Discrepancy between preclinical and clinical trials. (A) MRI findings in a rat stroke model: T2-weighted MRI at 14 days after transient (90 minutes) middle cerebral artery (MCA) occlusion shows large cortical and subcortical infarcts sparing the subventricular zone (square). (B,C) Stimulated neurogenesis after application of human mesenchymal stem cells (hMSCs) in a stroke rat model: bromodeoxyuridine (BrdU) immunostaining in the subventricular zone of the ipsilateral hemisphere at day 14 showed enhancement of neurogenesis in the treated group (stroke rat that received intravenous hMSCs) (C) compared to placebo-treated stroke rat (B) (modified from Li et al. ). The arrow indicates BrdU-positive cells. Bars = 20 μm. Example of autologous hMSCs administered to a patient with stroke (D,E). (D) Diffusion-weighted image demonstrates massive infarction involving most subventricular area (arrowhead). (E) Magnetic resonance angiography reveals persistent occlusion at the time of intravenous administration of autologous MSCs.