Brain-derived neurotrophic factor (BDNF) plays an important role in the differentiation, development, and survival of neural stem cells. In this study, we analyzed its effects on the stimulation of human umbilical cord blood-derived mesenchymal stem cells in terms of their potential to differentiate into neuron-like cells, their survival characteristics, and the molecular mechanisms involved. The treatment of cells with neural induction medium (NIM) and BDNF generated more cells that were neuron-like and produced stronger expression of neural-lineage markers than cells treated with NIM and without BDNF. Raf-1 and ERK phosphorylation and p35 expression levels increased significantly in cells treated with both NIM and BDNF. This treatment also effectively blocked cell death following neural induction and increased Akt phosphorylation and Bcl2 expression compared with cells treated with NIM without BDNF. Inhibition of ERKs inhibited the BDNF-stimulated up-regulation of p35 and Bcl2. In addition, the inhibition of PI3K abrogated Akt phosphorylation and Bcl2 expression, but not p35 expression. Thus, MAPK/ERK-dependent p35 up-regulation and MAPK/ERK-dependent and PI3K/Akt-dependent Bcl2 up-regulation contribute to BDNF-stimulated neural differentiation and to the survival of differentiated cells.

Numerous studies have reported that mesenchymal stem cells (MSCs) can ameliorate neurological deficits in ischemic stroke models. Among the various hypotheses that have been suggested to explain the therapeutic mechanism underlying these observations, neurogenesis is thought to be critical. To enhance the therapeutic benefits of human bone marrow-derived MSCs (hBM-MSCs), we efficiently modified hBM-MSCs by introduction of the brain-derived neurotrophic factor (BDNF) gene via adenoviral transduction mediated by cell-permeable peptides and investigated whether BDNF-modified hBM-MSCs (MSCs-BDNF) contributed to functional recovery and endogenous neurogenesis in a rat model of middle cerebral artery occlusion (MCAO). Transplantation of MSCs induced the proliferation of 5-bromo-2′-deoxyuridine (BrdU-) positive cells in the subventricular zone. Transplantation of MSCs-BDNF enhanced the proliferation of endogenous neural stem cells more significantly, while suppressing cell death. Newborn cells differentiated into doublecortin (DCX-) positive neuroblasts and Neuronal Nuclei (NeuN-) positive mature neurons in the subventricular zone and ischemic boundary at higher rates in animals with MSCs-BDNF compared with treatment using solely phosphate buffered saline (PBS) or MSCs. Triphenyltetrazolium chloride staining and behavioral analysis revealed greater functional recovery in animals with MSCs-BDNF compared with the other groups. MSCs-BDNF exhibited effective therapeutic potential by protecting cell from apoptotic death and enhancing endogenous neurogenesis.

IntroductionStem cell transplantation is a promising therapeutic strategy for the treatment of stroke. Mesenchymal stem cells (MSCs) are a potential cell source for clinical application because they can be easily obtained and cultivated with a high proliferative capacity. The safety and efficacy of cell therapy depends on the mode of cell administration. To determine the therapeutic potential of intrathecal administration of MSCs by lumbar puncture (LP), we administrated human umbilical cord blood-derived MSCs (hUCB-MSCs) intrathecally into the lumbar spinal cord or intravenously into the tail vein in a rat model of stroke, and then investigated whether hUCB-MSCs could enter the brain, survive, and improve post-stroke neurological functional recovery.MethodshUCB-MSCs (1.0 × 106) were administrated three days after stroke induced by occlusion of the middle cerebral artery. The presence of hUCB-MSCs and their survival and differentiation in the brain tissue of the rats was examined by immunohistochemistry. Recovery of coordination of movement after administration of hUCB-MSCs was examined using a Rotarod test and adhesive-removal test on the 7th, 14th, 21st, and 28th days after ischemia. The volume of ischemic lesions seven days after the experimental procedure was evaluated using 2-3-5-triphenyltetrazolium (TTC) staining.ResultsRats receiving hUCB-MSCs intrathecally by LP had a significantly higher number of migrated cells within the ischemic area when compared with animals receiving cells intravenously. In addition, many of the cells administered intrathecally survived and a subset of them expressed mature neural-lineage markers, including the mature neuron marker NeuN and glial fibrillary acidic protein, typical of astrocytes. Animals that received hUCB-MSCs had significantly improved motor function and reduced ischemic damage when compared with untreated control animals. Regardless of the administration route, the group treated with 1 × 106 hUCB-MSCs showed better neurological recovery, without significant differences between the two treatment groups. Importantly, intrathecal administration of 5 × 105 hUCB-MSCs significantly reduced ischemic damage, but not in the intravenously treated group. Furthermore, the cells administered intrathecally survived and migrated into the ischemic area more extensively, and differentiated significantly into neurons and astrocytes.ConclusionsTogether, these results indicate that intrathecal administration of MSCs by LP may be useful and feasible for MSCs treatment of brain injuries, such as stroke, or neurodegenerative disorders.

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