Granulocyte-colony stimulating factor enhanced the recruitment of bone marrow cells into the heart: time course evaluation of phenotypic differentiation in the doxorubicin-induced cardiomyopathic model.

Objective: We traced and evaluated bone marrow-derived cells after granulocyte-colony stimulating factor (G-CSF) treatment in the doxorubicin-induced cardiomyopathic heart in the time course. Methods: C57BL/6 male mice received doxorubicin (15 mg/kg, i.p.). At 1 week after administration of doxorubicin, the mice were irradiated (900 cGy) followed by transplantation of bone marrow cells (BMT) derived from transgenic mice expressing green fluorescent protein (GFP) (1×106) via a tail vein (BMT). G-group (n=22) received G-CSF (50 µg/kg/day×8 days, s.c.) after BMT, while C-group (n=17) received saline. At 4 and 7 weeks after BMT, heart sections were fixed to evaluate bone marrow-derived GFP cells (BMD-GFP) with immunostaining for Troponin I (TnI), atrial-natriuretic peptide (ANP), connexin 43, von Willebrand factor, and Ki67. Result: There were migrated BMD-GFP in the whole heart of all animals. In the time course, migrated BMD-GFP increased in G-group. At 7 weeks the number of migrated BMD-GFP in G-group (56.2±15.6/HPF) was larger than that in C-group (18.9±10.7/HPF) (p<0.05). TnI- and connexin 43-positive BMD-GFP were spindle-shaped. Von Willebrand factor-positive BMD-GFP showed thinner-shape. ANP- and Ki67-positive BMD-GFP showed oval-shape. The numbers of these positive cells derived from BMD-GFP, not different between the 2 groups, did not change from 4 to 7 weeks. Conclusion: The migration of BMD-GFP into the heart increased from 4 to 7 weeks after BMT by G-CSF. However, cardiomyocytes and endothelial cells originating from BMD-GFP were very few and neither increased nor changed in their shapes and numbers in the short term.