Targeted delivery of erythropoietin by transcranial focused ultrasound for neuroprotection against ischemia/reperfusion-induced neuronal injury: a long-term and short-term study.

Authors: Wu SK, Yang MT, Kang KH, Liou HC, Lu DH, Fu WM, Lin WL

Erythropoietin (EPO) is a neuroprotective agent against cerebral ischemia/reperfusion (I/R)-induced brain injury. However, its crossing of blood-brain barrier is limited. Focused ultrasound (FUS) sonication with microbubbles (MBs) can effectively open blood-brain barrier to boost the vascular permeability. In this study, we investigated the effects of MBs/FUS on extending the therapeutic time window of EPO and its neuroprotective effects in both acute and chronic phases. Male Wistar rats were firstly subjected to two common carotid arteries and right middle cerebral artery occlusion (three vessels occlusion, 3VO) for 50 min, and then the rats were treated with hEPO (human recombinant EPO, 5000 IU/kg) with or without MBs/FUS at 5 h after occlusion/reperfusion. Acute phase investigation (I/R, I/R+MBs/FUS, I/R+hEPO, and I/R+hEPO+MBs/FUS) was performed 24 h after I/R; chronic tests including cylinder test and gait analysis were performed one month after I/R. The experimental results showed that MBs/FUS significantly increased the cerebral content of EPO by bettering vascular permeability. In acute phase, both significant improvement of neurological score and reduction of infarct volume were found in the I/R+hEPO+MBs/FUS group, as compared with I/R and I/R+hEPO groups. In chronic phase, long-term behavioral recovery and neuronal loss in brain cortex after I/R injury was significantly improved in the I/R+hEPO+MBs/FUS group. This study indicates that hEPO administration with MBs/FUS sonication even at 5 h after occlusion/reperfusion can produce a significant neuroprotection.

Introduction

Purpose Drug delivery with BBB opening

Study Objective To determine whether focused ultrasound with microbubbles can deliver human erythropoietin to ischemia/reperfusion-injured rat brains beyond the conventional therapeutic window and improve acute and chronic neuroprotection.

Animal model / Human subject Rattus norvegicus (Wistar), age not reported, male

Disease model Cerebral ischemia/reperfusion (ischemic stroke) model

Targeted brain region(s) Brain Cortex

Cargo name and characteristics Human recombinant erythropoietin (hEPO) — protein (neuroprotective agent), administered at 5000 IU/kg

Outcomes and Safety

Summary of Outcomes Transcranial focused ultrasound with microbubbles (MBs/FUS) markedly increased delivery of IV human EPO (5000 IU/kg) to cortex and CSF when administered 5 h after ischemia/reperfusion, resulting in reduced infarct volume, preserved neurons and reduced inflammation, improved acute neurological scores, and improved long‑term residual cortex volume, limb‑use symmetry and gait. Successful FUS conditions reported were targeted cortical sonication with microbubbles applied twice at a 15‑minute interval combined with systemic hEPO (5000 IU/kg).

Duration of biological effect 28 days

Safety-related matter The authors note that intracerebroventricular hEPO can cause severe hemorrhages and brain trauma, and that MBs/FUS oscillation/cavitation may produce small hemorrhages in the focal zone so parameters (acoustic pressure, duty cycle, sonication time, MB dose) were chosen to minimize brain tissue damage. They report no animals died from the 3VO surgery and do not report other observed adverse effects in this study.

Brain Region

Ultrasound Parameters

Focal Characteristics Focal depth: None; Focal length: None; Aperture size: None

Treatment frequency single

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