Rats given stem cell injections regained the ability to stand on four legs and walk, albeit not perfectly, within 2 weeks, McDonald says. All rats received drugs typically used to prevent rejection of transplants. Examination of the rats after 2 and 5 weeks showed that most of the transplanted stem cells had died off, but that enough had survived for the animals to have a growing supply of new nervous system cells, McDonald says. In the treated rats, the researchers observed some new neurons with axons that extended up to 1 centimeter away from the injection site. Oligodendrocytes form the myelin sheaths that protect axons, much like plastic coating insulates electric wires, and speed the signals that travel along axons.
Astrocytes are star-shaped cells that provide the scaffolding upon which neurons can grow.