Abstract WP104: Chemical Preconditioning Enhances the Effectiveness of Stem Cell Therapy in Ischemic Stroke

Abstract

Introduction: Transplantation of neural stem cells (NSCs) provides a promising therapy for stroke. Its efficacy, however, might be limited because of massive grafted-cell death following transplantation, as well as insufficient capability for tissue repair. Chemical preconditioning primes the cells to the ‘‘state of readiness’’ to withstand the rigors of lethal ischemia. In this study, we investigated whether cellular reprogramming of NSCs with minocycline or interleukin-6 (IL-6), both of which are known to possess cytoprotective properties, facilitates the effectiveness of stem cell therapy in ischemic stroke. Methods: NSCs harvested from the subventricular zone of fetal mice were preconditioned with minocycline (10 μM) or IL-6 (20 ng/ml) for 24 hours in vitro . For an in vitro study, the NSCs were subjected to oxygen-glucose deprivation and reoxygenation (n=4). For an in vivo study, the NSCs were transplanted into mouse brains 6 hours or 7 days after transient middle cerebral artery occlusion (n=8). Histological and behavioral tests were examined from days 0 to 28 after stroke. Results: Minocycline preconditioning up-regulated the expression of Nrf2 (2.7-fold), as well as Nrf2-regulated antioxidant genes (HO-1: 4.0-fold/NQO1: 20-fold), and induced the NSCs to release paracrine factors, including BDNF, NGF, GDNF, and VEGF. IL-6 preconditioning activated STAT3-mediated up-regulation of SOD2 (2.3-fold), a primary mitochondrial antioxidant enzyme, and induced VEGF secretion (2.2-fold). Transplantation of minocycline- or IL-6-preconditioned NSCs significantly reduced grafted cell death, attenuated infarct size, and improved neurological performance compared with non-preconditioned NSCs. This minocycline- or IL-6-induced amelioration of ischemic insults was abolished by transfecting the NSCs with Nrf2- or STAT3-small interfering RNA before transplantation. Conclusions: Chemical preconditioning, which reprograms NSCs to tolerate oxidative stress after ischemic reperfusion injury and to induce trophic effects, is a simple and beneficial approach for enhancing the effectiveness of cell transplantation therapy in ischemic stroke.