磁共振靶向成像检测大鼠纤维化心肌中肌腱蛋白X表达的实验研究

Experimental Study on Expression of Tenascin-X in Fibrotic Myocardium of Rat by Magnetic Resonance Targeted Imaging

目的合成anti-TNX-USPIO探针,通过磁共振靶向成像检测大鼠心肌纤维化过程中肌腱蛋白X表达的可行性。方法36只SD大鼠,随机选取12只作为空白对照组皮下注射生理盐水,24只皮下注射异丙肾上腺素,随机分为单纯对照组和实验组各12只,每日剂量均为5 mg/kg,连续注射7 d,建立心肌纤维化大鼠模型。制备anti-TNX-USPIO合成探针,进行相关表征分析。实验组尾静脉注射anti-TNX-USPIO合成探针,空白对照组及单纯对照组分别尾静脉注射同等级剂量单纯超微超顺磁性氧化铁(USPIO),分别于打药前及打药10 h后行磁共振成像,观察心肌信号强度变化,扫描完成后进行病理学观察。结果注射异丙肾上腺素后,实验组及单纯对照组均显示为T2WI信号减低,心室壁变薄。空白对照组相对信号强度(rSI)为2.33±0.59,与实验组及单纯对照组的rSI(1.25±0.11)比较有统计学差异(P<0.001),表明实验组与单纯对照组心室壁纤维化改变,建模成功。注入探针后,实验组可见心肌信号强度减低,实验组打药后rSI为1.06±0.12,与打药前的rSI(1.21±0.11)比较有统计学差异(P<0.001);单纯对照组及空白对照组心肌信号强度未见明显减低,合成探针anti-TNX-USPIO对T2WI信号有明显减低作用。Masson染色显示单纯对照组及实验组心肌细胞间纤维组织大量增生,表明心肌纤维化改变。普鲁士蓝染色显示实验组心肌细胞内可见明显铁颗粒沉积,验证了纤维化心肌细胞中TNX抗体探针的存在。结论纤维化心肌细胞中存在心肌表达TNX,anti-TNX-USPIO合成探针可实现大鼠心肌纤维化细胞中TNX体内靶向成像的检测目的,可将TNX作为心肌纤维化治疗的特异性靶点,为下一步临床研究提供思路。

Objective An anti-TNX-USPIO probe was synthesized to detect the feasibility of tenascin-X(TNX)protein expression in myocardial fibrosis by magnetic resonance targeted imaging.Methods Thirty-six SD rats were randomly selected as blank control group by subcutaneous injection of normal saline,and 24 rats by subcutaneous injection of isoproterenol were randomly divided into simple control group(n=12)and experimental group(n=12),with a daily dose of 5 mg/kg for 7 days,to establish myocardial fibrosis rat model.The anti-TNX-USPIO synthesis probe was prepared and the characterization analysis was carried out.In the experimental group,anti-TNX-USPIO synthetic probe was injected into the tail vein,and in the blank control group and the simple control group,USPIO with the same grade of dose was injected into the tail vein respectively.Magnetic resonance imaging was performed before administration and 10 hours after administration to observe changes in myocardial signal intensity,and pathological observation was performed after scanning.Results After injection of isoproterenol,both the experimental group and the simple control group showed decreased T2WI signal and thinner ventricular wall.The relative signal intensity(rSI)in the blank control group was 2.33±0.59,which was statistically significant compared with the rSI(1.25±0.11)of the experimental group and the simple control group(P<0.001),indicating that the experimental group and the simple control group had fibrotic changes in ventricular wall,and the modeling was successful.After probe injection,the intensity of myocardial signal decreased in the experimental group,and the rSI of the experimental group after administration was 1.06±0.12,which was statistically significant compared with that before administration(1.21±0.11)(P<0.001).There was no significant decrease in the intensity of myocardial signal in the simple control group and the blank control group,and the synthetic probe anti-TNX-USPIO had a significant reduction in the intensity of T2WI signal.Masson staining showed a large number of fibrous tissues between the simple control group and the experimental group,indicating myocardial fibrosis changes.Prussian blue staining showed iron particles deposition in myocardial cells of the experimental group,confirming the presence of TNX antibody probes in fibrotic myocardial cells.Conclusion TNX protein is expressed in myocardium in fibrotic cardiomyocytes,and the anti-TNX-USPIO synthetic probe can achieve the purpose of in vivo targeted imaging detection of TNX protein in rat myocardial fibrosis cells,and TNX can be used as a specific target for the treatment of myocardial fibrosis,providing ideas for the next clinical study.