Development of the bronchial tree in Monodelphis domestica (Marsupialia)

The Gray Short-tailed opossum (Monodelphis domestica) is a pouchless marsupial from Brazil. The newborn Monodelphis domestica represents the morphotype of the marsupial and mammalian neonate and is suitable to inform on the evolution of the mammalian lung. Phase-contrast X-ray computed tomography (Micro-CT) has been applied to three-dimensionally reconstruct the bronchial tree of Monodelphis domestica in order to reveal the timeline of branching morphogenesis during the postnatal period. Based on the reconstructions, the generation of end-branching airways, the median and maximum generation and the number of branches were calculated for each pulmonary lobe. The lung development was examined from embryonic day 13, during the postnatal period (neonate to 57 days) and in adults. The lung of the newborn Monodelphis domestica has a primitive appearance. Lobar bronchioles and first segmental bronchioles form a simple system of branching airways that end in a number of large terminal air spaces. During the postnatal period development, differentiation and expansion of the bronchial tree takes place. The fundamental bronchial tree, consisting of lobar, segmental and sub-segmental bronchioles, is present by day 14. By 35 days a mature bronchial tree, including respiratory bronchioles and alveolar ducts is established. A peculiarity found in the mature lung of Monodelphis domestica, alveoli located at the walls of large conducting airways, might be a remnant of the transformation of former respiratory epithelium into bronchiolar epithelium and results from the postnatal formation of the bronchial tree in a functioning lung. In marsupials, the process of branching morphogenesis follows similar patterns as described in placentals. However, while this developmental process takes place intrauterine in the placental fetus, it is shifted to the postnatal period in marsupial species. Lung maturation in general and the branching morphogenesis in particular seems to be highly conservative within mammalian evolution. This data set contains original files (videos, images, tables, data sheets) to the publication "3-D-Reconstruction of the bronchial tree of the Gray short-tailed opossum (Monodelphis domestica) in the postnatal period". Images taken from all perspectives and videos of the reconstructed bronchial tree allow for a thoroughly 3-dimensional impression and are a supplement to the published article.

灰短尾负鼠（Monodelphis domestica）是一种产自巴西的无袋有袋动物。新生的灰短尾负鼠代表了有袋类与哺乳动物新生儿的形态型，可用于探究哺乳动物肺的演化。研究人员采用相衬X射线计算机断层扫描（Phase-contrast X-ray computed tomography, Micro-CT）技术，对灰短尾负鼠的支气管树进行三维重建，以揭示其出生后阶段分支形态发生的时间进程。基于重建结果，研究人员为每个肺叶计算了终末分支气道的生成级数、中位生成级数、最大生成级数以及分支总数。本次研究涵盖了胚胎第13天、出生后时期（从新生儿至57日龄）以及成年个体的肺发育情况。新生灰短尾负鼠的肺外观原始，大叶支气管与第一级段支气管构成了简单的分支气道系统，末端连接多个大型终末气腔。在出生后发育阶段，支气管树发生分化与扩张。至第14天时，包含大叶、段级与亚段级支气管的基础支气管树已形成。至35日龄时，包含呼吸性细支气管与肺泡管在内的成熟支气管树得以构建。研究还发现灰短尾负鼠成熟肺的一项特征：大型传导气道壁上分布有肺泡，这可能是昔日呼吸上皮转化为细支气管上皮的遗留特征，且源于功能化肺中支气管树的出生后形成过程。在有袋类动物中，分支形态发生过程与胎盘类动物已报道的模式相似。不过，胎盘类胎儿的该发育过程发生于子宫内，而有袋类物种则将其推迟至出生后时期。总体而言，肺成熟尤其是分支形态发生在哺乳动物演化中呈现出高度的保守性。本数据集包含对应发表论文《出生后时期灰短尾负鼠（Monodelphis domestica）支气管树的三维重建》的原始文件（视频、图像、表格、数据表）。从全视角拍摄的图像以及重建支气管树的视频可提供完整的三维视觉观感，作为已发表论文的补充材料。