Imaging inflammation in vivo in ischemic stroke : development of a multimodal NANOprobe & BRAIN imaging methods – NanoBrain

Stroke is one of the most common causes of death in the world and a major cause of long-term disability. Ischemic stroke, which results from the occlusion of a cerebral artery, accounts for 88% of all stroke cases. Reperfusion therapy is the only treatment approved by the health authorities; however only a small percentage of stroke patients are eligible for this therapy. Inflammation is one of the main contributors to post-stroke brain injury and thus represents an important therapeutic target. Limiting the inflammatory response to ischemic brain injury can improve outcome in animal models of stroke. However, the results of the few prospective clinical trials employing anti-inflammatory strategies were either negative or inconclusive. There is therefore an urgent need to couple the search for novel therapeutic approaches with the development of companion diagnostic tools that will allow for: (i) stratification of patients; and (ii) treatment assessment and monitoring.
NanoBrain is based on the ground-breaking concept of using Mac-1, an integrin widely used by neuropathologists and basic scientists to assess neuroinflammation, as a translational imaging target in stroke. Our specific aims are two-fold: 1) To develop a multimodal imaging probe (MRI, spectral CT, intravital microscopy) with optimal properties for in-vivo molecular imaging and a safe profile; and 2) To establish the proof-of-concept that Mac-1 imaging is valuable and feasible in rodent models of stroke. The nanoparticle (NP) platform was developed by Prof. Parola (Partner 2, LC ENS) in EU FP-7 project LUPAS. It consists in an inorganic core (GdF3) decorated with polyethylene glycol (PEG) and equipped with a fluorescent label. Preliminary data obtained by M. Wiart (Partner 1, Creatis) showed that those multimodal nanoparticles have a favourable pharmacokinetic for molecular imaging and that they may be visualized with K-edge imaging of Gadolinium with Synchrotron radiation x-rays, which led to joint communications at the European Molecular Imaging Meeting in 2014 and 2015.
In NanoBrain, the NPs will be functionalized with a new selective human-derived Mac-1 antagonist designed by Prof. Vorup-Jensen (Partner 7, University of Aarhus, Danemark), thanks to a linker developed by Prof. M. Lecouvey (Partner 4, CSPBAT Paris). Immunotoxicity of each NP will be thoroughly assessed by Prof. Marche (Partner 6, AICD). The dynamic interaction between the NP ligand (Mac-1 antagonist) and its target (Mac-1) will be studied with state-of-the-art NMR spectroscopy by Prof. Lancelin (Partner 5, ISA). The most promising imaging probes will be screened using in-vitro cellular models (with oxygen and glucose deprivation to mimick ischemic stroke) and their in-vivo characteristics will be fully investigated (pharmacokinetic, biodistribution, elimination, leakage through the damaged brain blood barrier) in order to select the lead candidate. The final imaging probe will be upscaled by a nanotech SME (Partner 8, MATHYM). Proof-of-concept of molecular imaging of Mac-1 occurrence will finally be established in-vivo in a mouse model of ischemic stroke by O. Pascual using intravital microscopy (Partner 3, CRNL) and by M. Wiart using high resolution MRI and K-edge imaging with a unique preclinical photon-counting spectral CT scanner (Partner 1). Validation of the approach will be performed thanks to immunofluorescence and standard biological assays. Image analysis automatization via segmentation and quantification of NPs-related signals also represents an important part of the project (Partner 1).
Supervision of NanoBrain by a radiologist (Prof. Berthezène, Coordinator) and a stroke neurologist (Prof. Nighoghossian) guarantees that clinical transfer is taken into account at each stage. Through public-private partnership, NanoBrain fosters streamlined translation of new discoveries to clinical stroke applications and facilitates the commercialization of research outcomes.