Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington, Seattle, WA, 98195, United States.
Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, United States.
Hear Res. 2020 Jan;385:107839. doi: 10.1016/j.heares.2019.107839. Epub 2019 Nov 8.
Hair cells in the auditory organ of the vertebrate inner ear are the sensory receptors that convert acoustic stimuli into electrical signals that are conveyed along the auditory nerve to the brainstem. Hair cells are highly susceptible to ototoxic drugs, infection, and acoustic trauma, which can cause cellular degeneration. In mammals, hair cells that are lost after damage are not replaced, leading to permanent hearing impairments. By contrast, supporting cells in birds and other non-mammalian vertebrates regenerate hair cells after damage, which restores hearing function. The cellular mechanisms that regulate hair cell regeneration are not well understood. We investigated the role of vascular endothelial growth factor (VEGF) during regeneration of auditory hair cells in chickens after ototoxic injury. Using RNA-Seq, immunolabeling, and in situ hybridization, we found that VEGFA, VEGFC, VEGFR1, VEGFR2, and VEGFR3 were expressed in the auditory epithelium, with VEGFA expressed in hair cells and VEGFR1 and VEGFR2 expressed in supporting cells. Using organotypic cultures of the chicken cochlear duct, we found that blocking VEGF receptor activity during hair cell injury reduced supporting cell proliferation as well as the numbers of regenerated hair cells. By contrast, addition of recombinant human VEGFA to organ cultures caused an increase in both supporting cell division and hair cell regeneration. VEGF's effects on supporting cells were preserved in isolated supporting cell cultures, indicating that VEGF can act directly upon supporting cells. These observations demonstrate a heretofore uncharacterized function for VEGF signaling as a critical positive regulator of hair cell regeneration in the avian inner ear.
脊椎动物内耳的听觉器官中的毛细胞是将声刺激转化为电信号的感觉受体，这些电信号沿着听神经传递到脑干。毛细胞极易受到耳毒性药物、感染和声音创伤的影响，这些因素会导致细胞变性。在哺乳动物中，受损后丢失的毛细胞不会被替换，从而导致永久性听力损伤。相比之下，鸟类和其他非哺乳动物脊椎动物的支持细胞在受损后会再生毛细胞，从而恢复听力功能。调节毛细胞再生的细胞机制尚未得到很好的理解。我们研究了血管内皮生长因子（VEGF）在鸡听觉毛细胞受损后的再生过程中的作用。通过 RNA-Seq、免疫标记和原位杂交，我们发现 VEGFA、VEGFC、VEGFR1、VEGFR2 和 VEGFR3 在听觉上皮中表达，其中 VEGFA 在毛细胞中表达，VEGFR1 和 VEGFR2 在支持细胞中表达。通过鸡耳蜗管的器官培养实验，我们发现阻断 VEGF 受体活性会减少支持细胞的增殖以及再生毛细胞的数量。相比之下，向器官培养物中添加重组人 VEGFA 会导致支持细胞分裂和毛细胞再生的数量增加。VEGF 对支持细胞的作用在分离的支持细胞培养物中得以保留，表明 VEGF 可以直接作用于支持细胞。这些观察结果表明，VEGF 信号作为禽类内耳毛细胞再生的关键正调控因子，具有以前未知的功能。
