体内示踪腺病毒转铁蛋白标记的骨髓来源树突状细胞的磁粒子成像研究

BACKGROUND: Despite widespread study of dendritic cell (DC)-based cancer immunotherapies, the in vivo postinjection fate of DC remains largely unknown. Due in part to a lack of quantifiable imaging modalities, this is troubling as the amount of DC migration to secondary lymphoid organs correlates with therapeutic efficacy. Magnetic particle imaging (MPI) has emerged as a suitable modality to quantify in vivo migration of superparamagnetic iron oxide (SPIO)-labeled DC. Herein, we describe a popliteal lymph node (pLN)-focused MPI scan to quantify DC in vivo migration accurately and consistently. METHODS: Adenovirus (Ad)-transduced SPIO (Ad SPIO) and SPIO C57BL/6 bone marrow-derived DC were generated and assessed for viability and phenotype, then fluorescently labeled and injected into mouse hind footpads (n = 6). Two days later, in vivo DC migration was quantified using whole animal, pLN-focused, and ex vivo pLN MPI scans. RESULTS: No significant differences in viability, phenotype and in vivo pLN migration were noted for Ad SPIO and SPIO DC. Day 2 pLN-focused MPI quantified DC migration in all instances while whole animal MPI only quantified pLN migration in 75% of cases. Ex vivo MPI and fluorescence microscopy confirmed that pLN MPI signal was due to originally injected Ad SPIO and SPIO DC. CONCLUSION: We overcame a reported limitation of MPI by using a pLN-focused MPI scan to quantify pLN-migrated Ad SPIO and SPIO DC in 100% of cases and detected as few as 1000 DC (4.4 ng Fe) in vivo. MPI is a suitable preclinical imaging modality to assess DC-based cancer immunotherapeutic efficacy. RELEVANCE STATEMENT: Tracking the in vivo fate of DC using noninvasive quantifiable magnetic particle imaging can potentially serve as a surrogate marker of therapeutic effectiveness. KEY POINTS: • Adenoviral-transduced and iron oxide-labeled dendritic cells are in vivo migration competent. • Magnetic particle imaging is a suitable modality to quantify in vivo dendritic cell migration. • Magnetic particle imaging focused field of view overcomes dynamic range limitation.

背景：尽管针对树突状细胞（DC）的癌症免疫疗法进行了广泛的研究，但 DC 的体内注射后命运在很大程度上仍然未知。部分原因是缺乏可量化的成像方式，这令人困扰，因为 DC 向次级淋巴器官的迁移量与治疗效果相关。磁性粒子成像（MPI）已成为定量超顺磁氧化铁（SPIO）标记的 DC 体内迁移的合适方式。在此，我们描述了一种聚焦于腘淋巴结（pLN）的 MPI 扫描，以准确且一致地定量体内 DC 的迁移。

方法：生成腺病毒（Ad）转导的 SPIO（Ad SPIO）和 SPIO C57BL/6 骨髓来源的 DC，并评估其活力和表型，然后进行荧光标记并注入小鼠后足垫（n=6）。两天后，使用全身、pLN 聚焦和离体 pLN MPI 扫描定量体内 DC 迁移。

结果：Ad SPIO 和 SPIO DC 的活力、表型和体内 pLN 迁移没有明显差异。第 2 天的 pLN 聚焦 MPI 定量了所有情况下的 DC 迁移，而全身 MPI 仅在 75%的情况下定量了 pLN 迁移。离体 MPI 和荧光显微镜证实，pLN MPI 信号归因于最初注入的 Ad SPIO 和 SPIO DC。

结论：我们通过使用 pLN 聚焦 MPI 扫描来定量 100%情况下的 pLN 迁移的 Ad SPIO 和 SPIO DC，并在体内检测到少至 1000 个 DC（4.4ng Fe），克服了 MPI 的一项报道限制。MPI 是一种合适的临床前成像方式，可用于评估基于 DC 的癌症免疫治疗效果。

重要性声明：使用非侵入性可量化的磁性粒子成像来跟踪 DC 的体内命运，可能成为治疗效果的替代标志物。

关键点：• 腺病毒转导和氧化铁标记的树突状细胞具有体内迁移能力。• 磁性粒子成像是定量体内树突状细胞迁移的合适方式。• 磁性粒子成像聚焦视场克服了动态范围限制。