Anatomic characteristics of epididymis based on histology, proteomic, and 3D reconstruction.

BACKGROUND The epididymis is a popular research topic in urology and reproduction. OBJECTIVES To explore and identify the anatomical characteristics of the epididymis based on histology, proteomics and 3D reconstruction of epididymal tubules. MATERIALS AND METHODS A 3D reconstruction of epididymal tubules was generated based on 7 μm thick transverse serial sections of an epididymis. The proteins in the subcompartments of the epididymis were obtained and analyzed by nonlabeled sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH MS). Protein function, signaling pathways, protein expression and the histology in different subcompartments were analyzed. RESULTS The caput (Cap), corpus (Cor) and cauda (Cau) of the epididymis were divided into 6, 10 and 4 subcompartments, respectively, and the subcompartment between the Cap and Cor is mixed together. A total of 3411 proteins were identified, and 854 proteins were accurately quantified after screening. When the subcompartment Cap 5 transitioned to Cap 6 and Cap 6 to Cap 7, 87 and 52 proteins were upregulated and 14 and 7 proteins were downregulated, respectively. The Cor 9 transition to Cau 1 was marked by 230 proteins that were downregulated, while 74 proteins were upregulated. At the junction of the cauda and the vas deferens, 57 proteins were downregulated, and 410 proteins were upregulated. Cap 6 histology was consistent with that of Cor 1. DISCUSSION AND CONCLUSION The epididymis contains distinct connective tissue septa that can be identified under a surgical tabletop microscope, enabling it to be divided into 20 subcompartments.