Study On VEGF Induced Directional Migration Of Neuronal Differentiating MSCs

Central nervous system functional recovery after injury is difficult due to the poor regeneration of neurons at the lesion site. Bone marrow-derived mesenchymal stem cells (BM-MSCs, MSCs), which can be obtained easily and more importantly display a low immunosuppression property, are multipotential. MSCs can differentiate into several types of mesenchymal cells, including osteocytes, chondrocytes, and adipocytes, but can also differentiate into non-mesenchymal cells, such as neural cells, under appropriate experimental conditions. Therefore, they are expected to be used in cell replacement therapy for the treatment of nervous system diseases. Transplantation for healing CNS disease consists of two aspects: MSCs migrating to lesion site; MSCs differentiating to neuron-like cells.In vitro experiment demonstrates that vascular endothelial growth factor can induce MSCs migration, and lesion site release VEGF, which induce MSCs migrating towards injured tissue. VEGF, via downstream signaling molecules, such as extracellular signal-regulated kinase-1/2 (ERK1/2), stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK), p38MAPK, and phosphatidylinositol 3-kinase/Akt (PI3K/Akt), is involved in cell survival, differentiation and migration. In response to external stimuli, activation of these mitogen-activated protein kinases (MAPKs) and PI3K/Akt cascade, in turn, activates intracellular signaling molecules and/or induces crucial alterations in several cytoskeleton-related proteins that are essential for cell migration.Our previous results indicate that the glioma C6 condition medium and SDF-1alpha induced migration cell number of different states MSCs are different. Therefore, we guess the differentiation of MSCs influences their chemotaxis. To further investigate the relationship between the neuronal differentiation of MSCs and their migration behavior, we used Dunn chamber and Boyden chamber to examine the chemotaxis of every state of MSCs during differentiation, and we also detected the responses of PI3K/Akt and MAPKs to VEGF, which relate to MSCs migration.In our experiment, MSCs were isolated by Percoll gradient centrifugation from rat and induced to neuron-like cells. Then, we take advantage of Boyden chamber and Dunn chamber to study the behavior of direct migration from the population level and single cell level respectively. Data from Boyden chamber experiment reveal the migration number of cells differ among the differentiation states and the concentration of VEGF also affect the number of migrating cells. Meanwhile, time-lapse video analysis reveals MSCs at certain stage (24 h pre-induction) possess higher FMI (forward migration index). Results from western blot reveal the time that maximum activation of sigalings appeared are different between states, the extents of signalings phosphorylation in the same time point are different as well, and meanwhile, these phenomena change as the state of MSCs change. In addition, blocking PI3K/Akt and MAPKs impair the ability of direct migration, which is also related to the differentiation states, suggesting these pathways selectively play roles in neuronal differentiating MSCs migration.Our results indicate differentiation of MSCs influences their chemotactic responses to VEGF. These phenomenon, which is similar with the results of our lab on the hepatocyte growth factor (HGF), stem cell factor (SCF), platelet derived growth factor (PDGF) and stromal cell-derived factor-1alpha (SDF-1α) effect of inducing migration of MSCs, indicated the commonness of cell behavior. Although the deeper molecule mechanism is still unclear, our results supply rationale to clinical MSCs transplantion for curing CNS diseases.