Representative images are shown (= 3 for each condition). BBB/BTB permeability was measured using fluorimetry, microscopy, and immunofluorescence. An in vitro endothelial cell model was also used to corroborate findings. Results LITT substantially disrupted the BBB and BTB locally, with increased permeability up to 30 days after the intervention. Remarkably, molecules as large as human immunoglobulin extravasated through blood vessels and permeated laser-treated brain tissue and tumors. Mechanistically, LITT decreased tight junction integrity and increased brain endothelial cell transcytosis. Treatment of mice bearing glioblastoma tumors with LITT and adjuvant doxorubicin, which is typically brain-impermeant, significantly increased animal survival. Conclusions Together, these results suggest that LITT can locally disrupt the BBB and BTB, enabling the targeted delivery of systemic therapies, including, potentially, antibody-based agents. .05 was considered significant. Results Establishing Radiprodil a Mouse Model of LITT We established a mouse model to stereotactically deliver laser treatment into either the mouse somatosensory cortex or an orthotopically implanted brain tumor (Figure 1A). To model glioblastoma, GL261 cells were stereotactically injected into the somatosensory cortex of C57BL/6J mice and then treated with LITT 7C10 days later (Figure 1BCE). Laser treatment was delivered for up to 3 min Radiprodil while a co-inserted thermocouple sensor 1 mm from the laser fiber was used to maintain tissue temperatures at least 43C (Supplementary Figure S1) to model laser therapy delivered in humans. Temperatures Radiprodil at the laser-treated core of the tumor reached more than 50C, resulting in irreversible cell death (Figure 1E; Supp1ementary Figures S1 and S2). Magnetic resonance imaging (MRI) was performed pre- and post-LITT on tumor-bearing mice, which demonstrated reproducible targeting of brain tumors (Figure 1B). Post-LITT MRI of tumor-bearing mice showed a central area of heterogeneous T2W hypointensity, consistent with coagulative necrosis and blood Radiprodil products as well as a halo of T2W hyperintensity, indicating edema (Figure 1B), similar to the imaging characteristics described in human LITT.18 To demonstrate that LITT can ablate tumor cells in vivo, we stereotactically injected luciferase-expressing GL261 intracranially in mice to monitor tumor RCBTB1 burden by BLI. Tumor burden was significantly lower in laser- versus sham-treated mice 3 days after treatment (Figure 1C and ?andD).D). Accordingly, histopathological analysis of laser-treated tumors showed loss of nuclei and increased eosin staining in the laser core, consistent with tumor cell necrosis.19 Transmission electron microscopy of Radiprodil the native brain treated with LITT showed similar results. Three days after laser treatment, we observed widespread necrotic tissue injury, loss of cellular adhesion, and the presence of red blood cells from vessel destruction in the core. In a concentric area of the brain adjacent to and outside of the necrotic laser core, we observed relatively preserved blood vessels and normal surrounding neuropil (Supplementary Figure S3). Open in a separate window Figure 1. Establishment of a LITT mouse model. (A) Schematic depiction of the LITT delivery system in mice. The laser fiber (right arrow) is positioned 1 mm caudal to the thermo-sensor (left arrow). (B) Animals stereotactically implanted with GL261 tumor cells were subjected to MRI 7 days later. Representative T2-weighted MR images of 2 mice before and 24 h after LITT are shown. Tumor (dashed circle) and LITT-treated area (black arrow) are highlighted (= 3 for each). Scale bar = 2 mm. (C) Animals stereotactically implanted with luciferase-expressing GL261 tumor cells were treated 8 days later with LITT or sham. (D) Tumor volume was quantified by BLI 3 days posttreatment. LITT-treated animals had significantly lower tumor burden compared to sham (= 5 for each condition, unpaired .01). (E) Representative H&E stained sections of sham (top) and laser-treated (bottom) mouse brains are shown (= 3 for each condition). Loss of nuclear hematoxylin staining and enhanced eosin staining are observed in the necrotic laser core. Scale bar = 500 m, 100 m. BBB and BTB Permeability Are Increased by Laser Treatment To determine if LITT directly affects BBB permeability in mice, we intravenously injected fluorescein at.