Department of Anatomy (Cell Biology), Iwate Medical University, 1-1-1 Idaidori, Yahaba-cho, Shiwa-gun, Iwate, 028-3694, Japan.
Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate, 020-8550, Japan.
Histochem Cell Biol. 2024 Oct;162(4):287-297. doi: 10.1007/s00418-024-02309-6. Epub 2024 Jul 20.
Mast cells (MCs) in rat airways have been classified into two subtypes: epithelial MCs and connective tissue MCs (CTMCs). However, the immunohistochemical characteristics, cellular morphology, and distribution of epithelial MCs in the upper airways remain unclear. The present study investigated the morphological characteristics and distribution of epithelial MCs using 5-hydroxytryptamine (5-HT) and other immunohistochemical markers in sectioned or whole-mount preparations of the rat larynx and trachea. A double immunofluorescence analysis revealed the colocalization of 5-HT immunoreactivity with c-kit, a stem cell factor receptor commonly used as a MC marker, in both epithelial MCs and CTMCs. Dopa decarboxylase, an enzyme involved in 5-HT synthesis, was detected in both subtypes, suggesting their ability to synthesize and release 5-HT. Tryptase and histidine decarboxylase (a biosynthetic enzyme of histamine), which are well-known mediators of MCs, were exclusive to CTMCs. Epithelial MCs were pleomorphic with long cytoplasmic processes, whereas CTMCs were round and lacked cytoplasmic processes. The density of epithelial MCs was significantly higher in the glottis and cranial part of the trachea than in the epiglottis and other parts of the trachea. The present results showed that the morphology and immunohistochemical characteristics of epithelial MCs were different from those of CTMCs in the rat larynx and trachea, and variform epithelial MCs were predominantly located at the entrance of the upper airways. Epithelial MCs may release 5-HT to regulate innate immune responses by modulating epithelial cell functions at the entrance gate of the upper airways.
气道中的肥大细胞（MCs）已被分为两种亚型：上皮 MCs 和结缔组织 MCs（CTMCs）。然而，在上呼吸道中，上皮 MCs 的免疫组织化学特征、细胞形态和分布仍不清楚。本研究使用 5-羟色胺（5-HT）和其他免疫组织化学标志物，在大鼠喉和气管的切片或全器官制剂中，研究了上皮 MCs 的形态特征和分布。双重免疫荧光分析显示，5-HT 免疫反应性与干细胞因子受体 c-kit 共定位，c-kit 通常被用作 MC 标志物，存在于上皮 MCs 和 CTMCs 中。多巴脱羧酶，一种参与 5-HT 合成的酶，在两种亚型中均有检测到，表明它们具有合成和释放 5-HT 的能力。胰蛋白酶和组氨酸脱羧酶（组氨酸的生物合成酶）是 MCs 的众所周知的介质，仅存在于 CTMCs 中。上皮 MCs 具有长的细胞质突起，形态多样，而 CTMCs 呈圆形，缺乏细胞质突起。与会厌和气管的其他部位相比，声带和气管颅侧的上皮 MCs 密度显著更高。本研究结果表明，大鼠喉和气管中的上皮 MCs 的形态和免疫组织化学特征与 CTMCs 不同，形态多样的上皮 MCs 主要位于上呼吸道的入口处。上皮 MCs 可能通过调节上呼吸道入口处上皮细胞的功能，释放 5-HT 来调节固有免疫反应。
