Nanotargeted endothelial progenitor cells-secretome therapy through endovascular delivery for ischaemic stroke

Abstract

Stroke remains a leading cause of death and disability worldwide. Hence there is an urgent need to develop therapeutic strategies beyond acute recanalisation. However, this therapeutic development is hampered by a highly complex pathophysiology, added to the challenge of brain drug delivery. In this regard, endothelial progenitor cells (EPCs)-secretome represents a promising cell-free therapy for post-stroke neurovascular repair. Furthermore, mechanical thrombectomy for recanalisation has opened the window to brain drug delivery, which could be further improved by nanomedicine. This doctoral thesis aimed to enhance brain targeting and neurovascular repair in the context of cerebral ischaemia, through the endovascular delivery and magnetic retention of EPCs-secretome encapsulated in biocompatible and biodegradable polymeric nanocarriers. The proposed nanocarriers have been functionalised with superparamagnetic iron-oxide nanoparticles (SPIONs) and fluorescent tags for magnetic retention and magnetic resonance/fluorescent molecular imaging (MRI/FMI), respectively. An exhaustive study of their biodistribution by MRI/FMI has shown a great advantage of the intraarterial route combined with magnetic retention through focused magnet devices, to safely enhance brain targeting in a mouse model of cerebral ischaemia. And, importantly, it has been demonstrated that the nanocarriers remain in the target ischaemic brain up to one week, easing the sought-after sustained release of cargo therapeutic factors. Furthermore, the EPCs-secretome has been successfully encapsulated into the polymeric nanocarriers, as seen through both total and specific EPCs-secretome cargo proteins, and the pro-angiogenic therapeutic effects were preserved after the encapsulation-release process, as demonstrated in endothelial cell culture in vitro models. The present study demonstrates the advantage of the therapeutic application of EPCs-secretome through this selective nanotargeted approach against the equivalent free treatment at similar doses. The results presented herein suggest that hyperacute endovascular delivery of free EPCs-secretome, at the tested dose, might exacerbate the acute post-ischaemic brain damage along with an increased neuro-inflammatory response, while ubiquitously enhancing brain angiogenesis. In contrast, the nanotargeted treatment could selectively enhance brain angiogenesis in the target peri-infarct brain, in the absence of the aforementioned detrimental effects. As preliminary steps towards the translation of the proposed therapeutic approach to the clinical setting, large animals with gyrencephalic brains and an ex vivo humanised vascular model were also used. The present study demonstrates the safety and feasibility of endovascular delivery for brain nanotargeting in pigs, and the efficacy of endovascular delivery and magnetic retention in an ex vivo model adapted to the human vascular anatomy and biodynamics. In summary, this doctoral thesis places the use of polymeric magnetised nanocarriers through endovascular delivery as a promising approach to enhance specific brain targeting of multiple therapeutic agents, such as EPCs-secretome, which could be implemented in the context of mechanical thrombectomies in the clinical scenario.

Date of Award	17 Jun 2022
Original language	English
Supervisor	Montaner Villalonga, Juan Bernardo (Tutor) & Anna Rosell Novel (Director)