磁化标记胎盘间质干细胞参与结直肠癌增殖、侵袭、血管生成的MR示踪研究

Colorectal cancer is a lethal disease which threating to human health ,studies have shown that stem cells can specifically homing to the tumor site and participating in tumor angiogenesis,however,there is a controversy on its funtion in tumor angiogenesis,and there is still needs a further research on how to dynamic ,non-invasive tracking the distribution of transplanted stem cells in vivo at molecular cellular level ..The key purpose of this subject is to researching the tracer imaging in 3.0TMRI of magnetization marked placenta mesenchymal stem cells in colorectal cancer xenografts . First,selecting the highly invasive and poorly differentiated human colorectal cancer cell line LOVO as the research object,and establishing the xenograft model of colorectal cancer subcutaneously with the combined immunodeficiency mice .Second,culturing mesenchymal stem cells which isolated from human placenta,and labeled human placental mesenchymal stem cells with USPIO,and then study the labeling efficiency and the imaging quality of magentic resonance in vitro;At last,injecting the USPIO labeled placental mesenchymal stem cells into tail vein,due to its tumor homing property ,it can specifically distributed to the tumor site ,through the MR molecular imaging it can hopefully detect the placenta mesenchymal stem cells distributed in tumor tissue and to study its role in tumor angiogenesis..The results of this subject can provide a theoretical basis for the early diagnosis of colorectal cancer and the treatment efficacy ,as well as the targeted gene therapy.

结直肠癌是一种威胁人类健康的重要致命性疾病，已有研究表明干细胞能特异性归巢到肿瘤部位，参与血管形成，但是它在肿瘤血管生长中所发挥的作用尚存在争议，且如何在分子细胞水平动态、无创性追踪活体内移植干细胞的分布，有待进一步研究支持。本课题拟重点研究磁化标记的胎盘间质干细胞在结直肠癌移植瘤的3.0T磁共振示踪成像，包括：1）选取具有高侵袭性低分化人结直肠癌细胞株LOVO为研究对象，建立重度联合免疫缺陷小鼠皮下结直肠癌移植瘤模型；2）从人胎盘分离、培养间充质干细胞，利用USPIO标记人胎盘间质干细胞，研究其标记效率及体外磁共振成像效果；3）尾静脉注射标记USPIO的胎盘间质干细胞，由于归巢作用，故能特异性地分布到肿瘤部位，通过磁共振分子成像，有望显示出肿瘤组织内分布的胎盘间充质干细胞，研究其在肿瘤血管生成中的作用。课题研究成果将为结直肠癌的早期诊断、疗效评估以及靶向基因治疗，提供理论依据。

结直肠癌是一种威胁人类健康的重要致命性疾病，已有研究表明干细胞能特异性归巢到肿瘤部位，参与血管形成，但是它在肿瘤血管生长中所发挥的作用尚存在争议，且如何在分子细胞水平动态、无创性追踪活体内移植干细胞的分布，有待进一步研究支持，本项目拟重点研究磁化标记的胎盘间质干细胞在结直肠癌移植瘤的3.0T磁共振示踪成像。主要研究内容：以多聚赖氨酸（PLL）为转染剂，与不同浓度超微超顺磁性氧化铁颗粒（USPIO）形成PLL-USPIO复合物对PMSCs进行标记，考察标记效率及标记后hPMSCs的存活率、增殖能力和凋亡率等生物学特性以确定最佳标记浓度。制备不同数量级细胞琼脂糖凝胶模型，3.0 T磁共振下分别在T2WI、T2mapping、T2*mapping序列下扫描观察成像规律以调试扫描参数。建立裸鼠HT-29皮下移植瘤模型随机分为实验组和对照组，实验组瘤内注射磁化标记的PMSCs进行扫描，观察两组移植瘤生长情况及MR信号变化，扫描结束后取移植瘤分析病理结果。研究结果：标记浓度≥10μg·mL-1时标记率均＞95%，USPIO浓度区间为5～15μg·mL-1时对hPMSCs活性、增殖能力和凋亡率等生物学特性无明显影响(p>0.05)。标记终浓度为10μg·mL-1时在3.0T MR下可显示的最低hPMSCs数量为104，T2*mapping序列对于USPIO标记细胞的敏感性优于T2WI、T2mapping序列。3.0T MR扫描体内实验组第1 d 可见结直肠肿瘤内局部低信号，第3d起随时间增加低信号范围减少，第14d与对照组差异不明显，T2、T2*值逐渐增加且肿瘤体积有减慢趋势，但实验组与对照组肿瘤体积及重量比较无明显统计学意义(p>0.05)，CD31、CD34与Ki67阳性率两组间比较无明显差异(p>0.05)。 研究成果将为胎盘间充质干细胞的MR活体追踪、结直肠癌的靶向治疗和疗效评估提供一定的理论依据。