FUS-Enhanced AAV-PHP.eB Delivery for Microglial IGFBPL1 Expression

This hybrid approach combines focused ultrasound (FUS) microbubble-mediated blood-brain barrier (BBB) disruption with AAV-PHP.eB viral vectors carrying CX3CR1-driven IGFBPL1 expression cassettes to achieve enhanced microglial-specific therapeutic delivery. The molecular mechanism begins with systemic administration of perfluorocarbon microbubbles (1-10 μm diameter) followed by targeted FUS application at 0.2-1.5 MHz to specific brain regions. Acoustic cavitation generates localized mechanical stress exceeding 1000 atmospheres, temporarily disrupting tight junction proteins (claudin-5, occludin, ZO-1) and creating transient 10-100 nm paracellular gaps in the BBB endothelium. This mechanical disruption is coupled with activation of mechanosensitive ion channels and release of vasoactive mediators including nitric oxide, further enhancing vascular permeability. During this critical temporal window of BBB opening, co-administered AAV-PHP.eB vectors carrying IGFBPL1 expression cassettes under CX3CR1 promoter control achieve enhanced brain parenchyma penetration. The PHP.eB capsid’s engineered modifications facilitate binding to AAVR, GPR108, and VPS29 receptors, but the FUS-induced BBB disruption dramatically increases vector extravasation beyond normal transcytosis capacity. Once in the brain parenchyma, vectors undergo CX3CR1-mediated microglial uptake, driven by transcription factors PU.1, IRF8, and RUNX1. Expressed IGFBPL1 then modulates microglial IGF-1/IGF-1R/PI3K/Akt signaling cascades, regulating activation states and phagocytic capacity while interacting with αvβ3 and α5β1 integrins through RGD motifs to influence microglial adhesion and migration patterns in neuroinflammatory contexts.