BACKGROUND: Previous studies demonstrate that eccrine sweat glands are innervated by both cholinergic and adrenergic nerves. However, it is still unknown whether the secretory coils and ducts of eccrine sweat glands are equally innervated by the sympathetic nerve fibers. To well understand the mechanisms on sweat secretion and reabsorption, the differential innervation of secretory coils and ducts in human eccrine sweat glands was investigated in the study.
METHODS: From June 2016 to June 2017, six human skins were fixed, paraffin-embedded, and cut into 5 μm-thick sections, followed by costaining for nerve fiber markers protein gene product 9.5 (PGP 9.5), tyrosine hydroxylase (TH) and vasoactive intestinal peptide (VIP), and eccrine sweat gland markers K7, S100P, and K14 by combining standard immunofluorescence with tyramide signal amplification (IF-TSA). Stained sections were observed under the microscope, photographed, and analyzed.
RESULTS: The fluorescent signals of PGP 9.5, TH, and VIP were easily visualized, by IF-TSA, as circular patterns surrounding eccrine sweat glands, but only PGP 9.5 could be observed by standard IF. The IF-TSA method is more sensitivity than standard IF in detecting antigens expressed at low levels. PGP 9.5, TH, and VIP appeared primarily surrounding the secretory coils and sparsely surrounding the sweat ducts.
CONCLUSIONS: Sweat secretion is mainly controlled by autonomic nerves whereas sweat reabsorption is less affected by nerve activity.
人汗腺分泌部和导管部神经支配的差异表达摘要背景: 先前的研究表明人汗腺受胆碱能和肾上腺素能神经双重支配，但并不太清楚是否分泌部和导管部等同受到交感神经纤维支配。本研究的目的是调查分泌部和导管部的差异神经纤维支配。 方法: 从2016年6月-2017年6月，六个人皮肤标本常规固定、石蜡包埋、切成5 μm 厚的切片。采用共免疫荧光组织化学-酪氨酸信号放大系统（IF-TSA）方法检测神经标志物：蛋白基因产物 9.5 (PGP 9.5), 酪氨酸羟化酶 (TH)和血管活性肠肽(VIP)，和汗腺标志物：K7，S100P 和K14，的表达。显微镜下观察、拍照和分析染色结果。 结果: IF-TSA 方法能够很容易的检测到PGP 9.5，TH和VIP荧光信号呈环状分布于汗腺周围，而传统的IF法仅检测到PGP 9.5在汗腺的表达。IF-TSA方法比传统的IF法在检测低表达抗原方面更敏感。PGP 9.5，TH和VIP主要分布于分泌部周围，较少分布于导管部周围。 结论: 汗液分泌主要受神经支配，而汗液重吸收较少受神经影响。.

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.

Eccrine sweat glands are comprised of secretory coils and ducts, which are distinct in morphology and function. To better understand the roles of the two parts in development, homeostasis, wound repair and regeneration of eccrine sweat glands, we must distinguish between them. In this study, the localization of keratins and alpha-SMA in human eccrine sweat glands was examined by immunofluorescence staining. Based on the differential localization of keratins and alpha-SMA in different cell types, four pairs of antibodies (K5/K7, K5/alpha-SMA, K14/K7 and K14/alpha-SMA) were used to differentiate secretory coils from ducts by double-immunofluorescence staining. Immunofluorescence staining showed that myoepithelial cells of secretory coils expressed K5, K14 and alpha-SMA, whereas secretory cells of secretory coils expressed K7, K8, K15, K18 and K19. Ductal cells expressed K5, K8, K14 and K19. Double-staining showed that the secretory coils were K5(+)/K7(+), K5(+)/alpha-SMA(+), K14(+)/K7(+) and K14(+)/alpha-SMA(+), whereas ducts were K5(+)/K7(-), K5(+)/alpha-SMA(-), K14(+)/K7(-) and K14(+)/alpha-SMA(-). In conclusion, by combining use of keratins and alpha-SMA antibodies, secretory coils can be easily differentiated from ducts in morphology.