Quick Quincy A, Serrano Elba E
Department of Biology, New Mexico State University, Las Cruces, New Mexico 88033, USA.
Int J Dev Biol. 2007;51(3):201-9. doi: 10.1387/ijdb.062176qq.
The auditory and vestibular endorgans of the inner ear which are essential for the senses of hearing and balance form early during development when the otocyst undergoes a period of rapid growth and compartmentalization. Here we show the spatial and temporal patterns of proliferating cells in the Xenopus laevis inner ear as this organ develops from an otic vesicle at stage 31 until stage 47, an age at which compartmentalization and the initial appearance of sensory structures are evident. Sites of new cell production were identified in specimens at stages 31, 37, 42, 45 and 47 using immunohistochemical methods to detect bromodeoxyuridine (BrdU) incorporation three hours after exposure to this thymidine analogue. Cells undergoing terminal mitosis at stages 37, 42 and 45 were detected by exposing specimens at these stages to BrdU and permitting development to proceed until stage 47. Our results show that while newly replicating cells are uniformly distributed throughout the stage 31 otic vesicle, they are spatially restricted in stages 37 through 45, with few dividing cells visible in the central patches of the emerging sensory epithelia. In contrast, no clear proliferative pattern was discerned at stage 47. BrdU-positive cells that had undergone terminal mitosis at stage 37, 42 and 45 were detected in the central regions of nascent sensory epithelia at stage 47. These findings are consistent with a developmental mechanism in which cells undergoing terminal mitosis during early X. laevis stages contribute to sensory epithelia and in which cell mixing and migration are features of inner ear compartmentalization.
内耳的听觉和前庭终器对于听觉和平衡感至关重要，它们在发育早期形成，此时耳囊经历快速生长和分隔阶段。在此，我们展示了非洲爪蟾内耳中增殖细胞的时空模式，该器官从第31期的耳泡发育至第47期，在这个年龄段，分隔和感觉结构的初步出现很明显。使用免疫组织化学方法，在暴露于胸腺嘧啶核苷类似物溴脱氧尿苷（BrdU）三小时后，在第31、37、42、45和47期的标本中鉴定出新细胞产生的部位。通过在第37、42和45期将标本暴露于BrdU并使其发育至第47期，检测到处于终末有丝分裂的细胞。我们的结果表明，虽然新复制的细胞在第31期的耳泡中均匀分布，但在第37至45期它们在空间上受到限制，在新兴感觉上皮的中央区域几乎看不到分裂细胞。相比之下，在第47期未发现明显的增殖模式。在第47期，在新生感觉上皮的中央区域检测到在第37、42和45期经历终末有丝分裂的BrdU阳性细胞。这些发现与一种发育机制一致，即在非洲爪蟾早期阶段经历终末有丝分裂的细胞有助于形成感觉上皮，并且细胞混合和迁移是内耳分隔的特征。
