Focused ultrasound (FUS) with microbubbles opens the blood-brain barrier (BBB) for targeted drug delivery into the brain. How brain endothelial cells (BECs) respond to low acoustic pressures known to open the BBB transiently, or high pressures that cause brain damage, is incompletely characterized. Here, we apply FUS at low (450 kPa) and high (750 kPa) pressures in mice where BBB tight junctions are labeled with eGFP to characterize their abnormalities. Arteriole and capillary BECs respond to low pressure by a transient BBB tight junction reorganization and opening. In contrast, high pressure induces tight junction obliteration and persistent BBB opening in BECs even after 72 hours, associated with microglial activation. Transcriptomic analyses of BECs show that high pressure upregulates genes related to the stress response and cell junction disassembly, whereas low pressure upregulates intracellular repair genes. Thus, transient reorganization and repair of tight junctions mediate safe BBB opening for therapeutic delivery. Focused ultrasound can transiently open the blood–brain barrier for drug delivery, but the cellular responses of brain endothelial cells remain unclear. Rebecca Lynn Noel and colleagues report how low or high ultrasound pressures differently reorganize tight junction proteins, defining conditions for safe and reversible barrier opening.
Noel et al. (Sat,) studied this question.