spatial inductive cues for enhancing specific differentiation of epidermal lineages to regenerate sweat glands, which is critical for treating deep burns or other wounds. Our studies are encouraging given the overwhelming advantages of our designed 3D bioprinting construct over other cell delivery technology in maintaining high cell proliferation; another interesting finding is that adult tissue components retain a gland lineage-inductive power as embryonic tissue, which can facilitate translation.

BrdU-label-retaining cells in rat eccrine sweat glands over time

Cell proliferation and turnover are fueled by stem cells. In a previous study, we demonstrated that rat eccrine sweat glands contained abundant bromodeoxyuridine (BrdU)-label-retaining cells (LRCs). However, morphological observations showed that eccrine sweat glands usually show little or no signs of homeostatic change. In this study, we account for why the homeostatic change is rare in eccrine sweat glands based on cytokinetic changes in BrdU-LRC turnover, and also determine the BrdU-labeled cell type. Thirty-six newborn SD rats, were injected intraperitoneally with 50mg/kg BrdU twice daily at a 2h interval for 4 consecutive days. After a chase period of 4, 6, 8, 12, 24 and 32 weeks, rats were euthanized, and the hind footpads were removed and processed for BrdU immunostaining, and BrdU/α-SMA and BrdU/K14 double-immunostaining. BrdU-LRCs were observed in the ducts, secretory coils and mesenchymal cells at all survival time points. The percentage of BrdU+ cells in rat eccrine sweat glands averaged 4.2±1.2% after 4 weeks of chase, increased slightly by the 6th week, averaging 4.4±0.9%, and peaked at 8 weeks, averaging 5.3±1.0%. Subsequently, the average percentage of BrdU+ cells declined to 3.2±0.8% by the 32nd week. There was no difference in the percentage of BrdU-LRCs among the different survival time points except that a significant difference in the percentage of BrdU-LRCs detected at 24 weeks versus 8 weeks, and 32 weeks versus 8 weeks, was observed. We concluded that the BrdU-LRCs turnover is slow in eccrine sweat glands.

Cytokeratin Expression at Different Stages in Sweat Gland Development of C57BL/6J Mice.

Sweat glands exhibit a documented role in epidermal reepithelialization after wounding. However, the regenerative potential of sweat glands has remained underappreciated due to the absence of useful markers for the analysis of determination and differentiation processes in the developing eccrine sweat gland from epithelium. Although the current knowledge of keratin expression in most of the different origins has been described, it remains widely shared and not unified in eccrine sweat glands of C57BL/6J mice that are commonly used as animal models for sweat gland and wound healing studies, both at the molecular and cellular levels. Aiming to answer this question, we have investigated the changes in cytokeratin expression patterns during the embryonic, neonatal, juvenile, and young adult stages (E12.5, E17.5, P0.5, P5, and P28). In this article, we demonstrate that the morphology of murine sweat gland progenitor cells are similar to epidermal stem cells before birth (E12.5 and E17.5); at postnatal stages, the duct formed gradually and curled to glob. K8 and K19 were expressed in the eccrine sweat gland cells at all times and highly expressed after birth at both gene and protein levels. Also, histological results revealed K8 and K19 positive cells localized in the secretary portion of glands. Meanwhile, K14 strongly expressed both in vivo and in vitro at E12.5, while it weakly expressed at other stages. Moreover, K10 was rarely detected before birth, but it expressed positively in vivo and in vitro only at the protein level after birth. These data indicate the pattern of main cytokeratin expression at different stages during murine sweat gland development and might provide an efficient tool for sweat gland research and exciting potential for developing targeted therapies for wound healing.

KIT (CD117) Expression in Benign and Malignant Sweat Gland Tumors.

:KIT (CD117, c-kit) is a receptor tyrosine kinase involved in the tumorigenesis of several neoplasms. KIT is expressed by the secretory cells of normal sweat glands. We studied the KIT expression and KIT mutational status in various benign and malignant tumors of eccrine and apocrine glands. We included a total of 108 cases comprising 10 benign and 6 malignant sweat gland tumors, and KIT expression was immunohistochemically detected (positive rate): 10 syringomas (0%), 8 poromas (25%), 20 mixed tumors (40%), 21 spiradenomas (43%), 1 cylindroma (0%), 5 hidradenomas (40%), 7 syringocystadenoma papilliferum cases (0%), 1 papillary hidradenoma (100%), 2 tubulopapillary hidradenomas (50%), 8 hidrocystomas (29%), 2 adenoid cystic carcinomas (100%), 5 porocarcinomas (20%), 6 apocrine carcinomas (33%), 10 extramammary Paget diseases (30%), 1 spiradenocarcinoma (100%), and 1 syringocystadenocarcinoma papilliferum (0%). Most KIT-positive cells were luminal cells, arising from glandular structures. We performed polymerase chain reaction–single-strand conformation polymorphism for detecting KIT mutational status. All cases showed no mutations at hot spots for KIT (exons 9, 11, 13, and 17). KIT mutation does not seem to be mechanism for KIT expression, but the expression may be from native sweat glands.

Serum carcinoembryonic antigen (CEA) as a clinical marker in acquired idiopathic generalized anhidrosis: a close correlation between serum CEA level and disease activity

Hypohidrosis/anhidrosis are congenital or acquired sweating impairments. Among them, acquired idiopathic generalized anhidrosis/hypohidrosis (AIGA) is the most common, and characterized by favourable response to systemic corticosteroid, however, no clinical markers for disease severity or activity have been developed. Our aim was to verify the usefulness of serum carcinoembryonic antigen (CEA) level monitoring as a clinical marker for disease activity of AIGA. Ten cases of AIGA diagnosed at Asahikawa Medical University, from 1980 to 2014 were included in the study. CEA and/or CEACAM1 expression level was analysed using immunohistochemistry and enzyme-linked immunosorbent assay. CEA expression was restricted to the apical membrane of glandular cells in eccrine sweat glands in most of the three types of cases we examined [healthy control, patients with atopic dermatitis (AD) or urticaria]. However, CEA expression was detected diffusely and much more intensively in eight of the 10 AIGA cases included in this study. CEACAM1-expression was much more restricted on the apical membrane of glandular cells of both the AIGA cases and the other control subjects. While serum CEA levels increased in all five AIGA cases examined (5.8-43.2 ng/mL), it remained within normal limits in all control subjects: nine healthy individuals; 10 cases of AD; 10 cases of idiopathic urticaria; four cases of normohidrotic cholinergic urticaria (Mann-Whitney's U-test, P < 0.05). The increased serum CEA levels in AIGA decreased in conjunction with improved sweating during methyl prednisolone pulse therapy or repeated bathing. Serum CEA level may serve as a clinical marker for AIGA activity.

Three-dimensional co-culture of BM-MSCs and eccrine sweat gland cells in Matrigel promotes transdifferentiation of BM-MSCs.

Victims with extensive and deep burns are unable to regenerate eccrine sweat glands. Combining of stem cells and biomimetic ECM to generate cell-based 3D tissues is showing promise for tissue repair and regeneration. We co-cultured BrdU-labeled bone marrow-derived mesenchymal stem cells (BM-MSCs) and eccrine sweat gland cells in Matrigel for 2weeks in vitro and then evaluated for BM-MSCs differentiation into functional eccrine sweat gland cells by morphological assessment and immunohistochemical double staining for BrdU/pancytokeratin, BrdU/ZO-2, BrdU/E-cadherin, BrdU/desmoglein-2, BrdU/Na(+)-K(+)-ATPase α, BrdU/NHE1 and BrdU/CFTR. Cells formed spheroid-like structures in Matrigel, and BrdU-labeled BM-MSCs were involved in the 3D reconstitution of eccrine sweat gland tissues, and the incorporated BM-MSCs expressed an epithelial cell marker (pancytokeratin), epithelial cell junction proteins (ZO-2, E-cadherin and desmoglein-2) and functional proteins of eccrine sweat glands (Na(+)-K(+)-ATPase α, NHE1 and CFTR). In conclusion, three-dimensional co-culture of BM-MSCs and eccrine sweat gland cells in Matrigel promotes the transdifferentiation of BM-MSCs into potentially functional eccrine sweat gland cells.

Sweating chloride bullets: understanding the role of calcium in eccrine sweat glands and possible implications for hyperhidrosis.

Sweating chloride bullets: understanding the role of calcium in eccrine sweat glands and possible implications for hyperhidrosis.

Matrigel basement membrane matrix induces eccrine sweat gland cells to reconstitute sweat gland-like structures in nude mice

BackgroundSevere burn results in irreversible damage to eccrine sweat glands, for which no effective treatment is available. Interaction between the extracellular matrix and epithelial cells is critical for proper three-dimensional organization and function of the epithelium.Methods: Matrigel-embedded eccrine sweat gland cells were subcutaneously implanted into the inguinal regions of nude mice. Two weeks later, the Matrigel plugs were removed and evaluated for series of detection items.Results: Sweat gland cells developed into sweat gland-like structures in the Matrigel plugs based on: (1) de novo formation of tubular-like structures with one or more hollow lumens, (2) expression of epithelial and sweat gland markers (pancytokeratin, CK5/7/14/19, α–SMA and CEA), (3) basement membrane formation, (4) myoepithelial cells presenting in and encompassing the tubular-like structures, (5) cellular polarization, evident by the expression of tight junction proteins (claudin-1 and ZO-2), anchoring junctions (desmoglein-1 and -2 and E-cadherin) and CEA in the luminal membrane, (6) expression of proteins related to sweat secretion and absorption (Na+–K+–ATPase α/β, Na+–K+–2Cl-cotranspoter 1, Na+/H+ exchanger 1, aquaporin-5, epithelial sodium channel, cystic fibrosis transmembrane conductance regulator, potassium channel and vacuolar-type H+-ATPase), and (7) about 20% of the tubular-like structures are de novo coils and 80% are de novo ducts.Conclusions: This study provides not only an excellent model to study eccrine sweat gland development, cytodifferentiation and reconstitution, but also an in vivo model for regeneration of eccrine sweat glands.

Electrophysiological Characterization of TMEM16A

Sweating is an essential physiological process to regulate body temperature in humans and various disorders are associated with dysregulated sweat formation.Primary sweat secretion in human eccrine sweat glands is initiated by Ca2+-activated Cl- channels (CaCC). Recently, members of the TMEM16 family were identified as CaCCs in various secretory epithelia, however, their molecular identity in sweat glands remained elusive. Here we investigated the function of TMEM16A in sweat glands. Gene expression analysis revealed that TMEM16A is expressed in human NCL-SG3 sweat gland cells as well as in isolated human eccrine sweat gland biopsy samples. Sweat gland cells express several previously described TMEM16A splice variants, as well as one novel splice variant, TMEM16A(ace3) lacking the TMEM16A-dimerization domain. Chloride-flux assays using halide-sensitive YFP revealed that TMEM16A is functionally involved in Ca2+-dependent Cl- transport in NCL-SG3 cells. Recombinant expression in NCL-SG3 cells showed that TMEM16A(ace3) is forming a functional CaCC, with basal and Ca2+-activated Cl-permeability distinct from canonical TMEM16A(ac). Our results suggest that various TMEM16A isoforms contribute to sweat gland-specific Cl- transport providing opportunities to develop sweat gland-specific therapeutics for the treatment of sweating disorders.HEK cells expressing TMEM16a were investigated by high throughput giga seal patch clamping with the SyncroPatch 384PE. Currents were activated by internal Ca and could be blocked by Niflumic Acid.

Protease-Activated Receptor-2 Is Associated with Terminal Differentiation of Epidermis and Eccrine Sweat Glands.

BackgroundProtease-activated receptor 2 (PAR-2) participates in various biological activities, including the regulation of epidermal barrier homeostasis, inflammation, pain perception, and melanosome transfer in the skin.ObjectiveTo evaluate the basic physiological role of PAR-2 in skin.MethodsWe investigated PAR-2 expression in human epidermis, skin tumors, and cultured epidermal cells using western blot and immunohistochemical analysis. Additionally, we examined the effect of the PAR-2 agonist, SLIGRL-NH2, on cultured keratinocytes.ResultsStrong PAR-2 immunoreactivity was observed in the granular layer of normal human skin and the acrosyringium of the eccrine sweat glands. In contrast, weak PAR-2 immunoreactivity was seen in the granular layer of callused skin and in the duct and gland cells of the eccrine sweat glands. Interestingly, PAR-2 immunoreactivity was very weak or absent in the tumor cells of squamous cell carcinoma (SCC) and syringoma. PAR-2 was detected in primary keratinocytes and SV-40T-transformed human epidermal keratinocytes (SV-HEKs), an immortalized keratinocyte cell line, but not in SCC12 cells. SV-HEKs that were fully differentiated following calcium treatment displayed higher PAR-2 expression than undifferentiated SV-HEKs. Treatment of cultured SV-HEKs with PAR-2 agonist increased loricrin and filaggrin expression, a terminal differentiation marker.ConclusionOur data suggest that PAR-2 is associated with terminal differentiation of epidermis and eccrine sweat glands.

A novel TMEM16A splice variant lacking the dimerization domain contributes to calcium‐activated chloride secretion in human sweat gland epithelial cells

Sweating is an important physiological process to regulate body temperature in humans, and various disorders are associated with dysregulated sweat formation. Primary sweat secretion in human eccrine sweat glands involves Ca(2+) -activated Cl(-) channels (CaCC). Recently, members of the TMEM16 family were identified as CaCCs in various secretory epithelia; however, their molecular identity in sweat glands remained elusive. Here, we investigated the function of TMEM16A in sweat glands. Gene expression analysis revealed that TMEM16A is expressed in human NCL-SG3 sweat gland cells as well as in isolated human eccrine sweat gland biopsy samples. Sweat gland cells express several previously described TMEM16A splice variants, as well as one novel splice variant, TMEM16A(acΔe3) lacking the TMEM16A-dimerization domain. Chloride flux assays using halide-sensitive YFP revealed that TMEM16A is functionally involved in Ca(2+) -dependent Cl(-) secretion in NCL-SG3 cells. Recombinant expression in NCL-SG3 cells showed that TMEM16A(acΔe3) is forming a functional CaCC, with basal and Ca(2+) -activated Cl(-) permeability distinct from canonical TMEM16A(ac). Our results suggest that various TMEM16A isoforms contribute to sweat gland-specific Cl(-) secretion providing opportunities to develop sweat gland-specific therapeutics for treatment of sweating disorders.

Isolation, culture and phenotypic characterization of human sweat gland epithelial cells.

Sweat gland epithelial cells (SGECs) have been identified as essential for the regeneration of sweat glands and for the construction of skin substitutes containing skin appendages. Consequently, the isolation, culture and phenotypic characterization of SGECs are of paramount importance. In the present study study, human sweat glands were isolated by pipetting under a phase contrast microscope following digestion with collagenase type I. Subsequently, a microscopic organ culture technique was used for the primary culture of human SGECs, and the culture conditions were modified in order to achieve optimal cell growth status. Primary SGECs were identified based on their expression of markers specific for sweat glands, including carcinoembryonic antigen (CEA), CK7, CK8, CK14, CK15, CK18 and CK19. We explored the possible presence of stem cells in human sweat glands by detecting their expression of leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5). Primary SGECs achieved a good growth state when cultured under serum-free conditions. After one passage, the cells cultured in keratinocyte serum-free medium with 1% fetal bovine serum (FBS) still showed a prominent proliferative activity. Phenotypic analysis by immunofluorescence microscopy, reverse transcription-polymerase chain reaction (RT-PCR), and western blot analysis demonstrated the expression of sweat gland-specific markers, including CEA, CK7, CK8, CK14, CK15, CK18 and CK19. In addition, RT-PCR and immunochemistry detected the expression of LGR5. In comparison with traditional serum-containing conditions, serum-free culture provides the preferred culture conditions for human SGECs. LGR5 is a novel marker that identifies human sweat gland-derived stem cells.

De Novo Epidermal Regeneration Using Human Eccrine Sweat Gland Cells: Higher Competence of Secretory over Absorptive Cells

In our previous work, we showed that human sweat gland-derived epithelial cells represent an alternative source of keratinocytes to grow a near normal autologous epidermis. The role of subtypes of sweat gland cells in epidermal regeneration and maintenance remained unclear. In this study, we compare the regenerative potential of both secretory and absorptive sweat gland cell subpopulations. We demonstrate the superiority of secretory over absorptive cells in forming a new epidermis on two levels: first, the proliferative and colony-forming efficiencies in vitro are significantly higher for secretory cells (SCs), and second, SCs show a higher frequency of successful epidermis formation as well as an increase in the thickness of the formed epidermis in the in vitro and in vivo functional analyses using a 3D dermo-epidermal skin model. However, the ability of forming functional skin substitutes is not limited to SCs, which supports the hypothesis that multiple subtypes of sweat gland epithelial cells hold regenerative properties, while the existence and exact localization of a keratinocyte stem cell population in the human eccrine sweat gland remain elusive.

Pharmacological blockers of STIM1 inhibit increases in intracellular calcium in horse sweat gland cells (650.2)

Calcium is a key second messenger in stimulus‐secretion coupling in human and Equidae sweat gland secretory cells. Upon stimulation, calcium is released from internal stores, facilitating the opening of membrane ion channels and the subsequent formation of secretion in the lumen of the gland. Sustained secretion requires an influx of calcium from the external milieu. This calcium influx is thought to enter the secretory cells via store operated calcium channels. Little is known about store‐operated calcium entry (SOCE) and so we studied its role in horse sweat gland cells from control animals and those that had developed anhidrosis, an inability to produce sweat.We had previously shown the presence of STIM and Orai proteins in cell lines derived from control and anhidrotic animals. The results also indicated a reduction in STIM1 mRNA and protein expression in anhidrotic sweat gland cells. The functionality of the SOCE pathway in both cell lines was investigated in response to agonist stimulation using FURA‐2AM calcium‐imaging techniques. Increases in [Ca2+]i could be abolished to varying degrees in control cells by a variety of known pharmacological blockers of SOCE. Additionally anhidrotic cells showed a significant decrease in [Ca2+]i FURA‐2 ratio in response to agonists when compared to control cells.The results suggest that a reduction of STIM1 expression in the SOCE pathway may play a role in anhidrosis in horses.Grant Funding Source: Supported by Glasgow Caledonian University.

Isolation and characterization of sweat gland myoepithelial cells from human skin.

Stem cells routinely maintain the main epidermal components, i.e. the interfollicular epidermis, hair follicles, and sweat glands. Human sweat glands present throughout the body are glandular exocrine organs that mainly play a role in thermoregulation by sweating. Emerging evidence points to the presence of stem cells in sweat glands, but it remains unclear whether such stem cells exist in human sweat glands. Here, we attempted to gather evidence for stem cells in human sweat glands, which would be characterized by self-renewal ability and multipotency. First, we explored human sweat gland cells for expression of stem cell markers. CD29 and Notch, epidermal stem cell markers, were found to reside among α-smooth muscle actin-positive myoepithelial cells in human sweat glands. Next, sweat gland myoepithelial cells were isolated from human skin as a CD29(hi)CD49f (hi) subpopulation. The myoepithelial cell-enriched CD29(hi)CD49f (hi) subpopulation possessed the ability to differentiate into sweat gland luminal cells in sphere-forming assays. Furthermore, CD29(hi)CD49f (hi) subpopulation-derived sphere-forming cells exhibited long-term proliferative potential upon multiple passaging, indicating that the CD29(hi)CD49f (hi) myoepithelial subpopulation includes stem cells with self-renewal ability. These findings provide evidence that human sweat gland myoepithelial cells contain stem cells that possess both self-renewal ability and multipotency to differentiate into sweat glands.

Lineage Analysis of Epidermal Stem Cells

Lineage tracing involves labeling cells to track their subsequent behavior within the normal tissue environment. The advent of genetic lineage tracing and cell proliferation assays, together with high resolution three-dimensional (3D) imaging and quantitative methods to infer cell behavior from lineage-tracing data, has transformed our understanding of murine epidermal stem and progenitor cells. Here, we review recent insights that reveal how a progenitor cell population maintains interfollicular epidermis, whereas stem cells, quiescent under homeostatic conditions, are mobilized in response to wounding. We discuss progress in understanding how the various stem cell populations of the hair follicle sustain this complex and highly dynamic structure, and recent analysis of stem cells in sweat and sebaceous glands. The extent to which insights from mouse studies can be applied to human epidermis is also considered.