Feline chronic kidney disease is associated with shortened telomeres and increased cellular senescence

Telomeres are protective structures at the ends of chromosomes that have important implications for aging. To address the question of whether telomeres contribute to feline chronic kidney disease (CKD), we evaluated kidney, liver, and skin samples from 12 cats with naturally occurring CKD, 12 young normal cats, and 6 old normal cats. Telomere length was assessed using standard telomere fluorescent in situ hybridization (TEL-FISH) combined with immunohistochemistry (TELI-FISH) to identify proximal (PTEC) and distal tubular epithelial cells (DTEC), whereas senescence-associated β-galactosidase (SABG) staining was used to evaluate senescence. Results revealed statistically significant decreases in the average telomere fluorescence intensity (TFI) of PTEC in CKD cats compared with young and geriatric normal cats, and in the DTEC of CKD cats compared with young normal cats. When histograms of individual TFI were compared, statistically significant decreases in the PTEC and DTEC of CKD cats were observed compared with young and geriatric normal cats. Concomitantly, a statistically significant increase in SABG staining was seen in CKD kidney samples compared with young normal cats. CKD cats tended to have increased SABG staining in the kidney compared with normal geriatric cats, but this did not reach statistical significance. No significant telomere shortening in liver or skin from any group was observed. Real-time quantitative telomeric repeat amplification protocol assessment of renal telomerase activity revealed comparable low levels of telomerase activity in all groups. Our results suggest that shortened telomeres and increased senescence in the kidneys of CKD cats may represent novel targets for interventional therapy.