Department of Radiology, Erasmus MC, Rotterdam, The Netherlands.
PLoS One. 2011 Feb 23;6(2):e17001. doi: 10.1371/journal.pone.0017001.
Articular cartilage has very limited intrinsic regenerative capacity, making cell-based therapy a tempting approach for cartilage repair. Cell tracking can be a major step towards unraveling and improving the repair process of these therapies. We studied superparamagnetic iron oxides (SPIO) for labeling human bone marrow-derived mesenchymal stem cells (hBMSCs) regarding effectivity, cell viability, long term metabolic cell activity, chondrogenic differentiation and hBMSC secretion profile. We additionally examined the capacity of synovial cells to endocytose SPIO from dead, labeled cells, together with the use of magnetic resonance imaging (MRI) for intra-articular visualization and quantification of SPIO labeled cells.
METHODOLOGY/PRINICIPAL FINDINGS: Efficacy and various safety aspects of SPIO cell labeling were determined using appropriate assays. Synovial SPIO re-uptake was investigated in vitro by co-labeling cells with SPIO and green fluorescent protein (GFP). MRI experiments were performed on a clinical 3.0T MRI scanner. Two cell-based cartilage repair techniques were mimicked for evaluating MRI traceability of labeled cells: intra-articular cell injection and cell implantation in cartilage defects. Cells were applied ex vivo or in vitro in an intra-articular environment and immediately scanned. SPIO labeling was effective and did not impair any of the studied safety aspects, including hBMSC secretion profile. SPIO from dead, labeled cells could be taken up by synovial cells. Both injected and implanted SPIO-labeled cells could accurately be visualized by MRI in a clinically relevant sized joint model using clinically applied cell doses. Finally, we quantified the amount of labeled cells seeded in cartilage defects using MR-based relaxometry.
SPIO labeling appears to be safe without influencing cell behavior. SPIO labeled cells can be visualized in an intra-articular environment and quantified when seeded in cartilage defects.
关节软骨的内在再生能力非常有限，因此细胞疗法成为软骨修复的一种诱人方法。细胞示踪可以是揭示和改善这些疗法修复过程的重要步骤。我们研究了超顺磁氧化铁（SPIO）标记人骨髓间充质干细胞（hBMSC）的效果、细胞活力、长期代谢细胞活性、软骨分化和 hBMSC 分泌谱。我们还研究了滑膜细胞从死亡的、标记的细胞中内吞 SPIO 的能力，以及使用磁共振成像（MRI）进行关节内可视化和定量 SPIO 标记细胞。
方法/主要发现：使用适当的测定法确定 SPIO 细胞标记的功效和各种安全方面。通过用 SPIO 和绿色荧光蛋白（GFP）共标记细胞，在体外研究滑膜 SPIO 再摄取。MRI 实验在临床 3.0T MRI 扫描仪上进行。模拟了两种基于细胞的软骨修复技术来评估标记细胞的 MRI 可追踪性：关节内细胞注射和软骨缺陷内细胞植入。将细胞应用于关节内环境中的离体或体外，并立即进行扫描。SPIO 标记是有效的，并且不会损害任何研究的安全方面，包括 hBMSC 分泌谱。可以从死亡的、标记的细胞中摄取滑膜细胞中的 SPIO。使用临床应用的细胞剂量，在具有临床相关性的关节模型中，可以通过 MRI 准确地观察到注射和植入的 SPIO 标记细胞。最后，我们使用基于 MR 的弛豫定量法来量化在软骨缺陷中接种的标记细胞的数量。
SPIO 标记似乎是安全的，不会影响细胞行为。当在软骨缺陷中播种时，可以在关节内环境中观察到 SPIO 标记的细胞并进行定量。
