The effect of an external magnetic force on cell adhesion and proliferation of magnetically labeled mesenchymal stem cells

BACKGROUND As the strategy for tissue regeneration using mesenchymal stem cells (MSCs) for transplantation, it is necessary that MSCs be accumulated and kept in the target area. To accumulate MSCs effectively, we developed a novel technique for a magnetic targeting system with magnetically labeled MSCs and an external magnetic force. In this study, we examined the effect of an external magnetic force on magnetically labeled MSCs in terms of cell adhesion and proliferation. METHODS Magnetically labeled MSCs were plated at the bottom of an insert under the influence of an external magnetic force for 1 hour. Then the inserts were turned upside down for between 1 and 24 hours, and the number of MSCs which had fallen from the membrane was counted. The gene expression of MSCs affected magnetic force was analyzed with microarray. In the control group, the same procedure was done without the external magnetic force. RESULTS At 1 hour after the inserts were turned upside down, the average number of fallen MSCs in the magnetic group was significantly smaller than that in the control group, indicating enhanced cell adhesion. At 24 hours, the average number of fallen MSCs in the magnetic group was also significantly smaller than that in control group. In the magnetic group, integrin alpha2, alpha6, beta3 BP, intercellular adhesion molecule-2 (ICAM-2), platelet/endothelial cell adhesion molecule-1 (PECAM-1) were upregulated. At 1, 2 and 3 weeks after incubation, there was no statistical significant difference in the numbers of MSCs in the magnetic group and control group. CONCLUSIONS The results indicate that an external magnetic force for 1 hour enhances cell adhesion of MSCs. Moreover, there is no difference in cell proliferation after using an external magnetic force on magnetically labeled MSCs.