Liu Ning, Ding Hongliu, Vanderheyden Jean-Luc, Zhu Zhihong, Zhang Yumin
Department of Radiology/Nuclear Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Nucl Med Biol. 2007 May;34(4):399-404. doi: 10.1016/j.nucmedbio.2007.02.006.
To develop a noninvasive direct method for the in vivo tracking of small interfering RNA (siRNA) used in RNA interference, two 18-nucleotide oligoribonucleotides were radiolabeled with technetium-99m ((99m)Tc-RNA). The ability of (99m)Tc-RNA to track delivery was tested in cultured cells and living mice. The cellular delivery of (99m)Tc-RNAs could be quantified by gamma counting and could be visualized by microautoradiography. Radiolabeled RNAs can be efficiently delivered into cells by reaching up to 3x10(5) molecules of small RNAs per cell. Moreover, RNAs were internalized with homogeneous distribution throughout the cytoplasm and nucleus. In tumor-bearing mice, whole-body images and biodistribution studies showed that (99m)Tc-RNAs were delivered to almost all tissues after intravenous injection. The imaging of living animals allowed noninvasive and longitudinal monitoring of the in vivo delivery of these small RNAs. In conclusion, using (99m)Tc radiolabeling, the delivery of small RNAs could be measured quantitatively in cultured cells and could be noninvasively visualized in living animals using a gamma camera. The results of this study could open up a new approach for measuring the in vivo delivery of small RNAs that might further facilitate the development of siRNAs as targeted therapies.
为开发一种用于体内追踪RNA干扰中使用的小干扰RNA（siRNA）的非侵入性直接方法，将两个18核苷酸的寡核糖核苷酸用99m锝进行放射性标记（99mTc-RNA）。在培养细胞和活体小鼠中测试了99mTc-RNA追踪递送的能力。99mTc-RNA的细胞递送可通过γ计数进行定量，并可通过显微放射自显影进行可视化。放射性标记的RNA可以通过每个细胞达到高达3×10^5个小RNA分子的效率递送至细胞中。此外，RNA以均匀分布内化于整个细胞质和细胞核中。在荷瘤小鼠中，全身图像和生物分布研究表明，静脉注射后99mTc-RNA被递送至几乎所有组织。对活体动物的成像允许对这些小RNA的体内递送进行非侵入性和纵向监测。总之，使用99mTc放射性标记，可以在培养细胞中定量测量小RNA的递送，并使用γ相机在活体动物中进行非侵入性可视化。本研究结果可能为测量小RNA的体内递送开辟一种新方法，这可能进一步促进siRNA作为靶向治疗的发展。
