Focused ultrasound-mediated blood-brain barrier modulation is associated with adult hippocampal neurogenic responses linked to zinc-dependent signaling.

Abstract

Rationale: Transcranial focused ultrasound (FUS)-mediated blood-brain barrier (BBB) modulation is a promising non-invasive therapeutic strategy for targeted brain drug delivery. However, its direct regenerative potential to actively remodel the brain microenvironment and promote adult hippocampal neurogenesis remains largely unexplored owing to elusive molecular mediators. Here, we investigated whether zinc-dependent signaling contributes to adult hippocampal neurogenic responses following FUS-mediated BBB modulation.

Methods: We integrated pharmacological and genetic approaches in adult rodent models subjected to hippocampal-targeted low-intensity FUS with microbubbles. Neural progenitor proliferation and differentiation were quantified using BrdU and DCX labeling. To assess the contributions of extracellular/labile zinc availability and ZnT3-associated vesicular zinc physiology, intracerebroventricular zinc chelation with CaEDTA was performed in rats, and ZnT3^-/- mice were used. Molecular assays and exploratory bulk RNA sequencing were conducted to characterize candidate downstream molecular pathways.

Results: FUS-mediated BBB modulation significantly increased dentate gyrus progenitor proliferation, neuroblast abundance, and newborn neuron survival. These effects were markedly attenuated by acute zinc chelation and were not observed in ZnT3^-/- mice, indicating that intact zinc availability and ZnT3-associated zinc physiology are required for the full FUS-associated neurogenic response. FUS was associated with increased expression of brain-derived neurotrophic factor, Zrt-/Irt-like protein 3 (ZIP-3), and Piezo1 proteins, and zinc chelation attenuated these increases. ZIP-3 and Piezo1 signals overlapped with NeuN-positive cells, suggesting neuronal enrichment. In addition, exploratory bulk transcriptomic profiling of whole hippocampal tissue revealed candidate signatures associated with neurovascular and glial responses following FUS in ZnT3⁺/⁺ mice, whereas the corresponding transcriptomic responses appeared reduced or altered in ZnT3^-/- mice.

Conclusions: Our findings support a framework in which intact zinc availability, including ZnT3-associated zinc physiology, contributes to adult hippocampal neurogenic responses following FUS-mediated BBB modulation. This work provides a mechanistic framework for the development of ultrasound-guided therapeutic strategies aimed at promoting repair-associated plasticity in neurological disorders.