Tissue-specific Fixation Methods Are Required for Optimal In Situ Visualization of Hyaluronan in the Ovary, Kidney,...

Hyaluronan (HA) is a ubiquitous component of the extracellular matrix. The spatial-temporal localization of HA can be visualized in situ using biotinylated HA binding proteins (HABPs). This assay is sensitive to fixation conditions, and there are currently no best practices for HA detection. Thus, the goal of this study was to optimize fixation conditions for visualizing HA in the ovary, kidney, and liver through analysis of six commonly used fixatives for HA detection: Bouin's Solution, Carnoy's Solution, Ethanol-Formalin-Glacial Acetic Acid (EFG), Histochoice, Modified Davidson's Solution, and 10% Neutral Buffered Formalin. Organs were harvested from CB6F1 mice and fixed with one of the identified fixatives. Fixed organs were sectioned, and the HABP assay was performed on sections in parallel. Hematoxylin and eosin staining was also performed to visualize tissue architecture. HABP signal localization and intensity varied between fixatives. EFG and Carnoy's Solution best preserved the HA signal intensity in the ovary and liver, showing HA localization in various sub-organ structures. In the kidney, only Modified Davidson's Solution was less than optimal. Our findings demonstrate that fixation can alter the ability to detect HA in tissue macro- and microstructures, as well as localization in a tissue-specific manner, in situ.