A mouse model of renal fibrosis to overcome the technical variability in ischaemia/reperfusion injury among operators

The ischaemia-reperfusion (I/R) model is a widely used model of acute kidney injury (AKI) and renal fibrosis. However, the ischaemia duration that is long enough to cause broad fibrosis shows that a high mortality rate and a short ischaemia duration does not cause fibrosis, resulting in a large variation in fibrosis progression in this experimental model. Inter-operator variation occurs for I/R injury severity because the I/R procedure is complex, which results in poor reproducibility of subsequent fibrosis in the model. In the present study, we developed a renal fibrosis model in which the fibrosis progression for 8 weeks is predictable within 8 days. Three operators independently performed I/R followed by uninephrectomy at day 7 in mice. The aim was to create a model that would show a blood urea nitrogen (BUN) level >100 mg/dL at day 8 after I/R (day 1 after uninephrectomy). Although the ischaemia duration to satisfy this BUN criterion differed among operators, the mice developed anaemia, polyuria, and fibrosis in a similar manner under the same BUN criterion with a low mortality rate. Interstitial fibrosis had developed at week 8, which was strongly correlated with the BUN at day 8. This protocol allows operators to adjust the ischaemia duration based on the BUN criterion and to separate mice into the desired number of groups based on the BUN to study interventions against renal fibrosis.