A New Window for Stroke Recovery
An ischemic stroke occurs when blood flow to part of the brain becomes blocked, potentially affecting movement, strength, speech, and independence. While treatments during the earliest stage of stroke have advanced, researchers are also looking for ways to better support recovery in the weeks and months that follow.
A 2026 Phase I clinical trial explored whether human umbilical cord-derived mesenchymal stem cells (UC-MSCs) could be safely given intravenously to people recovering from ischemic stroke.
The study focused on patients in the subacute stage, meaning several months had passed since their stroke. This period is particularly interesting to researchers because there may still be opportunities to support neurological recovery.
Inside the MERIT Trial
The study included 18 adults with ischemic stroke, with an average age of about 52 years. Participants received a single intravenous infusion of UC-MSCs approximately 12 to 24 weeks after their stroke.
Researchers tested three different doses:
- 50 million UC-MSCs
- 100 million UC-MSCs
- 200 million UC-MSCs
Six patients were included in each dose group, and participants were followed for 24 weeks after treatment.
Because this was a Phase I trial, the primary goal was to evaluate safety and tolerability. Researchers also followed changes in neurological function, independence, movement, brain imaging, and immune activity.
Encouraging Safety and Functional Findings
The safety results were an important positive finding. Researchers reported no serious adverse events or dose-limiting toxicities following UC-MSC administration. The adverse events that did occur were classified as mild or moderate, and most were considered unrelated or unlikely to be related to the stem cell treatment.
Several encouraging functional changes were also observed during follow-up.
- weeks after treatment:
- 14 of 18 patients improved by one to two points on a scale measuring overall disability and independence.
- Neurological scores also showed improvement in many participants.
At 24 weeks, 13 of the 16 patients who completed the assessment continued to show improvements in overall disability scores compared with the beginning of the study.
Researchers also reported decreases in National Institutes of Health Stroke Scale (NIHSS) scores. Lower NIHSS scores generally represent fewer neurological difficulties, and reductions of one to five points were observed in 14 patients during follow-up.
Why Umbilical Cord MSCs?
UC-MSCs have attracted growing attention because of the biological signals they release and their ability to interact with the surrounding tissue environment.
Rather than simply replacing damaged brain cells, researchers believe MSCs may work largely through their ability to influence processes involved in:
- Immune and inflammatory activity
- Protection of existing nerve cells
- Blood vessel support
- Communication between cells involved in recovery
The study also examined immune changes after treatment, providing researchers with additional information about how UC-MSCs may interact with the body following a stroke.
Another advantage explored in this trial was the use of an intravenous infusion, which provides a relatively simple and minimally invasive way to administer the cells.
An Important Step Forward
This trial provides encouraging early human evidence for intravenous UC-MSC therapy during the recovery period following ischemic stroke.
Across three different doses, treatment was generally well tolerated, no serious adverse events occurred, and many participants experienced improvements in neurological and functional measurements during the six-month follow-up.
Because this was a small Phase I trial without a placebo comparison group, the study was not designed to prove that UC-MSCs caused the improvements observed. Larger randomized clinical trials will be needed to better determine effectiveness and identify the most appropriate treatment strategies. Still, the findings provide a positive foundation for continued research and demonstrate that intravenous umbilical cord-derived MSCs can be studied safely across multiple dose levels in people recovering from ischemic stroke.
As regenerative medicine continues to advance, research like the MERIT trial may help researchers better understand how UC-MSCs could one day contribute to supporting neurological recovery.
Source
Cui L, Xiao M, Zhang Q, et al. Intravenous human umbilical cord-derived mesenchymal stem cell transplantation for ischemic stroke (MERIT): A phase 1 trial. Cell Reports Medicine. 2026;7(6):102836. doi: 10.1016/j.xcrm.2026.102836. PMID: 42208543; PMCID: PMC13293954. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC13293954/
Related Treatment Pages