Molecular and immunohistochemical characterization of intestinal macrophages subsets in goldfish

Abstract

Abstract Macrophage-colony stimulating factor (M-CSF) plays a crucial role in the proliferation and differentiation of the monocyte-macrophage lineage across vertebrates. In this study, we identified and characterized two CSF1 paralogues and their corresponding receptor genes in the intestine of the goldfish ( Carassius auratus ), showing sequence homology with known teleost species. Immunohistochemical analysis confirmed the presence of CSF, its receptor CSF-R1, and bone morphogenetic protein 2 (BMP2) in intestinal macrophages. These macrophages were localized within mucosal, submucosal, and muscularis layers, suggesting distinct functional subtypes. Quantitative PCR analysis revealed differential gene expression patterns, with csf1a , csf1b , and csf1ra highly expressed in the brain, while csf1rb transcripts were predominant in the intestine. Immunophenotypic characterization using CD14 and CD86 markers further demonstrated macrophage heterogeneity. Additionally, BMP2-expressing macrophages were observed in the muscularis externa, implying a potential role in neuromuscular regulation. These findings provide novel insights into the molecular and immunohistochemical profiles of goldfish intestinal macrophages, highlighting their potential role in immune responses and gut homeostasis.