Robust neurogenesis in chronic stroke monkeys following mesenchymal stem cell transplantation plus intermittent theta-burst stimulation

A significant population of chronic stroke patients urgently requires more effective therapies because of functional plateaus and limited intervention options. Intermittent theta-burst stimulation (iTBS) has been increasingly adopted in chronic-phase ischemic stroke management. However, the efficacy decreases over time. Mesenchymal stem cells (MSCs) have emerged as a promising therapeutic strategy for chronic stroke management through multiple mechanisms. Whether combined MSC transplantation and iTBS confers superior synergistic efficacy warrants further investigation. In this study, human umbilical cord-derived MSCs were stereotactically injected into the penumbra of the brain parenchyma adjacent to infarct sites in cynomolgus monkeys with chronic-stage middle cerebral artery occlusion (MCAO)-induced ischemic stroke. iTBS commenced at 1 week post-transplantation (5 sessions/week until week 17). Behavioral tests, electrophysiological recordings, functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), and plasma proteomic analysis were conducted longitudinally, with terminal histological and spatial proteomic analysis at week 17. The results indicated that combined MSC/iTBS therapy enhanced motor function, reduced cortical excitation thresholds, shortened motor-evoked potential (MEP) latency, increased neural activity intensity/synchronization, strengthened functional connectivity, and optimized motor cortex metabolism. In addition to the commonly attributed therapeutic mechanisms of MSCs and iTBS, the combined therapy additionally triggered neurogenesis and stem cell chemotaxis, which was potentially mediated by iTBS-enhanced CXCL12 secretion from MSCs. Therefore, MSC/iTBS combination therapy can effectively treat chronic stroke through multiple mechanisms, particularly involving the activation of endogenous neural stem cells (NSCs), representing a promising interdisciplinary treatment strategy.