磁共振成像对猪不同心脏状态下经冠状动脉干细胞移植后体内再分布的评价

In vivo re-distribution of intra-coronary transplanted stem calls into beating and arrested hearts by magnetic resonance imaging in an acute myocardial infarction swine model

目的 探讨磁共振成像在停跳与不停跳两种心脏状态下,对猪心肌梗死模型经冠状动脉注射骨髓间充质干细胞后全身各主要脏器干细胞早期再分布中的应用价值.方法 用带球囊导管经股动脉选择性插管至雌猪左冠状动脉前降支,在第二对角支的近端将球囊扩张90 min建立急性心肌梗死模型.模型建立后7 d,随机分为4组,分别为不停跳心脏细胞移植组（不停跳组,n=6）与对照组（n=6）,停跳心脏细胞移植组（停跳组,n=6）与对照组（n=6）.超顺磁氧化铁颗粒（SPIO）标记的干细胞移植3 d后,行磁共振T2＊WI示踪检查.取动物心、肝、脾、肺、肾脏的标本,用实时定量聚合酶链反应检测雄性细胞特异性的SRY基因,切片进行普鲁士蓝染色,观察细胞在体内的分布和形态.结果 除肾脏外,心、脾、肝中干细胞移植组T2＊值较对照组差异均有统计学意义,但移植组在不同心脏状态下不停跳组与停跳组心肌T2＊值差异无统计学意义[（-7.81±2.03）ms比（-6.56±1.72）ms,P＞0.05],而不停跳组脾脏及肝脏的T2＊值明显低于停跳组[脾脏：（-16.72±2.83）ms比（-22.18±3.98）ms,P＜0.01,肝脏：（-2.40±0.44）ms比（-5.32±3.40）ms,P＜0.05],在肾脏中两组差异无统计学意义.SRY基因在不停跳组及停跳组的脾脏及肝脏的表达差异有统计学意义,病理学检查见移植细胞呈普鲁士蓝染色阳性.结论 干细胞SPIO标记后,磁共振成像可以作为方便而有效的手段在移植早期活体示踪干细胞,评价其在体内的分布情况.经冠状动脉途径注射骨髓间充质干细胞后,许多细胞流向心脏以外的器官,尤其是脾脏.心脏停跳与不停跳状态下经冠状动脉注射骨髓间充质干细胞对干细胞在心脏的滞留无明显差别.

Objective To analyze the stem cell re-distribution after intra-coronary infusion （ICI）into arrested and beating hearts in a swine myocardial infarction （ MI ） model using magnetic resonance imaging （MRI）. Methods Bone marrow-derived mesenchymal stem cells were obtained from male swine and labeled with iron oxide during culture. One week after MI in female swine, the survivors were randomly divided into 4 groups. Cardiopulmonary bypass was set up to arrest the heart, and then SPIO labeled male stem cells （ 1 × 10^8 ） were infused through coronary of beating heart （ n = 6） and the arrested heart （ n = 6）.Saline was injected in either the beating or arresting heart as respective controls. Three days later, cell distribution was assessed by T2＊ change with magnetic resonance imaging and Y-chromosome （SRY） was detected with quantitative polymerase chain reaction. Results The reduction of T2＊ values was significantly different in the hearts, spleens, livers and lung between the transplantation groups and the control groups. Only few transplanted cells were localized in the heart and T2 ＊ values were similar between beating and arrest heart groups [ （ -7.81 ±2.03） ms vs. （ -6.56 ± 1.72）ms, P〉0.05], while T2＊ value reduction was more significant in the spleen and liver in arrest heart group than in beating heart group [spleen： （-16.72 ±2.83）ms vs. （ -22.18 ±3.98）ms, P〈0.01, liver： （ -2.40±0.44）ms vs.（ -5.32 ± 3.40 ） ms, P 〈 0. 05 ] . T2 ＊ value was similar in kidney among the four groups. qRT-PCR detected SRY gene was similar in the heart, less in the spleen and liver while more in the lung in beating heart group compared to arrested heart group. In vitro Prussian blue stained positively transplanted cells were found in the above organs in transplantation group. Conclusions The majority of stem cells transplanted by ICI would be entrapped by the extracardial organs. Stem cell transplantation via ICI into the arrested heart does not favor more cells retention in the injured myocardium. Further investigation is needed to optimize the approach of stem cell delivery.