Brain Disorders (Stroke, Parkinson's, Dementia, ALS, MS)

Summary — Brain and nerve disorders are the area of greatest interest in regenerative medicine. In Japan, Sapporo Medical University reported giving stroke patients intravenous mesenchymal stem cells expanded in their own serum (2011), and Kyoto University published phase I/II results of transplanting iPS cell-derived dopamine neurons into patients with Parkinson's disease in 2025. In multiple sclerosis, a randomised study of autologous haematopoietic stem cell transplantation reported less disability progression. Meanwhile, randomised studies in acute stroke and ALS did not meet their primary outcomes.

Conditions in this field

The brain and nerves recover poorly once damaged. This field includes stroke, Parkinson's disease, Alzheimer's dementia, amyotrophic lateral sclerosis (ALS), multiple sclerosis and epilepsy. These conditions differ greatly — whether damage occurs suddenly (stroke), progresses gradually (Parkinson's, dementia, ALS), involves the immune system attacking nerves (multiple sclerosis) or reflects disrupted electrical balance (epilepsy) — so the cells studied and how they are given also differ by disease.

Three approaches for different diseases

• Indirect effects through intravenous administration — in stroke and spinal cord injury, mesenchymal stem cells are given intravenously and researchers study indirect effects: secreted factors reducing inflammation, protecting nerves and supporting network reorganisation.
• Directly replacing lost cells — in diseases where the type of cell lost is clear, such as Parkinson's, neurons made from iPS or ES cells are surgically transplanted into the brain. Early trials transplanting inhibitory neurons have also begun in epilepsy.
• Resetting the immune system — in multiple sclerosis, autologous haematopoietic stem cell transplantation, which suppresses the existing immune system with chemotherapy and rebuilds it from the patient's own blood stem cells, has been studied.

Key research results by condition

• Stroke — the Sapporo Medical University study (2011, 12 patients) reported improved neurological scores and reduced lesion volume on MRI after intravenous mesenchymal stem cells expanded in autologous serum, and a US phase 1/2 study (2019, 36 chronic patients) reported improved functional scales. The randomised phase 2 MASTERS study in acute patients (2017) did not meet its primary outcome.
• Parkinson's disease — Kyoto University confirmed engraftment and function of iPS cell-derived dopamine neurons in a primate model (2017) and, in a phase I/II trial of seven patients, reported dopamine production by grafted cells and improved motor scores in some patients (2025). Phase I results of ES cell-derived cells were published the same year.
• Multiple sclerosis — a randomised study of autologous haematopoietic stem cell transplantation (2019, 110 patients) reported clearly less disability progression than continued drug therapy, and a mesenchymal stem cell phase 2a study (2012) reported improved visual function measures.
• ALS — a randomised phase 3 study of mesenchymal stem cells secreting neurotrophic factors (2022) showed no difference from placebo on its primary outcome, with changes reported in a subgroup and in biomarkers.
• Alzheimer's dementia and epilepsy — at the early clinical research stage; no stem cell treatment has yet shown effects on cognition or seizures in large randomised studies.

Background for understanding research in this field

After stroke or spinal cord injury, spontaneous recovery occurs over months and rehabilitation has a large effect; in progressive diseases, the rate of progression varies greatly. Changes seen in uncontrolled studies are therefore hard to attribute to cell administration, and within the same disease results can change as study design becomes more rigorous. Whether intravenously given cells cross the blood–brain barrier (BBB) to reach the brain directly or act indirectly through secreted factors has also not been established. A review of the clinical use of mesenchymal stromal cells lists mechanism of action and potency measurement as key challenges.

Condition pages

The topics below give details for stroke, Parkinson's disease, Alzheimer's dementia, ALS, multiple sclerosis and epilepsy: overview, standard care, research approaches, reported results and how outcomes are measured.

Frequently asked questions

Q. Are there stem cell products actually approved for brain and nerve disorders?
In Japan, an autologous bone marrow-derived mesenchymal stem cell product for spinal cord injury received conditional, time-limited approval in 2018, and a cell product for chronic motor paralysis after traumatic brain injury received conditional approval in 2024. No mesenchymal stem cell product has yet been approved for the conditions on this page: stroke, Parkinson's disease, dementia, ALS, multiple sclerosis or epilepsy.

Q. How far has iPS cell research in Parkinson's disease come?
Results of Kyoto University's phase I/II clinical trial were published in 2025, confirming engraftment and dopamine production by the transplanted cells. Further stages to confirm efficacy are under way.

Q. How do intravenous injection and brain transplantation differ?
Intravenous injection seeks indirect effects through factors the cells secrete, while brain transplantation directly replaces lost neurons. Their risks and levels of evidence also differ.

Q. Where can research results be checked?
The reference links at the bottom of each page lead to the original papers, and ongoing studies can be found on ClinicalTrials.gov and Japan's jRCT.

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.