Transcriptomic Response of Brain Tissue to Focused Ultrasound-Mediated Blood-Brain Barrier Disruption Depends Strongly on Anesthesia - Bulk RNA-seq
Focused ultrasound (FUS) mediated blood brain barrier disruption (BBBD) is a promising strategy for the targeted delivery of systemically-administered therapeutics to the central nervous system (CNS). Pre-clinical investigations of BBBD have been performed on different anesthetic backgrounds; however, the potential influence of the choice of anesthetic on the molecular response to BBBD is unknown, despite its potential to critically affect interpretation of experimental therapeutic outcomes. Here, using bulk RNA sequencing approaches, we comprehensively examined the transcriptomic response of both normal brain tissue and brain tissue exposed to FUS-induced BBBD in mice anesthetized with either Isoflurane with medical air (Iso) or Ketamine/Dexmedetomidine (KD). In normal murine brain tissue, Iso alone elicited minimal differential gene expression (DGE) and repressed pathways associated with neuronal signaling. KD alone, however, led to massive DGE and enrichment of pathways associated with protein synthesis. In brain tissue exposed to BBBD (1 MHz, 0.5 Hz pulse repetition frequency, 0.4 MPa peak-negative pressure), we systematically evaluated the relative effects of anesthesia, microbubbles, and FUS on the transcriptome. Of particular interest, we observed that gene sets associated with sterile inflammatory responses and cell-cell junctional activity were induced by BBBD, regardless of the choice of anesthesia. Meanwhile, gene sets associated with metabolism, platelet activity, tissue repair, and signaling pathways, were differentially affected by BBBD, with a strong dependence on the anesthetic. We conclude that the underlying transcriptomic response to FUS-mediated BBBD may be powerfully influenced by anesthesia. These findings raise considerations for the translation of FUS-BBBD delivery approaches that impact, in particular, metabolism, tissue repair, and intracellular signaling. Overall design: Groups of 3 mice were treated with sham, isoflurane in medical air (iso), ketamine/dexmedetomidine (KD), iso+microbubbles (MB), KD+MB, iso+MB+FUS, or KD+MB+FUS. At either 6 hours following FUS activation of plasmid-bearing MBs, the front right quadrant of the brain was harvested and processed for bulk mRNA sequencing followed by bioinformatics analyses.