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Nerve rescuers
Cells from pig snouts reverse spinal cord damage in rats
Edward R. Winstead

Researchers have used pig cells to facilitate repairs on severed spinal cords in rats. A month after injecting cells from pig snouts into the damaged areas, impulse conduction returned in seven of ten rats. The donor pigs had been genetically modified to express a human protein that suppresses immune response, a prerequisite for undertaking similar studies in humans.

Regeneration of nerve fibers (top) Spinal cord is cut and pig olfactory ensheathing cells are injected; (bottom) one month later, the regenerated nerve conducts impulses faster than normal nerves.

Jeffery Kocsis, of the Yale University School of Medicine, in New Haven, CT, and colleagues report that the engineered pig cells survived in the rodents, promoted the regeneration of nerves, and formed myelin, the insulating sheath around nerve fibers. Previous studies have identified the potential of olfactory ensheathing cells, or OECs, to regenerate nerves. The current study demonstrates that these cells in pigs can express a human protein, be grafted to another species, and have functional effects.

To get around the problem of immune rejection, Kocsis developed pigs that carry a gene for the human complement-inhibitory protein (hCD59). The presence of this protein conveys a form of protection from immune attack. A paper describing the work appears in the September issue of Nature Biotechnology.

Nerve fibers grew about one millimeter per day, and the regenerated nerves conducted impulses faster than normal nerves, according to the researchers.

In an accompanying News & Views article, Lars Olson, of Karolinska Institute, in Stockholm, Sweden, summarizes previous reports on the reparative properties of OECs when grafted to the central nervous system: "They populate the engrafted area, orient themselves in a directionally organized manner, migrate into adjacent non-injured sites, and stimulate and guide axonal regeneration both in the spinal cord and in the brain."

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Imaizumi, T. et al. Xenotransplantation of transgenic pig olfactory ensheathing cells promotes axonal regeneration in rat spinal cord. Nat Biotechnol 18, 949-953 (September 2000).

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