Nature reports on regenerative research centering on the Notch protein: "Researchers believe that many of the body's tissues harbour stem cells capable of dividing to make new tissue. But some of these are recalcitrant and do not naturally divide to repair damage wreaked by severe injuries such as stroke or spinal-cord damage. ... one protein, called Notch, can boost the survival of three different types of stem cell. ... researchers do not yet know whether this could be used to treat humans after a stroke, because stimulating Notch could have many other, perhaps unwanted, effects in the brain. But it does suggest that drugs that provoke Notch or a related protein might one day be used to persuade stem cells in the brain or other tissues to do what doctors want."