Using unfixed, frozen tissues to study natural mucin distribution

Area of Science:

• Biochemistry
• Histology
• Immunology

Background:

• Mucins are heavily glycosylated O-linked glycoproteins forming a mucus layer crucial for host innate immunity.
• The mucus layer, a first line of defense, interacts with microbes and is studied using histological methods.
• Standard histological methods like formalin fixation and paraffin embedding alter mucin epitopes and extract mucins/lipids.

Purpose of the Study:

• To evaluate the effectiveness of frozen tissue sections compared to paraffin embedding for preserving mucus layer integrity.
• To demonstrate the utility of frozen sections for studying mucin-glycan interactions using immunohistochemistry.

Main Methods:

• Comparison of frozen tissue sections embedded in Optimal Cutting Temperature (OCT) medium versus paraffin-embedded sections.
• Immunofluorescence staining of glycan epitopes on mucins using plant lectins.
• Analysis of secreted mucus layer thickness and preservation in both methods.

Main Results:

• Frozen tissue sections in OCT medium preserved the micrometers-thick secreted mucus layer.
• Paraffin embedding drastically reduced the mucus layer, extracting mucins and lipids.
• Immunofluorescence staining of mucin glycan epitopes was successful on frozen sections without special fixatives.

Conclusions:

• Frozen tissue sectioning is superior to paraffin embedding for preserving the native mucus layer and mucin structure.
• This method facilitates the study of mucin-glycan interactions and the role of mucins in epithelial biology.
• Frozen tissue sections offer a valuable approach for analyzing mucins and mucus in a hydrated state.