A timeline of stem cell regenerative medicine in Japan — from the discovery of iPS cells (2006) to Parkinson's trial results (2025)

Summary — Japan is where iPS cells were first reported, and a country that built a legal framework for regenerative medicine early and has approved several stem cell products. This article sets out the key events in Japanese regenerative medicine as a timeline, from the report of iPS cells in 2006 to the Parkinson's clinical trial results of 2025, explaining what each event means and how 'approval' differs from a 'provision plan'.

2006 — first report of iPS cells

Professor Shinya Yamanaka's team at Kyoto University reported in the journal Cell that introducing four genes into mouse skin cells could produce 'induced pluripotent stem cells' (iPS cells) with properties similar to embryonic stem cells, and succeeded with human cells the following year. iPS cells opened a way to make many cell types without using embryos, and Professor Yamanaka received the 2012 Nobel Prize in Physiology or Medicine. The discovery prompted Japan to develop regenerative medicine as a national research field.

2014 — first iPS cell transplant and the regenerative medicine act

In 2014 a team from RIKEN and Kobe City Medical Center General Hospital carried out the world's first clinical study transplanting a sheet of retinal pigment epithelium made from the patient's own iPS cells into a patient with age-related macular degeneration. Results published in NEJM in 2017 reported that the graft remained in place for a year and vision did not worsen. In November of the same year, the Act on the Safety of Regenerative Medicine and the revised Pharmaceuticals and Medical Devices Act came into force: the former manages cell-based care provided by medical institutions in Class I, II and III by risk, and the latter created the conditional, time-limited approval pathway for regenerative medical products.

2015 — first allogeneic mesenchymal stem cell product approved

An allogeneic bone marrow-derived mesenchymal stem cell product for acute graft-versus-host disease (GVHD) after haematopoietic stem cell transplantation was approved. In this area, a phase II study (2008) by European investigators including teams in Sweden had reported responses in many steroid-refractory patients, and the Japanese product was approved on the basis of domestic clinical trial results. The same year, sheets made from patients' own skeletal myoblasts received conditional, time-limited approval for severe heart failure.

2018 — conditional approval for spinal cord injury

Based on Sapporo Medical University research, a product in which mesenchymal stem cells from the patient's own bone marrow are expanded in the patient's serum and given intravenously received conditional, time-limited approval for spinal cord injury. In 2021 the team reported improved motor and sensory scores in a case series of 13 patients. This approval became emblematic of Japan's conditional pathway, discussed both for enabling faster patient access and for concerns about the level of evidence.

2021 and 2024 — broader applications

In 2021 an allogeneic adipose-derived mesenchymal stem cell product for complex perianal fistulas in Crohn's disease was approved, and in 2024 an allogeneic bone marrow-derived cell product for chronic motor paralysis after traumatic brain injury received conditional, time-limited approval.

2025 — Parkinson's iPS cell trial results

Kyoto University's Center for iPS Cell Research and Application and Kyoto University Hospital published in Nature the results of a phase I/II clinical trial transplanting dopamine neuron progenitors made from iPS cells into seven patients with Parkinson's disease. Without serious safety problems, engraftment and dopamine production by the grafted cells were confirmed on imaging, and improvements in motor symptom scores were reported in some patients. Some 20 years after their discovery, iPS cells had led to clinical results in patients with a neurological disease.

Points to remember when reading the timeline

The timeline includes both 'approved products' and 'clinical research'. Approved products have been reviewed on the basis of clinical trial data, and conditional, time-limited approvals must confirm efficacy again within a set period; clinical research is still in the process of confirming efficacy. Care for which a medical institution has submitted a provision plan under the regenerative medicine act has followed a procedure, which does not mean its efficacy has been recognised. A 2018 commentary in Nature highlighted the sale of unproven interventions without such distinctions. See the 'Japan's Regulatory System' page for details of the system.

Frequently asked questions

Q. Have iPS cell-based treatments been approved in Japan?
Research using iPS cell-derived cells, such as for Parkinson's disease, is at the clinical trial stage; the approved products in the timeline use somatic cells (mesenchymal stem cells, skeletal myoblasts, cartilage and skin cells), not iPS cells. Whether any iPS cell-derived product has been approved can be checked in public materials from the Ministry of Health, Labour and Welfare and the Pharmaceuticals and Medical Devices Agency (PMDA).

Q. Can a conditionally approved product lose its approval later?
Data confirming efficacy must be submitted within the set period to obtain full approval; if efficacy is not confirmed, the approval is not maintained. That is why conditional approval should be distinguished from standard approval.

Q. Where can information on Japanese regenerative medicine be found?
Laws on e-Gov, system and committee information from the Ministry of Health, Labour and Welfare, research registrations on jRCT, and review documents for approved products from the PMDA.

The above summarises published papers and public-agency materials. University and institute names are given to identify research sources, not to introduce or recommend any medical institution. The suitability of any treatment is decided by the medical team.

Regulation & Other (Crohn's, Pain, etc.) →