Histological differences between lumbar and tail intervertebral discs in mice.

Area of Science:

• Biomedical Engineering
• Comparative Anatomy
• Histology

Background:

• Mouse lumbar and tail intervertebral discs (IVDs) are used as models for degenerative disc disease.
• Recent studies indicate significant mechanical and physical differences between lumbar and tail IVD-endplate (EP) interfaces in mature mice.
• These disparities suggest underlying variations in soft tissue composition influencing spinal biomechanics.

Purpose of the Study:

• To investigate the histological differences between lumbar and tail IVD-EP interfaces in mice.
• To compare the composition and organization of soft tissue elements in lumbar versus tail IVDs.
• To determine if observed histological disparities correlate with age and strain.

Main Methods:

• Coronal sections of lumbar and tail vertebral segments and discs were collected from C57BL/6N and C57BL/6JRj mice.
• Histological comparisons were performed at ages 4 weeks (weaned), 3 months (mature), 12 months (middle-aged), and 18 months (old).
• Key components analyzed included the EP, nucleus pulposus (NP), and anuli fibrosi (AF).

Main Results:

• Mature mouse lumbar IVD-EP interfaces featured broad cartilaginous EPs, while tail IVD-EP interfaces had thin cartilage layers adjacent to broad bony layers.
• Lumbar NP comprised compact clusters of large, uni-vacuolated cells in an amorphous matrix; tail NP had loose aggregates of varied cells.
• Tail IVD AFs showed more abundant and defined lamellae compared to lumbar discs.
• Histological differences in EPs were most prominent in weaned mice and remained discernible in older mice.

Conclusions:

• Significant histological differences exist between mouse lumbar and tail IVD components, including the EP, NP, and AF.
• These structural variations are evident from a young age and persist throughout life.
• Understanding these distinct histological features is essential for accurate interpretation of mouse IVD studies and spinal biomechanics research.