1B). Kidney size and weight were significantly reduced in CBDL mice (Fig. 1C), whereas kidney/body weight ratio (not shown) did not differ significantly, compared to sham-operated controls. These structural changes were associated with increased serum urea levels (Fig. 1C) and an increased urinary volume indicative of polyuric renal failure in 8-week CBDL mice (5.2 ± 2.0 versus 1.3 ± 0.7 mL/24 hours in controls; P = 0.009). Kidneys of 8-week CBDL mice showed dilated tubuli and renal tubulointersititial
nephritis and pronounced fibrosis on H&E-stained sections (Fig. 1E). Cytologic urinalysis revealed characteristic findings for tubular injury in CBDL mice, reflected by a significantly increased number of tubular cell cylinders and urinary casts (Fig. 1F). In contrast, the urine of 8-week sham-operated controls was almost free of cells and debris. Consequently, the characteristic kidney phenotype of cholemic nephropathy in long-term CBDL mice called Protein Tyrosine Kinase inhibitor for more-detailed mechanistic time-course studies. Already after 3 day CBDL, kidneys showed tubular epithelial injury at the border region between the outer and the inner strip and in the inner medulla, with small foci of coagulation necrosis and tubular casts detectable only on PAS-stained sections at Opaganib that early time point (Fig. 2B). From day 7, we observed dilated tubules and an increasing number of protein and cell casts occasionally
in distal tubules and most prominent in collecting ducts in the inner medulla (Fig. 2C). In addition, kidneys frequently showed progressive partial occlusion and dilatation of distal tubules and collecting ducts in 3-, 6-, and 8-week CBDL mice (Fig. 1D-F). Concomitantly, we observed an increasing number of atrophic glomeruli over time with a dilated Bowman’s space. Additional support for the conclusion that the predominant injury in response to 3-day see more CBDL was to collecting ducts was achieved by IHC and IF staining of AQP2 (specifically expressed in the apical plasma membrane and apical vesicles of collecting duct cells[25,
26]), showing a partial lack of AQP2 positivity and parallel loss of nuclear staining in necrotic collecting duct epithelial cells (Fig. 3A-D). In addition, serial sections convincingly showed that injured tubuli observed on PAS-stained sections corresponded nicely to AQP2-positive collecting ducts (Fig. 3D-F), whereas NKCC2-positive cells of the thick ascending limb of Henle appeared normal (Supporting Fig. 1). We found no evidence that the observed reduced AQP2 staining of collecting ducts observed in CBDL mice was the result of an increased relative number of intercalated cells, as demonstrated by double IF staining for AQP2 and AE1 for type A intercalated cells or pendrin for non-type-A intercalated cells[21, 22] (Fig. 3C and Supporting Fig. 2). Together, these findings were indicative of a loss of epithelial barrier continuity of collecting ducts in 3-day CBDL mice (Fig. 3A,C,D).