Background/Aims: Mitochondrial permeability transition has a critical role in ischemia/reperfusion (I/R)-induced kidney injury. It is thought that mitochondrial permeability transition occurs after the opening of the permeability transition pore, a channel which putatively consists of a voltage-dependent anion channel, adenine nucleotide translocator and cyclophilin D (CypD). Much evidence shows that CypD plays an important role in I/R-induced injury. Methods: To evaluate the role of CypD following I/R renal injury, we tested the hypothesis that knockdown of CypD gene by RNA interference (RNAi) protects rat from I/R-induced renal injury. Results: Our data show that knockdown of CypD by RNAi protects normal rat kidney cell line from hypoxia-induced necrotic death. Infection of lentivirus expressing CypD RNAi sequence produces a significant reduction of CypD at both mRNA and protein levels. Both pathologic and biochemical analyses show that knockdown of CypD by RNAi protects rat kidney from I/R-induced renal injury. Conclusion: Our study provides the evidence that CypD may be a potential target for protecting I/R-induced renal injury. Copyright (C) 2010 S. Karger AG, Basel