Erratum: Granulocyte Colony-Stimulating Factor Improves Cerebrovascular Reserve Capacity by Enhancing Collateral Growth in the Circle of Willis

<i>Background and Purpose:</i> Restoration of cerebrovascular reserve capacity (CVRC) depends on the recruitment and positive outward remodeling of preexistent collaterals (arteriogenesis). With this study, we provide functional evidence that granulocyte colony-stimulating factor (G-CSF) augments therapeutic arteriogenesis in two animal models of cerebral hypoperfusion. We identified an effective dosing regimen that improved CVRC and stimulated collateral growth, thereby improving the outcome after experimentally induced stroke. <i>Methods:</i> We used two established animal models of (a) cerebral hypoperfusion (mouse, common carotid artery ligation) and (b) cerebral arteriogenesis (rat, 3-vessel occlusion). Following therapeutic dose determination, both models received either G-CSF, 40 µg/kg every other day, or vehicle for 1 week. Collateral vessel diameters were measured following latex angiography. Cerebrovascular reserve capacities were assessed after acetazolamide stimulation. Mice with left common carotid artery occlusion (CCAO) were additionally subjected to middle cerebral artery occlusion, and stroke volumes were assessed after triphenyltetrazolium chloride staining. Given the vital role of monocytes in arteriogenesis, we assessed (a) the influence of G-CSF on monocyte migration in vitro and (b) monocyte counts in the adventitial tissues of the growing collaterals in vivo. <i>Results:</i> CVRC was impaired in both animal models 1 week after induction of hypoperfusion. While G-CSF, 40 µg/kg every other day, significantly augmented cerebral arteriogenesis in the rat model, 50 or 150 µg/kg every day did not show any noticeable therapeutic impact. G-CSF restored CVRC in mice (5 ± 2 to 12 ± 6%) and rats (3 ± 4 to 19 ± 12%). Vessel diameters changed accordingly: in rats, the diameters of posterior cerebral arteries (ipsilateral: 209 ± 7–271 ± 57 µm; contralateral: 208 ± 11–252 ± 28 µm) and in mice the diameter of anterior cerebral arteries (185 ± 15–222 ± 12 µm) significantly increased in the G-CSF groups compared to controls. Stroke volume in mice (10 ± 2%) was diminished following CCAO (7 ± 4%) and G-CSF treatment (4 ± 2%). G-CSF significantly increased monocyte migration in vitro and perivascular monocyte numbers in vivo. <i>Conclusion:</i> G-CSF augments cerebral collateral artery growth, increases CVRC and protects from experimentally induced ischemic stroke. When comparing three different dosing regimens, a relatively low dosage of G-CSF was most effective, indicating that the common side effects of this cytokine might be significantly reduced or possibly even avoided in this indication.

<i>背景与目的：</i>脑血管储备能力（cerebrovascular reserve capacity, CVRC）的恢复依赖于已存在侧支血管的募集与正向外向重塑（动脉生成，arteriogenesis）。本研究提供了功能学证据，证明粒细胞集落刺激因子（granulocyte colony-stimulating factor, G-CSF）可在两种脑低灌注（cerebral hypoperfusion）动物模型中增强治疗性动脉生成。我们确定了可改善CVRC并刺激侧支血管生长的有效给药方案，进而改善实验性脑卒中的预后。
<i>方法：</i>我们采用两种已成熟的动物模型：（a）脑低灌注模型（小鼠，颈总动脉结扎术，common carotid artery ligation）；（b）脑动脉生成（cerebral arteriogenesis）模型（大鼠，三血管闭塞模型，3-vessel occlusion）。在确定治疗剂量后，两种模型分别接受隔日一次40 µg/kg的G-CSF或赋形剂处理，持续1周。通过乳胶血管造影术（latex angiography）测量侧支血管直径。在乙酰唑胺（acetazolamide）激发后评估脑血管储备能力。对接受左侧颈总动脉闭塞（common carotid artery occlusion, CCAO）的小鼠额外施加大脑中动脉闭塞（middle cerebral artery occlusion），并通过氯化三苯基四氮唑（triphenyltetrazolium chloride, TTC）染色评估脑梗死体积。鉴于单核细胞（monocytes）在动脉生成过程中的关键作用，我们分别评估了：（a）G-CSF对单核细胞体外（in vitro）迁移的影响；（b）体内（in vivo）生长侧支血管外膜组织中的单核细胞计数。
<i>结果：</i>脑低灌注造模1周后，两种动物模型的CVRC均出现受损。隔日一次40 µg/kg的G-CSF可显著增强大鼠模型的脑动脉生成，而每日一次50 µg/kg或150 µg/kg的G-CSF未表现出明显治疗效果。G-CSF可恢复小鼠（5±2至12±6%）和大鼠（3±4至19±12%）的CVRC。血管直径也随之改变：与对照组相比，G-CSF组大鼠的大脑后动脉（posterior cerebral arteries）直径[同侧（ipsilateral）：209±7至271±57 µm；对侧（contralateral）：208±11至252±28 µm]以及小鼠的大脑前动脉直径（185±15至222±12 µm）均显著增加。单纯CCAO处理的小鼠脑梗死体积为（7±4%），经G-CSF治疗后降至（4±2%），均低于对照组的（10±2%）。G-CSF可显著促进单核细胞的体外迁移，并增加体内血管周围的单核细胞数量。
<i>结论：</i>G-CSF可促进脑侧支动脉生长，提升CVRC，并对实验性缺血性脑卒中（ischemic stroke）起到保护作用。通过对比三种不同给药方案，我们发现相对低剂量的G-CSF效果最佳，这表明该细胞因子（cytokine）的常见不良反应在该适应症（indication）中可显著降低，甚至完全避免。