"Off the shelf" allogeneic stem cell transplants and stem cell nano-composites are being used for the treatment of degenerative bone diseases. However, major and minor histocompatibility antigens of therapeutic cell transplants can be recognized as foreign and lead to their rejection by the host immune system. If a host immune response is identified within the first week post-transplant, immune modulating therapies could be applied to prevent graft failure and support engraftment. Ferumoxytol (Feraheme™) is an FDA approved iron oxide nanoparticle preparation for the treatment of anemia in patients. Ferumoxytol can be used "off label" as an magnetic resonance (MR) contrast agent, as these nanoparticles provide measurable signal changes on magnetic resonance imaging (MRI). In this focused review article, we will discuss three methods to localize and identify innate immune responses to stem cell transplants using ferumoxytol-enhanced MRI, which are based on tracking stem cells, tracking macrophages or detecting mediators of cell death: (a) monitor MRI signal changes of ferumoxytol-labeled stem cells in the presence or absence of innate immune responses, (b) monitor influx of ferumoxytol-labeled macrophages into stem cell implants, and (c) monitor apoptosis of stem cell implants with caspase-3 activatable nanoparticles. These techniques can detect transplant failure at an early stage, when immune-modulating interventions can potentially preserve the viability of the cell transplants and thereby improve bone and cartilage repair outcomes. Approaches 1 and 2 are immediately translatable to clinical practice. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Cells at the Nanoscale Diagnostic Tools > Biosensing.

中文翻译：

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干细胞-巨噬细胞与 ferumoxytol 和 ferumoxytol 衍生纳米粒子相互作用的磁共振成像。

“现成的”同种异体干细胞移植和干细胞纳米复合材料正用于治疗退行性骨病。然而，治疗性细胞移植物的主要和次要组织相容性抗原可被识别为外来物并导致它们被宿主免疫系统排斥。如果在移植后第一周内发现宿主免疫反应，则可以应用免疫调节疗法来防止移植失败和支持植入。Ferumoxytol (Feraheme™) 是 FDA 批准的氧化铁纳米颗粒制剂，用于治疗患者的贫血。Ferumoxytol 可以“标签外”用作磁共振 (MR) 造影剂，因为这些纳米颗粒在磁共振成像 (MRI) 上提供可测量的信号变化。在这篇重点评论文章中，我们将讨论三种使用 ferumoxytol 增强 MRI 定位和识别对干细胞移植的先天免疫反应的方法，这些方法基于跟踪干细胞、跟踪巨噬细胞或检测细胞死亡介质：(a) 监测 ferumoxytol 标记的 MRI 信号变化存在或不存在先天免疫反应的干细胞，(b) 监测 ferumoxytol 标记的巨噬细胞流入干细胞植入物，以及 (c) 用 caspase-3 可激活纳米颗粒监测干细胞植入物的凋亡。这些技术可以在早期检测到移植失败，此时免疫调节干预可能会保持细胞移植的活力，从而改善骨骼和软骨修复结果。方法 1 和 2 可立即转化为临床实践。本文分类如下：