Figure 4.

Local tubular cell–derived MIF was responsible for the antifibrotic effects. (A) First bone marrow transplantation was performed in UUO model of fibrosis. Compared with WT recipients with bone marrow from WT donors (WT^BM/WT; n=9), Mif^−/− recipients with bone marrow from Mif^−/− donors (Mif^−/−BM/Mif^−/−; n=7) had increased matrix deposition, myofibroblast accumulation, and immune cell infiltration, as expected. Similar fibrosis and inflammation was found in WT recipients with bone marrow from Mif^−/− donors (Mif^−/−BM/WT; n=8) compared with WT mice with WT bone marrow (WT^BM/WT), showing that bone marrow–derived MIF is not involved in mediating the antifibrotic effects. Mif^−/− mice with WT bone marrow (WT^BM/Mif^−/−; n=10) had similar expression as Mif^−/− mice with Mif^−/− bone marrow (Mif^−/−BM/Mif^−/−), collectively suggesting that MIF expressed in nonmyeloid cells is involved in the observed antifibrotic effects. (B) To specifically address whether local renal tubular cell–derived MIF is involved in the antifibrotic effects, tubular-specific Mif–deficient mice were generated by crossbreeding of a tubular-specific Cre driver (Pax8^Cre/+) with Mif^flox/flox mice. The deletion was confirmed by Western blot and immunofluorescence staining, showing normal interstitial but undetectable tubular MIF staining. (C) Compared with control Pax8^+/+::Mif^flox/flox mice (+/+; n=6), Pax8^Cre/+::Mif^flox/flox mice (Cre/+; n=5) had significantly more severe fibrosis and inflammation in UUO day 5 analyzed by immunohistochemical evaluation of collagen I, α-SMA, F4/80, and ErHr3 staining. Data are mean±SD. Values of healthy contralateral kidneys of WT^BM/WT or Pax8^+/+::Mif^flox/flox were set as 1, represented by the orange, dashed line. *P<0.05 versus WT^BM/WT; ^§P<0.05 versus Mif^−/−BM/WT; ^#P<0.05 versus WT^BM/WT; ^##P<0.01 versus WT^BM/WT; ^$P<0.05 versus Mif^−/−BM/WT; ^$$P<0.01 versus Mif^−/−BM/WT. AU, arbitrary unit; BMT, bone marrow transplantation; WT, wild-type.