June 21, 2006 -- With some chemical help, embryonic stem cells may help reverse paralysis, tests done on paralyzed rats show.
The technique, described in the July issue of the Annals of Neurology, hasn't been tested on people yet.
But, based on the results seen in adult rats, the method may be a "potential therapeutic intervention for humans with paralysis," write the researchers. They include Deepa Deshpande, MS, MBIOT, and Douglas Kerr, MD, PhD, both of Johns Hopkins University in Baltimore, Md.
This isn't the first time scientists have tested stem cells in paralyzed animals. But the new study's method differs from that in past experiments.
Stem cells can develop into different types of cells, although embryonic stem cells may have a wider range of possibilities than adult stem cells.
Stem Cell Test
In this experiment, the scientists first did some lab work on embryonic mice stem cells. They used chemicals to tell the cells to become motor neurons, which are nerve cells that control muscles.
The mouse stem cells spent 3.5 days growing into motor neurons in the lab.
Then, researchers transplanted them into the spinal cords of 120 paralyzed adult rats.
As part of the experiment, the scientists created a key test group of 15 paralyzed rats. Those rats got a deluxe stem cell package souped up with three extras:
- Chemical pretreatment of the stem cells to help new motor neurons survive
- Chemicals to help the rats' bodies accept the stem cells
- Chemicals that told the stem cells where to park to help one of the rats' hind paws
For comparison, the other rats got few or none of these additives with their stem cells.
Partial Reversal of Paralysis
Six months later, 11 of the 15 rats in the key test group could put weight on the paralyzed hind paw their stem cells had been instructed to target. Those rats could also step off from that paw.
None of the other rats in the study were able to do that.
But even in the key test group, paralysis recovery was only partial; the rats couldn't move the hind paw that hadn't been targeted by the stem cells.
Rats in the key test group made 125 new nerve connections to muscle, 50 of which reached and worked in the targeted hind paw.
The other rats had similar numbers of surviving, transplant-derived motor neurons. But without the full package of chemical perks, those motor neurons didn't bring paralysis recovery, the study showed.
In short, embryonic stem cells show promise against paralysis in rats, but it may take extra chemical help to get the biggest benefits.