Rat Paralysis Improved
The story receiving a lot of press right now is that researchers at Johns Hopkins University in Baltimore have used a combination of embryonic stem cells derived from mice and a chemical “soup” to rewire nerves in paralyzed rats, enabling them to walk again. The researchers emphasize that it is a very complex process and that it is years before this is even a potential in people; at this point, it is a proof of concept but not at all a potential therapy. A Bloomberg
story gives some basic scientific detail: the embryonic stem cells were differentiated in culture into motor neurons and then injected into the rats. Motor neurons are the cells that send messages to muscles telling them what to do. Three out of every four animals were able to use their hind legs again after six months. An AP story in the Boston Globe
(and other papers) reports that the difference between this work and other work using stem cells is that this essentially grows new motor neurons, rather than trying to heal the damage in the spinal cord. There were several different groups of rats: some received extra neurons treated with substances, some received chemicals to neutralize the rejection of the new neurons by the myelin on surrounding cells, and some received a growth factor that signaled the new neurons where to connect. Only rats that received all of the extra substances had improvement. The scientists will now try to duplicate the results in pigs.
Some other interesting facts from the press release
are that the rats had a 50% improvement in hind limb grip strength and that when one group was treated with the growth factor on only one limb, function was improved in that limb. The press release also iterates some of the remaining questions: can this treatment work in a larger animal, where the neurons have further to go? Do human embryonic stem cells behave the same way that mouse embryonic stem cells do?
This procedure is seen as a potential treatment for diseases caused by degeneration of the motor neurons, such as ALS or spinal muscular atrophy. In a paralysis where the motor neurons were intact but were not receiving signals from the spinal cord, it might still be more useful to try to repair the spinal damage directly instead of growing new neurons.
Obviously this is a major scientific advance, and equally obviously nothing is certain yet as relates to people.