The cellular architecture of the intestine poses a unique challenge in maintaining its structural integrity when intestinal tissue is being preserved for immunostaining. The small intestine is made up of elongated fingerlike structures known as villi1. These villi often become malformed during embedding processes. Ensuring that researchers have techniques for properly embedding intestines to achieve cross sections, allowing visualization of all regions of the intestine, as well as the layers that make up the intestine (i.e., muscularis propria, mucosa, and the serosa), is crucial for robust experimental analysis2. Inadequate fixation, excessive fixation, and improper tissue handling will compromise tissue integrity, resulting in inadvertent damage to the intestinal epithelium3,4. Damaging the intestinal epithelium during these steps can significantly diminish the quality of subsequent analyses, like immunofluorescence, irrespective of the efficacy of immunohistochemistry protocols and antibodies employed.
Immunostaining, like proper tissue fixation, is an important part of biomedical research. When done well, immunostaining can illuminate previously unknown aspects of cellular structure and function. Immunofluorescence staining of paraffin sections can be challenging due to physicochemical modifications resulting from the fixation and paraffin embedding process5. Fixation and paraffin embedding results in antigen masking that can interfere with immunofluorescence detection of epitopes of interest6. Delayed fixation can induce proteolytic degradation, which results in weakened or absent staining of critical epitopes7. Additionally, antibodies are often inaccurate with high levels of background. Immunostaining protocols that promote consistent and specific antibody binding and a high signal-to-noise ratio can provide valuable information for researchers.
Here, we provide a comprehensive protocol designed to obtain high-quality immunofluorescence images through intestinal tissue fixation, Swiss roll preparation8, and immunostaining. Emphasizing guidelines to preserve the integrity of the intestine, the protocol aims to provide researchers with a robust methodology to enhance the quality and reliability of immunofluorescence imaging studies. We have also sought to use cost-effective resources, including filter paper and homemade antigen retrieval, blocking solutions, and antibody diluents to make the protocol more accessible to labs that may have restricted funds. As for all experimental protocols, researchers should optimize the current protocol based on their experimental approach and areas of interest.