In Vivo Bioluminescence Imaging for Prolonged Survival of Transplanted Human Neural Stem Cells Using 3D Biocompatible Scaffold in Corticectomized Rat Model

Stem cell-based treatment of traumatic brain injury has been limited in its capacity to bring about complete functional recovery, because of the poor survival rate of the implanted stem cells. It is known that biocompatible biomaterials play a critical role in enhancing survival and proliferation of transplanted stem cells via provision of mechanical support. In this study, we noninvasively monitored in vivo behavior of implanted neural stem cells embedded within poly-l-lactic acid (PLLA) scaffold, and showed that they survived over prolonged periods in corticectomized rat model. Corticectomized rat models were established by motor-cortex ablation of the rat. F3 cells expressing enhanced firefly luciferase (F3-effLuc) were established through retroviral infection. The F3-effLuc within PLLA was monitored using IVIS-100 imaging system 7 days after corticectomized surgery. F3-effLuc within PLLA robustly adhered, and gradually increased luciferase signals of F3-effLuc within PLLA were detected in a day dependent manner. The implantation of F3-effLuc cells/PLLA complex into corticectomized rats showed longer-lasting luciferase activity than F3-effLuc cells alone. The bioluminescence signals from the PLLA-encapsulated cells were maintained for 14 days, compared with 8 days for the non-encapsulated cells. Immunostaining results revealed expression of the early neuronal marker, Tuj-1, in PLLA-F3-effLuc cells in the motor-cortex-ablated area. We observed noninvasively that the mechanical support by PLLA scaffold increased the survival of implanted neural stem cells in the corticectomized rat. The image-guided approach easily proved that scaffolds could provide supportive effect to implanted cells, increasing their viability in terms of enhancing therapeutic efficacy of stem-cell therapy.

基于干细胞的创伤性脑损伤治疗在实现完全功能恢复方面能力有限，根源在于植入干细胞的存活率偏低。现有研究表明，生物相容性生物材料可通过提供机械支持，在提升移植干细胞的存活与增殖能力方面发挥关键作用。本研究对植入聚左旋乳酸（poly-l-lactic acid, PLLA）支架内的神经干细胞的体内行为进行了无创监测，并证实其在皮质切除大鼠模型中可长期存活。皮质切除大鼠模型通过对大鼠运动皮层进行消融构建而成。通过逆转录病毒感染构建了表达增强型萤火虫荧光素酶的F3细胞（F3-effLuc）。皮质切除术后7天，利用IVIS-100成像系统对聚左旋乳酸支架内的F3-effLuc细胞进行监测。结果显示，聚左旋乳酸支架内的F3-effLuc细胞黏附性良好，且其荧光素酶信号随时间呈逐日递增趋势。将F3-effLuc细胞/聚左旋乳酸复合物植入皮质切除大鼠体内，其荧光素酶活性持续时间较单纯植入F3-effLuc细胞更长：封装于聚左旋乳酸支架内的细胞的生物发光信号可维持14天，而非封装细胞仅能维持8天。免疫染色结果显示，在运动皮层消融区域的聚左旋乳酸-F3-effLuc细胞中，早期神经元标志物Tuj-1得以表达。本研究无创证实，聚左旋乳酸支架提供的机械支持可提升皮质切除大鼠体内植入神经干细胞的存活率。该影像引导监测方法可便捷证明，支架能够为植入细胞提供支持效应，进而提升细胞存活率，增强干细胞疗法的治疗效果。