Triptolide reduces cyst formation in a neonatal to adult transition Pkd1 model of ADPKD.

BACKGROUND Autosomal dominant polycystic kidney disease (ADPKD), a major cause of end-stage renal failure, results from genetic mutation of either polycystin-1 (Pkd1) or polycystin-2 (Pkd2). In order to develop novel therapies to treat the advancement of disease progression, numerous rodent models of different genetic backgrounds are available to study cyst development. METHODS Here, a Pkd1-floxed inducible mouse model using the interferon responsive Mx1Cre-recombinase was utilized to test the effect of the small molecule triptolide. Relative to other Pkd1 inactivation models, cyst progression in this neonatal to adult transition model is attenuated. Following the characterization of inducible cyst formation in these mice, the development of kidney cysts from triptolide or vehicle-treated animals was analysed. RESULTS Although Pkd1 deletion on postnatal Days P10 and P12 resulted in numerous cysts by P35, daily injections with triptolide beginning on Day P16 significantly reduced the total number of cysts per kidney, with a pronounced effect on the number of microcysts and the overall cystic burden. Additionally, renal function as assessed by blood urea nitrogen levels was also improved in triptolide-treated mice at both the P22 and P35 time points. As the Pkd1(flox/flox);Mx1Cre model has not been previously used for drug development studies, the feasibility of a 6-month adult Pkd1 inactivation study was also tested. While kidney cyst formation was minimal and focal in nature, livers of these Pkd1-deficient mice were severely cystic, enlarged and pale. CONCLUSIONS These results suggest that the Pkd1(flox/flox);Mx1Cre model of ADPKD is amenable to short-term kidney cyst formation drug studies; however, it may be problematic for long-term therapeutic research where widespread liver cysts and fibrosis could compromise drug metabolism.