Saldanha K J, Piper S L, Ainslie K M, Kim H T, Majumdar S
MQIR, Department of Radiology, University of California, San Francisco, CA, USA.
Eur Cell Mater. 2008 Aug 1;16:17-25. doi: 10.22203/ecm.v016a03.
Minimally-invasive monitoring of regeneration in diseased tissue is an important aspect of stem cell therapy. Magnetic resonance imaging (MRI) based tracking of cells labelled with ferumoxides has the potential for non-invasive in vivo detection and longitudinal assessment of implanted cells. Cells labelled with ferumoxides appear as hypointense regions on MR images and thus can be distinguished from the surroundings. Application of this methodology to intervertebral disc degeneration (IVD), and detection of labelled cells implanted into the disc for tissue regeneration was examined. Mesenchymal stem cells labelled with a ferumoxide contrast agent were imaged in vitro to quantitatively characterize the signal intensity loss using MRI relaxation parameters (T1, T2, and T2*). To determine whether labelled cells could be detected within scaffolds suitable for implantation, labelled cells were seeded within both natural and synthetic polymers and imaged using MRI. Labelled cells were loaded within poly(ethylene glycol) hydrogels and imaged in vitro using both MRI and confocal microscopy. Labelled cells were also loaded into fibrin gels, and detected ex vivo within rat IVDs using MRI. Lastly, the effect of ferumoxide labelling on cell viability was investigated. Quantitatively, labelled cells demonstrate the greatest signal intensity loss and contrast on T2*-weighted images. Labelled cells can be detected in both synthetic and natural polymers, and can be distinguished from the native tissue environment of the rat IVD. Finally, labelling does not significantly impair cell viability. Consequently, this technique shows promise as a potential method for in vivo longitudinal tracking of stem cell based regeneration of the IVD.
对患病组织再生进行微创监测是干细胞治疗的一个重要方面。基于磁共振成像（MRI）对用超顺磁性氧化铁标记的细胞进行追踪，具有对植入细胞进行无创体内检测和纵向评估的潜力。用超顺磁性氧化铁标记的细胞在磁共振图像上表现为低信号区域，因此可以与周围组织区分开来。研究了将该方法应用于椎间盘退变（IVD）以及检测植入椎间盘用于组织再生的标记细胞。用超顺磁性氧化铁造影剂标记的间充质干细胞在体外成像，以使用MRI弛豫参数（T1、T2和T2*）定量表征信号强度损失。为了确定是否能在适合植入的支架内检测到标记细胞，将标记细胞接种在天然和合成聚合物中，并使用MRI成像。将标记细胞加载到聚乙二醇水凝胶中，并使用MRI和共聚焦显微镜在体外成像。还将标记细胞加载到纤维蛋白凝胶中，并使用MRI在大鼠IVD的离体组织中进行检测。最后，研究了超顺磁性氧化铁标记对细胞活力的影响。定量分析表明，标记细胞在T2*加权图像上表现出最大的信号强度损失和对比度。标记细胞可以在合成和天然聚合物中被检测到，并且可以与大鼠IVD的天然组织环境区分开来。最后，标记不会显著损害细胞活力。因此，这项技术有望成为一种对基于干细胞的IVD再生进行体内纵向追踪的潜在方法。
