[Controlling Cell Dynamics by Cell-surface Modification]

Although the concept of a drug delivery system (DDS) is usually applied to conventional drug therapy, it is also important for cell-based therapy. The surface manipulation of living cells represents a powerful tool for controlling cell behaviors in the body, such as enhancement of cell-cell interactions, targeted delivery of cells, and protection from immunological rejection. Functional groups, including amines, thiols, and carbonyls, offer excellent opportunities for chemical modification through the formation of covalent bonds with exogenous molecules. Non-natural reactive groups introduced by metabolic labeling were recently utilized for targeted chemical modification. On the other hand, noncovalent strategies are also available; two major examples are electrostatic interaction with a negative charge on the cell surface and hydrophobic insertion or interaction with the cell membrane. In this study, we analyzed factors affecting cell surface modifications using PEG-lipid and succeeded in enhancing the efficacy of modification by cyclodextrin. Then, mesenchymal stem cells (MSCs), whose therapeutic effect has been demonstrated at the clinical stage and which have been clinically used as a drug, were decorated with PEG-lipid conjugates having a targeted ligand such as peptide or scFv, which are recognized by ICAM1. The peptide or scFv decoration enhanced the cell adhesion of MSCs on cytokine treated-endothelial cells. This technique will prompt the targeted delivery of MSCs to intended therapy sites, and underscores the promise of cell surface engineering as a tool for improving cell-based therapy.