京都大学 大学院医学研究科 人間健康科学系専攻 病理学研究室（形態形成医療科学）

４回生の卒業研究発表会が、基礎系、理工系、臨床系にわかれて行われました（2022.1.26-28，杉浦ホール）。

今年も、教員数名以外は遠隔での参加の形でした。練習通り、制限時間いっぱいに発表できてよかったと思います。

発表者の皆さん、ご苦労様でした。

ヒト胎児期における手根骨の三次元的解析　石毛浩太
MRIを用いたヒト胎児の腹直筋形成過程の解析　岩佐結生
ヒト胎児期における足根骨の三次元解析　木村健太郎
ヒト胎児の主要血管径および血行動態の胎齢に伴う変化　中井　尚一
ヒト胎児期における咽頭の形態形成の観察　古田万紀子

山崎さんの修士論文がCells Tissues Organsに受諾されました。

気管軟骨、喉頭軟骨の形態形成について軟骨の発生段階を立体的に細かく示しました。頭尾方向の分化の同調性については、これまでの報告と異なっています。

• Phase 2の最初の分化 は正中面ではなく、舌骨、甲状軟骨、輪状軟骨、気管軟骨ともに両外側に 一つずつあり、それぞれのタイムラインに従って分化し正中面で融合した。
• 気管軟骨のPhase2 の分化は頭側で始まり、体軸に沿って短期間で伝播し、Phase 3 の分化が始まる前に同調する。
• Phase 3 分化は正中で始まり、側方に伝播する。頭尾方向については、同調して分化し、差はない。
• 気管気管支軟骨の数と分布は成人と同様である。

54. Yamazaki Y, Kanahashi T, Yamada S, Männer J, Takakuwa T. Three-dimensional analysis of human laryngeal and tracheobronchial cartilages during the late embryonic and early fetal period. Cells Tissues Organs, 2021 in press

Abstract

Laryngeal and tracheobronchial cartilages are present as unique U-shaped forms around the respiratory tract and contribute to the formation of rigid structures required for the airway. Certain discrepancies still exist concerning cartilage formation in humans. To visualize the accurate timeline of cartilage formation, tracheobronchial and laryngeal cartilages were 3D reconstructed based on serial tissue sections during the embryonic period (Carnegie stage [CS] 18–23) and early fetal period (crown rump length [CRL] = 35–45 mm). The developmental phases of the cartilage were estimated by histological studies, which were performed on the reconstructed tissue sections. The hyoid greater horns were recognizable at CS18 (phase 2). Fusion of 2 chondrification centers in the mid-sagittal region was observed at CS19 in the hyoid bone, at CS20 in the cricoid cartilage, and in the specimen with CRL 39 mm in the thyroid cartilage. Phase 3 differentiation was observed at the median part of the hyoid body at CS19, which was the earliest among all other laryngeal and tracheobronchial cartilages. Most of the laryngeal cartilages were in phase 3 differentiation at CS22 and in phase 4 differentiation at CS23. The U-shaped tracheobronchial cartilages with phase 2 differentiation covered the entire extrapulmonary region at CS20. Phase 3 differentiation started on the median section and propagates laterally at CS21. The tracheobronchial cartilages may form simultaneously during the embryonic period at CS22-23 and early fetal periods, similar to adults in number and distribution. The spatial propagation of the tracheal cartilage differentiation provided in the present study indicates that cartilage differentiation may have propagated differently on phase 2 and phase 3. This study demonstrates a comprehensible timeline of cartilage formation. Such detailed information of the timeline of cartilage formation would be useful to improve our understanding of the development and pathophysiology of congenital airway anomalies.

寺島さんの修士論文がJ Anatomyに受諾されました。おめでとうございます。

• 胎児期のみに出現し、大脳皮質の形成、自発活動の開始に関わる可能性のあるプレサブプレート(pSP)の形成について、連続組織画像を用いて立体的に視覚化し、定量化した。
• PSPはCS21で大脳壁の中外側領域に存在し、この領域を中心とした拡大が観察され、胎児期の初期（CRL 39 mm）に大脳半球全体で観察した。
• pSP-IZ の厚さは 3D で表示され、中外側領域で大きかった。CRL 64 mm)に、厚い領域は、島の原基の周りの外側、上部、および後部領域に拡大しました。
• 層構造は、発達初期に厚くなるのではなく、薄く成長して広がった。

Terashima, M., Ishikawa A., Männer J., Yamada S.&Takakuwa T. (2021) Early development of the cortical layers in the human brain. Journal of Anatomy, 239, 1039–1049. https://doi.org/10.1111/joa.13488

Abstract

The cortical plate (CP) first appears at seven postconceptional weeks (pcw), when it splits the preexisting preplate into two layers, the marginal zone and the presubplate (pSP). Although three-dimensional (3D) analysis using fetal magnetic resonance imaging and two-dimensional tissue observations have been reported, there have been no studies analyzing the early development of the layer structure corresponding to the pSP stage in 3D. Here, we reconstructed 3-D models of the brain with a focus on the cortical layers in pSP stage. To achieve this, we digitized serial tissue sections of embryos between CS20 and CS23 from the Kyoto Collection (n = 7, approximately 7–8.5 pcw), and specimens at early fetal phase from the Blechschmidt Collection (n = 2, approximately 9.5–12 pcw, crown rump length [CRL] 39 and 64 mm). We observed tissue sections and 3D images and performed quantitative analysis of the thickness, surface area, and volume. Because the boundary between pSP and the intermediate zone (IZ) could not be distinguished in hematoxylin and eosin-stained sections, the two layers were analyzed together as a single layer in this study. The histology of the layers was observed from CS21 and became distinct at CS22. Subsequently, we observed the 3-D models; pSP-IZ was present in a midlateral region of the cerebral wall at CS21, and an expansion centered around this region was observed after CS22. We observed it over the entire cerebral hemisphere at early fetal phase (CRL 39 mm). The thickness of pSP-IZ was visible in 3D and was greater in the midlateral region. At the end of the pSP stage (CRL 64 mm), the thick region expanded to lateral, superior, and posterior regions around the primordium of the insula. While, the region near the basal ganglia was not included in the thickest 10% of the pSP-IZ area. Middle cerebral artery was found in the midlateral region of the cerebral wall, near the area where pSP-IZ was observed. Feature of layer structure growth was revealed by quantitative assessment as thickness, surface area, and volume. The maximum thickness value of pSP-IZ and CP increased significantly according to CRL, whereas the median value increased slightly. The layer structure appeared to grow and spread thin, rather than thickening during early development, which is characteristic during pSP stages. The surface area of the cerebral total tissue, CP, and pSP-IZ increased in proportion to the square of CRL. The surface area of CP and pSP-IZ approached that of the total tissue at the end of the pSP stage. Volume of each layer increased in proportion to the cube of CRL. pSP-IZ and CP constituted over 50% of the total tissue in volume at the end of the pSP stages. We could visualize the growth of pSP-IZ in 3D and quantify it during pSP stage. Our approach allowed us to observe the process of rapid expansion of pSP-IZ from the midlateral regions of the cerebral wall, which subsequently becomes the insula.

ヒト胎児期初期の脳の形態形成についての論文がJ Anatomyに掲載されました。５年以上かけて、ようやくまとめることができました。

• 高解像度MRIを用いて胎児期初期の(受胎後 9 ～ 13 週) の脳の形態計測学的分析を行った。
• 脳梁の出現(CRL62mm), 皮質内側の脳溝の出現(CRL114mm),
• 小脳半球、後外側裂溝、小脳半分の結合、虫部の形成(CRL43.5mm), 一次裂溝の出(CRL56mm), 錐体前裂(CRL75mm),　
• 大脳側面における大脳の比率 (長さ/高さ) と基準線に対する大脳の角度は、大脳の成長と C 字型の形成を反映している可能性がある。
• これらの所見は、胎児期初期を細分化するための候補となる可能性がある。

52. Takakuwa T, Shiraishi N, Terashima M,Yamanaka M, Okamoto I, Imai H, Ishizu K, Yamada S, Ishikawa A, Kanahashi T. Morphology and morphometry of the human early fetal brain: A three-dimensional analysis. J Anatomy; 239 (2) 498-516, 2021, doi.org/10.1111/joa.13433

Abstract

Morphometric analyses in the early foetal phase (9-13 postconceptional week) are critical for evaluating normal brain growth. In this study, we assessed sequential morphological and morphometric changes in the foetal brain during this period using high-resolution T1-weighted magnetic resonance imaging (MRI) scans from 21 samples preserved at Kyoto University. MRI sectional views (coronal, mid-sagittal, and horizontal sections) and 3D reconstructions of the whole brain revealed sequential changes in its external morphology and internal structures. The cerebrum’s gross external view, lateral ventricle and choroid plexus, cerebral wall, basal ganglia and thalamus, and corpus callosum were assessed. The development of the cerebral cortex, white matter microstructure, and basal ganglia can be well-characterized using MRI scans. The insula became apparent and deeply impressed as brain growth progressed. A thick, densely packed cellular ventricular/subventricular zone and ganglionic eminence became apparent at high signal intensity. We detected the emergence of important landmarks which may be candidates in the subdivision processes during the early foetal period; the corpus callosum was first detected in the sample with crown-rump length (CRL) 62 mm. A primary sulcus on the medial part of the cortex (cingulate sulcus) was observed in the sample with CRL 114 mm. In the cerebellum, the hemispheres, posterolateral fissure, union of the cerebellar halves, and definition of the vermis were observed in the sample with CRL 43.5 mm, alongside the appearance of a primary fissure in the sample with CRL 56 mm and the prepyramidal fissure in the sample with CRL 75 mm. The volumetric, linear, and angle measurements revealed the comprehensive and regional development, growth, and differentiation of brain structures during the early foetal phase. The early foetal period was neither morphologically nor morphometrically uniform. The cerebral proportion (length/height) and the angle of cerebrum to the standard line at the lateral view of the cerebrum, which may reflect the growth and C-shape formation of the cerebrum, may be a candidate for subdividing the early foetal period. Future precise analyses must establish a staging system for the brain during the early foetal period. This study provides insights into brain structure, allowing for a correlation with functional maturation and facilitating the early detection of brain damage and abnormal development.