What stem cell research has been done in human SCI populations?

Author: Sharon Jang , Vanessa Mok | Reviewer: Peggy Assinck | Published: 13 May 2020 | Updated: ~

SCI research on stem cells has largely focused on laboratory and animal experiments. Human studies are in their initial phase.²⁰

There are a number of ongoing and completed studies of weak to moderate evidence that evaluates the safety and efficacy of stem cells in people with SCI. Given that stem cells are still experimental, there is no specific stem cell type that is proven to be more effective over another. In research, studies have tested a large variation of stem cell sources, including blood, bone marrow, the nose, umbilical cords, and other nerves. While some of these stem cell sources come from fetuses, most studies have used stem cells from the person’s own body.

Care should be taken when interpreting these findings as they are derived from small trials with flaws in study design and documentation. Many more large-scale studies are required to determine whether stem cells have a role in treating people with SCI and if so, how transplantation should be done to minimize the health risks and maximize the potential of stem cell-based therapy.

In research, a common way to determine the success of any treatment is through comparing ASIA Impairment Scale (AIS) scores before and after transplantation. An individual’s AIS score consists of their muscle strength and sensation below their level of injury, in addition to anal sensation and contraction. Two weak evidence studies with a small number of participants (less than 10) found that stem cell treatments improved the AIS score of all participants. Conversely, two weak evidence studies found that only a portion (29-66.7%) of their participants saw an improvement in AIS scores.

Refer to our article on Spinal Cord Injury Basics for more information on AIS scores.

There have been some mixed findings on the efficacy of stem cells on sensation. Some weak evidence research studies have seen improvements in sensation for some individuals, but no large-scale study has found improvements for their entire sample. A moderate evidence study found significant changes in sensation when compared to individuals who did not receive stem cell therapy. However, a second moderate evidence study found that sensation improved over a year, but the amount of improvement was not significantly different than individuals who did not receive stem cell therapy. Currently, it is hard to conclude whether the use of stem cells is effective for the restoration of sensation.

There is some weak to moderate evidence showing that stem cells may help the recovery of motor function. The type of recovery in these studies has been quite diverse, ranging from a tetraplegic individual regaining the ability to hold their head up and move their upper limb, to the ability to walk with crutches and braces. However, the percentage of people who re-develop the ability to walk again in studies is low (i.e., 1-2 people out of 10-20 total participants). Moderate evidence suggests that stem cells may be more beneficial for movement in the arms and hands than the legs compared to people who did not receive stem cell therapy. Similar to sensation, no large-scale study has shown a high success rate in the recovery of motor functioning in response to stem cell therapy. In fact, there have been several studies that have found no improvements in motor function amongst their participants.

The signals relayed from the brain to the muscles are disrupted when a spinal cord injury occurs. To observe what connection remains, researchers apply stimulation to the brain and observe whether or not a signal is received at the arms/legs. If there is a signal present, researchers then note of how long it takes for the signal to get to the arms/legs, and the strength of the signal. As stem cells are supposed to theoretically help repair the spinal cord, it is thought that these signals would start to reappear/improve with stem cell therapy.

Motor evoked potentials are used to evaluate the connections between the brain and the muscles. Four low to moderate evidence studies have seen a reappearance of motor evoked potentials in individuals who were lacking them before, although the proportion of individuals who see a return is quite low (i.e., a range of 3-10 participants out of 20). Weak-moderate evidence research has also found improvements in the time it takes for signals to go through after stem cell therapy. It is important to note that these improvements are not always associated with improvements in AIS grades. Contrary to the previous findings, one research group found that the time taken for signals to travel from the brain to the muscle did not change, despite increases in AIS grade. This means that while functional improvements were seen, the connections between the brain and the muscle did not improve.

The brain normally interprets sensation through a pathway (in green) of nerves that travel from the limb, to the spinal cord, to the brain.²⁴

are used to evaluate the sensory connections between the brain and the rest of the body. Several studies have found a reappearance of sensory signals in the wrist and/or ankles in a portion of their participants. For participants with sensory signals present prior to receiving stem cells, evidence shows that these signals may be strengthened, and that these signals may travel faster. Although these findings appear promising, the longevity of the strengthening effect is brought to light by one group of researchers who showed that the newly obtained sensory signals disappeared after one year. More research is required to determine how to consistently obtain these results, and to determine whether these effects are truly non-lasting.

Refer to our article on Understanding Research Evidence for more information on spontaneous recovery.

Individuals with spinal cord injury often experience a lack of sensation and control of their bowel and bladder. Some research suggests that stem cell therapy may restore some sensation of bladder fullness and anal sensation. There are also some positive reports on the restoration of voluntary bladder contractions and anal control. Moreover, one study (moderate evidence) indicates that stem cell therapy may further improve bladder function by allowing individuals to hold more urine in their bladder, to increase the rate of urine passage, and to empty urine with less effort from by the bladder. However, the proportion of people in these studies who receive these bladder benefits are low.

There is limited evidence that stem cell therapy has a positive impact on functional independence and quality of life. Participants from three studies (weak evidence) reported that their self-care ability has improved in areas including bowel/bladder management, grooming, feeding, transferring, dressing, and mobility.

Most of the research on the effects of stem cell therapy and sexual functioning has been conducted with men. One weak study found that 31% of the men had improved erections while another found that sexual functioning improved as a result of increased sensitivity in the genital area. More research is required to determine the consistency of the effects in addition to the impact on sexual functioning of women.

While there have been some successful findings from stem cell therapy use in SCI, there are trials that have found no effects. Three studies found that none of their participants experienced any changes in their sensory or motor function. Meanwhile, other studies with a small number of participants (e.g., 5-20) have found that stem cell therapy may have an effect for some individuals, but not others. The number of people who do not experience any positive benefits from stem cell therapy is unpredictable, and has ranged from 40-87%.