In vivo distribution of U87MG cells injected into the lateral ventricle of rats with spinal cord injury

Stem cells could be the next generation therapeutic option for neurodegenerative diseases including spinal cord injury (SCI). However, several critical factors such as delivery method should be determined before their clinical applications. Previously, we have demonstrated that lateral ventricle (LV) injection as preclinical simulation could be used for intrathecal administration in clinical trials using rodent animal models. In this study, we further analyzed in vivo distribution of cells that were injected into LVs of rats with SCI at thoracic level using in vivo imaging techniques. When 5 × 106 U87MG cells labelled with fluorescent magnetic nanoparticle (FMNP-labelled U87MG) were administrated into LVs at 7 days after SCI, FMNP-labelled U87MG cells were observed in all regions of the spinal cord at 24 hours after the injection. Compared to water-soluble Cy5.5 fluorescent dye or rats without SCI, in vivo distribution pattern of FMNP-labelled U87MG cells was not different, although migration to the spinal cord was significantly reduced in both Cy5.5 fluorescent dye and FMNP-labelled U87MG cells caused by the injury. The presence of FMNP-labelled U87MG cells in the spinal cord was confirmed by quantitative PCR for human specific sequence and immunohistochemistry staining using antibody against human specific antigen. These data indicate that LV injection could recapitulate intrathecal administration of stem cells for SCI patients. Results of this study might be applied further to the planning of optimal preclinical and clinical trials of stem cell therapeutics for SCI.

干细胞可作为包括脊髓损伤（spinal cord injury, SCI）在内的神经退行性疾病的下一代治疗选择。然而，在其进入临床应用前，仍需明确包括递送方式在内的多项关键因素。此前，我们已通过啮齿类动物模型（rodent animal models）证实，作为临床前模拟手段的侧脑室（lateral ventricle, LV）注射可用于临床试验中的鞘内给药（intrathecal administration）。本研究中，我们进一步利用活体成像技术（in vivo imaging techniques），分析了胸段脊髓损伤大鼠侧脑室注射后的细胞体内分布情况。当在脊髓损伤后第7天向大鼠侧脑室注射5×10^6个经荧光磁性纳米颗粒（fluorescent magnetic nanoparticle, FMNP）标记的U87MG细胞后，注射后24小时即可在脊髓所有区域观察到FMNP标记U87MG细胞。与水溶性Cy5.5荧光染料组及未受脊髓损伤的大鼠相比，FMNP标记U87MG细胞的体内分布模式并无显著差异；但脊髓损伤可显著降低Cy5.5荧光染料标记物及FMNP标记U87MG细胞向脊髓的迁移能力。通过针对人类特异性序列的定量PCR（quantitative PCR）及抗人类特异性抗原抗体的免疫组织化学染色（immunohistochemistry staining），可证实脊髓内存在FMNP标记U87MG细胞。上述数据表明，侧脑室注射可模拟脊髓损伤患者的干细胞鞘内给药过程。本研究结果可进一步用于脊髓损伤干细胞治疗的最优临床前及临床试验方案规划。