A Novel Stem Cell Line Derived from Mesenchymal Stem Cells and Its Culture Supernatant Ameliorates Spinal Cord Injury in Rats

Mesenchymal stem cells were immortalized by introducing the telomerase gene, and clones with high differentiation potential were selected. Furthermore, Sox2, a transcription factor and neural stem cell marker, was introduced into these cells to establish a new stem cell line. This stem cell line proliferates indefinitely in stem cell culture medium and differentiates into cells expressing motor neuron-specific marker genes when cultured in neural differentiation medium. Transplantation of these stem cells into a rat spinal cord injury model restored walking ability and led to structural recovery of damaged spinal tissues. Furthermore, intravenous injection of the culture supernatant alone from this stem cell line into spinal cord-injured rats resulted in a recovery of motor function, with rats regaining the ability to walk. This culture supernatant contained over 10¹⁰ exosomes/ml, and these exosomes were found to contain large amounts of brain-derived neurotrophic factor.