Vasculotide restores the blood-brain barrier after focused ultrasound-induced permeability in a mouse model of Alzheimer's disease

Abstract

Focused ultrasound (FUS) is used to locally and transiently induce blood-brain barrier (BBB) permeability, allowing targeted drug delivery to the brain. The purpose of the current study is to evaluate the potential of Vasculotide to accelerate the recovery of the BBB following FUS disruption in the TgCRND8 mouse model of amyloidosis, characteristic of Alzheimer's disease (AD). Accelerating the restoration of the BBB post-FUS would represent an additional safety procedure, which could be beneficial for clinical applications. Methods: TgCRND8 mice and their non-transgenic littermates were treated with Vasculotide (250 ng, intraperitoneal) every 48 hours for 3 months. BBB permeability was induced using FUS, in presence of intravenously injected microbubbles, in TgCRND8 and non-transgenic mice, and confirmed at time 0 by MRI enhancement using the contrast agent gadolinium. BBB closure was assessed at 6, 12 and 20 hours by MRI. In a separate cohort of animals, BBB closure was assessed at 24-hours post-FUS using Evans blue injected intravenously and followed by histological evaluation. Results: Chronic Vasculotide administration significantly reduces the ultra-harmonic threshold required for FUS-induced BBB permeability in the TgCRND8 mice. In addition, Vasculotide treatment led to a faster restoration of the BBB following FUS in TgCRND8 mice. BBB closure after FUS is not significantly different between TgCRND8 and non-transgenic mice. BBB permeability was assessed by gadolinium up to 20-hours post-FUS, demonstrating 87% closure in Vasculotide treated TgCRND8 mice, as opposed to 52% in PBS treated TgCRND8 mice, 58% in PBS treated non-transgenic mice, and 74% in Vasculotide treated non-transgenic mice. In both TgCRND8 mice and non-transgenic littermates the BBB was impermeable to Evans blue dye at 24-hours post-FUS. Conclusion: Vasculotide reduces the pressure required for microbubble ultra-harmonic onset for FUS-induced BBB permeability and it accelerates BBB restoration in a mouse model of amyloidosis, suggesting its potential clinical utility to promote vascular health, plasticity and repair in AD.

The Applications of Focused Ultrasound (FUS) in Alzheimer’s Disease Treatment: A Systematic Review on Both Animal and Human Studies

“…Only one study (Jordao et al 2013) used twice the dose of MB (Definity) for 4 months old TgCRND8 mice, suggesting an altered vascular response to FUS in TgCRND8 mice [ 15 ]. Although several studies have demonstrated that the peak acoustic pressure induced subharmonic emission has no significant difference between TgCRND8 mice and non-Tg mice [ 13 , 16 , 71 , 72 ], a recent study showed that TgCRND8 mice treated with vasculotide (neuroprotective properties of protection from BBB breakdown and reduction in neuroinflammation) can lower the threshold to sub- and ultra-harmonic bubble behavior [ 72 ], might be benefit for lowering the likelihood of adverse effects and death.…”

“…These tight junction proteins and Pgp were shown to be restored at 24 h and 72 h post-FUS in normal brains [ 74 , 76 ] The restoration of the tight junction proteins and Pgp is regarded as the underlying mechanism of the reversibility of FUS induced BBB opening. Lynch et al [ 72 ] showed that the BBB was impermeable to Evan’s Blue dye at 24h after FUS-MB treatment in both 5-7 months old TgCRND8 mice and non-Tg mice, suggesting that CAA pathology may not affect BBB closure. However, Evan’s Blue is a relatively large molecule (~70 kDa) that may produce more rapid closure time.…”

Making waves: how ultrasound-targeted drug delivery is changing pharmaceutical approaches

“…106,107 Focused ultrasound (with peak negative pressures 4200 kPa and transmit frequencies o2 MHz) and UCA microbubbles (most frequently Definity) have been used to transiently increase the permeability of the BBB in various pre-clinical settings both paracellularly and transcellularly, including more recently in primates. [108][109][110][111] Omata et al investigated whether the encapsulated gas core had an effect on the in vivo contrast and cavitation behavior of drug-loaded lipid microbubbles composed of DSPC, DSPG, and DSPE-PEG2000 (30 : 60 : 10 molar ratio) during circulation in a mouse model. 112 In their study, perfluoropropane and perfluorobutane were most effective at retaining contrast properties as well as delivering Evans blue dye as a model drug to the brain when the agents were insonated at 3 MHz (0.5 W cm À2 intensity) for 3 minutes.…”

Taking Advantages of Blood–Brain or Spinal Cord Barrier Alterations or Restoring Them to Optimize Therapy in ALS?

“…However, this restoration might be impaired in neurodegenerative diseases with preexisting alterations in TJs, thus leading to a longer exposure of the CNS to neurotoxic blood components. For this matter, Lynch et al explored the capacity of vasculotide, an angiopoietin 1 mimetic peptide, to restore BBB permeability after focused ultrasounds application [ 85 ]. Vasculotide was chronically administrated to a mouse transgenic model of Alzheimer’s disease.…”