Melatonin-incorporated brain extracellular matrix hydrogel enhances NSCs mitochondrial metabolism to promote neuroregeneration via the AMPK-PGC-1α-NRF1/TFAM axis after spinal cord injury

Spinal cord injury (SCI) results in severe and debilitating neurological damage. Mitochondria play a crucial role in the differentiation of neural stem cells (NSCs) and neural regeneration. However, mitochondrial dysfunction occurs following SCI, manifesting as dysregulation of oxidative stress and ATP depletion, which impede neural regeneration. In this study, we developed a multi-functional, injectable hydrogel platform by integrating a brain-derived extracellular matrix (BEM), the neuroprotective agent melatonin (MT), and NSCs. We hypothesized that this NSCs@MT/BEM system would create a synergistic niche in which BEM provided tissue-specific signals, and melatonin metabolically reprogramed NSCs to enhance the regenerative potential. In vitro, melatonin directed NSCs differentiation towards a neuronal fate by enhancing mitochondrial function through AMPK signaling. When transplanted into a rat model of thoracic spinal cord contusion, the NSCs@MT/BEM hydrogel elicited robust functional recovery, evidenced by significantly improved Basso-Beattie-Bresnahan (BBB) scores, restored gait patterns, and enhanced electrophysiological conduction. This functional repair was supported by profound structural changes: enhanced survival of transplanted NSCs, preserved host neurons, attenuated glial scarring, and robust serotonergic axon regeneration across the lesion. Our findings demonstrated that a strategy combining a biomimetic scaffold with targeted metabolic modulation created a pro-regenerative microenvironment, significantly enhancing the therapeutic efficacy of NSCs transplantation for SCI repair.