G-CSF, rt-PA and combination therapy after experimental thromboembolic stroke

Abstract

Background: Granulocyte Colony-Stimulating Factor (G-CSF) has remarkable neuroprotective properties. Due to its proven safety profile, G-CSF is currently used in clinical stroke trials. As neuroprotectants are considered to be more effective in the early phase of cerebral ischemia and during reperfusion, G-CSF should to be tested in combination with thrombolysis. Therefore, combination therapy was investigated in an experimental model of thromboembolic stroke.

Methods: Male Wistar rats (n = 72) were subjected to a model of thromboembolic occlusion (TE) of the middle cerebral artery. Different groups (n = 12 each) treated by recombinant tissue-plasminogen activator (rt-PA) or/and G-CSF: group control (control), group early G-CSF (G-CSF 60 min after TE), group rt-PA (rt-PA 60 min after TE), group com (combination rt-PA/G-CSF), group delayed rt-PA (rt-PA after 180 min), group deco (G-CSF after 60 min, rt-PA after 180 min). Animals were investigated by magnetic resonance imaging (MRI) and silver infarct staining (SIS) 24 hours after TE.

Results: Early G-CSF or rt-PA reduced the infarct size compared to all groups (p < 0.05 to p < 0.01) with the exception of group com, (p = n.s.) as measured by T2, DWI, and SIS. Late administration of rt-PA lead to high mortality and larger infarcts compared to all other groups (p < 0.05 to p < 0.01). Pre-treatment by G-CSF (deco) reduced infarct site compared to delayed rt-PA treatment (p < 0.05). G-CSF did not significantly influence PWI when combined with rt-PA. All animals treated by rt-PA showed improved parameters in PWI indicating reperfusion.

Conclusions: G-CSF was neuroprotective when given early after TE. Early combination with rt-PA showed no additional benefit compared to rt-PA or G-CSF alone, but did not lead to side effects. Pretreatment by G-CSF was able to reduce deleterious effects of late rt-PA treatment.

Figure 1

Infarct volume in SIS. Cerebral infarct is shown as calculated from SIS after 24 hours. Infarct size is larger in the control group (control) compared to early G-CSF (G-CSF), early rt-PA (rt-PA), and early combination (com) as indicated by the asterisks (p < 0.05).

Figure 2

Infarct volume in SIS after delayed rt-PA treatment. Cerebral infarct is shown as calculated from SIS after 24 hours. Infarct size is larger in the delayed rt-PA group (delayed rt-PA) compared to the control group (control), and delayed combination (deco) as indicated by the asterisks (p < 0.05).

Figure 3

Lesion volume in MRI. Lesion volume is shown as calculated from DWI and expressed as means ± SD. The lesion volume in the control group was larger compared to early rt-PA (rt-PA) and early combination group (com) after 2.5 hours, and larger than the early rt-PA, early G-CSF (G-CSF) and early combination group after 4 and 24 hours as shown by the single asterisks. Delayed rt-PA treatment (delayed rt-PA) resulted in larger lesion volume than the early rt-PA, early G-CSF and early combination group after 2.5 hours, and additionally larger than the control group after 4 hours. It was larger than all others after 24 hours as shown by the string sign. The late combination group (deco) showed larger infarcts than the early combination after 2.5 hours. After 4 hours, lesion volume was larger than all others with exception of delayed rt-PA. After 24 hours, there was a difference compared to the early rt-PA and early combination as indicated by the double asterisks. Levels of significance are given in table 2.