ScienceDaily (Oct. 23, 2009)

Adult stem cells tested for defects before being implanted in the injured spinal cords of mice helped the animals recover with no cancerous side effects, according to new research. In recent years, scientists found that some experimental stem cell therapies can cause cancerous tumors. Pre-screened cells could result in potentially life- saving treatments without such side effects.

These new findings were presented at Neuroscience 2009, the annual meeting of the Society for Neuroscience and the world's largest source of emerging news about brain science and health. "We tried to identify induced pluripotent stem cells from adult tissue that would be safe when applied to cell therapy for central nervous system disorders," said Masaya Nakamura, MD, PhD, at Keio University School of Medicine, a co-author of the study. "These results suggest that properly pre-evaluated cells may be a promising source for future transplantation therapy."

Here, the authors investigated the possibility of making transplantation therapies safer and more efficient by examining different types of stem cells. They generated 36 induced pluripotent stem cell clones, which differed in their origins and other characteristics. They found that the cell's origin was a crucial indicator of whether the cells would result in tumors.

Results showed that immature (undifferentiated) stem cells are more likely to form tumors than mature ones. The transplantation of "safe" cells into mice with spinal cord injuries resulted in the formation of new neurons, while "unsafe" cells sped recovery for a short period but ultimately formed tumors.

"This study confirms that before human clinical trials go forward involving treatment of central nervous system disorders with induced pluripotent stem cells, pre-evaluating each cell clone carefully is essential," Nakamura said.

Research was supported by the project for realization of regenerative medicine by the Ministry of Education, Culture, Sports, Science and Technology of Japan.