A protein that helps broken bones and damaged kidneys to heal now looks as though it may speed the recovery of stroke patients. It works by rewiring the connections around damaged brain cells. There is also a chance that the protein may be able to improve memory in Alzheimer's patients. "It looks very encouraging at this point," says Marc Charette of Creative BioMolecules in Massachusetts, the company that is developing the protein. "The region of the brain that's damaged dies, but the protein rewires the circuitry around the damage, through tissue surviving the stroke," he says.
The experiment, reported in NeuroReport (vol. 9, p 1441), used rats in which the researchers had induced strokes. Osteogenic protein-1 (OP-1) was injected into their brains and it quickly helped them to recover lost movement in their limbs. OP-1 has already proved its ability to help bridge gaps between broken bones (New Scientist, Science, 18 December 1993, p 20) and Creative BioMolecules is now close to having the procedure approved by the US Food and Drug Administration. The company is also progressing with work showing that OP-1 helps to heal damaged kidneys (Technology, 25 May 1996, p 25).
The substance, a member of a family of proteins called transforming growth factor-b, seems to orchestrate the repair of several types of tissue. The company has established that OP-1 directs primordial stem cells to differentiate into tissue that matches the damaged tissue. When the company discovered that OP-1 triggers the growth of tendril-like projections on neurons, called dendrites, it decided to test the protein's potential for brain repair after strokes. "Dendrites receive signals from other neurons," says Charette. "They behave like a switchboard, so you can rewire around the damage."
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To test OP-1 in rats after artificially induced strokes, Charette and his colleagues from Massachusetts General Hospital and Harvard Medical School injected it into the cisterna magna, a brain cavity containing cerebral fluid. Through tests that measured how easily the rats could place their limbs on a nearby platform, the researchers proved that rats on the higher dose-10 micrograms-recovered faster than those on the 1 microgram dose (see Graph). All the rats receiving OP-1 recovered far faster than those in the control group.
Source: New Scientist issue 20th June 1998, page 14
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