Abstract: Treating diseased or damaged tissue, particularly the liver, using stem cells. The hepatic stem cell population of a subject suffering from diseased or damaged tissue can be expanded by administering at least one regulator of the sympathetic nervous system. The regulator can be an adrenoceptor agonist or antagonist, adrenoceptor antagonists, prazocin, being particularly preferred. The invention also includes the use of agents which mobilize stem cells in the manufacture of medicaments for the treatment of diseased or damaged tissue.