Age-related morphological changes in kidneys of SPF C57BL/6Cr mice maintained under controlled conditions

Abstract

Age-related morphological changes were examined in the kidneys of inbred C57BL/6Cr mice maintained in a controlled environment. The specific pathogen free status of animals used in the present study was confirmed by microbiological monitoring. Kidneys were histologically and histometrically investigated at 3, 5, 12, 15, 24 and 27-months-old. Kidney weights did not change with age. Renal corpuscles increased in number at 24- and 27-months-old, but diameter remained constant. The percentage of renal corpuscles with a cuboidal glomerular capsule decreased at 24- and 27-months-old. Score indicating glomerular damage increased from 5- to 27-months-old. Changes to the proximal convoluted tubules were severe. Vacuolar degeneration was observed from 12-months-old. Tubular atrophy was observed at 24- and 27-months-old, with number of nuclei per unit area increasing at the same ages. Amyloidosis and scar lesions were observed at 27-months-old. Focal cell infiltration around vessels was found at 24- and 27-months-old. Electron microscopy at 27-months-old revealed expansion of the mesangial matrices and fusion of foot processes in the glomeruli. Enlarged lysosomes with lipid content were observed in the proximal convoluted tubules.