Repetitive Transcranial Magnetic Stimulation Activates Glial Cells and Inhibits Neurogenesis after Pneumococcal Meningitis

Continuous and intermitted theta-burst rTMS protocols (cTBS and iTBS) were shown to significantly upregulate genes involved in angiogenesis, injury response and cellular repair, structural remodelling, neuroprotection, neurogenesis and neuronal plasticity after experimental stroke. Previous studies in experimental pneumococcal meningitis indicate a beneficial effect of neurogenesis induction after the acute infection by reducing neurologic complications. This study aimed to assess the potential of rTMS in inducing neurogenesis after acute pneumococcal meningitis to eventually improve disease outcome by reducing neurofunctional sequelae. After an acute episode of pneumococcal meningitis, infant rats were exposed to cTBS, iTBS or sham stimulation on two consecutive days with 4 stimulation procedures per day. Cortices and hippocampi were dissected and RNA was extracted from one hemisphere for gene expression analysis. The second hemisphere was used for histologic assessment of neurogenesis.cTBS stimulation for two days induced microglial M1-polarisation and astrocyte activation in the cortex and hippocampus of infant rats. TBS induced a downregulation of genes related to neurogenesis, neuroplasticity and nervous system processes associated with cognition, learning and memory, most likely as a consequence of accentuated neuroinflammation. We conclude that TBS – especially cTBS – after PM is detrimental for the disease outcome as it increases neuroinflammation and reduces neuroregeneration.