Transport epithelia maintain the volume, ion concentration and acid-base balance of blood and extracellular fluids. In teleost fish, mitochondrion-rich cells (MRCs) are specialized ionocytes that perform this role. These cells are found in epithelia of the gills and buccal surface of the operculum (the bony structure covering the gills). Proliferation of MRCs in response to changes in water salinity and other environmental stressors is well documented, but the cellular mechanisms underlying MRC proliferation are poorly understood. Recently, regeneration and epithelial cell replacement in the gill filaments was demonstrated in the model vertebrate, zebrafish (Danio rerio), raising the question of whether MRCs are replaced during regrowth of transport epithelia. We chose two anatomical sites where MRCs are found—the gills and the opercular epithelium—to investigate whether MRCs were replaced following surgical resection of these structures. In live imaging experiments, we observed gradual replacement of the branchiostegal valve, an extension of the operculum, in zebrafish over a period of 21 days post-resection (dpr). In regenerating epithelia of both the operculum and gills, we detected MRCs by immunohistochemical localization of the α subunit of plasma membrane Na⁺/K⁺-ATPase. In both tissues, MRCs appeared soon after resection, and as early as 1 dpr in the gill filaments. We report regeneration of the operculum and proliferation of MRCs in regenerating tissue in adult zebrafish. These studies may contribute to our understanding of how MRC populations are regulated during the regenerative process, which may occur following exposure to environmental stressors, chemical toxicity or disease.

运输上皮细胞维持血液和细胞外液的体积、离子浓度和酸碱平衡。在硬骨鱼中，富含线粒体的细胞 (MRC) 是专门的离子细胞，可以发挥这种作用。这些细胞存在于鳃的上皮细胞和鳃盖的颊面（覆盖鳃的骨结构）。MRC 响应水盐度和其他环境压力的变化而增殖已得到充分证明，但 MRC 增殖的细胞机制却知之甚少。最近，在模型脊椎动物斑马鱼（斑马鱼）中证实了鳃丝的再生和上皮细胞替代。)，提出了在运输上皮细胞再生过程中是否更换 MRC 的问题。我们选择了发现 MRC 的两个解剖部位——鳃和鳃盖上皮——来研究在手术切除这些结构后是否更换了 MRC。在实时成像实验中，我们观察到斑马鱼在切除后 21 天 (dpr) 中逐渐更换了鳃瓣，即鳃盖的延伸。在鳃盖和鳃的再生上皮细胞中，我们通过质膜 Na ⁺ /K ^{+的 α 亚基的免疫组织化学定位来检测 MRC。}-ATP酶。在这两种组织中，MRCs 在切除后不久就出现了，早在 1 dpr 就出现在鳃丝中。我们报告了成年斑马鱼再生组织中鳃盖的再生和 MRC 的增殖。这些研究可能有助于我们了解 MRC 种群在再生过程中是如何受到调节的，这可能发生在暴露于环境压力源、化学毒性或疾病之后。