In Silico Approach to Model Heat Distribution of Magnetic Hyperthermia in the Tumoral and Healthy Vascular Network Using Tumor-on-a-Chip to Evaluate Effective Therapy.

Glioblastoma multiforme (GBM) is the most severe form of brain cancer in adults, characterized by its complex vascular network that contributes to resistance to conventional therapies. Thermal therapies, such as magnetic hyperthermia (MHT), emerge as promising alternatives, using heat to selectively target tumor cells while minimizing damage to healthy tissues. The organ-on-a-chip can replicate this complex vascular network of GBM, allowing for detailed investigations of heat dissipation in MHT, while computational simulations refine treatment parameters. In this in silico study, tumor-on-a-chip models were used to optimize MHT therapy by comparing heat dissipation in normal and abnormal vascular networks, considering geometries, flow rates, and concentrations of magnetic nanoparticles (MNPs). In the high vascular complexity model, the maximum velocity was 19 times lower than in the normal vasculature model and 4 times lower than in the low-complexity tumor model, highlighting the influence of vascular complexity on velocity and temperature distribution. The MHT simulation showed greater heat intensity in the central region, with a flow rate of 1 µL/min and 0.5 mg/mL of MNPs being the best conditions to achieve the therapeutic temperature. The complex vasculature model had the lowest heat dissipation, reaching 44.15 °C, compared to 42.01 °C in the low-complexity model and 37.80 °C in the normal model. These results show that greater vascular complexity improves heat retention, making it essential to consider this heterogeneity to optimize MHT treatment. Therefore, for an efficient MHT process, it is necessary to simulate ideal blood flow and MNP conditions to ensure heat retention at the tumor site, considering its irregular vascularization and heat dissipation for effective destruction.

Regeneration and Plasticity Induced by Epidural Stimulation in a Rodent Model of Spinal Cord Injury.

Traumatic spinal cord injury is a major cause of disability for which there are currently no fully effective treatments. Recent studies using epidural electrical stimulation have shown significant advances in motor rehabilitation, even when applied during chronic phases of the disease. The present study aimed to investigate the effectiveness of epidural electric stimulation in the motor recovery of rats with spinal cord injury. Furthermore, we aimed to elucidate the neurophysiological mechanisms underlying motor recovery. First, we improved upon the impact spinal cord injury model to cause severe and permanent motor deficits lasting up to 2 months. Next, we developed and tested an implantable epidural spinal cord stimulator device for rats containing an electrode and an implantable generator. Finally, we evaluated the efficacy of epidural electrical stimulation on motor recovery after spinal cord injury in Wistar rats. A total of 60 animals were divided into the following groups: (i) severe injury with epidural electrical stimulation (injury + stim, n = 15), (ii) severe injury without stimulation (group injury, n = 15), (iii) sham implantation without battery (sham, n = 15), and (iv) a control group, without surgical intervention (control, n = 15). All animals underwent weekly evaluations using the Basso, Beattie, Bresnahan (BBB) locomotor rating scale index, inclined plane, and OpenField test starting one week before the lesion and continuing for eight weeks. After this period, the animals were sacrificed and their spinal cords were explanted and prepared for histological analysis (hematoxylin-eosin) and immunohistochemistry for NeuN, ß-III-tubulin, synaptophysin, and Caspase 3. Finally, NeuN-positive neuronal nuclei were quantified through stereology; fluorescence signal intensities for ß-tubulin, synaptophyin, and Caspase 3 were quantified using an epifluorescence microscope. The injury + stim group showed significant improvement on the BBB scale compared with the injured group after the 5th week (p < 0.05). Stereological analysis showed a significantly higher average count of neural cells in the injury + stim group in relation to the injury group (1783 ± 2 vs. 897 ± 3, p < 0.001). Additionally, fluorescence signal intensity for synaptophysin was significantly higher in the injury + stim group in relation to the injury group (1294 ± 46 vs. 1198 ± 23, p < 0.01); no statistically significant difference was found in ß-III-tubulin signal intensity. Finally, Caspase 3 signal intensity was significantly lower in the stim group (727 ± 123) compared with the injury group (1225 ± 87 p < 0.05), approaching levels observed in the sham and control groups. Our data suggest a regenerative and protective effect of epidural electrical stimulation in rats subjected to impact-induced traumatic spinal cord injury.