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间充质干细胞(mesenchymal stem cells,MSCs)能自主地聚集到肿瘤组织的间质,并分化为多种肿瘤间质相关的细胞,如脉管系统相关的内皮细胞、间质成纤维细胞样细胞等。正是由于存在这种内在的肿瘤归巢特性,MSCs成为理想的肿瘤靶向递送载体,近年来以MSCs作为载体对肿瘤进行靶向治疗已成为研究热点[1-5]。MSCs作为递送载体作用非常重要,从MSCs归巢至肿瘤组织的时间和空间分布关系到其是否能完成靶向治疗,这就需要实时、动态掌握MSCs在体内的运行状态,因此分子影像示踪MSCs具有重要的研究意义。骨髓起源的MSCs表面表达多种抗原,如CD90、CD73和CD105等[6]。本研究使用125I标记CD90单克隆抗体(monoclonal antibody,mAb)进行体外、体内实验,探讨125I-CD90 mAb示踪MSCs的可能性。
125I标记CD90单克隆抗体靶向结合间充质干细胞的实验研究
Experimental study on 125I labeled CD90 monoclonal antibody for targetedly binding mesenchymal stem cells
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摘要:
目的 制备125I标记的CD90单克隆抗体(mAb),探讨其示踪间充质干细胞(MSCs)的可能性。 方法 采用氯胺T法对CD90 mAb进行125I标记,测定标记率。(1)体外实验:检测MSCs和125I-CD90 mAb孵育后上清液和沉淀的放射性计数,分别计算6个不同时间点的细胞结合率。(2)体内实验:构建荷瘤BALB/c裸鼠,采用完全随机法分为4组(每组3只),a组经腹腔注射MSCs,b组经腹腔注射生理盐水,c组经瘤内注射MSCs,d组经瘤内注射生理盐水。每只荷瘤裸鼠尾静脉注射125I-CD90 mAb(3.7 MBq/0.2 mL)后行Micro-SPECT/CT显像,测定并计算在4个不同时间点肿瘤及主要器官和组织的放射性摄取值[每克组织百分注射剂量率(%ID/g)]。2组均数之间的比较采用独立样本t检验。 结果 125I-CD90 mAb标记率为54.4%,放射化学纯度为98.79%。(1) 在10 min、30 min、1 h、2 h、6 h、8 h 时,125I-CD90 mAb与MSCs的结合率分别为0.86%、1.73%、1.88%、5.67%、12.20%、10.69%,6 h时最高。(2)荷瘤裸鼠的肿瘤长至150~200 mm3时用于实验。在注射后6 h、1 d、2 d、3 d时,Micro-SPECT/CT显示125I-CD90 mAb在荷瘤裸鼠的肿瘤及主要器官和组织中有着不同程度的分布,其中 a组肿瘤组织的放射性摄取值分别为(3.66±1.69)、(2.35±1.30)、(1.36±0.95)、(1.33±0.84)%ID/g,均高于b组的(2.93±1.74)、(1.92±1.15)、(1.12±0.78)、(1.03±0.72)%ID/g,但差异均无统计学意义(t=0.35~0.52,均P>0.05);c组肿瘤组织的放射性摄取值分别为(5.75±1.30)、(3.75±0.77)、(2.70±0.44)、(1.88±0.48)%ID/g,均高于d组的(3.17±0.75)、(2.03±0.54)、(1.44±0.39)、(1.38±0.27)%ID/g,且差异均有统计学意义(t=1.59~3.70,均P<0.05)。 结论 成功制备的125I-CD90 mAb具有良好的与MSCs结合的能力,有潜力作为核素探针示踪MSCs。 -
关键词:
- 间质干细胞 /
- 抗体,单克隆 /
- Thy-1抗原 /
- 碘放射性同位素 /
- 体层摄影术,发射型计算机,单光子
Abstract:Objective To prepare 125I-CD90 monoclonal antibody (mAb) and evaluate its potential as a molecular imaging agent to trace mesenchymal stem cells (MSCs). Methods 125I-CD90 mAb was prepared by chloramine T method, and labeling rate was tested. (1) In in vitro experiment, the radioactive count of the supernatant and precipitate was measured after incubating 125I-CD90 mAb with MSCs. Binding fraction was calculated at six time points. (2) In in vivo experiment, tumor-bearing BALB/c mice were constructed and divided into four groups (a, b, c and d) by completely random design. MSCs and normal saline were administered by intraperitoneal injection in groups a and b, respectively. MSCs and normal saline were given by intratumoral injection in groups c and d, respectively. 125I-CD90 mAb (3.7 MBq/0.2 mL) was injected via caudal vein in each mouse, and Micro-SPECT/CT analysis was performed. The radioactive uptake values (percentage activity of injection dose per gram of tissue (%ID/g)) in tumor and main organs was calculated at four different time points. The difference between two groups was analyzed by two independent sample t test. Results The labeling rate and radiochemical purity of 125I-CD90 mAb were 54.4% and 98.79%, respectively. (1) After incubation for 10 min, 30 min, 1 h, 2 h, 6 h and 8 h, the binding ratios of 125I-CD90 mAb in MSCs were 0.86%, 1.73%, 1.88%, 5.67%, 12.20% and 10.69%, respectively. The highest binding ratio was detected at 6 h of incubation. (2) Tumors of tumor-bearing mice (150−200 mm3) were used. Micro-SPECT/CT images showed varying degrees of 125I-CD90 mAb distribution in the tumor and main organs of MSCs tumor-bearing mice after 6 h, 1 d, 2 d and 3 d of incubation. The radioactive uptake values in the tumor were (3.66±1.69), (2.35±1.30), (1.36±0.95) and (1.33±0.84)%ID/g in group a, which were higher than those ((2.93±1.74), (1.92±1.15), (1.12±0.78) and (1.03±0.72)%ID/g) in group b, at 6 h, 1 d, 2 d and 3 d, respectively, but the differences were not statistically significant (t=0.35−0.52, all P>0.05). The radioactive uptake values in the tumor were (5.75±1.30), (3.75±0.77), (2.70±0.44) and (1.88±0.48)%ID/g in group c, which were higher than those ((3.17±0.75), (2.03±0.54), (1.44±0.39) and (1.38±0.27)%ID/g) in group d, at 6 h, 1 d, 2 d and 3 d, respectively, and all the differences were statistically significant (t=1.59−3.70, all P<0.05). Conclusion The prepared 125I-CD90 mAb exhibits good binding ability to MSCs and has the potential as a nuclide probe to trace MSCs. -
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