Computerized extraction of the time dimension in histopathological sections

Area of Science:

• Cell biology
• Tissue renewal dynamics
• Biophysics

Background:

• Most organism tissues continuously renew cells via a two-compartment system: progenitor (P) and functional (Q) compartments.
• Cells move outward along a tissue radius, ordered by age, with older cells located further from the origin.
• This radial movement reflects a continuous cell stream, where each cell's position indicates its age and history.

Purpose of the Study:

• To investigate the relationship between cell age and DNA content in renewing tissues.
• To validate the concept of using radial distance as a proxy for cell age.
• To demonstrate a method for quantifying cell age and its biological correlates.

Main Methods:

• Developing a tissue analyzer software to sample cells along the tissue radius.
• Utilizing Feulgen staining to label DNA in hepatocytes.
• Measuring the optical density of stained hepatocytes to infer DNA content.

Main Results:

• Cellular age is directly proportional to its distance from the origin within the tissue radius.
• Hepatocyte optical density, indicative of DNA content, increases with cell age.
• Feulgen staining binds stoichiometrically to DNA, confirming DNA content increases with hepatocyte age.

Conclusions:

• Cellular age in renewing tissues can be accurately determined by measuring radial distance.
• Hepatocyte DNA content is a reliable biomarker for cell age.
• The developed methodology provides a quantitative approach to study cell aging and renewal processes.