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.