Rapamycin and Zoledronic acid exert a potent antifibrotic effect in murine biliary fibrosis

There is an urgent need for effective antifibrotic therapies for biliary fibrosis. The in vivo microenvironment, especially macrophages, can modulate hepatic stellate cell (HSC) activation. We therefore assessed the antifibrotic efficacy of a combination of two clinically used drugs, Zoledronic acid (ZA) and Rapamycin (RA), that affect macrophage polarization and putative fibrogenic activation.

Methods:

Mdr2-knockout (Mdr2KO) mice that had received one dose of diethylnitrosamine (DEN) at day 5 after birth were treated from month 5 – 6 (stage of advanced fibrosis with emerging HCC) with 1) ZA alone (100 µg/kg body weight i.p., thrice weekly), 2) RA alone (5 mg/kg body weight in the chow), 3) the combination of both drugs. A fourth group of Mdr2KO mice (without DEN and no signs of HCC) was treated with the combination. The degree of fibrosis and extent of inflammation was quantified histologically using staining with H&E, Sirius Red, for αSMA and CD68. Collagen deposition was confirmed by hydroxyproline determination. Moreover, the hepatic expressions of TNF-α, CCL2, TGFβ1, HIF1α and several MMPs, liver SECs (VEGF) were significantly reduced in the treated group compare to control mice.

Results:

Compared to the untreated controls and to animals treated with the single drugs alone, Mdr2KO KO mice that received the ZA/RA combination for only one month demonstrated a twofold reduced collagen deposition, with elimination of bridging fibrosis (p < 0.0001). This was accompnied by a similar reduction of αSMA expression and a significant suppression of profibrogenic transcripts like Col1a1, Col3a1, Asma, Tnfa, and of markers of M2 macrophage polarization, including Hif1a and Mmp9. Moreover, the number of YM-1 relative to CD68 positive macrophages was significanatly reduced in the combination treatment vs. the other groups.

Conclusion:

The combination of RA and ZA, two agents with macrophage modulating activity, induces a remarkable regression of even advanced biliary fibrosis. This antifibrotic effect goes along with a marked antitumorous activity. Since both drugs are used in the clinic for other indications, with a reasonable safety profile, their clinical testing should be considered in patients with fibrotic and (pre) cancerous PSC and other unaddressed indications.