Explanting is an ex vivo model of renal epithelial-mesenchymal transition

Recognised by their de novo expression of alpha-smooth muscle actin (SMA), recruitment of myofibroblasts is key to the pathogenesis of fibrosis in chronic kidney disease. Increasingly, we realise that epithelial-mesenchymal transition (EMT) may be an important source of these cells. In this study we describe a novel model of renal EMT. Rat kidney explants were finely diced on gelatin-coated Petri dishes and cultured in serum-supplemented media. Morphology and immunocytochemistry were used to identify mesenchymal (vimentin+, α-smooth muscle actin (SMA)+, desmin+), epithelial (cytokeratin+), and endothelial (RECA+) cells at various time points. Cell outgrowths were all epithelial in origin (cytokeratin+) at day 3. By day 10, 50 ± 12% (mean ± SE) of cytokeratin+ cells double-labelled for SMA, indicating EMT. Lectin staining established a proximal tubule origin. By day 17, cultures consisted only of myofibroblasts (SMA+/cytokeratin-). Explanting is a reproducible ex vivo model of EMT. The ability to modify this change in phenotype provides a useful tool to study the regulation and mechanisms of renal tubulointerstitial fibrosis.