Japan has bioethical regulations and clinical guidelines in place for experimental stem-cell therapies and for stem-cell-based pharmaceuticals. As a forensic pathologist who has worked on a patient who died after mesenchymal stem-cell therapy in Japan, I am aware that other patients receiving this treatment have developed serious and even fatal complications. These cases indicate that Japan's regulatory infrastructure needs to be more strongly enforced.

Reaction in Japan to these cases has been minimal. This contrasts with the tough approach of the US Food and Drug Administration, which led to the prompt prosecution of clinicians and companies involved in similar cases in Colorado and Texas (Nature 477, 377–378; 2011).

Japan's Investigative Commission for Institutional Framework in Regenerative Medicine recommended establishing a punitive system for physicians and clinics practising unethical activities, but its 2011 report made no mention of such plans. The country's specialist medical organizations should push for government collaboration if an effective disciplinary system is to be established (E. Dolgin Nature Med. 16, 495; 2010).

The Japanese Medical Ethics Committee, for example, needs to work more like the UK General Medical Council, which does not depend on the country's judiciary system to exercise its powers.

The Japanese Society for Regenerative Medicine and the International Society for Stem Cell Research should collaborate with Japan's health ministry to establish a system to prevent further stem-cell-related deaths.