The effects of microwave-irradiated fixation for postmortem changes of the kidney

Area of Science:

• Renal pathology
• Histology
• Biomedical imaging

Background:

• Accurate postmortem tissue preservation is crucial for accurate histological and ultrastructural analysis.
• Conventional formalin immersion fixation can be time-consuming and may lead to autolytic changes.
• Microwave-irradiated fixation (MWI) is explored as a rapid alternative fixation method.

Purpose of the Study:

• To evaluate the efficacy of microwave-irradiated fixation (MWI) for preserving mouse kidney tissue against postmortem autolysis.
• To compare MWI with conventional immersion fixation in terms of structural preservation and ultrastructural integrity.

Main Methods:

• Mouse kidneys were collected at various postmortem time points (0-25 hours).
• Tissues were fixed using either MWI (20 sec/500 W) or conventional formalin immersion.
• Analyses included light and electron microscopy, morphometrics, and immunohistochemistry for renin and alpha-smooth muscle actin.

Main Results:

• MWI demonstrated structural preservation limited to proximal convoluted tubules at 25 hours postmortem.
• Mild ultrastructural damage was observed in glomeruli fixed by MWI at 0 and 15 hours.
• Immunohistochemical staining for renin and alpha-smooth muscle actin showed no significant differences between MWI and immersion fixation.

Conclusions:

• MWI shows limited advantages over conventional immersion for preserving overall mouse kidney structure and ultrastructure postmortem.
• Specific regions like proximal tubules may benefit from MWI, but glomerular integrity can be compromised.
• Further optimization of MWI protocols may be necessary to mitigate potential damage and enhance preservation efficacy.