MicroRNA-124-loaded nanoparticles increase survival and neuronal differentiation of neural stem cells in vitro but do not contribute to stroke outcome in vivo.

Cláudia Saraiva,Daniela Talhada,Karsten Ruscher,Lino Ferreira,Raquel Ferreira,Liliana Bernardino,Akhilesh Rai,Johannes Boltze

doi:10.1371/journal.pone.0193609

Cláudia Saraiva, Daniela Talhada + Show 6 more

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https://doi.org/10.1371/journal.pone.0193609

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Abstract

There is a high quest for novel therapeutic strategies to enhance recovery after stroke. MicroRNA-124 (miR-124) has been described as neuroprotective and anti-inflammatory molecule. Moreover, miR-124 is a well described enhancer of adult neurogenesis that could offer potentially beneficial effects. Herein, we used miR-124-loaded nanoparticles (miR-124 NPs) to evaluate their therapeutic potential in an in vitro and in vivo model of stroke. For that, neuroprotective and neurogenic responses were assessed in an in vitro model of stroke. Here, we found that miR-124 NPs decreased cell death and improved neuronal differentiation of subventricular zone (SVZ) neural stem cell cultures after oxygen and glucose deprivation. In contrast, intravenous injection of miR-124 NPs immediately after permanent focal ischemia induced by photothrombosis (PT) did not provide a better neurological outcome. In addition, treatment did not affect the number of 5-bromo-2'-deoxyuridine (BrdU)- and doublecortin/BrdU- positive cells in the SVZ at the study endpoint of 14 days after PT. Likewise, the ischemic insult did not affect the numbers of neuronal progenitors in the SVZ. However, in PT mice miR-124 NPs were able to specifically augment interleukin-6 levels at day 2 post-stroke. Furthermore, we also showed that NPs reached the brain parenchyma and were internalized by brain resident cells. Although, promising in vitro data could not be verified in vivo as miR-124 NPs treatment did not improve functional outcome nor presented beneficial actions on neurogenesis or post-stroke inflammation, we showed that our NP formulation can be a safe alternative for drug delivery into the brain.

Highlights

After stroke, the adult brain attempts to compensate lost function by reorganizing itself, an action that involves multiple interconnected mechanisms such as cell genesis, astrogliosis, inflammation and neuronal plasticity
Previous reports showed that miR-124 levels were decreased in neural progenitor cells of the subventricular zone (SVZ) and in the ischemic core [8,9], but seemed to be elevated in the plasma of rodents subjected to permanent occlusion of the middle cerebral artery (MCAO) [10,11]
Despite some reports suggesting the migration of SVZ neuroblasts into the peri-infarcted area [30,31] we found very few DCXpositive cells in this area (Fig 5H; PT saline 0.00 ± 0.00; PT void NPs 1.17 ± 0.79; PT scramblemIR NPs 0.75 ± 0.49; PT miR-124 NPs 0.38 ± 0.38; medians with the 1st and 3rd quartile)

Summary

Introduction

The adult brain attempts to compensate lost function by reorganizing itself, an action that involves multiple interconnected mechanisms such as cell genesis, astrogliosis, inflammation and neuronal plasticity. An increased activation of immune cells as well as inflammatory molecules can be observed weeks after the insult and may contribute to restoration of brain function [4]. Therapeutic experimental approaches targeting detrimental inflammatory cascades have been translated into clinical trials aiming at improving neurological outcome of stroke patients, reviewed at Lakhan et al, 2009 and Simats et al, 2016 [5,6]. Another study showed increased plasma levels of miR-124 and those were correlated with higher mortality during the first 3 months after stroke and a worse outcome based on post-stroke modified Rankin Score (mRS) [13]. Others have demonstrated that downregulation of miR-124 resulted in lower infarct volumes while no changes in terms of infarct volumes have been observed after overexpression of miR-124 [18,19]

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