Glyoxal is a superior fixative to formaldehyde in promoting antigenicity and structural integrity in murine cardiac tissues

Abstract

Background

Immunofluorescence (IF) is an essential technique for evaluating histological and biochemical changes in tissue specimens. A critical step in IF is sample fixation, typically achieved using formaldehyde-based fixatives, such as 4 % paraformaldehyde (PFA) or 10 % formalin. However, these fixatives are prone to over-fixation, which can alter antigenicity and promote artifacts. This study investigated glyoxal, a two‑carbon dialdehyde, as a potential alternative fixative for murine cardiac tissues for IF and crosslinking immunoprecipitation-mass spectrometry (xIP-MS) applications.

Methods

Various concentrations and fixation durations of glyoxal were compared with 4 % PFA. Tissue structural integrity was assessed using Hematoxylin and Eosin (H&E) staining, while antigen preservation in cardiomyocytes was evaluated through fluorescent microscopy. Immunofluorescence of cardiac resident cells, including cardiac fibroblasts, smooth muscle cells, and endothelial cells were also investigated. xIP-MS assays were carried by phospholamban (PLN) immunoprecipitation in glyoxal-fixed mouse hearts, followed by mass spectrometry analysis.

Results

Glyoxal showed comparable preservation of cardiac tissue architecture and myofiber integrity to PFA, but with superior antigen retention and protein detection. Fluorescent imaging was performed for sarcoplasmic reticulum markers (SERCA2 and PLN), intercalated disc proteins (N-Cadherin and Cx43), and contractile proteins (F-Actin and MyHC). Quantitative image analysis confirmed that glyoxal enhanced antibody penetration in thicker tissues (30 μm) and maintained the antigenicity of various cardiac resident cell markers. Glyoxal fixation allowed for xIP-MS by lightly crosslinking PLN with its associated protein complexes, enabling the identification of novel PLN-interacting proteins in mouse hearts.

Conclusion

Our findings underscore the utility of glyoxal as a superior alternative to PFA in cardiac biochemistry research, offering improvements in the preservation of tissue morphology, antigen detection, and protein complex conservation in murine cardiac tissues.