Monitoring ferumoxide-labelled neural progenitor cells and lesion evolution by magnetic resonance imaging in a model of cell transplantation in cerebral ischaemia

Abstract

Efficacy of neural stem/progenitor cell (NPC) therapies after cerebral ischaemia could be better evaluated by monitoring in vivo migration and distribution of cells post-engraftment in parallel with analysis of lesion volume and functional recovery. Magnetic resonance imaging (MRI) is ideally placed to achieve this, but still poses several challenges. We show that combining the ferumoxide MRI contrast agent Endorem with protamine sulphate (FePro) improves iron oxide uptake in cells compared to Endorem alone and is non-toxic. Hence FePro complex is a better contrast agent than Endorem for monitoring NPCs. FePro complex-labelled NPCs proliferated and differentiated normally in vitro, and upon grafting into the brain 48 hours post-ischaemia they were detected in vivo by MRI. Imaging over four weeks showed the development of a confounding endogenous hypointense contrast evolution at later timepoints within the lesioned tissue. This was at least partly due to accumulation within the lesion of macrophages and endogenous iron. Neither significant NPC migration, assessed by MRI and histologically, nor a reduction in the ischaemic lesion volume was observed in NPC-grafted brains. Crucially, while MRI provides reliable information on engrafted cell location early after an ischaemic insult, pathophysiological changes to ischaemic lesions can interfere with cellular imaging at later timepoints.

Quantifications of in vivo labeled stem cells based on measurements of magnetic moments

“…Values for cell iron uptake depend on the cell labeling agent and process, along with the type of cell being used. We chose 14.5 pg/cell from Panizzo et al [34], as they used the same labeling agent, process, and cell type provided in [28]. …”

Antiphospholipid antibodies exacerbate damage following oxygen deprivation-reperfusion injury in anin vivomodel for stroke and inex vivoblood derived endothelial cells

“…Fifteen minutes post IgG injection, a sterile microfilament was introduced into the CCA and positioned to fully occlude the right MCA. 35,36 After 0.5hr or 1hr ischemia, the microfilament was removed to enable reperfusion. Animals were allowed to recover, provided with soft tissue bedding, unrestricted access to water and food and euthanized 24hr post reperfusion (endpoint).…”