Tokyo, August 29, 2025 – The Ministry of Health, Labour and Welfare announced the cause of a fatal accident that occurred during stem cell administration.
According to the investigation, the incident was triggered by clusters of dead or damaged cells obstructing the pulmonary capillaries, which resulted in a pulmonary embolism.
The clinic where the accident occurred had outsourced its stem cell culture to an external laboratory. That laboratory froze the cultured cells and delivered them at a later date. Because freezing and thawing can damage cells, it is common practice to add a cryoprotectant (DMSO) before freezing. Before administration, clinics are required to remove the DMSO through centrifugation or other appropriate methods. However, insufficient removal of DMSO, or repeated cycles of freezing and thawing, are suspected to have contributed to the accident.
At our clinic, stem cells are cultured exclusively at our own in-house cell-processing facility and administered on the same day, without any freezing. As a result, the use of cryoprotectants such as DMSO is not required, and none are added at any stage.
We therefore confirm that the circumstances identified as the cause of the recent accident cannot occur at our clinic, and the safety of stem cell administration at our facility remains extremely high.
