Spontaneous and granulocyte–colony-stimulating factor-enhanced marrow response and progenitor cell mobilization in mice after myocardial infarction.

BACKGROUND AIMS: Hematopoietic (HPC), mesenchymal (MPC) and/or endothelial (EPC) progenitor cells are being studied to repair the myocardium after acute or chronic ischemia. We examined marrow response to myocardial infarction (MI) and the ability of granulocyte-colony-stimulating factor (G-CSF) to enhance mobilization of HPC, MPC and EPC in peripheral blood (PB) and bone marrow (BM) of MI mice. METHODS: We induced MI in C57Bl/6 mice, while sham-operated (SO) animals were similarly operated on but without coronary artery ligation. Animals were treated with either saline or G-CSF, from day -5 to day +5 after MI or from day 0 to day +5. Progenitor cell numbers in PB and BM were evaluated by fluorescence-activated cell sorting (FACS) analysis and cell culture. RESULTS: White blood cells (WBC) decreased in BM and increased in PB after MI; G-CSF amplified this effect in BM but not in PB. HPC numbers decreased in BM after MI, while HPC and granulocyte-macrophage colony-forming units (GM-CFU) increased in PB only after G-CSF treatment, and more prominently so in MI than in SO mice. MPC and fibroblast-colony-forming units (F-CFU) as well as EPC were mobilized into the PB after MI and further after G-CSF treatment. Plasma troponin T concentrations decreased after G-CSF treatment. CONCLUSIONS: BM is globally affected by acute MI, but not simple body injury, with intense mobilization of marrow MPC and EPC into the PB but inhibition of HPC. Progenitor cell entry into the PB may be paralleled by depletion of their BM pools. G-CSF is required for HPC mobilization and enhances MPC and EPC entry into the PB.