Early temporal suppression of SPARC inhibits oxidative stress, inflammation, and fibrosis in the chronic phase after renal ischemia/reperfusion.

Acute kidney injury is associated with not only high morbidity in the acute phase but also the development of chronic kidney disease (CKD). Recently, we found that suppression of secreted protein acidic and rich in cysteine (SPARC) exhibits renoprotective effects in acute ischemia/reperfusion (I/R) injury. The present study investigated the hypothesis that temporal suppression of SPARC in the early stages of I/R-injury might lead to the prevention of renal injury in the chronic phase. The left renal pedicle of male BALB/c mice was occluded for 45 min after right uninephrectomy and subsequently reperfused for 28 days. Small interfering RNA (siRNA) targeting SPARC was injected intravenously 1 day before and 3 days after I/R. Histological assessment revealed that SPARC knockdown by siRNA attenuated tubular injury, tubulointerstitial fibrosis, and the overexpression of 4-hydroxynonenal, a marker of lipid peroxidation. I/R-induced overexpression of a major source of superoxide NADPH oxidase, tumor necrosis factor-α, and matrix metalloproteinase-9 was suppressed by siRNA targeting SPARC. Treatment with siRNA targeting SPARC reduced the expression of a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1), which colocalizes with SPARC. In conclusion, SPARC might be a potential therapeutic target for preventing CKD development following acute I/R injury.