Enhanced Expression of N-Formyl Peptide Receptor in Mesenchymal Stem Cells Facilitates Homing to Inflammatory Lungs

Abstract

Marrow-derived mesenchymal stem cells (MSCs) exhibit certain intrinsic tropism to inflammatory tissues. However, effective stem cell therapy often requires high levels of engraftment, which may not be sufficed by the MSC natural homing process. Here we investigated if lentiviral vector-enhanced expression of N-formyl peptide receptor (FPR) in MSCs could increase their sensitivity to N-formylated peptides (N-FP) and facilitates MSC homing to inflammatory lungs. HIV-6 1-based lentiviral vectors, expressing the FPR-EGFP fusion protein (HIV-FPR-EGFP) or co-7 expression of the FPR and EGFP proteins (HIV-FPR-IRES2-EGFP), were engineered. Expression of 8 FPR in 293T cells, a cell line without the endogenous receptor, rendered the cells responsive to N-FP by intracellular calcium mobilization. Human MSCs, transduced with the FPR-IRES2-EGFP vector, showed a greater sensitivity to and an enhanced chemotaxis towards a low level of N-FP. The FPR-11 engineered hMSCs, expressing a luciferase reporter, were infused systemically into nu/nu mice which were pre-intubated intratracheally with or without a sublethal dose of Pseudomonas aeruginosa. In both groups, the MSCs were largely located in the lungs initially and cleared rapidly within days as shown by in vivo whole body bioluminescence imaging. However, MSC retention in the bacterium- challenged lungs a week after infusion was ~2-fold higher than the non-challenged controls. Biochemical measurement of luciferase enzymatic activity demonstrated low but definite homing of the MSCs in the bacteriumchallenged lungs. Engraftment of MSCs to the lungs was immunohistochemically confirmed. These data provide a proof of principle that engineering MSCs with FPR can enhance the stem cell homing to inflammatory tissues for potential repair.