The 20th Congress of International Federation of Associations of Anatomists (IFAA2022) 2022,8/5-7, Istanbul,Turkey/Onlineで発表しました。
Ishikawa A, Nagai-Tanima M, Ishida K, Imai H, Aoyama T, Takakuwa T. Three-dimensional analysis of knee joint development during the human fetal period.
Nohara A, Owaki N, Matsubayashi J, Katsube M, Imai H, Yoneyama A, Yamada S, Kanahashi T, Takakuwa T. Morphometric analysis of secondary palate development in human embryos. J Anatomy, 2022, in press, DOI:10.1111/joa.13745
Rapid shelf elevation and contact of the secondary palate and fusion reportedly occur due to a growth-related equilibrium change in the structures within the oro-nasal cavity. This study aimed to quantitatively evaluate complex three-dimensional morphological changes and their effects on rapid movements, such as shelf elevation and contact, and fusion. Morphological changes during secondary palate formation were analyzed using high-resolution digitalized imaging data (phase-contrast X-ray computed tomography and magnetic resonance images) obtained from 22 human embryonic and fetal samples. The three-dimensional images of the oro-nasal structures, including the maxilla, palate, pterygoid hamulus, tongue, Meckel’s cartilage, nasal cavity, pharyngeal cavity, and nasal septum, were reconstructed manually.
palatal shelves were not elevated in all the samples at Carnegie stage (CS)21 and CS22 and in three samples at CS23. In contrast, the palatal shelves were elevated but not in contact in one sample at CS23. Further, the palatal shelves were elevated and fused in the remaining four samples at CS23 and all three samples from the early fetal period. For each sample, 70 landmarks were subjected to Procrustes and principal component (PC) analysis. PC-1 accounted for 67.4% of the extracted gross changes before and after shelf elevations. Notably, the PC-1 values of the negative and positive value groups differed significantly. The PC-2 value changed during the phases in which the change in the PC-1 value was unnaturally slow and stopped at CS22 and the first half of CS23. This period, defined as the “approach period”, corresponds to the time before dynamic changes occur as the palatal shelves elevate, the tongue and mandibular tip change their position and shape, and secondary palatal shelves contact and fuse. During the “approach period”, measurements of PC-2 changes showed that structures on the mandible (Meckel’s cartilage and tongue) and maxilla (palate and nasal cavity) did not change positions, albeit both groups of structures appeared to be compressed anterior-posteriorly. However, during and after shelf elevation, measurements of PC-1 changes showed significant changes between maxillary and mandibular structures, particularly positioning of the shelves above the tongue and protrusion of the tongue and mandible. These results suggest an active role for Meckel’s cartilage growth in repositioning the tongue to facilitate shelf elevation. The present data representing three distinct phases of secondary palate closure in humans can advance the understanding of morphological growth changes occurring before and after the horizontal positioning of palatal shelves and their fusion to close the secondary palate in humans successfully.
高桑徹也；三次元デジタル情報を活用したヒト胚子・胎児の解析 Analysis of human embryos and fetuses using three-dimensional digitalized images
＠座長もさせていただきました。現地に出席の方も結構おられ、かなり盛況でした。
一般演題
藤井 瀬菜、村中 太河、松林 潤、米山 明男、兵藤 一行、山田 重人、高桑徹也; ヒト胚子期における気管支樹の三次元的変化の定量的検討 The quantitative analysis of morphological change of the human embrionic bronchial tree
金橋 徹、今井宏彦、大谷 浩、山田重人、米山明男、高桑徹也; 拡散テンソルイメージングを応用したヒト胎児横隔膜形成の三次元的解析 Three-dimensional morphogenesis of the human diaphragm during the late embryonic and early fetal period: Analysis using diffusion tensor imaging
KakeyaM, Matsubayashi J, Kanahashi T, Männer J, Yamada S, Takakuwa T. The return process of physiological umbilical herniation in human fetuses: the possible role of the vascular tree and umbilical ring. J Anatomy 2022, in press
Abstract
The human intestine elongates during the early fetal period, herniates into the extraembryonic coelom (EC), and subsequently returns to the abdominal cavity (AC). The process by which the intestinal loop returns to the abdomen remains unclear. This study aimed to document positional changes in the intestinal tract with the superior mesenteric artery (SMA) and branches in 3D to elucidate the intestinal loop return process (transition phase). Serial histological cross-sections from human fetuses (crown–rump length [CRL] range: 30–50 mm) in the herniation (n = 1), transition (n = 7), and return (n = 2) phases were selected from the Blechschmidt Collection. The distribution of the SMA trunk and all intestinal and sister branches entering the intestines was visualized so that positional changes in branches were continuous from the herniation to return phases. Positional changes in SMA branches proceeded in an orderly and structured manner; this is essential for continuous blood supply via the SMA to the intestine during transition and for safe intestinal return. Changes in the SMA distribution proceeded prior to the detection of initiation of intestinal tract return, which might start earlier and last much longer than our consensus (i.e., that the return of the herniated intestine begins when the CRL is approximately 40 mm and ends within a short time). In the cross-section of the umbilical ring in the herniation and transition phases, one proximal limb and one distal limb were observed with SMA intestinal branches, which were fully packed in the umbilical ring. The SMA branches were aligned from inferior to superior along the SMA main trunk. In the herniation phase, the distribution of 3rd–13th branches aligned from proximal inferior medial to distal superior left with a slight spiral in the EC, the tips of which suggested an orderly running course of the small intestine. In the transition phase, SMA branches running across the umbilical ring that fed the small intestine were observed, suggesting that the intestine was uncoiled and ran across the umbilical ring almost vertically. The estimated curvature value supported the phenomenon of uncoiling at the umbilical ring; the value at the umbilical ring was lesser than that in the AC and EC. During the transition phase, the proximal and distal limbs transversely ran side by side in the AC, umbilical ring, limbs on the cranial side, and mesentery on the caudal side. The SMA trunk and its branches ran in parallel, cranially to caudally aligned in the mesentery. This layout of the umbilical ring was maintained during the transition phase. In the return phase, the SMA trunk was gently curved from the upper left to the lower right of the AC; around 12 branches spread with a winding staircase appearance. The intestinal tract reached its definitive position immediately after all tissues crossed the umbilical ring and released any restriction. Each SMA branch and the corresponding region of the intestinal tract form a unit and change their position, though the conformation may change within each unit when running across the umbilical ring. We suggest that the slide–stack model requires revision.
Kumano Y, Tanaka S, Sakamoto R, Kanahashi T, Imai H, Yoneyama A, Yamada S, Takakuwa T. Upper arm posture during human embryonic and fetal development. Anatomical Rec 2022, 305 1682-1691, https://doi.org/10.1002/ar.24796
Abstract
The upper extremity posture is characteristic of each Carnegie stage (CS), particularly between CS18 and CS23. Morphogenesis of the shoulder joint complex largely contributes to posture, although the exact position of the shoulder joints has not been described. In the present study, the position of the upper arm was first quantitatively measured, and the contribution of the position of the shoulder girdle, including the scapula and glenohumeral (GH) joint, was then evaluated. Twenty-nine human fetal specimens from the Kyoto Collection were used in this study. The morphogenesis and three-dimensional position of the shoulder girdle and humerus were analyzed using phase-contrast X-ray computed tomography and magnetic resonance imaging. Both abduction and flexion of the upper arm displayed a local maximum at CS20. Abduction gradually decreased until the middle fetal period, which was a prominent feature. Flexion was less than 90° at the local maximum, which was discrepant between appearance and measurement value in our study. The scapular body exhibited a unique position, being oriented internally and in the upward direction, with the glenoid cavity oriented cranially and ventrally. However, this unique scapular position had little effect on the upper arm posture because the angle of the scapula on the thorax was canceled as the angle of the GH joint had changed to a mirror image of that angle. Our present study suggested that measuring the angle of the scapula on the thorax and that of the GH joint using sonography leads to improved staging of the human embryo.
Details of the bronchial tree formation remain unknown because of the difficulty in analyzing extremely small embryos. We aimed to elucidate the morphogenesis of the human embryonic bronchial tree using phase-contrast X-ray computed tomography (PXCT) images. The three-dimensional (3D) branching of the bronchial trees was reconstructed using PXCT images in a sample of embryos (between n. The images revealed that branching variants arose during the embryonic period and continued throughout life. All proximal bronchi, except the were formed by a monopodial branching mode. The 3D reconstructions of the embryonic bronchial trees provided novel insights into how bronchial trees are generated in the small embryos.
The bronchial tree of the human lung is composed of conducting and respiratory airways [1]. This organ has a highly ramified structure in the lungs. An understanding of branching morphogenesis is essential for the diagnosis and treatment of congenital anomalies. However, how such complicated branching networks are generated during development remains unclear because of the difficulty in analyzing extremely small embryos. Recently, we provided new insights into the branching tree formation in the human embryonic lung by analyzing 3D reconstructions of the human embryonic bronchial tree [2, 3].
Figure 1: Image processing of the bronchial tree and illustration showing the change of bronchus length with monopodial and dipodial branching. a (i) Transverse section using phase-contrast X-ray computed tomography. Heart (H). (ii) Reconstructed bronchial tree. Scale bar: 1mm. (iii) Centerline was calculated based on reconstruction. b The parent bronchus (PBr) length may shrink with monopodial branching just after generation of child bronchus (CBr) (i), but may not shrink or elongate with dipodial branching (ii).
First, we extended the morphological analysis to the end of the embryonic period [2]. The embryonic period is from the time of fertilization to 8 weeks post-fertilization. It begins with the formation of the body structures, generally described by a standardized system of 23 stages called the Carnegie stages (CS) [4]. Previous morphological studies have demonstrated the general morphogenetic processes of the human bronchial tree during the embryonic period. The primordium of the tree buds extends from the middle of the foregut at approximately CS 12 (at approximately 4 weeks after fertilization) [5]. After that, this pulmonary primordium bud continues to extend and branches out continuously to form the lobar, segmental, and more peripheral branches. The first generation of sub-segmental bronchi is complete at CS19 [6]. However, morphological changes in the trees after CS20 have not been elucidated.
Second, we analyzed how the proximal bronchus of the human lung branched off [3]. Previous studies have proposed two simple branching modes: monopodial and dipodial [7, 8]. With monopodial branching, the child branches extend from the sidewall of the parent branch. With dipodial branching, the tip of the bronchus bifurcates. Previous studies estimated the branching mode based only on visual assessments.
Thus, we aimed to describe the morphogenesis of bronchial trees during the human embryonic period. We reconstructed 3D branching trees using phase-contrast X-ray computed tomography (PXCT) images, observed the morphological changes in the trees in detail, and categorized the branching mode as monopodial and dipodial based on the bronchus length.
A total of 48 embryos between CS15 and CS23 (about 5-8 weeks after fertilization, 8-30 mm crown-rump length) [4] of the Kyoto Collection were selected [9]. Imaging data of all samples were acquired using PXCT. The system was set up at the vertical wiggler beamline (BL-14C). The PXCT imaging data provided a resolution of ≥ 18 μm/pixel [10], which enabled the non-destructive observation of intrabody structures in detail, and the highly sensitive morphometry of the embryos. The structure of the bronchial tree was reconstructed for all samples using Amira software (version 6.2.0; Visage Imaging GmbH, Berlin, Germany) (Fig. 1a). The center of the airway was observed linearly with the centerline module. The coordinates were analyzed using MATLAB v. R2018a (MathWorks, Inc., Natick, MA, USA) to calculate the generation of all branches and branch lengths.
We categorized the branching modes of the lobar, segmental, and subsegmental bronchi. After calculating each bronchus length, we categorized the branching mode of the analyzed bronchi based on whether the parent bronchus was divided after generating the analyzed bronchi (Fig.1b).
Figure 2: 3D reconstructions enable novel analyses of the human embryonic bronchial tree. a Representative reconstructions of the bronchial tree. Scale bar: 1mm. b (left) Generation of end-branching (rainbow color) at CS18, CS21, and CS23. The colored circle indicates generations of each end-branch when the lobar bronchus was defined as 0th branch. Color bar indicates the corresponding colors. (right) Change of generation in each lobe by Carnegie stage during CS18 and CS23. LIL, left inferior lobe; LSL, left superior lobe; RIL, right inferior lobe; RML, right middle lobe; RSL, right superior lobe. c Branching mode of the right superior and middle lobar bronchi. The length changes of the right proximal bronchi are shown. Compared with the right primary bronchial bud (RPBB) length before branching, temRMB length and total length of right main bronchus (RMB) and intermediate bronchus (IB) were shorter. RIB, right inferior bronchus; temRMB, temporary RMB branch from the tracheal bifurcation to the base of the right middle lobe.
Three-dimensionally reconstructed bronchial trees revealed a timeline of morphogenesis during the embryonic period (Fig. 2a). The right superior lobar bronchus was formed after the generation of both the right middle and left superior lobar bronchi. The distribution of the end-branch generation among the five lobes was significantly different (Fig. 2b). The median branching generation value in the right middle lobe was significantly lower than that in the other four lobes. Variations found between CS20 and CS23 were all described in the human adult lung, indicating that variation in the bronchial tree may arise during the embryonic period and continue throughout life.
All lobar bronchi were formed with monopodial branching (Fig. 2c). Twenty-five bifurcations were analyzed to categorize the branching mode of the segmental and subsegmental bronchi. Of these, 22 bifurcations were categorized as monopodial branching, two bifurcations were not categorized as any branching pattern, and the only lingular bronchus that bifurcated from the left superior lobar bronchus was categorized as dipodial branching.
High-resolution imaging data of human embryonic specimens using PXCT enabled the reconstruction of the three-dimensional bronchial tree, revealing morphogenetic changes during the human embryonic period. Our novel understanding of bronchial tree development will provide a crucial resource for elucidating congenital anomalies.
Fujii, T. Takakuwa (Kyoto Univ.)
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