medicine, neurology, stem cells

Stem Cell Trials to Treat Spinal Cord Injuries

While human embryonic stem cells (hESCs) were originally created in 1998, it wasn’t until 2009 — over a decade later — that they were approved by the FDA for use in a clinical trial in people. It was a long wait, but the trial was quite the promising one. The clinical trial, undertaken by the Geron Corporation, was for using hESCs to treat patients with spinal cord injuries and paralysis.

oligodendrocyte myelin sheath neuron spinal cord trial hESCs stem cells

This drawing shows how an oligodendrocyte protects part of a neuron (in red) with a myelin sheath. In spinal cord injuries, oligodendrocytes die in large numbers and can no longer protect the neurons with myelin, often resulting in paralysis. (Image credit: Andrew C)

Very unfortunately, the trial became stalled in late 2011, mostly due to financial concerns (but it did undoubtedly help pave the way for other hESC-based clinical trials to get FDA approval starting in 2010). At that point, Geron stated that they’d withdraw from the stem cell field entirely — in early 2013, Geron’s hESC-related assets, including the FDA-approved clinical trial, were bought by another company, BioTime Inc. But now, at long last, it looks as though the trial may resume through BioTime Inc.

So how can hESCs be used to treat spinal cord injuries? It comes down to the different types of cells in the spinal cord, and their vital roles in making sure that everything works as it should. The two key cell types are neurons and oligodendrocytes. Neurons transmit information in the spinal cord, while oligodendrocytes protect these neurons. Oligodendrocytes do this mostly by making myelin, which is an insulating material that forms a sheath around part of the neuron (similar to how an electrical wire must be insulated to work properly). When the spinal cord is injured, large numbers of oligodendrocytes die and so the neurons no longer have a protective sheath. The oligodendrocytes can be so damaged, and are so important, that a person can become paralyzed even if the neurons themselves survive. To treat a spinal cord injury, it’s thought the best approach is to introduce new oligodendrocytes into the damaged spinal cord area.

In 2005, researchers found that hESCs could make oligodendrocyte progenitors, and these cells could improve the motor functions of rats with acute spinal cord injuries. So far hESCs have been the only type of stem cell found to be able to turn into oligodendrocytes, or oligodendrocyte progenitors, making them the best source of cells for spinal cord therapies. To find out more about these efforts and scientific experiments, check out the book Biology Bytes: Digestible Essays on Stem Cells and Modern Medicine.

In late 2011, when Geron halted the clinical trial, four patients had already each received a one-time injection. While it was too early to know whether the treatment had been effective, preliminary results indicated that no adverse effects had been observed. BioTime Inc. has not yet made formal announcements, but it is highly suspected that it will resume the trial because the California Institute for Regenerative Medicine (CIRM) recently awarded BioTime Inc. $14 million to treat spinal cord injuries (CIRM had previously awarded $25 million to Geron for the project).

This ongoing story — which holds much promise for people with spinal cord injuries — shows that, once again, it is only with considerable support that potential stem cell-based therapies can reach the individuals who need them.


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