Modified formalin and methanol fixation methods for molecular biological and morphological analyses

Area of Science:

• Histology
• Molecular Biology
• Pathology

Background:

• Standard formalin fixation can compromise nucleic acid integrity.
• Evaluating alternative fixation methods is crucial for integrating molecular analyses with traditional histopathology.

Purpose of the Study:

• To assess simplified fixation techniques for combined molecular and morphological analyses.
• To identify optimal fixatives for preserving both DNA/RNA and tissue structure.

Main Methods:

• Comparison of 10% formalin at 4°C, formalin with EDTA at room temperature, and room temperature formalin.
• Evaluation of dehydration fixatives: 100% methanol, acetone, and ethanol.
• Assessment of high-molecular-weight DNA and RNA preservation.
• Morphological evaluation of fixed tissues.

Main Results:

• Formalin with EDTA and cold formalin significantly preserved more high-molecular-weight DNA than room temperature formalin.
• Morphological differences between modified and conventional formalin fixation were minimal.
• 100% methanol showed superior morphology preservation and no artificial shrinkage compared to acetone and ethanol.
• All dehydration fixatives preserved higher-molecular-weight DNA and RNA better than formalin.

Conclusions:

• Cold formalin, formalin with EDTA, and 100% methanol are recommended for routine clinicopathological laboratories.
• These methods offer a balance between molecular preservation and morphological integrity.
• Simplified fixation protocols can enhance the utility of tissue samples for diverse analyses.