Suppressing SPARC gene with siRNA exerts therapeutic effects and inhibits MMP-2/9 and ADAMTS1 overexpression in a murine model of ischemia/reperfusion-induced acute kidney injury

Secreted protein acidic and rich in cysteine (SPARC), a collagen-binding matricellular protein, is reported to facilitate inflammation and fibrosis in various tissues including the kidneys. Ischemia/reperfusion (I/R) is a major process of acute kidney injury. To investigate whether SPARC inhibition might attenuate renal I/R injury, we injected small interfering RNA (siRNA) targeting SPARC into male BALB/c mice one day before 45 min of renal ischemia followed by 72 h of reperfusion. Serum creatinine concentration, blood urea nitrogen, histological tubular damage, tubulointerstitial fibrosis, and expression of collagen I and transforming growth factor-β were increased after I/R. Expression of 4-hydroxy-2-nonenal, an oxidative stress marker, and the inflammatory cytokines monocyte chemoattractant protein-1 and tumor necrosis factor-α, were also upregulated in I/R kidneys. Overexpression of SPARC mRNA was observed after I/R, and immunohistochemistry revealed that SPARC was localized mainly in damaged tubuloepithelial cells. Additionally, a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1) expression colocalized with SPARC. Injection of siRNA targeting SPARC attenuated renal dysfunction, histological abnormalities, collagen deposition, oxidative stress, and renal inflammation. In addition, SPARC gene knockdown suppressed the I/R-induced increases in ADAMTS1 and matrix metalloproteinase-2/9 expression. In conclusion, I/R-induced SPARC could be a novel therapeutic target against acute kidney injury.