Investigations of cell types that are ciliated in regenerating Zebrafish (Danio rerio) hearts.

Abstract

Human heart disease is one of the leading causes of death in the United States. Myocardial infarction (heart attack) is a possible result of human heart disease, which leads to scar tissue formation at the injury site. The scar tissue is inelastic and does not allow for efficient heart contractions thus reducing overall cardiac function. Zebrafish can regenerate injured heart tissue within 30 days after injury. The regeneration of the zebrafish heart tissue is accomplished through immediate clotting of the injury site, activation of the three cardiac tissue types (epicardium, myocardium, and endocardium), neovascularization, redifferentiation, cardiomyocyte proliferation, ultimately fully replacing the scar tissue. Primary cilia are sensory organelles found on the surface of many eukaryotic cells, and cilia play many essential roles. Cilia have been observed on regenerating cardiac tissue of zebrafish, however, the exact tissue types that cilia are present on are unknown. Determining where cilia are present is important as it will provide insight into how cilia facilitate regeneration involving the three cardiac tissue types. We hypothesize that cilia are found preferably on epicardial tissue along with a detectable presence in endocardial and myocardial cells during cardiac regeneration. Also, we hypothesize that cilia are present longer than 7 days post amputation (dpa), as the entire regeneration process takes a month. The hypotheses were tested using injured transgenic zebrafish hearts, which identifies each tissue type along with uninjured EK zebrafish (wild type) hearts at various dpas. This was to be followed by immunofluorescence staining to identify the cilia and quantification to determine cilia quantity and location, however, this was not possible due to the spring 2020 coronavirus pandemic. Regardless, understanding the possible roles of cilia in the three cardiac tissues may lead to advancements in diagnostic procedures and treatments for individuals suffering from heart disease.