Renal fibrosis is a serious clinical problem resulting in the greatest need for renal replacement therapy. No adequate preventive or curative therapy is available that could be clinically used to target renal fibrosis specifically. The search for new efficacious treatment strategies is therefore warranted. Although in vitro models using homogeneous cell populations have contributed to the understanding of the pathogenetic mechanisms involved in renal fibrosis, these models poorly mimic the complex in vivo milieu. Therefore, we here evaluated a precision-cut kidney slice (PCKS) model as a new, multicellular ex vivo model to study the development of fibrosis and its prevention using anti-fibrotic compounds. Precision-cut slices (200300 mu m thickness) were prepared from healthy C57BL/6 mouse kidneys using a Krumdieck tissue slicer. To induce changes mimicking the fibrotic process, slices were incubated with TGF beta 1 (5 ng/ml) for 48 h in the presence or absence of the anti-fibrotic cytokine IFN gamma (1 mu g/ml) or an IFN gamma conjugate targeted to PDGFR beta (PPB-PEG-IFN gamma). Following culture, tissue viability (ATP-content) and expression of alpha-SMA, fibronectin, collagen I and collagen III were determined using real-time PCR and immunohistochemistry. Slices remained viable up to 72 h of incubation, and no significant effects of TGF beta 1 and IFN gamma on viability were observed. TGF beta 1 markedly increased alpha-SMA, fibronectin and collagen I mRNA and protein expression levels. IFN gamma and PPB-PEG-IFN gamma significantly reduced TGF beta 1-induced fibronectin, collagen I and collagen III mRNA expression, which was confirmed by immunohistochemistry. The PKCS model is a novel tool to test the pathophysiology of fibrosis and to screen the efficacy of anti-fibrotic drugs ex vivo in a multicellular and pro-fibrotic milieu. A major advantage of the slice model is that it can be used not only for animal but also for (fibrotic) human kidney tissue.