Variations in mitochondrial ultrastructure and dynamics observed by high resolution scanning electron microscopy...

Area of Science:

• Cell Biology
• Microscopy
• Biochemistry

Background:

• Mitochondrial cristae morphology varies across cell types.
• Transmission electron microscopy (TEM) has limitations in resolving 3D ultrastructure.
• Previous TEM studies suggested tubular cristae in adrenal cortex mitochondria.

Purpose of the Study:

• To confirm tubular cristae in rat adrenal cortex mitochondria using HRSEM.
• To investigate and compare mitochondrial ultrastructure in various mammalian tissues.
• To establish a baseline for understanding normal mitochondrial morphology for diagnostic purposes.

Main Methods:

• High-resolution scanning electron microscopy (HRSEM) was employed.
• Samples included rat adrenal cortex, hepatocytes, human hepatocytes, human skin fibroblasts, brown fat cells, and rat striated muscle.
• Three-dimensional (3D) imaging and stereo microscopy were utilized.

Main Results:

• HRSEM confirmed tubular cristae (approx. 30 nm diameter) in rat adrenal cortex mitochondria.
• Mitochondria in rat and human hepatocytes and human fibroblasts exhibited tubular cristae.
• Fibroblast mitochondria were long and branching (up to 46 µm), unlike spherical liver mitochondria.
• Brown fat mitochondria displayed plate-like cristae.
• Striated muscle mitochondria showed both tubular and plate-like cristae, with variable ratios.

Conclusions:

• Mitochondrial cristae exhibit significant tissue-specific ultrastructural diversity.
• HRSEM provides crucial 3D insights into mitochondrial morphology, overcoming TEM resolution limits.
• Accurate understanding of normal mitochondrial ultrastructure via HRSEM is essential for differential diagnosis.