2. Academic Validation
  3. Ultrasound delivery of a TrkA agonist confers neuroprotection to Alzheimer-associated pathologies

Ultrasound delivery of a TrkA agonist confers neuroprotection to Alzheimer-associated pathologies

  • Brain. 2022 Aug 27;145(8):2806-2822. doi: 10.1093/brain/awab460.
Kristiana Xhima 1 2,  Kelly Markham-Coultes 1,  Rikke Hahn Kofoed 1,  H Uri Saragovi 3 4 5,  Kullervo Hynynen 6 7,  Isabelle Aubert 1 2
Affiliations

Affiliations

  • 1 Hurvitz Brain Sciences Research Program, Biological Sciences, Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada.
  • 2 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada.
  • 3 Lady Davis Institute, Jewish General Hospital, Montreal, QC H3T 1E2, Canada.
  • 4 Department of Pharmacology and Therapeutics, McGill University, Montreal, QC H3G 1Y6, Canada.
  • 5 Department of Ophthalmology and Vision Sciences, McGill University, Montreal, QC H4A 3S5, Canada.
  • 6 Physical Sciences, Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada.
  • 7 Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada.
PMID: 34919633 DOI: 10.1093/brain/awab460
Abstract

Early degeneration of basal forebrain cholinergic neurons contributes substantially to cognitive decline in Alzheimer's disease. Evidence from preclinical models of neuronal injury and aging support a pivotal role for nerve growth factor (NGF) in neuroprotection, resilience, and cognitive function. However, whether NGF can provide therapeutic benefit in the presence of Alzheimer's disease-related pathologies still unresolved. Perturbations in the NGF signalling system in Alzheimer's disease may render neurons unable to benefit from NGF administration. Additionally, challenges related to brain delivery remain for clinical translation of NGF-based therapies in Alzheimer's disease. To be safe and efficient, NGF-related agents should stimulate the NGF receptor, tropomyosin receptor kinase A (TrkA), avoid activation through the p75 neurotrophin receptor (p75NTR), and be delivered non-invasively to targeted brain areas using real-time monitoring. We addressed these limitations using MRI-guided focused ultrasound (MRIgFUS) to increase blood-brain barrier permeability locally and transiently, allowing an intravenously administered TrkA Agonist that does not activate p75NTR, termed D3, to enter targeted brain areas. Here, we report the therapeutic potential of selective TrkA activation in a transgenic mouse model that recapitulates numerous Alzheimer's disease-associated pathologies. Repeated MRIgFUS-mediated delivery of D3 (D3/FUS) improved cognitive function in the TgCRND8 model of Alzheimer's disease. Mechanistically, D3/FUS treatment effectively attenuated cholinergic degeneration and promoted functional recovery. D3/FUS treatment also resulted in widespread reduction of brain amyloid pathology and dystrophic neurites surrounding amyloid plaques. Furthermore, D3/FUS markedly enhanced hippocampal neurogenesis in TgCRND8 mice, implicating TrkA agonism as a novel therapeutic target to promote neurogenesis in the context of Alzheimer's disease-related pathology. Thus, this study provides evidence that selective TrkA agonism confers neuroprotection to effectively counteract Alzheimer's disease-related vulnerability. Recent clinical trials demonstrate that non-invasive blood-brain barrier modulation using MRIgFUS is safe, feasible and reversible in Alzheimer's disease patients. TrkA receptor agonists coupled with MRIgFUS delivery constitute a promising disease-modifying strategy to foster brain health and counteract cognitive decline in Alzheimer's disease.

Keywords

Alzheimer’s disease; basal forebrain cholinergic neurons; drug delivery‌; focused ultrasound; tropomyosin receptor kinase A.

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