Ischemia-reperfusion (I/R) sets off a devastating cascade of events, leading to cell death and possible organ failure. Treatments to limit I/R-associated damage are lacking, and the pathways that drive injury are poorly understood. In this issue of the JCI, Wei and colleagues identify microRNA-668 (miR-668) as a protective factor in acute kidney injury (AKI). miR-668 was shown to repress mitochondrial fission-associated protein MTP18, thereby inhibiting pathogenic mitochondrial fragmentation. In murine models of I/R-induced AKI, treatment with a miR-668 mimetic reduced mitochondrial fragmentation and improved renal function. Moreover, HIF-1α was shown to be required for miR-688 expression in response to I/R. Importantly, Wei et al. show miR-668 upregulation in a cohort of human patients with AKI. Together, these results identify a HIF-1α/miR-668/MTP18 axis that may have potential as a therapeutic target for AKI.

This study tested whether inducible pluripotent stem cell (iPSC)-derived mesenchymal stem cell (MSC) therapy could effectively protect kidney from acute ischemia (1 h) - reperfusion (5 day) injury (IRI). Male-adult SD-rats (n = 24) were equally categorized into groups 1 (sham-control), 2 [sham-control + iPSC-MSC (1.2 × 106 cells/rat)], 3 (IR only) and 4 (IR + iPSC-MSC). Blood urine nitrogen/creatinine levels and ratio of urine protein to creatinine, kidney weight and expressions of inflammation (TNF-α/NF-κB), oxidative-stress (NOX-1/NOX-2/oxidized protein) and apoptosis (mitochondrial-Bax/cleaved caspase-3/PARP) were significantly higher in group 3 than in groups 1, 2 and 4 and significantly higher in group 4 than in groups 1 and 2 (all P<0.0001), but showed no differences between groups 1 and 2, whereas the protein expressions of anti-inflammation (IL-4/IL-10) and endothelial (CD31/vWF) markers exhibited an opposite pattern to inflammation among the four groups (all P<0.0001). Protein expressions of angiogenesis (VEGF/CXCR4/SDF-1α) markers progressively increased from groups 1 to 4 (all P<0.0001). Cellular expressions of kidney injury score/DNA-damage (γ-H2AX)/apoptotic nuclei and glomerulus-tubular-damage (KIM/FSP-1) displayed an identical pattern to inflammation, whereas the cellular expressions of glomerulus-tubular-integrity (dystroglycan/podocin/p-cadherin/synaptopodin/ZO-1/fibronectin) revealed an opposite pattern to inflammation among the four groups (all P<0.0001). In conclusion, iPSC-derived MSC therapy effectively protected kidney against IRI.