Annexin A1 as Neuroprotective Determinant for Blood-Brain Barrier Integrity in Neonatal Hypoxic-Ischemic Encephalopathy.

Ruth Gussenhoven,Chris Reutelingsperger,Luise Klein,Daan Ophelders,Leon Schurgers,Denise Habets,Bernd Giebel,Boris Kramer,Tim Wolfs

doi:10.3390/jcm8020137

Ruth Gussenhoven, Chris Reutelingsperger + Show 7 more

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https://doi.org/10.3390/jcm8020137

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Abstract

Blood-brain barrier (BBB) disruption is associated with hypoxia-ischemia (HI) induced brain injury and life-long neurological pathologies. Treatment options are limited. Recently, we found that mesenchymal stem/stromal cell derived extracellular vesicles (MSC-EVs) protected the brain in ovine fetuses exposed to HI. We hypothesized that Annexin A1 (ANXA1), present in MSC-EVs, contributed to their therapeutic potential by targeting the ANXA1/Formyl peptide receptor (FPR), thereby preventing loss of the BBB integrity. Cerebral ANXA1 expression and leakage of albumin into the fetal ovine brain parenchyma after HI were analyzed by immunohistochemistry. For mechanistic insights, barrier integrity of primary fetal endothelial cells was assessed after oxygen-glucose deprivation (OGD) followed by treatment with MSC-EVs or human recombinant ANXA1 in the presence or absence of FPR inhibitors. Our study revealed that BBB integrity was compromised after HI which was improved by MSC-EVs containing ANXA1. Treatment with these MSC-EVs or ANXA1 improved BBB integrity after OGD, an effect abolished by FPR inhibitors. Furthermore, endogenous ANXA1 was depleted within 24 h after induction of HI in cerebovasculature and ependyma and upregulated 72 h after HI in microglia. Targeting ANXA1/FPR with ANXA1 in the immature brain has great potential in preventing BBB loss and concomitant brain injury following HI.

Highlights

Hypoxic ischemic encephalopathy (HIE) in new-borns is defined as a brain injury caused by insufficient blood flow and oxygen supply to the brain generally, due to placental insufficiency or umbilical cord occlusion in the perinatal period [1]
As Annexin A1 (ANXA1) is an appreciated agonist of Formyl peptide receptor (FPR) and known to strengthen blood-brain barrier (BBB) integrity in adult neuropathologies, we investigated whether ANXA1 is present in mesenchymal stem/stromal cell derived extracellular vesicles (MSC-EVs) and confirmed its presence by a western blot (Figure 4g)
We show in our translational fetal sheep model of global HI that the BBB integrity is compromised, as indicated by an increased albumin leakage into the brain parenchyma

Summary

Introduction

Hypoxic ischemic encephalopathy (HIE) in new-borns is defined as a brain injury caused by insufficient blood flow and oxygen supply to the brain generally, due to placental insufficiency or umbilical cord occlusion in the perinatal period [1]. Besides direct effects of hypoxia and reperfusion, and chronic neuroinflammation, the disruption of the blood-brain barrier (BBB) is increasingly recognized as an important cause of brain injury following neonatal HIE [5,7,8,9,10]. The contribution of BBB injury in the pathophysiology of HIE indicates that strengthening the BBB integrity in the course of HI can attenuate brain injury. This idea mandates the understanding of the mechanisms regulating BBB integrity in order to exploit them as potential therapeutic targets

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