Regenerative medicine for spinal cord injury using induced pluripotent stem cells: from animals to humans.

Spinal cord injury (SCI) results in permanent neurological dysfunction and neuropathic pain. To address this pathology, we recently conducted a clinical study in which we transplanted neural precursor cells (NPCs) derived from human induced pluripotent stem cells into patients during the subacute phase of SCI. One of the therapeutic mechanisms of cell transplantation is the formation of synaptic connections with the host's neural tissues, which we demonstrated using a chemogenetic tool. In addition, we have developed innovative strategies to enhance the effectiveness of cell transplantation through gene therapy. Moreover, our current study is focused on developing cell therapy for chronic SCI, a more challenging pathology characterized by the formation of cavities and scar tissue. In such situations, transplanting NPCs with neurogenic properties could effectively penetrate scar tissue and form functional synapses with the host neurons. To improve the outcomes of cell transplantation alone, we have found that incorporating rehabilitation is beneficial. In animal models of SCI, we have established an effective rehabilitative training program in which NPCs were transplanted during the chronic phase. Robotic rehabilitation has demonstrated improvements in gait ability and trunk function in clinical situations. Therefore, regenerative medicine shows promise for chronic SCI, particularly when rehabilitation strategies are incorporated.