Kallikrein-modified mesenchymal stem cell implantation provides enhanced protection against acute ischemic kidney injury by inhibiting apoptosis and inflammation

Mesenchymal stem cells (MSCs) migrate to sites of tissue injury and serve as an ideal vehicle for cellular gene transfer. As tissue kallikrein has pleiotropic effects in protection against oxidative organ damage, we investigated the potential of kallikrein-modified MSCs (TK-MSCs) in healing injured kidney after acute ischemia/reperfusion (I/R). TK-MSCs secreted recombinant human kallikrein with elevated vascular endothelial growth factor levels in culture medium, and were more resistant to oxidative stress-induced apoptosis than control MSCs. Expression of human kallikrein was identified in rat glomeruli after I/R injury and systemic TK-MSC injection. Engrafted TK-MSCs exhibited advanced protection against renal injury by reducing blood urea nitrogen, serum creatinine levels, and tubular injury. Six hours after I/R, TK-MSC implantation significantly reduced renal cell apoptosis in association with decreased inducible nitric oxide synthase expression and nitric oxide levels. Forty-eight hours after I/R, TK-MSCs inhibited interstitial neutrophil and monocyte/macrophage infiltration and decreased myeloperoxidase activity, superoxide formation, p38 mitogen-activated protein kinase phosphorylation, and expression of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1. In addition, tissue kallikrein and kinin significantly inhibited H2O2-induced apoptosis and increased Akt phosphorylation and cell viability in cultured proximal tubular cells. These results indicate that implantation of kallikrein-modified MSCs in the kidney provides advanced benefits in protection against ischemia-induced kidney injury by suppression of apoptosis and inflammation.