Regulation of CXCR4 expression in human mesenchymal stem cells by cytokine treatment: role in homing efficiency in NOD/SCID mice

TLDR

Mesenchymal stem cell therapy depends on their ability to home to target tissues, yet homing to bone marrow after transplantation is inefficient. The study aimed to determine whether the SDF‑1/CXCR4 signaling axis regulates homing of human fetal bone marrow–derived Flk1⁺ MSC. Researchers stimulated Flk1⁺ MSC with a cytokine cocktail to induce CXCR4 expression and then assessed their migration toward SDF‑1 in vitro and homing to bone marrow 24 h after intravenous injection into sublethally irradiated NOD/SCID mice. Cytokine treatment rapidly increased surface and intracellular CXCR4, enhancing SDF‑1–driven migration and bone‑marrow homing, which in turn accelerated hematologic recovery and donor chimerism; CXCR4 blockade markedly reduced engraftment, indicating that up‑regulating CXCR4 could improve MSC engraftment and hematopoietic recovery.

Abstract

Background and Objectives The use of mesenchymal stem cells (MSC) for cell therapy relies on the capacity of these cells to home and engraft long-term into the appropriate target tissue(s). Homing of MSC to bone marrow (BM) post-transplantation can occur, but does so with only poor efficiency. This study was designed to evaluate the role of the SDF-1/CXCR4 axis in the homing of Flk1+ MSC derived from human fetal BM.Design and Methods We investigated the expression of CXCR4 in Flk1+ MSC stimulated with a cytokine cocktail and explored their homing ability 24 hours after intravenous infusion into sublethally irradiated NOD/SCID mice. The peripheral blood was analyzed and human cells in recipients' BM were quantified from 2 to 6 months after transplantation.Results We found that Flk1+ MSC harbored intracellular CXCR4 which can be rapidly induced to the cell surface within a few hours. Short-term (24 hours) stimulation with the cocktail of cytokines resulted in up-regulation of both cell surface and intracellular CXCR4, increasing in vitro migration capacity to SDF-1 and homing to the BM of irradiated NOD/SCID mice. Moreover, compared to non-treated cells, transplantation of cytokine-treated Flk1+ MSC resulted in faster hematologic recovery and higher levels of donor chimerism in BM. Neutralization of CXCR4 significantly reduced homing and engraftment of Flk1+ MSC in murine BM.Interpretation and Conclusions These results suggest that the SDF-1/CXCR4 axis plays an important role in the regulation of motility of Flk1+ MSC. Increasing CXCR4 expression might be a potential strategy to improve engraftment of MSC in BM and accelerate the recovery of hematopoiesis.