Alan Trounson's decision to show the particular spinal regeneration video in question has rankled some scientists. Although the same video had already been shown to US politicians and reported in American newspapers, the paper with which it is associated is still undergoing peer review.
The work used embryonic germ stem cells derived by John Gearhart at Johns Hopkins University School of Medicine. These are cells derived from the germ primordia that, after nine weeks gestation, will form egg or sperm cells, but if dissected out before that time can be established to form stem-cell cultures. Although the cells had been cultured as embryoid bodies (embryo-like balls that form when cells are suspended rather than plated), they were not differentiated to become neurons, raising theoretical concerns about their ability to form tumors. However, author Doug Kerr, "we've injected a hundred rats and never seen tumors derived from the cells."
Furthermore, Kerr's rat model is comparatively new and not as well understood as others. It involves the loss of motor neurons after injection with sindbis virus, with recovery 12 weeks after injection of embryonic germ stem cells. Steven Goldman of Weill Medical College in New York, says, "I'm intrigued by what I've seen, but it remains to be seen what the [regrowth] mechanism is."
Harvard Medical School neurologist, Evan Snyder, suggests that the mechanism could be antiviral rather than regenerative. But even so, "that is also very dramatic; it makes the point that stem cells have a rich repertoire of behaviors." He sympathizes with Trounson's decision. "He felt the need to bring home the power of cellular therapy to people who could obstruct the advance of knowledge". Still, he says Trounson could have used videos of published work instead. For example, Snyder's own work shows a video of a rat with spinal injury that improves after being treated with neural stem cells made from newborn rats (PNAS99, 3024; 2002), also making the point that "...primitive cells in general will be important."
