Abstract 241: Direct Injection of Bone Marrow Mononuclear Cells Reversed Experimental Diabetic Neuropathy by Augmenting Neovascularization and Providing Angio-neurotrophic Cytokines

Abstract

Background: Bone marrow (BM)-derived mononuclear cells (MNCs) have been shown to effectively treat ischemic cardiovascular diseases. Recent evidence suggested that diabetic neuropathy (DN) is causally related to impaired angio-vasculogenesis in vasa nervorum and deficiency of angiogenic and neurotrophic factors. Accordingly, we sought to investigate whether DN can be ameliorated by local injection of BM-derived MNCs. Methods and Results: A severe peripheral neuropathy, characterized by significant slowing of motor nerve conduction velocities (MCV) developed 12 wks after the induction of diabetes with streptozotocin in Fisher rats (vs normal rats; 46.6±2.6 vs 32.0±2.5 m/s, P < 0.05). These rats were randomly assigned to MNC or saline injection groups (n = 9, each group) and received either 5x106 MNCs or saline intramuscularly around the sciatic nerves. In the MNC group, MCV were significantly improved within 4 wks after treatment (MNC vs Saline, 41.9±3.2 vs 32.7±2.8 m/s, P < 0.01). Microvascular circulation of sciatic nerve, measured by laser Doppler perfusion imaging was markedly increased only in the MNC group. Capillary density at 4 wks was significantly higher in the MNC group than in the saline group (68±5.9 vs 37±4.4 /cross section, P < 0.01). Robust engraftment of MNCs were observed in sciatic nerves, which sustained over 4 wks. A fraction of engrafted MNCs expressed endothelial markers suggestive of transdifferentiation into endothelial cells in the vasa nervorum. Intriguingly, a large number of the engrafted MNCs are following the course of vasa nervorum in close proximity. Real-time RT-PCR on sciatic nerves revealed that the expression of angio-neurotrophic factors were significantly increased in the MNC group compared to the saline group: VEGF (2.1 fold), FGF-2 (2.4), eNOS (18.1), Brain-derived neurotrophic factor (35.1), IGF-1 (25.5) (all P < 0.05). The protein levels were well correlated with mRNA expression levels. Conclusion: Local transplantation of BM-derived MNCs could improve experimental DN by augmenting neovascularization and increasing angiogenic and neurotrophic factors in peripheral nerves. These findings suggest that BM-MNC transplantation may represent a novel therapeutic option for treating DN.