Intravenous transplantation of multi-lineage differentiating stress enduring cell promotes functional recovery after traumatic brain injury in mice.

Multilineage-differentiating stress-enduring (Muse) cells are a unique subset of endogenous stem cells that are non-tumorigenic and possess pluripotent-like traits with macrophage-like functions. These cells are naturally present in bone marrow, peripheral blood, connective tissues of various organs, and the umbilical cord. Muse cells are defined by their expression of stage-specific embryonic antigen-3 (SSEA-3) and their high tolerance to cellular stress such as ischemia, oxidative injury, and inflammation. This study aimed to explore the therapeutic effects of intravenous administration of Muse cells on functional recovery after traumatic brain injury (TBI). Mouse TBI model was produced by applying a 3.5-mm-diameter copper cylinder cooled with liquid nitrogen to the right parietal bone. At 7 days after TBI, the animals randomly received an injection of either 6.0×104 human Muse cells (Muse group), 6.0×104 human mesenchymal stromal cells (low-dose MSC group), 1.6×106 human MSCs (high-dose MSC group), or PBS (vehicle group) through the tail vein (n=10 in each group). Motor function was assessed using a rotarod and cylinder test for 84 days after TBI. Subsequently, histological analysis was performed to explore the engraftment and phenotypic fate of Muse cells in the brain. Functional recovery was significantly enhanced on both rotarod and cylinder tests at 28 days and 42 days after TBI in Muse group, respectively, but not in vehicle group and low-dose MSCs group. Only limited effect was observed on cylinder test at 84 days after TBI in high-dose MSCs. Human mitochondria-positive cells were densely engrafted in the peri-TBI area in Muse group, but their number was very few in low- and high-dose MSC groups. About 60% and 20% of Muse cells were positive for NeuN and GSTpi, respectively. The findings strongly suggest that intravenously administered Muse cells aggressively migrate towards the injured brain, express specific markers for neurons and oligodendrocytes, and enhance the recovery of motor function in mice TBI model.