Mice with CB2 deficiency are protected against renal fibrosis after obstructive injury. (a) Representative micrographs show Masson’s trichrome staining (MTS) of the obstructed kidneys in CB2 null mice (CB2−/−) and wild-type controls (CB2+/+) at 7 days after UUO. Blue staining (arrow) indicates fibrotic collagen deposition. Scale bar, 50 μm. (b) Quantitative determination of the fibrotic area in CB2−/−null mice and CB2+/+ wild-type controls at 7 days after UUO. *P < 0.05 versus CB2+/+ group (n = 5 to 6). (c) Western blot analyses show that ablation of CB2 reduced renal expression of fibronectin and α-SMA after UUO. Numbers (1 to 4) represent different individual animals in a given group. (d, e) Graphic presentations of relative renal fibronectin (d) and α-SMA (e) protein levels in two groups as indicated. *P < 0.05 versus CB2+/+ group. (f) Immunostaining for renal fibronectin and α-SMA proteins in CB2+/+ and CB2+/+ mice as indicated. Frozen sections and paraffin sections were stained with different antibodies against fibronectin and α-SMA, respectively. Arrow indicates positive staining. Scale bar, 50 μm. (g) Western blot analyses show renal expression of β-catenin and its downstream MMP-7 after UUO. Numbers (1 to 4) represent different individual animals in a given group. (h, i) Graphic presentations of renal β-catenin (h) and MMP-7 (i) expressions in two groups as indicated. *P < 0.05 versus CB2+/+ mice. (j) Immunostaining for renal β-catenin proteins in CB2+/+ and CB2+/+ mice as indicated. Arrow indicates positive staining. Scale bar, 50 μm.