Modeling chronic cervical spinal cord injury in aged rats for cell therapy studies

•Rats showed reduced performance in behavior tests as they aged.•Aged rats had high death rates during training and after injury and cell transplantation.•Neural progenitor cells were present in the spinal cord 4 weeks after transplantation.•Neural progenitor cells could migrate and differentiate and did not cause tumors.•Aged rats failed to recover locomotor activity one month after cell transplantation.