Ozaki Taku, Utsumi Shinto, Iwamoto Takeshi, Tanaka Makoto, Tomita Hiroshi, Sugano Eriko, Ishiyama Eri, Ishida Kinji
Department of Biological Science, Graduate School of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan.
Technical Support Center for Life Science Research, Iwate Medical University, Morioka, Japan.
Data Brief. 2020 Apr 20;30:105544. doi: 10.1016/j.dib.2020.105544. eCollection 2020 Jun.
Photoreceptors are one of the most energy-consuming cell types within the human body. To meet their high energy demand, photoreceptors possess a mitochondrial cluster in the inner segment of the cell. Interestingly, in several species, the inner segment of cone photoreceptors contains extremely large mitochondria that exceed 2 µm in diameter, called mega-mitochondria. We previously reported that pig retinas also contain mega-mitochondria, however, there are few reports whether mega-mitochondria are present in mammalian photoreceptors. In the present experiment, we analyzed pig, rabbit, and mouse photoreceptors under a scanning electron microscope (SEM), and compared the mitochondrial morphology. Our data showed that all three species present numerous mitochondrial clusters in the ellipsoid zone of photoreceptors, adjacent to the outer segment. In the pig retina, the inner segments of cone and rod photoreceptors were localized in different layers; consequently, we were able to distinguish them easily. Mega-mitochondria were identified only in the inner segment of cone photoreceptors. Also, mitochondria of cone photoreceptors, including mega-mitochondria, were dense cristae and high electron-densities compared to those of rod photoreceptors. In the rabbit retina, cone photoreceptors were existed within the layer of rod photoreceptor outer segment. The rod photoreceptors had a characteristic long outer segment. Cone photoreceptors had a short outer segment, and also had a thick inner segment compared to rod photoreceptors. Most of the mitochondria present in the rod photoreceptor inner segment were long and narrow, whereas mitochondria of cone photoreceptors were fragmented and short. Mega-mitochondria was not detected in rabbit retina. In the mouse retina, most of the photoreceptor cells were rod photoreceptors. Since the shape of the inner segments were very similar, we distinguished cone and rod photoreceptors based on the shape of the outer segments. Some mitochondria of both rod and cone photoreceptors were long and narrow, and there was no significant difference in mitochondrial morphology. Our data showed that mitochondrial morphology in the inner segment of photoreceptors vary among mammalian species. Although mega-mitochondria were present in pig photoreceptors, we could not observe their presence in rabbit nor mouse retinas. To our knowledge, this is a first experiment that perform the wide field observation of rabbit and mouse retina using electron microscopy, and that compare the mitochondrial morphology of photoreceptor cells in pig, rabbit and mouse.
光感受器是人体中能量消耗最大的细胞类型之一。为了满足其高能量需求，光感受器在细胞内段拥有线粒体簇。有趣的是，在几个物种中，视锥光感受器的内段含有直径超过2微米的极大线粒体，称为巨型线粒体。我们之前报道过猪视网膜中也含有巨型线粒体，然而，关于巨型线粒体是否存在于哺乳动物光感受器中的报道很少。在本实验中，我们在扫描电子显微镜（SEM）下分析了猪、兔和小鼠的光感受器，并比较了线粒体形态。我们的数据表明，所有这三个物种在光感受器的椭球体区域（与外段相邻）都存在大量线粒体簇。在猪视网膜中，视锥和视杆光感受器的内段位于不同层；因此，我们能够很容易地将它们区分开来。仅在视锥光感受器的内段发现了巨型线粒体。此外，与视杆光感受器相比，视锥光感受器的线粒体，包括巨型线粒体，具有密集的嵴和高电子密度。在兔视网膜中，视锥光感受器存在于视杆光感受器外段层内。视杆光感受器有一个特征性的长外段。视锥光感受器有一个短外段，并且与视杆光感受器相比内段也更厚。视杆光感受器内段中的大多数线粒体又长又窄，而视锥光感受器的线粒体则是碎片化的且短。在兔视网膜中未检测到巨型线粒体。在小鼠视网膜中，大多数光感受器细胞是视杆光感受器。由于内段的形状非常相似，我们根据外段的形状区分视锥和视杆光感受器。视杆和视锥光感受器的一些线粒体又长又窄，并且线粒体形态没有显著差异。我们的数据表明，光感受器内段的线粒体形态在哺乳动物物种之间存在差异。虽然巨型线粒体存在于猪的光感受器中，但我们在兔和小鼠视网膜中未观察到它们的存在。据我们所知，这是首次使用电子显微镜对兔和小鼠视网膜进行广域观察，并比较猪、兔和小鼠光感受器细胞线粒体形态的实验。
