Melanocytes are present in various parts of the inner ear, including the stria vascularis in the cochlea and the dark cell areas in the vestibular organs, where they contribute to endolymph homeostasis. Developmental studies describing the distribution of vestibular melanocytes are scarce, especially in humans. In this study, we investigated the distribution and maturation of the vestibular melanocytes in relation to the developing dark cell epithelium in inner ear specimens from week 5 to week 14 of development and in surgical specimens of the adult ampulla. Vestibular melanocytes were located around the utricle and the ampullae of the semicircular canals before week 7 and were first seen underneath the transitional zones and dark cell areas between week 8 and week 10. At week 10, melanocytes made intimate contact with epithelial cells, interrupting the local basement membrane with their dendritic processes. At week 11, most melanocytes were positioned under the dark cell epithelia. No melanocytes were seen around or in the saccule during all investigated developmental stages. The dark cell areas gradually matured and showed an adult immunohistochemical profile of the characteristic ion transporter protein Na⁺/K⁺‐ATPase α1 by week 14. Furthermore, we investigated the expression of the migration‐related proteins ECAD, PCAD, KIT, and KITLG in melanocytes and dark cell epithelium. This is the first study to describe the spatiotemporal distribution of vestibular melanocytes during the human development and thereby contributes to understanding normal vestibular function and pathophysiological mechanisms underlying vestibular disorders.

中文翻译：

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人内耳发育过程中前庭黑素细胞的迁移和归宿

黑素细胞存在于内耳的各个部位，包括耳蜗中的血管纹和前庭器官中的暗细胞区，它们有助于内淋巴稳态。描述前庭黑素细胞分布的发育研究很少，尤其是在人类中。在这项研究中，我们调查了前庭黑素细胞的分布和成熟与发育的第 5 周至第 14 周内耳标本和成人壶腹手术标本中暗细胞上皮的发育有关。前庭黑素细胞在第 7 周前位于椭圆囊和半规管壶腹周围，并在第 8 周和第 10 周之间首次出现在过渡区和暗细胞区下方。在第 10 周，黑素细胞与上皮细胞密切接触，用它们的树突状突起打断局部基底膜。在第 11 周，大多数黑素细胞位于暗细胞上皮下。在所有研究的发育阶段，在球囊周围或球囊中都没有看到黑素细胞。暗细胞区域逐渐成熟并显示出特征性离子转运蛋白 Na 的成人免疫组织化学特征⁺ /K ⁺ -ATPase α1 到第 14 周。此外，我们研究了迁移相关蛋白 ECAD、PCAD、KIT 和 KITLG 在黑素细胞和暗细胞上皮中的表达。这是第一项描述人类发育过程中前庭黑素细胞时空分布的研究，从而有助于理解前庭疾病的正常前庭功能和病理生理机制。