Stem cell therapies are administered during the acute phase of stroke to preserve the penumbral tissues from ischemic injury. However, the effect of repeated cell therapy during the acute phase remains unclear. In this study, we investigated and compared the functional outcome of single (two days post-injury) and repeated (two and nine days post-injury) treatment with human umbilical cord derived mesenchymal stem cells (hUCB-MSCs) after middle cerebral artery occlusion (MCAO). The rotarod and limb placement tests were utilized to investigate functional outcomes, while infarct volume and tissue damage were measured by immunofluorescent staining for neovascularization, neurogenesis, apoptosis, and inflammation in the penumbral zones. We observed notable motor dysfunction and a significant decrease in infarcted brain volume, as well as increases in neurons and vessels in both single and repeated hUCB-MSC treatments compared to the control group. Interestingly, repeated administration of hUCB-MSCs was not found to elicit additional or synergistic improvements over monotherapy. This study suggests that a clearer understanding of the therapeutic window after stroke will facilitate the development of more efficient treatment protocols in the clinical application of stem cell therapy.

Keywords: Human umbilical cord blood mesenchymal stem cell, Ischemia, repeat therapy, Angiogenesis, Neurogenesis