BACKGROUND: Renal tubulointerstitial fibrosis is known to occur as a result of epithelial cell transformation into myofibroblasts via the epithelial-to-mesenchymal transition (EMT) process. It has been reported that macrophages, regulatory T (Treg) cells, and gamma delta T (γδ T) cells can promote fibrosis via EMT in vivo. OBJECTIVE: Our study intended to detect whether thymocytes can induce renal tubular cells to undergo the EMT. METHODS: Rat thymocytes were activated by phytohemagglutinin and concanavalin A. The rat renal tubular epithelial cells (NRK-52E) were incubated in a conditioned medium harvested from activated thymocytes or co-cultured with freshly isolated thymocytes for 48 hours. Real-time reverse transcription-polymerase chain reaction, immunofluorescence, and western blotting analysis were used to test the expression of the epithelial and mesenchymal markers in NRK-52E cells. Scratch assay was designed to test the cell migration abilities of NRK-52E cells. Student's t test and oneway analysis of variance test were used for statistical analysis. RESULTS: The combined stimulation with phytohemagglutinin and concanavalin A activated the primary isolated rat thymocytes. After treatment with conditioned medium or freshly isolated thymocytes, the expression levels of cytokeratin 19 and E-cadherin were downregulated in NRK-52E cells, while the mRNA and protein expression levels of alpha-smooth muscle actin, desmin, and vimentin were upregulated (P <
0.05). We found that the cell migration abilities of the induced NRK-52E cells were significantly improved. CONCLUSIONS: Both activated rat thymocytes (more percentage of CD8+ T cells) and freshly isolated thymocytes have promoting effects on the EMT of NRK-52E cells.