An extended window of opportunity for G-CSF treatment in cerebral ischemia

Abstract

Background: Granulocyte-colony stimulating factor (G-CSF) is known as a powerful regulator of white blood cell proliferation and differentiation in mammals. We, and others, have shown that G-CSF is effective in treating cerebral ischemia in rodents, both relating to infarct size as well as functional recovery. G-CSF and its receptor are expressed by neurons, and G-CSF regulates apoptosis and neurogenesis, providing a rational basis for its beneficial short- and long-term actions in ischemia. In addition, G-CSF may contribute to re-endothelialisation and arteriogenesis in the vasculature of the ischemic penumbra. In addition to these trophic effects, G-CSF is a potent neuroprotective factor reliably reducing infarct size in different stroke models.

Results: Here, we have further delayed treatment and studied effects of G-CSF on infarct volume in the middle cerebral artery occlusion (MCAO) model and functional outcome in the cortical photothrombotic model. In the MCAO model, we applied a single dose of 60 microg/kg bodyweight G-CSF in rats 4 h after onset of ischemia. Infarct volume was determined 24 h after onset of ischemia. In the rat photothrombotic model, we applied 10 microg/kg bodyweight G-CSF daily for a period of 10 days starting either 24 or 72 h after induction of ischemia. G-CSF both decreased acute infarct volume in the MCAO model, and improved recovery in the photothrombotic model at delayed timepoints.

Conclusion: These data further strengthen G-CSF's profile as a unique candidate stroke drug, and provide an experimental basis for application of G-CSF in the post-stroke recovery phase.

Figure 1

G-CSF reduces cortical and subcortical infarct volume in the rat MCAO model when applied 4 h after onset of ischemia. A. Shown are infarct volumes for the total infarct, cortical and subcortical areas. Infarct volumes were determined 24 h after onset of ischemia by TTC-staining and planimetry. B. Infarct volumes after edema correction. Edema-corrected infarct volumes were obtained by deducting the non-infarcted ipsilateral hemisphere volume from the contralateral hemisphere volume. Volumes are given in mm³ as means ± SEM.

Figure 2

G-CSF improves functional outcome when given as late as 72 h after photothrombotic ischemia. A. Design of the cortical photothrombotic experiment. B. Rotarod performance over the course of 6 weeks after ischemia. Rats received 10 μg/kg bodyweight/day G-CSF for 10 days starting either at 24 or 72 h after ischemia. The effect is also detectable by an analysis of individual areas-under-the-curve (AUC). (*,#: p < 0.05 by ANOVA and Student-Newman-Keuls post-hoc test for 24 h (#) and 72 h (*) treatment). C. Linear regression analysis of vehicle treatment and G-CSF treatment initiated at 72 h demonstrates that slopes are significantly different by a factor of 2 (p = 0.004)