BDNF-loaded cationic nanobubbles for targeted therapy of acute spinal cord injury in rats

Abstract:

Objective：To explore the effect of ultrasound（US）-mediated destruction of cationic nanobubbles（CNBs） expressing brain-derived neurotrophic factor（BDNF/CNBs） on nerve regeneration in rats following spinal cord injury（SCI）. Methods：Ninety-six adult male sprague-dawley rats were randomly divided into four treatment groups after Allen hit models of SCI being established. The groups were：normal saline（NS） group，BDNF/CNBs group，BDNF and US group，BDNF/CNBs and US group. Histological changes after SCI were observed by hematoxylin and eosin staining. Neuron viabi-lity was determined by Nissl staining. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling（TUNEL） staining was used to examine cell apoptosis. BDNF gene and protein expression were detected by quantitative reverse-trans-cription PCR and Western blot. Green fluorescent protein（GFP） expression in the spinal cord was examined using an inverted fluorescence microscope. The recovery of neural function was determined using the Basso, Beattie, and Bresnahan（BBB） test. Results：The mean diameter of the BDNF/CNBs was （339.8±210.3） nm and the zeta potential was （24.30±6.24） mV. BDNF therapy using US-mediated BDNF/CNBs destruction significantly increased BDNF expression（0.61±0.10 vs. 0.70±0.13 vs. 0.83±0.15 vs. 1.55±0.19，P=0.000；31.65±1.30 vs. 45.62±1.50 vs. 49.55±1.20 vs. 75.83±2.10，P=0.000）, attenuated histological injury, improved the expression of Nissl body and decreased neuron loss（51.00±4.95 vs. 90.80±6.87 vs. 99.60±7.50 vs. 159.40±8.56，P=0.000），inhibited neuronal apoptosis in injured spinal cords（60.19±1.84 vs. 54.97±2.40 vs. 36.70±2.23 vs. 17.08±1.42，P=0.000），and increased BBB scores in SCI rats（10.10±0.33 vs. 10.60±0.43 vs. 11.70±0.36 vs. 17.20±0.45，P=0.000）. Conclusions：UTMD-mediated BDNF/CNBs destruction effectively transfects the BDNF gene into target tissues and has a significant effect on the injured spinal cord. The combination of US irradiation and gene therapy through BDNF/CNBs holds great promise for the future of nanomedicine and the development of non-invasive treatment options for SCI and other diseases.