Unbiased Stereological Quantification of Key Features of Diabetic Nephropathy

Diabetic nephropathy (DN) is a serious long-term complication of diabetes. There is no curative treatment of DN, and the lack of knowledge about mechanisms leading to DN hampers the development of efficient therapies. To facilitate drug development, the ability to quantify key histopathological changes in animal models of human DN is essential. In order to develop a more precise determination of translatable nephrotic changes, we used novel and refined image analyses and stereological quantification of key features of DN in a model approach combining genetic diabetes (db/db mice) with uninephrectomy (UNx). UNx or sham-operation was performed in db/db or db/+ male and female mice (n=8-16 mice per group) and the study was terminated 10 or 16 weeks after surgery. Diabetes development was similar in sham and UNx db/db mice. Compared to sham-operation, UNx increased average kidney weight in db/db females both after 10 (43%) and 16 weeks (48%). Blood urea nitrogen (BUN) was increased in UNx vs. sham-operated animals 4 weeks post-surgery, but not at termination. Notably, kidney fibrosis was increased in UNx and sham db/db vs. sham db/+ females (16 weeks; mg total collagen; 12.7 ± 1.3 and 10.7 ± 1.8, respectively, vs. 5.7 ± 0.8, p<0.05). Urinary albumin was progressively increased in all db/db groups with significantly lower variance in UNx db/db females than sham (F-test, p=0.02), permitting smaller group sizes in pre-clinical studies. Unbiased stereological quantification is ongoing to establish volume of glomeruli and number of podocytes. Glomerular collagen is quantified by double-fluorescence imaging concomitantly detecting podocin and collagen.

In conclusion, renal hypertrophy and raised plasma BUN suggest increased pressure on the remaining kidney in UNx mice, leading to fibrosis and decreased kidney function. The thorough quantification of translatable features of DN in the db/db UNx model may provide refinement of this model enabling improved pharmacological testing of compounds targeting DN.