Development of the sympathetic trunks in human embryos

Area of Science:

• Developmental biology
• Neuroscience
• Human embryology

Background:

• The development of sympathetic trunks is well-documented, but their topographic evolution remains understudied.
• Understanding the precise spatial and temporal development of these structures is crucial for developmental biology and neuroscience.

Purpose of the Study:

• To visualize and analyze the topographic development of human sympathetic trunks from 4.5 to 10 weeks post-fertilization.
• To investigate the positional changes of sympathetic trunks at different vertebral levels and correlate them with embryonic developmental stages.

Main Methods:

• Utilized Amira 3D-reconstruction and Cinema 4D-remodelling software to visualize sympathetic trunks in human embryos.
• Examined embryos across various Carnegie Stages (CS14-CS23) to track developmental changes.
• Analyzed trunk positions at specific vertebral levels (T2, T7, L1, S1).

Main Results:

• Sympathetic trunks initially form as longitudinal columns of neural crest-derived cells lateral to the dorsal aorta.
• Nerve fibers from spinal cord communicating branches integrate into the trunks, leading to a 'pearls-on-a-string' appearance.
• Trunks migrate from a para-aortic to a prevertebral and eventually paravertebral position, with regional variations and timing (cervical/upper thoracic by CS15, lower thoracic/lumbar by CS18-CS20, thoracic by CS23).
• Sacral trunks maintain a para-aortic/prevertebral position and converge caudally.

Conclusions:

• The topographic repositioning of sympathetic trunks during human embryogenesis is a dynamic process.
• Differential growth is proposed as the primary mechanism driving the observed regional differences in sympathetic trunk positioning.
• This study provides detailed insights into the spatial development of the sympathetic nervous system in human embryos.