Abstract：
Crucian carp (Carassius carassius) is an important aquatic economic animal, and the immune barrier function of its intestine has been a focus of research into oral vaccines and drugs. However, the histological structures of the intestinal barrier and its adjacent areas have not been clearly established, and little subcellular evidence is available to elucidate the spatial distribution of intracellular biological processes. In this study, the spatial distribution of autophagy and endosome formation in the intestinal epithelial cells (IECs) of crucian carp were analyzed. These two biological activities are closely related to intestinal homeostasis, immunity, and cell communication. Periodic acid-Schiff (PAS) and Masson\'s trichrome staining were employed to elucidate the distinctive histological framework of the Crucian carp\'s myoid cell network, which resides within the subepithelial layer and is characterized by gap junctions. Transmission electron microscopy (TEM), immunohistochemistry (IHC), and immunofluorescence (IF) were used to detect the structural and functional aspects of the IEC in different intestinal segments. TEM and immunohistochemical analyses captured the biogenesis and maturation of early and late endosomes as well as multivesicular bodies (MVBs), as well as the initiation and progression of autophagy, including macroautophagy and mitophagy. The endosome and MVBs-specific marker CD63 and autophagy-related protein LC3 were highly expressed in IECs and were correlated with autophagy and endosome biosynthesis in the apical and basal regions of individual cells, and differed between different intestinal segments. In summary, this study elucidated the ubiquity and morphological characteristics of autophagy and endosome formation across different intestinal segments of crucian carp. A unique myoid cell network beneath the intestinal epithelium in crucian carp was also identified, expanding the histological understanding of this animal\'s intestinal tract.
摘要：
鲤鱼(Carassiuscarassius)是一种重要的水生经济动物,其肠道的免疫屏障功能一直是口服疫苗和药物研究的热点。然而,肠屏障及其邻近区域的组织学结构尚未明确建立，并且几乎没有亚细胞证据可用于阐明细胞内生物过程的空间分布。在这项研究中,分析了自噬和内体形成在cru鱼肠上皮细胞（IECs）中的空间分布。这两种生物活性与肠道稳态密切相关,豁免权,和细胞通讯。定期酸希夫（PAS）和马森的三色染色被用来阐明的独特的组织学框架的鲤鱼的肌样细胞网络，位于上皮层内，以间隙连接为特征。透射电子显微镜(TEM),免疫组织化学（IHC），和免疫荧光（IF）用于检测不同肠段IEC的结构和功能方面。TEM和免疫组织化学分析捕获了早期和晚期内体以及多囊小体（MVB）的生物发生和成熟，以及自噬的开始和进展，包括巨自噬和线粒体自噬。内体和MVBs特异性标志物CD63和自噬相关蛋白LC3在IECs中高表达，并与单个细胞顶端和基底区域的自噬和内体生物合成相关，并且在不同的肠段之间有所不同。总之,本研究阐明了在不同肠段的自噬和内体形成的普遍性和形态学特征。还发现了cru鱼肠上皮下方独特的肌样细胞网络，扩大对这种动物肠道的组织学认识。
