Modern medicine has still not managed to crack the problem of spinal cord injuries that result in significant paralysis or loss of functional status.
There are numerous factors that influence the inability to restore movement or autonomous bodily control to these patients. A prominent example of these is the inability to cultivate new neurons that make up and power the spinal cord.
However, some researchers have claimed that they have successfully induced ‘generic’ human stem cells to differentiate into stem cells that apply more specifically to the spine.
Why We Can’t Repair a Spine (Yet)
Strategies involving the implantation of any kind of donor cell - to regenerate or recreate damaged spinal tissue - have not shown much success. Furthermore, some medical researchers also believe that such forays into regenerative medicine are not feasible, in terms of costs and resources, at this point. Therefore, this area of cell-based therapy is still very much at the development stage.
The goals of many current projects in this area revolve around the restoration of the motor function in subjects (mostly rodents in animal models). This requires the full re-generation and reinstatement of the corticospinal tract (CST), an important spinal region that communicates with the relevant cortices in the brain.
A limited number of reports claim to have achieved this. However, this leaves the rest of the spine un-addressed, which may have a residual effect on movement and other functions.
New Direction in Cell-Based Therapy for Spinal Injuries
In the past, CST-based trials used grafts of multipotent cells, which were progenitor cells rather than true stem cells.
However, a newer study has documented a technique in which human pluripotent stem cells were used, which could differentiate into all the cells a spinal section needs, and not just the CST ones.
Reportedly, these neural stem cells further diversified into different types of neurons. Therefore, it can be concluded that neural stem cells may be capable of more complete regeneration of missing or damaged spinal tissue in living subjects.
The researchers behind the apparent breakthrough claimed that their cells were capable of doing this in an appropriate model. However, the research was conducted by causing the stem cells to ‘grow’ a customized spinal graft, which was then transplanted using the model.
A transverse spinal section showing some functions of various spinal region. (Source: Public Domain)
The scientists claimed that these grafts integrated well with the sections of pre-existing spinal tissue ‘upstream’ and ‘downstream’ of the graft location. These consisted of various intra-, supra- and cortico-spinal networks of neural connections, which allowed peripheral nervous functions, including movement, under normal circumstances.
In addition, it is necessary for these networks to distinguish between the dorsal (or backward-facing) and ventral portions of the spine. This is because these regions send different signals to the brain in different directions in the average healthy spine. The researchers asserted that their spinal grafts were indeed capable of these distinctions.
The scientists behind this project reported that their model’s subjects gained increased functional status as a result of receiving one of these grafts. However, it can be assumed that these assertions are getting slightly ahead of their time, in terms of being approved as a real-world treatment.
The researchers also noted that their new spinal stem cells – and the neurons that they differentiate into – can be used as an excellent in vitro model for the neurobiology of the spine. In addition, the cells may also now be used to test other novel potential treatments for spinal disorders.
The scientists behind this project collaborated across the departments of neurosciences and psychiatry & neurology at the University of California (Los Angeles), as well as the San Diego Veterans Administration’s Healthcare System. The team published their findings in an August 2018 issue of Nature Methods.
The researchers also hope that future work on this model could lead to the application of their cells to next-generation regenerative medicine that focuses on the spine and how to repair it after injury or damage.
Therefore, we may be able to look forward to a time, in which improved medicine could restore paraplegic patients to the health and autonomy that they may cherish.
Top Image: The spine is an important component of the human nervous system. (Source: Pixabay)
H. Kumamaru, et al. (2018) Generation and post-injury integration of human spinal cord neural stem cells. Nature Methods.
S. A. Goldman. (2016) Stem and Progenitor Cell-Based Therapy of the Central Nervous System: Hopes, Hype, and Wishful Thinking. Cell Stem Cell. 18:(2). pp.174-188.
K. Kadoya, et al. (2016) Spinal cord reconstitution with homologous neural grafts enables robust corticospinal regeneration. Nat Med. 22:(5). pp.479-487.