Researchers in Japan have developed a form of stem cell therapy that "reverses" paralysis. Though the treatment has only seen a 50% success rate so far, two of the four people who received it have regained the ability to stand or move their limbs, and no major negative side effects have been recorded.

The treatment begins with "reprogrammed" stem cells, known formally as induced pluripotent stem cells, or iPSCs. These are adult somatic (non-reproductive) cells that have been introduced to "reprogramming factors," or a suite of engineered genes, in the lab. The reprogramming factors trigger changes that effectively turn each cell into an embryonic stem cell, which can then be coaxed into any desired cell type found in the body.

At a press conference at Keio University Hospital in Tokyo, the researchers shared that they received iPSCs from a donor. They used the iPSCs to create neural precursor cells, which can divide and develop into neurons and other nervous system cells. Once the neural precursor cells had flourished in the lab, the team injected two million cells into the injury sites of four individuals who had each experienced paralyzing spinal cord injuries two to four weeks before treatment.

All four people received immunosuppressant drugs to prevent their immune systems from attacking the new cells.

Before receiving the experimental treatment, the four individuals had each experienced "class A" paralysis, which is defined by the American Spinal Injury Association Impairment Scale (AIS) as no sensory or motor function below the injury site. Within a year, one person regained the ability to stand with support, moving his level of paralysis down to class D; he's now undergoing rehabilitation to relearn how to walk. Another man can move some of his arm and leg muscles but cannot stand on his own, placing him at class C. The other two participants did not show any improvements in their ability to feel or move parts of the body affected by their injuries.

Although only half of the small study's participants improved, the researchers are still considering their trial a success. The point of this trial was to determine whether their treatment was safe. With none of the four individuals having experienced significant negative side effects, the team has now received the green light to perform larger clinical trials. Those trials will take place through K Pharma Inc., a venture capital firm established by Keio University.