BrainTech Lab INSERM U1205, Grenoble, France.
Grenoble Alpes University, France.
NMR Biomed. 2022 Jun;35(6):e4677. doi: 10.1002/nbm.4677. Epub 2022 Jan 19.
Our objective was to study NMR relaxometry of glioma invasion/migration at very low field (<2 mT) by fast-field-cycling NMR (FFC-NMR) and to decipher the pathophysiological processes of glioma that are responsible for relaxation changes in order to open a new diagnostic method that can be extended to imaging. The phenotypes of two new glioma mouse models, Glio6 and Glio96, were characterized by T -MRI, HE histology, Ki-67 immunohistochemistry (IHC) and CXCR4 RT-qPCR, and were compared with the U87 model. R dispersions of glioma tissues were acquired at low field (0.1 mT-0.8 T) ex vivo and were fitted with Lorentzian and power-law models to extract FFC biomarkers related to the molecular dynamics of water. In order to decipher relaxation changes, three main invasion/migration pathophysiological processes were studied: hypoxia, H O function and the water-channel aquaporin-4 (AQP4). Glio6 and Glio96 were characterized with invasion/migration phenotype and U87 with high cell proliferation as a solid glioma. At very low field, invasion/migration versus proliferation was characterized by a decrease in the relaxation-rate constant (ΔR ≈ -32% at 0.1 mT) and correlation time (≈-40%). These decreases corroborated the AQP4-IHC overexpression (Glio6/Glio96: +92%/+46%), suggesting rapid transcytolemmal water exchange, which was confirmed by the intracellular water-lifetime τ decrease (Δτ ≈ -30%). In functional experiments, AQP4 expression, τ and the relaxation-rate constant at very low field were all found to be sensitive to hypoxia and to H O stimuli. At very low field the role of water exchanges in relaxation modulation was confirmed, and for the first time it was linked to the glioma invasion/migration and to its main pathophysiological processes: hypoxia, H O redox signaling and AQP4 expression. The method appears appropriate to evaluate the effect of drugs that can target these pathophysiological mechanisms. Finally, FFC-NMR operating at low field is demonstrated to be sensitive to invasion glioma phenotype and can be straightforwardly extended to FFC-MRI as a new cancer invasion imaging method in the clinic.
我们的目标是通过快速场频循环 NMR（FFC-NMR）研究极低场（<2 mT）下胶质瘤侵袭/迁移的 NMR 弛豫率，并解析导致弛豫变化的胶质瘤病理生理过程，以期开辟一种新的诊断方法，从而可以扩展到成像领域。两种新型胶质瘤小鼠模型 Glio6 和 Glio96 的表型通过 T -MRI、HE 组织学、Ki-67 免疫组化（IHC）和 CXCR4 RT-qPCR 进行了表征，并与 U87 模型进行了比较。在低场（0.1 mT-0.8 T）下获取胶质瘤组织的 R 分散，并使用洛伦兹和幂律模型进行拟合，以提取与水的分子动力学相关的 FFC 生物标志物。为了解析弛豫变化，研究了三种主要的侵袭/迁移病理生理过程：缺氧、H 2 O 功能和水通道 aquaporin-4（AQP4）。Glio6 和 Glio96 的侵袭/迁移表型以及 U87 的高细胞增殖特征与实体胶质瘤一致。在极低场下，侵袭/迁移与增殖的区别在于弛豫率常数（ΔR≈-32%，在 0.1 mT 时）和相关时间（≈-40%）降低。这些降低与 AQP4-IHC 过表达（Glio6/Glio96：+92%/+46%）相符，表明跨细胞旁水交换迅速，这通过细胞内水寿命τ的降低得到证实（Δτ≈-30%）。在功能实验中，发现 AQP4 表达、τ 和极低场下的弛豫率常数均对缺氧和 H 2 O 刺激敏感。在极低场下，水交换在弛豫调节中的作用得到了证实，这是首次将其与胶质瘤侵袭/迁移及其主要病理生理过程联系起来：缺氧、H 2 O 氧化还原信号和 AQP4 表达。该方法似乎适用于评估可以靶向这些病理生理机制的药物的效果。最后，证明在低场下运行的 FFC-NMR 对侵袭性胶质瘤表型敏感，并可以直接扩展到 FFC-MRI，作为临床中新的癌症侵袭成像方法。
