Brain repair by hematopoietic growth factors in a rat model of stroke

Background and Purpose - Stem cell factor ( SCF) and granulocyte-colony stimulating factor ( G-CSF) are essential growth factors in hematopoiesis. We determined whether receptors for SCF and G-CSF exist in the brain and whether exogenous SCF and G-CSF are beneficial to brain repair after brain ischemia. Methods - A well-established rat model of experimental stroke was used in this study. SCF, G-CSF, SCF + G-CSF, or saline was subcutaneously administered 3 hours to 7 days after brain ischemia. Bromodeoxyuridine was administered simultaneously. Sensorimotor function was evaluated with a limb placement test and foot fault test over time. Results - We observed that receptors for SCF and G-CSF were expressed in both neurogenic regions and neurons. SCF-treated rats showed the best functional restoration at 1 week that was maintained 4, 7, and 10 weeks after the final injection. G-CSF-induced functional recovery was limited and unstable. Interestingly, stable but delayed functional improvement was seen in SCF + G-CSF-treated rats. Infarction size was significantly reduced in all growth factor-treated rats. In addition, SCF and SCF + G-CSF enhanced neural progenitor cell proliferation in the subventricular zone bilaterally, whereas G-CSF and SCF + G-CSF treatment increased bromodeoxyuridine -positive cells in periinfarct areas. Conclusions - SCF and G-CSF are neuroprotective and beneficial to functional restoration when administered during the acute phase after brain ischemia, indicating hematopoietic growth factors play a role in brain repair.