Laboratory Animal and Comparative Medicine ›› 2023, Vol. 43 ›› Issue (5): 531-540.DOI: 10.12300/j.issn.1674-5817.2023.070

• Research Reports • Previous Articles     Next Articles

Fine Structure of the Trunk Kidney and Distribution of Its Secreted Exosomes in the Adult Zebrafish

Jinxing LIN1()(), Xindong WANG2,3, Xuebing BAI2, Liping FENG1, Shuwu XIE1, Qiusheng CHEN2()()   

  1. 1.Shanghai Laboratory Animal Research Center, Shanghai 201203, China
    2.College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
    3.Zhijiang Animal Husbandry and Veterinary Service Center, Yichang 443200, China
  • Received:2023-06-05 Revised:2023-10-12 Online:2023-10-25 Published:2023-11-01
  • Contact: Jinxing LIN, Qiusheng CHEN


Objective To observe the fine structure of the trunk kidney in zebrafish, and to identify its secreted exosomes. Methods The microstructure and ultrastructure of the trunk kidney in zebrafish were observed by light microscopy and electron microscopy, and the particle size of exosomes was detected by nanoparticle tracking analysis (NTA). Results The trunk kidney was close and parallel to the spine in adult zebrafish. The nephron consisted of renal tubules and renal corpuscles. The renal tubules could be further divided into three types: proximal convoluted tubules, distal convoluted tubules, and cervical segments. The renal corpuscles were composed of glomerulus and renal capsules. The periodic acid-Schiff (PAS) staining results revealed that there were abundant glycogen granules in the proximal convoluted tubules, with brush-like outline in the apical surface of epithelial cells. Under transmission electron microscopy (TEM), there were exosomes distributed in the lumen of renal tubules, with numerous late endosomes and few number of multivesicular bodies (MVBs) in the cytoplasm of the epithelial cells concentrating on the apical side. Meanwhile, MVBs were also distributed in the apical regions of the renal tubules and the podocytes of the renal glomeruli. Immunohistochemical staining results showed that CD9, CD63 and TSG101 were strongly expressed in the lumen surface of the renal tubules, but weakly expressed in the corpuscles and lumen. NTA and TEM results showed that the exosomes isolated from zebrafish trunk kidney were saucer-like outline, and the particle size mode was 144.4 nm, which was consistent with the characteristics of morphological futures of exosome. Conclusion The zebrafish somatic kidney has the typical structure of the mammalian kidney and is the urinary organ in the body. The renal tubules have the ability to secrete exosomes, and their formation is a process of releasing poly-vesicles to the free surface of epithelial cells into the extracellular space. This study laid a morphological foundation for further study of exosomes in urinary function in aquatic experimental animals as well as the development and application of related models.

Key words: Zebrafish, Trunk kidney, Exosome, Multivesicular body

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