A new mechanisms of G-CSF effect against myocardial infarction - molecular mechanism of healing process acceleration -

本研究旨在探讨粒细胞集落刺激因子(G-CSF)改善心功能和心肌梗死后重塑(MI)是否与促进心肌再生、促进坏死组织吸收形成肉芽组织、继而形成瘢痕有关。在冠状动脉闭塞再灌注30min的模型上，心肌梗死后1~5d皮下注射生理盐水(S)或10μg/kg/d的重组人粒细胞集落刺激因子(G)。心肌梗死后3个月，心肌梗死组左心室(LV)内径缩小，左心室射血分数增加，心肌梗死左室壁增厚。心肌梗死后2天、7天、14天和3个月时，坏死区面积分别为14.2±1.5/13.4±1.1、0.4±0.1/1.8±0.5、0/0和0/0 mm^2/切片/kg，肉芽组织面积分别为0/0、4.0±0.7/8.5±1.0^*、3.9±0.8/5.7±0.7和0/0 mm^2/切片/公斤，瘢痕面积分别为0/0、0/0和0/0。G组和S组分别为0/0和4.2±0.5/7.9±0.9 mm^2/片/kg(^*：P&lt；0.05，G对S)。心肌梗死后7天，G组RAM11阳性巨噬细胞和基质金属蛋白酶(MW)1、9阳性细胞明显增多。提示G通过增加巨噬细胞促进坏死组织的吸收，通过MMPs的表达减少肉芽组织和瘢痕组织。同时，G组大鼠存活心肌组织面积明显增加，而心肌重量、室壁面积和心肌细胞大小与G组无明显差异。共聚焦显微镜显示G组心肌细胞DII阳性，心肌细胞标志物肌钙蛋白I和CD-31阳性的心肌细胞明显增多，提示G促进心肌再生。

The purpose of the present study was to define whether the improvement of cardiac function and remodeling after infarction (MI) by G-CSF relates to acceleration of the healing process from absorption of necrotic tissues into granulation and then scarring, in addition to myocardial regeneration. In a 30-minute coronary occlusion and reperfusion rabbit model, saline (S) or 10 μg/kg/day of human recombinant G-CSF (G) was subcutaneously injected from 1 to 5 days after MI. Smaller left ventricular (LV) dimension, increased LV ejection fraction and thicker infarct-LV wall were seen in G at 3 months after MI. At 2 days, 7 days, 14 days and 3 months after MI, necrotic tissue areas were 14.2±1.5/13.4±1.1, 0.4±0.1/1.8±0.5^*, 0/0 and 0/0 mm^2/slice/kg, granulation areas 0/0, 4.0±0.7/8.5±1.0^*, 3.9±0.8/5.7±0.7^* and 0/0 mm^2/slice/kg, scar areas 0/0, 0/0, 0/0 and 4.2±0.5/7.9±0.9^* mm^2/slice/kg in G and S, respectively (^* : p<0.05,G vs S). Clear increases of macrophages with positive RAM 11 and of matrix metalloproteinase (MW) 1 and 9 were seen in G at 7 days after MI. This suggests that G accelerates absorption of necrotic tissues via increase of macrophages and reduces granulation and scar tissues via expression of MMPs. Meanwhile, survived myocardial tissue areas within the risk areas were significantly increased in G despite no significant difference in LV weight, LV wall area and size of cardiomyocytes between G and S. Confocal microscopy revealed significant increases of cardiomyocytes with positive DiI (a marker of bone marrow cells) and positive troponin I (a marker of cardiomyocytes) or CD-31 (a marker of endothelial cells) in G, suggesting enhanced myocardial regeneration by G. In conclusion, the acceleration of the healing process as well as myocardial regeneration may play an important role for the beneficial effect of post-MI G-CSF treatment.