Background: Bone marrow mesenchymal stem cells (MSCs) can be used for myocardial repair following myocardial infarction. Increased expression of stromal cell-derived factor-1 (SDF-1) by an ischemic myocardium attracts CXCR4+ stem cells toward it. CXCR4, the receptor for SDF-1, is important in the migration, homing, and survival of hematopoietic stem cells. Although low levels of CXCR4 expression were found in minor subpopulations of cultured MSCs, most MSCs do not express CXCR4. To optimize the migration and survival of human MSCs, we expressed the CXCR4 gene in these cells using retroviral transduction.
Materials and methods: We isolated and cultured MSCs from healthy volunteers and transduced them with a retroviral vector containing either CXCR4 and green fluorescent protein (GFP; CXCR4/GFP vector) or GFP alone (control vector). Flow cytometry confirmed successful transduction and GFP and CXCR4 expression. We used a transwell migration system to study MSC migration to SDF-1. We used Annexin V and propidium iodide stains to assess cell survival before and after the survival challenge.
Results: Flow cytometry showed that, on average, 83.4+/-17.7% of transduced MSCs expressed CXCR4. Compared with control MSCs, MSCs transduced with CXCR4 showed significantly more migration toward SDF-1, threefold greater at 3 h and more than fivefold greater at 6 h. Mesenchymal stem cells transduced with CXCR4 showed no significant difference in survival under normal to serum-deprived growth conditions.
Conclusion: Mesenchymal stem cells can be efficiently transduced to express CXCR4, and transduced MSCs migrate rapidly toward SDF-1. CXCR4 expression does not render survival advantage to MSCs under serum-deprived conditions.