G1CSF DISPLAYS RESTRICTED ABILITY TO PROMOTE ADULT RESIDENT SCA-1+ CARDIAC STEM CELL PROLIFERATION IN VITRO

Aims: Myocardial homing of mobilized bone marrow-derived cells is thought to play a critical role in observed granulocyte colony-stimulating factor (G-CSF)-induced cardiac repair after myocardial infarction; how to harness the potential of cardiac stem cells (CSCs) residing in the heart holds a significant challenge. This study aims to investigate whether G-CSF receptor (G-CSFR) is expressed in adult resident Sca-1+ CSCs, the CSC proliferative and phenotypic changes after G-CSF treatment. Methods and results: The cells were isolated from 12-week-old mouse hearts. Magnetic activated cell sorting (MACS) was employed to acquire highly purified Sca-1+ CSCs. Immunofluorescence staining and Western blotting were performed to examine G-CSFR expression. Cell phenotypic profiles were observed by flow cytometry. Cell proliferation with G-CSF treatment was assessed by carboxyl fluorescein succinimidyl ester (CFSE) proliferation assay and cell cycle analysis. Immunofluorescence staining and Western blotting indicated that G-CSFR was expressed in Sca-1+ CSCs. Exposure of Sca-1+ CSCs to G-CSF existing culture medium for 72 hours induced a cell cycle acceleration with only limited increase in CFSE level and a reduction of CD44 expression that is required for cell-matrix adhesion and cell motility. Conclusions: The results show that G-CSFR is expressed in adult resident Sca-1+ CSCs. G-CSF stimulates CSC proliferation with a restricted ability, which may imply a suggestion to reappraise the clinical settings of G-CSF administration especially for cardiac cell therapy. By means of a combination of G-CSF-pharmacological and CSC-phenotypic investigations, we presume that adult resident Sca-1+ CSCs may play a role during G-CSF-induced cardiac repair.