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

Epidermal and dermal cells from adult rat eccrine sweat gland-containing skin can reconstruct the three-dimensional structure of eccrine sweat glands

BACKGROUND

Previously, we have demonstrated that eccrine sweat gland cells (ESGCs) can reconstruct the three-dimensional (3D) structure of eccrine sweat glands (ESGs). However, there is still a need to explore source cells capable of regenerating ESG to address the issue of ESG regeneration in ESGC-deficient conditions, such as severe burns.

METHODS

The epidermal cells and dermal cells in adult rat ventral foot skin (ESG-bearing) were isolated. The isolated single epidermal cells and dermal cells were mixed with Matrigel, and then the mixture was implanted into the axillary/inguinal fat pads of nude mice. Five weeks after implantation, the Matrigel plugs were harvested and the morphology and differentiation of the cells were examined by H&E staining and fluorescent immunohistochemical staining for ESG markers, such as Na+ -K+ -2Cl- cotransporter 1 (NKCC1), Na+ -K+ -ATPase (NKA), Foxa1 and K14.

RESULTS

The epidermal cells and dermal cells of adult rat ventral foot skin can reconstruct 3D structure and express specific markers of ESGs in skin, such as NKCC1, NKA and Foxa1, indicating the ESG-phenotypic differentiation of the 3D structures. Double immunofluorescence staining showed that some 3D structures expressed both the myoepithelial cell marker alpha-SMA and the common marker K14 of duct cells and myoepithelial cells, while some 3D structures expressed only K14, indicating that ESG-like 3D structures differentiated into duct-like and secretory coiled cells.

CONCLUSION

Epidermal and dermal cells from adult ESG-bearing skin can be used as a cell source for ESG regeneration.

The combination of hair follicle-specific marker LHX2 and co-expressed marker can distinguish between sweat gland placodes and hair placodes in rat

Eccrine sweat gland (ESG) and hair follicle (HF) are different skin appendages but share many common development characteristics. Although the morphology of adult ESG and HF is obviously different, it is difficult to distinguish ESG placodes from HFs placodes morphologically. To study the fate determination of ESG and HF, specific antigen markers for ESG placodes and HF placodes must be found first to distinguish them. In the study, we detected the expression of commonly used keratins 4, 5, 7-10, 12, 14, 15, 17-20, 27 and 73, and the reported ESG and HF specific markers, P-cadherin, Lymphoid enhancer factor 1 (LEF1), LIM Homeobox gene 2 (LHX2), Na⁺/K⁺-ATPase (NKA) and Na⁺-K⁺-2Cl^- cotransporter 1 (NKCC1) in ESG and HF placodes by single-immunofluorescence staining and double-immunofluorescence staining. To further verify the results of immunofluorescence staining, Western blot (WB) was used to detect the differential antigen and some co-expressed antigens of ESG and HF placodes. The results showed that both ESG and HF placodes expressed K4/5/14/1517/18, P-cadherin and LEF1, neither expressed K7/8/9/10/12/19/20/27/73, NKA or NKCC1. HF placodes specifically expressed LHX2. Combination of LHX2 and co-expressed antigen K14, can distinguish ESG placodes from HF placodes. We conclude that LHX2 is a specific marker for HF placodes, and ESG placodes and HF placodes can be distinguished by double immunofluorescence staining of the specific marker LHX2 and the co-expressed markers, such as K4, K5, K14, K15, K17, K18, P-cadherin and LEF1.

An innovative application of follicular unit extraction technique in the treatment of bromhidrosis

BACKGROUND

Surgery is the most effective way to treat bromhidrosis, but postoperative complications are still the biggest obstacles for patients to choose surgical treatment.

OBJECTIVES

To introduce an innovative application of follicular unit extraction (FUE) in the treatment of bromhidrosis.

METHODS

We conducted a case series study on 20 patients who received FUE technique for the treatment of bromhidrosis. The axillary hair follicles were extracted with a one-millimetre punch. The released hair follicles were collected for histological examination. After the operation, the wounds were wrapped with moderate pressure. The dressing was removed 24 h after the FUE operation. The postoperative complications were collected, and the improvement of malodour was evaluated by the 10-point visual analogue scale.

RESULTS

Immediately postoperation, many needle-shaped holes appeared in the armpits. The holes healed 7 days after the operation, with no scar or pinpoint-like scars. Except for a female who complained of mild pain in the left armpit, no other patients had any discomfort. The malodour level varied between 0 and 4 during the follow-up period. The tissue examination showed that more than 90% of the completely plucked hair follicles were accompanied by apocrine glands, and many blocked and dilated apocrine glands were observed. The lumens of the blocked glands were filled with decapitation products, which were positive for K5, Brst-2 and CEA.

CONCLUSIONS

Patients with bromhidrosis have a positive response to FUE technique. The FUE technique is well-tolerated, with only a few postoperative complications, which deserves to be widely promoted.

Human Three-Dimensional Models for Studying Skin Pathogens

Skin is the most exposed surface of the human body, separating the microbe-rich external environment, from the sterile inner part. When skin is breached or its homeostasis is perturbed, bacterial, fungal and viral pathogens can cause local infections or use the skin as an entry site to spread to other organs. In the last decades, it has become clear that skin provides niches for permanent microbial colonization, and it actively interacts with microorganisms. This crosstalk promotes skin homeostasis and immune maturation, preventing expansion of harmful organisms. Skin commensals, however, are often found to be skin most prevalent and dangerous pathogens. Despite the medical interest, mechanisms of colonization and invasion for most skin pathogens are poorly understood. This limitation is due to the lack of reliable skin models. Indeed, animal models do not adequately mimic neither the anatomy nor the immune response of human skin. Human 3D skin models overcome these limitations and can provide new insights into the molecular mechanisms of microbial pathogenesis. Herein, we address the strengths and weaknesses of different types of human skin models and we review the main findings obtained using these models to study skin pathogens.

EGFR inhibitor AG1478 blocks the formation of 3D structures mainly through ERK signaling pathway in Matrigel-induced 3D reconstruction of eccrine sweat gland-like structures

EGFR signaling plays important roles in the development of eccrine sweat glands. We previously demonstrate that Matrigel induces eccrine sweat gland cells to reconstruct the three-dimensional (3D) structures of eccrine sweat glands, but the mechanisms are still unknown. In the study, eccrine sweat gland cells were cultured within a 3D Matrigel, and EGFR inhibitor AG1478, or MEK1/2 inhibitor U0126, were added to the medium respectively. The morphology of the 3D-reconstructed eccrine sweat gland-like structures was observed, the localization of phospho-EGFR was detected, and protein levels of EGFR, phospho-EGFR, phospho-JAK, phospho-AKT and phospho-ERK were examined. The results showed that cells treatment with AG1478 from Day 0 of 3D cultures blocked formation of spheroid-like structures. AG1478 administration caused reduced phospho-EGFR, concomitant with downregulation of phospho-ERK1/2, but not phospho-JAK or phospho-AKT. Phospho-EGFR and phospho-ERK were reduced, and only a small number of 3D-structures were formed following treatment with U0126. We conclude that EGFR plays important roles in Matrigel-induced 3D structures of eccrine sweat gland-like structures, and ERK1/2 signaling is responsible, at least in part, for the effect of EGFR.

Detection of fluid secretion of three-dimensional reconstructed eccrine sweat glands by magnetic resonance imaging

We previously showed three-dimensional (3D) reconstructed eccrine sweat glands have similar structures as native eccrine sweat glands, but whether the 3D reconstructed sweat glands appropriately secrete fluid is still unknown. In this study, Matrigel-embedded human eccrine sweat gland cells or Matrigel alone were implanted into the groin subcutis of the nude mice. Ten weeks post-implantation, images of the subcutaneously formed plugs, as well as footpads of rats, pre- and post-pilocarpine/normal saline (NS) injection were acquired using a fat-suppressed proton density-weighted magnetic resonance imaging (MRI) sequence at 7.0 T, and the regions of interest (ROIs) in plugs and rat footpads were analysed and graphed. A significant increase in the ROI mean proton intensity occurred in both 3D reconstructed and native eccrine sweat glands after pilocarpine injection. The mean proton intensity had no noticeable changes in ROIs of Matrigel plugs between pre- and post-pilocarpine injection, and in ROIs of rat footpads between pre- and post-NS injection. In conclusion, the 3D reconstructed sweat glands possess fluid secretion, which is detectable by fat-suppressed proton density-weighted MRI.

Time course of differentiation of different cell types in 3D-reconstructed eccrine sweat glands

Epidermal basal cells invaginate into the dermis to form sweat ducts, which then grow downwards further to form secretory coils during the ontogenesis of eccrine sweat glands, but the time course of differentiation of different cell types in 3D-reconstructed eccrine sweat glands remain unclear. In this study, secretory cell-specific marker K7, clear secretory cell-specific marker CA II, dark secretory cell-specific marker GCDFP-15, myoepithelial cell-specific marker α-SMA, inner duct cell-specific marker S100P and outer duct cell-specific marker S100A2 were detected by immunofluorescence staining. The results showed that S100P and S100A2 were first detected at 2 weeks post implantation, K7 and α-SMA at 3 weeks, and GCDFP-15 and CA II at 4 weeks. The differentiation of ducts preceded secretory coils in 3D-reconstructed eccrine sweat glands. After 8 weeks post implantation, the distribution of these markers in 3D-reconstructed eccrine sweat glands was similar to that in native ones, and the percentage of the 3D-reconstructed glands expressing these markers maintained steady. We conclude that although the 3D-reconstructed and native eccrine sweat glands originated from different cells, the differentiation of different cell types in 3D-reconstructed eccrine sweat glands parallels the sequence observed during embryonic development.

Maintenance of the spheroid organization and properties of glandular progenitor cells by fabricated chitosan based biomaterials

Dysfunctional salivary gland (SG) is an unsolved clinical challenge, which is presented as xerostomia. Cell therapy is a promising treatment for restoring SG function. Salispheres are spheroid cellular organizations derived from SG stem cells. Benefitting from these cellular organizations, SG stem cells can be expanded to regenerate SG. During in vitro culture, the spontaneous reorganization of salispheres may change the features of residing SG stem cells. Therefore, it is imperative to explore ways to maintain the spheroid structure of salispheres during cell expansion in vitro. Herein, we explored biomaterial approaches using chitosan. Chitosan based biomaterials were fabricated in different forms to offer distinct interactive surfaces for cultured salispheres. The number and size of the salispheres increase in the chitosan-containing systems without increasing the incidence of spheroid cavitation. The effect of chitosan increases with high chitosan concentrations, which is optimum when chitosan is fabricated in a soluble form. The chitosan effect contributes to the regulation of the intercellular interactions and polarization within the spheroid structures. By retarding the process of salisphere cavitation, chitosan preserves the features of salivary gland progenitor cells in the cultured salispheres. The results suggest that the chitosan-containing system could effectively maintain the primitive structures and properties of salispheres during in vitro expansion, which demonstrates the potential application of salispheres for cell therapy of dysfunctional SG.

Expression and localization of Forkhead transcription factor A1 in the three-dimensional reconstructed eccrine sweat glands

Previously studies showed that Forkhead transcription factor A1 (FoxA1) was associated with sweat secretion. To investigate the expression and localization of FoxA1 in the three-dimensional (3D) reconstructed eccrine sweat glands, eccrine sweat gland cells were transplanted subcutaneously into nude mice with Matrigel, and at 2, 3, 4, 5, 6, 8, 10 and 12 weeks post-transplantation, the reconstructed eccrine sweat glands were removed and immunostained for FoxA1 and co-immunostained for FoxA1 and eccrine sweat markers, K7, carbonic anhydrase II (CA Ⅱ), gross cystic disease fluid protein-15 (GCDFP-15) and α-smooth muscle actin (α-SMA), and FoxA1 and sweat secretion-related proteins, Na⁺-K⁺-ATPase α and Na⁺-K⁺-2Cl- cotransporter 1 (NKCC1). The results showed that FoxA1-positive cells weren't detected until 3 weeks post-implantation, a time point of the differntiation of secretory coil-like structures. From the fourth week on, the number of FoxA1-positive cells increased and thereafter maintained at a high number. Double immunofluorescence staining showed that FoxA1-positive cells co-expressed dark cell marker GCDFP-15 and myoepithelial cell marker α-SMA, as well as secretion-related proteins, Na⁺-K⁺-ATPase α and NKCC1 in both the native and reconstructed eccrine sweat glands. In conclusion, FoxA1 might be related to the development and differentiation of secretory coil-like structures, as well as the secretory function of the 3D reconstructed eccrine sweat glands.

Three-dimensional reconstructed eccrine sweat glands with vascularization and cholinergic and adrenergic innervation

Functional integrity of the regenerated tissues requires not only structural integrity but also vascularization and innervation. We previously demonstrated that the three-dimensional (3D) reconstructed eccrine sweat glands had similar structures as those of the native ones did, but whether the 3D reconstructed glands possessing vascularization and innervation was still unknown. In the study, Matrigel-embedded eccrine sweat gland cells were implanted under the inguinal skin. Ten weeks post-implantation, the vascularization, and innervation in the 10-week reconstructed eccrine sweat glands and native human eccrine sweat glands were detected by immunofluorescence staining. The results showed that the fluorescent signals of general neuronal marker protein gene product 9.5, adrenergic nerve fiber marker tyrosine hydroxylase, and cholinergic nerve fiber markers acetylcholinesterase and vasoactive intestinal peptide embraced the 3D reconstructed glands in circular patterns, as the signals appeared in native eccrine sweat glands. There were many CD31- and von Willebrand factor-positive vessels growing into the plugs. We demonstrated that the 3D reconstructed eccrine sweat glands were nourished by blood vessels, and we for the first time demonstrated that the engineering sweat glands were innervated by both cholinergic and adrenergic fibers. In conclusion, the 3D reconstructed eccrine sweat glands may have functions as the native ones do.

A novel organotypic 3D sweat gland model with physiological functionality

Dysregulated human eccrine sweat glands can negatively impact the quality-of-life of people suffering from disorders like hyperhidrosis. Inability of sweating can even result in serious health effects in humans affected by anhidrosis. The underlying mechanisms must be elucidated and a reliable in vitro test system for drug screening must be developed. Here we describe a novel organotypic three-dimensional (3D) sweat gland model made of primary human eccrine sweat gland cells. Initial experiments revealed that eccrine sweat gland cells in a two-dimensional (2D) culture lose typical physiological markers. To resemble the in vivo situation as close as possible, we applied the hanging drop cultivation technology regaining most of the markers when cultured in its natural spherical environment. To compare the organotypic 3D sweat gland model versus human sweat glands in vivo, we compared markers relevant for the eccrine sweat gland using transcriptomic and proteomic analysis. Comparing the marker profile, a high in vitro-in vivo correlation was shown. Carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5), muscarinic acetylcholine receptor M3 (CHRM3), Na⁺-K⁺-Cl^- cotransporter 1 (NKCC1), calcium-activated chloride channel anoctamin-1 (ANO1/TMEM16A), and aquaporin-5 (AQP5) are found at significant expression levels in the 3D model. Moreover, cholinergic stimulation with acetylcholine or pilocarpine leads to calcium influx monitored in a calcium flux assay. Cholinergic stimulation cannot be achieved with the sweat gland cell line NCL-SG3 used as a sweat gland model system. Our results show clear benefits of the organotypic 3D sweat gland model versus 2D cultures in terms of the expression of essential eccrine sweat gland key regulators and in the physiological response to stimulation. Taken together, this novel organotypic 3D sweat gland model shows a good in vitro-in vivo correlation and is an appropriate alternative for screening of potential bioactives regulating the sweat mechanism.

Cells in 3D-reconstitutued eccrine sweat gland cell spheroids differentiate into gross cystic disease fluid protein 15-expressing dark secretory cells and carbonic anhydrase II-expressing clear secretory cells

Secretory coils of eccrine sweat glands are composed of myoepithelial cells, dark secretory cells and clear secretory cells. The two types of cells play important roles in sweat secretion. In our previous study, we demonstrated that the 3D-reconstituted eccrine sweat gland cell spheroids differentiate into secretory coil-like structures. However, whether the secretory coil-like structures further differentiate into dark secretory cells and clear secretory cells were is still unknown. In this study, we detected the differentiation of clear and dark secretory cells in the 3D-reconstituted eccrine sweat gland cell spheroids using the dark secretory cell-specific marker, GCDFP-15, and clear secretory cell-specific marker, CAII by immunofluorescence staining. Results showed that there were both GCDFP-15- and CAII-expressing cells in 12-week-old 3D spheroids, similar to native eccrine sweat glands, indicating that the spheroids possess a cellular structure capable of sweat secretion. We conclude that the 12-week 3D spheroids may have secretory capability.

Cell proliferation and differentiation during the three dimensional reconstitution of eccrine sweat glands

The aim of this study is to characterize the cell proliferation and proliferating cell types during three-dimensional reconstitution of eccrine sweat glands. Eccrine sweat gland cells suspended in Matrigel were injected subcutaneously into the inguinal regions of nude mice. At 1, 2, 4, 6, 8, 14, 21, 28, 35 and 42 days post-implantation, Matrigel plugs were immunostained for Ki67, to detect cycling cells, and the Ki67 labeling index at different time points was calculated. Three pairs of antibodies, Ki67/K7, Ki67/K14 and Ki67/α-SMA, were used to identify proliferating cell types in the plugs, on days 28, 35 and 42, by immunofluorescence double staining. The Ki67 labeling index on the first day of implantation was 30.53%, rapidly reached a peak value of 81.43% at 2 days post-implantation, and then decreased gradually to a low of 2.87% at 42 days. Double immunofluorescence staining showed that K14/Ki67 double-stained cells accounted for 80% of the Ki67-positive cells, whereas K7/Ki67 and α-SMA/Ki67 double-stained cells each accounted for 10% of the Ki67-positive population on days 28, 35, or 42 post-implantation. We conclude that eccrine sweat gland cells rapidly enter the cell cycle after implantation, but quickly show decreased cell proliferation and increased cell differentiation.

Human eccrine sweat gland cells reconstitute polarized spheroids when subcutaneously implanted with Matrigel in nude mice

Increasing evidence indicates that maintenance of cell polarity plays a pivotal role in the regulation of glandular homeostasis and function. We examine the markers for polarity at different time points to investigate the formation of cell polarity during 3D reconstitution of eccrine sweat glands. Mixtures of eccrine sweat gland cells and Matrigel were injected subcutaneously into the inguinal regions of nude mice. At 2, 3, 4, 5 and 6 weeks post-implantation, Matrigel plugs were removed and immunostained for basal collagen IV, lateral β-catenin, lateroapical ZO-1 and apical F-actin. The results showed that the cell polarity of the spheroids appeared in sequence. Formation of basal polarity was prior to lateral, apical and lateroapical polarity. Collagen IV was detected basally at 2 weeks, β-catenin laterally and ZO-1 lateroapically at 3 weeks, and F-actin apically at 4 weeks post-implantation. At week 5 and week 6, the localization and the positive percentage of collagen IV, β-catenin, ZO-1 or F-actin in spheroids was similar to that in native eccrine sweat glands. We conclude that the reconstituted 3D eccrine sweat glands are functional or potentially functional.