Lipophilic dye-compatible brain clearing technique allowing correlative magnetic resonance/high-resolution fluorescence imaging in rat models of glioblastoma

Abstract

In this work we optimized a novel approach for combining in vivo MRI and ex vivo high-resolution fluorescence microscopy that involves: (i) a method for slicing rat brain tissue into sections with the same thickness and spatial orientation as in in vivo MRI, to better correlate in vivo MRI analyses with ex-vivo imaging via scanning confocal microscope and (ii) an improved clearing protocol compatible with lipophilic dyes that highlight the neurovascular network, to obtain high tissue transparency while preserving tissue staining and morphology with no significant tissue shrinkage or expansion. We applied this methodology in two rat models of glioblastoma (GBM; U87 human glioma cells and patient-derived human glioblastoma cancer stem cells) to demonstrate how vital the information retrieved from the correlation between MRI and confocal images is and to highlight how the increased invasiveness of xenografts derived from cancer stem cells may not be clearly detected by standard in vivo MRI approaches. The protocol studied in this work could be implemented in pre-clinical GBM research to further the development and validation of more predictive and translatable MR imaging protocols that can be used as critical diagnostic and prognostic tools. The development of this protocol is part of the quest for more efficacious treatment approaches for this devastating and still uncurable disease. In particular, this approach could be instrumental in validating novel MRI-based techniques to assess cellular infiltration beyond the macroscopic tumor margins and to quantify neo-angiogenesis.

Hybrid System for Local Drug Delivery and Magnetic Hyperthermia Based on SPIONs Loaded with Doxorubicin and Epirubicin

“…Multiple studies show that multimodal therapy, including the application of SPIONs, gives a synergetic effect in killing cancer cells more efficiently than sole therapy, making spectacular improvement of the therapeutic effects, e.g., greatly extend the lives of patients, even with the most aggressive brain cancers like glioblastoma [ 34 , 35 ], cervical cancer [ 36 ] or application in other biomedical fields like to prevent memory dysfunctions or cargo delivery [ 37 , 38 ]. In general, SPIONs have tremendous potential in surface engineering, so they have been widely investigated as a leading strategy towards many diseases [ 39 ], especially there, where macromolecule delivery is needed [ 40 ] for the facile release of conjugates from their surface [ 41 ].…”