Ultrastructural study of upper surface layer in rat mandibular condylar cartilage by quick-freezing method

Area of Science:

• Biomedical Engineering
• Cell Biology
• Anatomy

Background:

• The temporomandibular joint (TMJ) relies on the condylar cartilage for smooth articulation.
• Understanding the native ultrastructure of the TMJ's upper surface is vital for biomechanical analysis.
• Previous studies lacked detailed ultrastructural information due to preservation challenges.

Purpose of the Study:

• To elucidate the native ultrastructure of the rat mandibular condylar cartilage's upper surface in vivo.
• To evaluate the efficacy of a quick-freezing method for preserving delicate cartilage structures.
• To identify key extracellular matrix components contributing to TMJ function.

Main Methods:

• Harvesting rat mandibular condylar cartilage with intact articular discs.
• Employing a quick-freezing technique for rapid specimen preservation.
• Utilizing light microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).
• Preparing deep-etching replica membranes for high-resolution imaging.

Main Results:

• Quick-freezing effectively preserved the native ultrastructure of the upper cartilage layer.
• Cartilage fixed with intact articular discs exhibited superior morphology.
• The upper surface layer was thicker than previously reported, featuring atypical extracellular matrices.
• Conventional and replica electron microscopy revealed amorphous components, filaments, and granular structures on collagen fibrils.
• 3D stereo-replica electron micrographs demonstrated compact filaments within this layer.

Conclusions:

• The quick-freezing method is highly effective for preserving the fragile native ultrastructure of mandibular condylar cartilage.
• The identified ultrastructural components of the upper surface layer are likely critical for the smooth function of the temporomandibular joint.
• Further research into these structures could inform treatments for TMJ disorders.