Pulse mTOR inhibitor treatment effectively controls cyst growth but leads to severe parenchymal and glomerular hypertrophy in rat polycystic kidney disease

Wu M, Arcaro A, Varga Z, Vogetseder A, Hir ML, Wuthrich RP, Serra AL. Pulse mTOR inhibitor treatment effectively controls cyst growth but leads to severe parenchymal and glomerular hypertrophy in rat polycystic kidney disease. Am J Physiol Renal Physiol 297: F1597-F1605, 2009. First published September 23, 2009; doi:10.1152/ajprenal.00430.2009.-The efficacy of mammalian target of rapamycin (mTOR) inhibitors is currently tested in patients affected by autosomal dominant polycystic kidney disease. Treatment with mTOR inhibitors has been associated with numerous side effects. However, the renal-specific effect of mTOR inhibitor treatment cessation in polycystic kidney disease is currently unknown. Therefore, we compared pulse and continuous everolimus treatment in Han: SPRD rats. Four-week-old male heterozygous polycystic and wildtype rats were administered everolimus or vehicle by gavage feeding for 5 wk, followed by 7 wk without treatment, or continuously for 12 wk. Cessation of everolimus did not result in the appearance of renal cysts up to 7 wk postwithdrawal despite the reemergence of S6 kinase activity coupled with an overall increase in cell proliferation. Pulse everolimus treatment resulted in striking noncystic renal parenchymal enlargement and glomerular hypertrophy that was not associated with compromised kidney function. Both treatment regimens ameliorated kidney function, preserved the glomerular-tubular connection, and reduced proteinuria. Pulse treatment at an early age delays cyst development but leads to striking glomerular and parenchymal hypertrophy. Our data might have an impact when long-term treatment using mTOR inhibitors in patients with autosomal dominant polycystic kidney disease is being considered.