Valvular heart disease is characterised by damage to or a defect in one of the four heart valves. While normally functioning valves ensure that blood flows with the right force in the right direction at the right time, in valvular heart disease the valves become too narrow and hardened to fully open or to close completely. One treatment option is valve surgery, which could involve repairing a damaged valve or, if it cannot be repaired, replacing the damaged valve with a replacement valve that is either artificial or made from animal tissue - this depends on the specific valve affected, as well as the patient's age and condition. Unfortunately, there are disadvantages associated with the valves that are currently used. For example, mechanical valves require anticoagulants, while the structures of those made from animal tissue tend to deteriorate over time. Dr Yoshiaki Takewa is Division Head of the Department of Artificial Organs at the National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan, is an expert in this field and wants to develop a tissue-engineered heart valve (TEHV) that can overcome these disadvantages.