Even in the opening days of the modern era of regenerative medicine it was the case that repairing spinal cord injuries was up at the top of the to-do list. It still is: numerous research groups investigating nerve repair aim to reverse the paralysis and dysfunction produced when the spinal cord is damaged. This has proven to be more of a challenge than we'd like it to be, however: work on the regeneration of heart tissue is arguably much further ahead, and the creation of decellularized replacement organs will probably overtake nerve regeneration on the way to the widespread availability of practical and effective therapies.
This doesn't mean that progress is absent. Modest advances in nerve regeneration research show up every month these days, and far more is possible in the laboratory today than was the case ten years ago. You might look at these examples of publicity for recently published studies, representative of what is presently going on in laboratory research and clinical translation of that research:
A team of researchers in Poland who treated three of six paraplegics with spinal cord injury using transplanted olfactory ensheathing cells (OECs) found that the three treated patients showed neurological improvement and no adverse effects while the three control patients who did not receive transplants saw no improvement.
In a phase one of this non-randomized controlled study, the team of researchers treated the three patients with transplanted self-donated (autologous) OECs and fibroblasts isolated from olfactory mucosa combined with "intense" neuro-rehabilitation. They found the treatment "safe and feasible" one year after transplantation. There was no evidence of neurological deterioration, neuropathic pain, neuroinfection or tumor growth.
"Neurophysiological examinations showed improvement in spinal cord transmission and activity of lower extremity muscles in the surgically treated patients, but not in patients receiving only neuro-rehabilitation. We consider that the transplantation of OECs was the main factor contributing to the neurologic improvements in the three transplanted patients. Among the possible mechanisms for improvement is that the transplanted OECs may have mediated some restitution along white matter tracts in these patients."
A life-threatening disability after complete spinal cord injury is urinary dysfunction, which is attributable to lack of regeneration of supraspinal pathways that control the bladder. Although numerous strategies have been proposed that can promote the regrowth of severed axons in the adult [central nervous system], at present, the approaches by which this can be accomplished after complete cord transection are quite limited.
In the present study, we modified a classic peripheral nerve grafting technique with the use of chondroitinase to facilitate the regeneration of axons across and beyond an extensive thoracic spinal cord transection lesion in adult rats. The novel combination treatment allows for remarkably lengthy regeneration of certain subtypes of brainstem and propriospinal axons across the injury site and is followed by markedly improved urinary function. Our studies provide evidence that an enhanced nerve grafting strategy represents a potential regenerative treatment after severe spinal cord injury.
It isn't yet possible to fully regenerate or repair a severed spinal cord and all associated function in humans or other mammals, but it's a lot closer to being possible than it was just a handful of years ago.