Three-dimensional DNA image cytometry by confocal scanning laser microscopy in thick tissue blocks

Area of Science:

• Biomedical Imaging
• Molecular Biology
• Histopathology

Background:

• Accurate nuclear DNA quantification is crucial for understanding cellular processes and disease.
• Traditional methods like flow cytometry and image cytometry often require cell dissociation, losing tissue context.

Purpose of the Study:

• To present a novel method for quantifying nuclear DNA in thick tissue blocks using 3D confocal scanning laser microscopy.
• To demonstrate the method's precision and utility in histopathology by analyzing rat liver and human esophageal carcinoma tissues.

Main Methods:

• Tissues were stained en bloc for DNA using chromomycin A3.
• 3D images (60 microns deep) were acquired by stacking confocal fluorescent images.
• Mathematical corrections were applied for fluorescence bleaching and attenuation.
• DNA content was quantified by summing pixel intensities from segmented nuclei.

Main Results:

• The method demonstrated precision in adult rat liver tissue and potential in human esophageal carcinoma.
• Ploidy peaks obtained via confocal image cytometry were well-separated, though wider than other methods.
• Comparisons with image cytometry on smears and flow cytometry validated the approach.

Conclusions:

• Confocal image cytometry enables accurate nuclear DNA quantification within intact tissue architecture.
• This technique preserves histological context, allowing for the selection of specific regions and assessment of tumor heterogeneity.
• The method holds significant potential for advancing histopathological diagnostics and research.