Spinal cord injuries occur when there is damage to
the spinal cord itself or to its vertebrae, ligaments, or disks. Depending on
its severity it can cause permanent loss of strength, sensation, or overall
function below the site of injury. Many approaches to the treatment of these
injuries have been extensively researched with some producing promising
results.
In their paper, “Corticospinal-motor
neuronal plasticity promotes exercise-mediated recovery in humans with spinal
cord injury”, Dr. Monica A. Perez and Dr. Hang Jin Jo put forth their findings
of using non-invasive stimulation of spinal synapses to improve locomotion
recovery in humans with varying degrees of spinal cord injuries (SCI). The researchers
performed two experiments which both involved studying the effects of paired
corticospinal-motor neuronal stimulation (PCMS). During PCMS, transcranial
magnetic stimulation (TMS) was used to deliver stimuli over the primary motor
cortex to specific corticospinal-motor neurons depending on the injury of the
individual. In the first experiment, they randomly placed 25 individuals with
different chronic incomplete SCI into two groups: one combined exercise with PCMS,
and the other combined exercise with sham-PCMS. Every individual of either
group completed 10 sessions over the course of 2-3 weeks. In the second
experiment, the effects of PCMS alone, without exercise, were observed in 13
individuals with similar timeframes as the first experiment. Motor evoked
potentials (MEPs) and the level of maximal voluntary contractions (MVCs) were
measured for each participant before and after each intervention. In addition, a
few of the participants from each group in both experiments were asked to
complete functional tasks, and some participants returned for a 6 month-follow
up session that also examined MEPs and MVCs; though, none of the participants
of the second experiment were a part of this 6 month follow up group. One of their
findings was that there were increases in corticospinal responses and MVCs of
the targeted muscles, but only in participants with PCMS, and not in those with
sham-PCMS. In addition, they found that, in the 6-month follow up group, the locomotion
improvements were preserved only for those receiving PCMS and not for those
receiving the sham-PCMS. Furthermore, the 10 sessions of either PCMS with or without
exercise resulted in similar increases in MEPs and MVCs. They hypothesize that
the use of PCMS activates mechanisms similar to that of long-term potentiation,
which depends on NMDA receptor activity, because an NMDA antagonist can block
the effects of PCMS. Overall, the findings obtained by Dr. Perez and her
colleague do conclude that PCMS could function as an effective clinical
strategy to improve recovery in humans with SCI.
A separate
approach to the treatment of SCI was discussed by Dr. Chizuka Ide and his
colleagues in the paper “Cell transplantation for the treatment of spinal cord
injury – bone marrow stromal cells and choroid plexus epithelial cells”. The several
studies looked at were conducted on rats with SCI and there were several
somatic cells mentioned in the article that have been transplanted and have had
their effects observed in terms of SCI treatment; however, this particular
article focused on bone marrow stromal cells (BMSC) and choroid plexus
epithelial cells (CPEC) as well as briefly touched on the main issues with
utilizing neural stem/progenitor cells (NSPC) as treatment. The transplants
were either done directly into the lesion or injected into the fourth ventricle
thereby infusing the cells with cerebrospinal fluid (CSF). They found that in
either method of transplantation the cells did not survive past 2-3 weeks after
transplant, although, they did result in locomotor improvements, tissue repair,
and axonal regeneration. The researchers pointed out that while the short
duration of the cells in the body may sound like a drawback, it is in fact a
positive characteristic of the cells in that it reduces the possibility of
long-term harmful side-effects. Furthermore, because of the short duration of
the cells it is hypothesized that the cells secret neurotrophic factors which enhance
the spinal cords natural ability to regenerate. As for neural stem cells, the
issue, as the article mentioned, is that there is no current way to manipulate
or control the cells tendency to proliferate and differentiate. In addition, there
is a difficulty in successfully integrating the cells into the host’s spinal
cord tissue, and NSPC transplant does not necessarily improve locomotion capabilities
in SCI patients which is a parameter that needs to be met for transplants to
serve as clinical applications.
Both
labs described possible solutions to, at the very least, mitigate the effects
of SCIs. Dr. Monica’s lab incorporated a common treatment of injury, that of rehabilitation
exercises, with a relatively safe technique, TMS, which yielded impressive results.
Although Dr. Chizuka’s article was conducted on rats and their approach is more
invasive than the one proposed by Dr. Monica, it touched on a very intriguing
concept which will definitely be around for others to continue studying. They
both provided information which could benefit the overall field of study and possibly
give patients a greater repertoire of options to give them back their previous
lives.
References
Ide C, Nakano N, Kanekiyo K (2016) Cell
transplantation for the treatment of spinal cord injury – bone marrow stromal
cells and choroid plexus epithelial cells. Neural Regen Res 11(9):1385-1388
Jo, Perez.
“Corticospinal-Motor Neuronal Plasticity Promotes Exercise-Mediated Recovery in
Humans with Spinal Cord Injury.” Brain (London, England : 1878), vol. 143, no. 5,
May 2020, pp. 1368–82, doi:10.1093/brain/awaa052.
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