Stem cell therapy as a treatment for Ischemic stroke

Abstract

Despite the high prevalence and devastating outcome of ischemic stroke, there remain few options for treatment following stroke onset. The treatments that are currently available remain limited both in the time window following stroke in which they are effective, as well as their success in ameliorating stroke injury in the brain and limiting functional impairment. Current therapies for stroke, such as tissue plasminogen activator (tPA) are only effective up to 4.5 hours following stroke onset. We have tested a human umbilical cord blood-derived stem cell line that has shown both a significant reduction in stroke infarct volume as well as improved functional recovery following stroke in the rat when administered 48 hours following stroke onset. In the present study we have compared high vs. low passage non-hematopoietic umbilical cord blood stem cells (nh-UCBSCs) to determine whether highly expanded nh-UCBSCs are as therapeutically effective as low passaged cells, and their mechanisms of action. Using the middle cerebral arterial occlusion (MCAO) model of stroke in Sprague-Dawley rats, we administered nh-UCBSC by intra-venous administration two days following stroke induction. These human cells were injected into rats without any immune suppression, and no adverse reactions were detected. Both behavioral and histological analyses have shown that the administration of these cells reduces the infarct volume by 50% as well as improve the functional outcome of these rats following stroke for both high and low passaged nh-UCBSC. The brain transcriptome was compared between normal rats, and those with ischemic brain injury, and injury with nh-UCBSC treatment using next generation RNAseq analysis. Differences in the brain transcriptome revealed that ischemic brain injury was associated with significant increases in transcripts related to macrophage, T cell, and microglia function. Flow cytometry analysis of immune cells present in the brains of animals, in each of these three groups, confirmed infiltration of macrophages and T cells consequent to ischemia reduction to normal levels with nh-UCBSC treatment. Flow cytometry also revealed a restoration of normal levels of microglia in the brain following treatment. Overall, these data show a blunting of immune cell migration and activation that are typically activated in the brain following stroke, suggesting that nh-UCBSCs may act by inhibiting immune cell migration into the brain from the periphery, and possibly by inhibition of immune cell activation within the brain. Non-hematopoietic umbilical cord blood stem cells exhibit great potential to provide a novel therapy for stroke with no known ill-effects, and are effective at later time points following stroke than methods that are currently available in the clinic.