Diabetes

Summary — Stem cell research in diabetes has mainly targeted type 1 diabetes and followed two directions. One transplants autologous haematopoietic stem cells after immune suppression to stop the immune attack on the pancreas: a Brazilian team (2007) reported that many newly diagnosed patients went without insulin injections for a period. The other makes insulin-producing islet cells from stem cells and transplants them: in 2025, NEJM reported that many participants no longer needed insulin injections after transplantation of stem cell-derived islet cells. In Japan, research on iPS cell-derived islet cells is under way, centred on Kyoto University Hospital.

Types of diabetes

Diabetes is a condition in which blood glucose stays high because insulin, the hormone that lowers it, is lacking or does not work properly. Type 1 diabetes is an autoimmune disease in which the immune system attacks and destroys the insulin-producing beta cells in the pancreatic islets (islets of Langerhans), so almost no insulin is made and lifelong insulin injections or a pump are needed. It usually begins in childhood or adolescence but can start in adults. Type 2 diabetes, which accounts for most diabetes, involves insulin resistance together with declining insulin secretion.

Long-term high blood glucose can cause complications in the eyes (retinopathy), kidneys (nephropathy), nerves (neuropathy), heart and brain blood vessels. In type 1 diabetes, large swings in blood glucose and recurrent hypoglycaemia are also important problems.

Current standard treatment

Insulin is essential in type 1 diabetes, and automated insulin delivery systems linking continuous glucose monitors with insulin pumps now greatly help glucose control. For some patients with frequent severe hypoglycaemia, pancreas or islet transplantation from deceased donors is performed, but donors are scarce and lifelong immunosuppression is required. In type 2 diabetes, lifestyle changes are combined with a range of oral and injectable medicines. Stem cell research aims to overcome the limits of these treatments — above all, to restore the ability to make one's own insulin in type 1 diabetes.

Direction 1: stopping the immune attack with autologous haematopoietic stem cell transplantation

This approach does not create new beta cells; it aims to 'reset' the immune system early in the disease, while some beta cells remain, to protect them. The patient's own blood stem cells are collected and stored, immunosuppressive treatment is given, and the stored stem cells are returned so that the immune system is rebuilt.

A Brazilian team treated patients with newly diagnosed type 1 diabetes in this way and reported in JAMA in 2007 that most went without insulin injections for a period and that levels of C-peptide, a marker of the pancreas's insulin-producing capacity, increased. However, the insulin-free period varied between patients, some later needed insulin again, and there are risks such as infection from immunosuppression, so it is not used as routine treatment.

Direction 2: making and transplanting islet cells from stem cells

Differentiating ES or iPS cells into islet cells for transplantation could solve the shortage of donors and provide enough cells of consistent quality. In 2025, NEJM reported a clinical trial in which fully differentiated islet cells made from stem cells were infused into the portal vein of patients with type 1 diabetes who had experienced severe hypoglycaemia. After transplantation, participants regained the ability to make their own insulin, severe hypoglycaemia disappeared, and many no longer needed insulin injections at one year. This approach requires immunosuppressive medication, and the research is continuing.

In Japan, clinical research transplanting sheets of islet cells made from iPS cells is being carried out, centred on Kyoto University Hospital.

What has been reported about safety

Risks related to immunosuppression are central to both directions. Autologous haematopoietic stem cell transplantation carries a high infection risk from strong immunosuppression, and transplanted stem cell-derived cells require continued immunosuppressive medication to protect them. For cells derived from pluripotent stem cells, the possibility of unwanted cell growth must also be monitored over the long term.

Open questions

Key tasks include protecting transplanted cells without immunosuppression (for example by gene editing or encapsulation) and confirming long-term efficacy and safety. The ISSCR guidelines require rigorous stepwise verification for the clinical use of pluripotent stem cell-derived cells.

How results are measured in diabetes research

The most basic measure in diabetes treatment studies is glycated haemoglobin (HbA1c), which reflects average blood glucose over the past two to three months. Cell therapy studies in type 1 diabetes also use C-peptide levels, which show how much insulin the pancreas makes on its own, daily insulin dose, time without insulin injections (insulin independence) and the number of severe hypoglycaemic episodes causing impaired consciousness.

Continuous glucose monitors are now also widely used to measure the percentage of time blood glucose stays within the target range (usually 70–180 mg/dL). Islet transplantation and stem cell-derived cell transplantation studies often define success as 'HbA1c maintained at target without insulin and no severe hypoglycaemia'. It is important to confirm over the long term how long such results last and whether the benefit outweighs the burden of immunosuppressive medication.

The above summarises results reported in published papers and public-agency materials. University and institute names are given to identify research sources, not to introduce or recommend any medical institution. Reported results do not mean the same effect for everyone, and the suitability of any treatment is decided by the medical team.

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