Bilateral cortical hyperactivity detected by fMRI associates with improved motor function following intravenous infusion of mesenchymal stem cells in a rat stroke model.

Intravenous transplantation of mesenchymal stem cells (MSCs) derived from bone marrow ameliorates functional deficits in rat cerebral infarction models. In this study, MSCs were intravenously administered 6h after right middle cerebral artery occlusion (MCAO) induction in rat. Functional MRI (fMRI) during electrical stimulation of the left forepaw and behavioral testing (treadmill stress test) were carried out at day 1, 4, 7, 14, 21, 28 and 42 following MCAO. In medium infused group (n=20) electrical stimulation of the left forepaw elicited a unilateral (right cortex) activated signal detected by fMRI in the infarcted somatosensory cortex. In the MSC infused animals two fMRI patterns were observed: unilateral (n=17) and bilateral (n=19) activation of sensorimotor cortex. In the MSC group both unilateral and bilateral cortical activated animals displayed significantly improved motor function compared to the medium infused group. However, the bilateral activated pattern in the MSC group showed the greatest functional recovery. Lesion volume as calculated from high intensity signals using T2WI was less in the MSC groups as compared to the medium group, but the lesion volume for the unilateral and bilateral signals in the MSC group was the same. These results suggest that the presence of a bilateral signal in sensorimotor cortex as detected by fMRI was more predictive of improved functional outcome than lesion volume alone.