Elevated brain derived neurotrophic factor levels in plasma reflect in vivo functional viability of infused mesenchymal stem cells for stroke in rats

Background Intravenous infusion of mesenchymal stem cells (MSCs) derived from adult bone marrow elicits functional recovery in rat stroke models and clinical studies in patients are ongoing. Brain derived neurotrophic factor (BDNF) is a neurotrophic factor produced by MSCs and may contribute to their therapeutic efficacy. The purpose of the current study was to determine if BDNF is elevated in infarcted brain and in which compartment of blood (plasma or serum) after intravenous MSC infusion in a middle cerebral artery occlusion (MCAO) model in the rat. Methods In rats, a permanent middle cerebral artery occlusion (MCAO) was induced by intraluminal vascular occlusion with a microfilament and MSCs were intravenously administered 6 h after right MCAO induction. Enzyme-linked immunosorbent assay (ELISA) analysis of brain, serum and plasma BDNF were performed after the MSC infusion following the MCAO induction. Lesion volume was assessed using magnetic resonance imaging. Functional outcome was assessed using the Limb Placement Test. Results Infused MSCs reduced lesion volume and elicited functional improvement compared to the vehicle infused group. ELISA analysis of the MSC treated group revealed an increase BDNF levels in the infarcted hemisphere of the brain and plasma, but not in serum. The MSC group showed a greater increase in BDNF levels than sham control. In the MSC group, the expression of increased plasma BDNF levels correlated with increased brain BDNF levels. Conclusions These results support the hypothesis that BDNF levels in plasma, but not serum, may be more appropriate to detect circulating BDNF in vivo following MSC infusion in a cerebral infarction rat model of ischemic stroke. Further, plasma BDNF might reflect in vivo functional viability of infused MSCs after stroke.