Role of Homing Regulation in Coculturing Human Cord blood–derived Mesenchymal Stem cells with CD34-Positive Cells from Umbilical Cord Blood

Background and Objectives Mesenchymal stem cells plays an important role in the hematopoietic stem cell engraftment condition with SDF-1 (CXCL12)-CXCR4 signaling and in their homing in various tissues. In this study, we evaluated that the regulation of homing efficiency for mesenchymal stem cells to support ex vivo expansion of hematopoietic stem cells from umbilical cord blood.

Methods We investigated the expression of CXCR4 and Stromal-Derived Factor-1 (SDF-1) in cocultured mesenchymal stem cell with umbilical cord blood-derived CD34-positive cell, which stimulated with granulocyte macrophage-colony stimulating factor (GM-CSF) and stem cell factor (SCF) cytokine.

Results In this study, we evaluated that coculturing of SDF-1⁺ mesenchymal stem cells with stimulated CD34⁺ cells significantly increased the expression of CD34, CD45, and CD19 for myeloid surface marker and intracellular CXCR4 within a few hours as compared with culturing of CD34-positive cells alone or with SDF-1⁻ mesenchymal stem cells or untreated mesenchymal stem cells by Flow cytometre. In the result of stimulation for 48 hours with various cytokines in CD34-positive cells, CXCR4 gene and ERK-1,2 protein up-regulated, and increased in vitro migration capacity of cocultured SDF-1⁺ mesenchymal stem cell with CD34⁺ cells as examined by quantitative RT-PCR of human GAPDH. To enhance homing effect by mesenchymal stem cell, we maintained expanded mesenchymal stem cells for up to 5–10 passages with monitoring of the expression of various tissue surface antigens, such as skeletal muscle, neural, liver, and endothelial cells. SDF-1⁺ mesenchymal stem cells induced the homing of cellular products of stimulated cord blood-derived CD34-positive cells for 10 days. Moreover, the tranfected SDF-1⁺ cells with a green fluorescent protein gene using lentivirus maintained their capacities of protein release and homing in culture system. SDF-1⁻ mesenchymal stem cells reduced CXCR4 expression in cocultured CD34-positive cells.

Conclusions: These results demonstrate that the role of the SDF-1/CXCR4 axis is an important rold in the regulation of homing and engraftment of mesenchymal and hematopoietic stem cells. SDF-1⁺ mesenchymal stem cells have clinical potential to regulate homing and short-term engraftment for hematopoietic stem cell transplantation.