By injecting stem cells directly into the brain, scientists have successfully reversed neural birth defects in mice whose mothers were given heroin during pregnancy. Even though most of the transplanted cells did not survive, they induced the brain's own cells to carry out extensive repairs.
Joseph Yanai, director of the Ross Laboratory for Studies in Neural Birth Defects at the Hebrew University-Hadassah Medical School, in Jerusalem, says that stem-cell therapies are ideal for treating birth defects where the mechanism of damage is multifaceted and poorly understood. "If you use neural stem cells," says Yanai, "they are your little doctors. They're looking for the defect, they're diagnosing it, and they're differentiating into what's needed to repair the defect. They are doing my job, in a way."
Yanai and his colleagues began with mice that had been exposed to heroin in the womb. These mice suffer from learning deficits; when placed in a tank of murky water, for instance, they take longer than normal mice to find their way back to a submerged platform. And in their hippocampus--an area of the brain associated with memory and navigation--critical biochemical pathways are disrupted, and fewer new cells are produced.
All of those problems are swiftly resolved when the researchers inject neural stem cells derived from embryonic mice into the brains of the heroin-exposed animals. When swimming, the treated mice caught up with their normal counterparts, and their cellular and biochemical deficits disappeared. Yanai announced these findings in 2007 and 2008.
Such dramatic results were surprising, considering that just a fraction of a percent of the transplanted stem cells survived inside the mice's brains. But they are consistent with an emerging consensus of how adult stem cells perform their many functions through so-called bystander or chaperone effects. Beyond simply generating replacements for damaged cells, stem cells seem to produce signals that spur other cells to carry out normal organ maintenance and initiate damage control.
From Technology Review, read more there.