Abstract 19194: Gene Therapy with the Angiogenic Factor Secretoneurin Improves Nerve Function in Diabetic Neuropathy
Introduction: Pathogenesis of diabetic neuropathy (DN) remains enigmatic and impact of diabetes on vasa nervorum might lead to this disease. We could previously show that therapeutic angiogenesis with vascular endothelial growth factor improves DN and that the angiogenic peptide secretoneurin (SN) induces angiogenesis. We therefore hypothesized that gene therapy with SN improves DN.
Methods and Results: As an animal model for DN db/db mice were used. Gene therapy was accomplished with intra-muscular injection of SN plasmid DNA along the sciatic nerve. Sciatic nerve motor and sensory nerve conduction velocity (MCV and SCV) and tail flick temperature was measured. Vascularity of sciatic nerves was assessed by fluorescent staining using BS-1 lectin. In vitro effects of SN on Schwann cells were determined. Heterozygote mice showed normal values for MCV (52.8±1.7 m/s) and SCV (58.7±2.1 m/s) that stayed unchanged for the observational period of 9 weeks. Homozygous mice showed severely reduced nerve conduction velocities. After control plasmid injection nerve conduction velocities did not change significantly (MCV: baseline 32.5±0.9 m/s, 9 wk 31.5±0.9 m/s; SCV: baseline 36.7±1.3 m/s, 9 wk 33.1±1.4 m/s). After SN gene therapy, MCV and SCV increased significantly (MCV: baseline 31.9±0.7 m/s, 9 wk 46.7±1.3 m/s; SCV: baseline 36.5±1.2 m/s, 9 wk 49.3±1.3 m/s) and yielded a significant better outcome of SN treated mice (P<0.01; n=24). Tail-flick temperature was: heterozygote mice: 44.4±0.2 °C; ctr treated mice: baseline 45.9±0.12 °C, 4 wks 45.8±0.14 °C; SN treated mice: baseline 45.8±0.18 °C, 4 wks 44.9±0.12 °C; P<0.05 SN vs. Ctr.; n=12. Improved density of vasa nervorum in SN treated mice was observed. Schwann cells were stained by DAPI for evaluation of cell proliferation. SN treatment increased cell number (relative cell number vs. Ctr: 2.7±0.15; n=4; P<0.05). For induction of apoptosis cells were treated by H2O2 and stained by DAPI. SN significantly decreased apoptosis (% apoptotic cells: Ctr 34.4±2.7%, SN 100 ng/ml 18.5±2.0%; n=4; P<0.05 SN vs. Ctr; n=4).
Conclusions: The present observations indicate that SN exerts beneficial effects on nerve function and vascularity in DN in vivo and additionally on Schwann cells in vitro.
- © 2010 by American Heart Association, Inc.