Transplantation of MSCs in Combination with Netrin-1 Improves Neoangiogenesis in a Rat Model of Hind Limb Ischemia

Background. Similar to the neural network, the vascular network is formed from central axial structures that send sprouts along predetermined trajectories to their distal destinations. Indeed, recent evidence indicates that neuronal guidance factors and their receptors function as angiogenic regulators. As neural guidance cues, netrin-1 is the most extensively studied gene in the field of angiogenesis. Despite achieving some advances in mesenchymal stem cell (MSC) therapy in angiogenesis, there are still a certain number of patients who fail to respond to cell therapy. Thus, a novel therapeutic strategy to enhance the angiogenic property of transplanted cells is desirable. This study examined the impact of combined netrin-1 protein and MSC implantation on therapeutic angiogenesis in a rat model of hind limb ischemia. Methods. Hind limb ischemic rats (n = 24) were divided randomly into four groups (six rats per group): control group (0.05 mL saline); netrin-1 group (1 mu g netrin-1 dissolved in 0.05 mL saline); MSC group (1 x 10(6) MSCs); and netrin-1/MSCs group (1 mu g netrin-1 combined with MSCs). Netrin-1 and/or MSCs were injected directly into the muscle of the ischemic limb. Gross appearance of ischemic limb, collateral vessel formation, and vascular endothelial growth factor (VEGF) level were assessed 28 d after treatment. Results. The results showed that pretreatment of MSCs with a recombinant netrin-1 protein markedly augmented the angiographic score and capillary density, improved function of the ischemic limb, and increased levels of VEGF in the plasma and damaged tissues. Further studies assaying the cell migration and network formation suggested that netrin-1 promoted MSC migration and enhanced its ability to participate in tube formation. Conclusions. These results demonstrated that transplantation of MSCs pretreated with netrin-1 protein significantly improved the therapeutic effect of MSCs and, therefore, may provide a novel therapeutic approach for ischemic disease. (C) 2011 Elsevier Inc. All rights reserved.