Postinfarction Cardiac Remodeling Proceeds Normally in Granulocyte Colony-Stimulating Factor Knockout Mice

Abstract

Treatment with granulocyte colony-stimulating factor (G-CSF) reportedly mitigates postinfarction cardiac remodeling and dysfunction. We herein examined the effects of G-CSF knockout (G-CSF-KO) on the postinfarction remodeling process in the hearts of mice. Unexpectedly, the acute infarct size 24 hours after ligation was similar in the two groups. At the chronic stage (4 weeks later), there was no difference in the left ventricular dimension, left ventricular function, or histological findings, including vascular density, between the two groups. In addition, expression of vascular endothelial growth factor (VEGF) was markedly up-regulated in hearts from G-CSF-KO mice, compared with wild-type mice. Microarray failed in detecting up-regulation of VEGF mRNA, whereas G-CSF administration significantly decreased myocardial VEGF expression in mice, indicating that G-CSF post-transcriptionally down-regulates VEGF expression. When G-CSF-KO mice were treated with an anti-VEGF antibody (bevacizumab), cardiac remodeling was significantly aggravated, with thinning of the infarct wall and reduction of the cellular component, including blood vessels. In the granulation tissue of bevacizumab-treated hearts 4 days after infarction, vascular development was scarce, with reduced cell proliferation and increased apoptosis, which likely contributed to the infarct wall thinning and the resultant increase in wall stress and cardiac remodeling at the chronic stage. In conclusion, overexpression of VEGF may compensate for the G-CSF deficit through preservation of cellular components, including blood vessels, in the postinfarction heart.