Reactive Neuroinflammation Research Articles

TMOD-16. HYPOXIA RESHAPES THE GLIOBLASTOMA MICROENVIRONMENT INVOKING NECROSIS AND TRIGGERING DISEASE PROGRESSION

Abstract Emerging necrosis within solid tumors corresponds with malignant progression. Current tumor model systems fail to adequately mimic the magnitude of post-necrotic restructuring within the microenvironment and remain overly reliant on post-mortem and descriptive analyses, obligating researchers to extrapolate causal relationships between necrosis and progression phenomena that emerge during tumor evolution. In glioblastoma (GBM; WHO grade 4), the most malignant primary brain tumor, vascular pathology and central necrosis precede rapid, radial expansion. Despite extensive genetic characterization in GBM, mechanisms enabling selective fitness within a hypoxic/anoxic setting remain poorly understood. Persistent nutrient deprivation culminates in necrosis, dramatically altering the tumor microenvironment (TME). We established mouse models that more aptly capture events found in human gliomas, exposing the dynamic temporal and spatial changes that facilitate expansive progression while including unique microenvironmental stressors typically absent from GBM animal models, specifically central necrosis. This model combines hypoxia-induced focal necrosis within GBM with real time intravital microscopy to capture TME restructuring and elucidate its impact on glioma progression. Our studies use genetically characterized patient-derived orthotopic GBM xenografts, alongside an immunocompetent RCAS/tv-a model, to determine how these processes impact disease progression and outcomes across multiple GBM molecular subtypes. Simultaneously, we employ in vitro models to scrutinize how hypoxia-related crosstalk between GBM, microglia and circulating monocytes alter tumor-associated macrophage (TAMs) recruitment and reprogramming. Our preliminary data suggests microenvironmental cues significantly alter microglia behavior and have demonstrated increased 3D invasion under hypoxic conditions as compared to normoxia. Monocyte invasion varies based on signals emanating from specific GBM subtypes, yet the signaling events that elicit differential responses remains unknown. However, exposure to any GBM conditioned media uniformly upregulates immunosuppressive TAM programming. Our ongoing investigations seek to uncover the mechanisms driving post-necrotic GBM evolution and reactive neuroinflammation

TAMI-56. HYPOXIA-DRIVEN NECROSIS DRIVES DYNAMIC TUMOR PROGRESSION IN GLIOBLASTOMA

Abstract The onset of necrosis correlates with aggressive malignant progression in solid tumors. Whether necrosis arises from or promotes accelerated tumor proliferation and progression remains unknown, primarily due to inadequate models systems that fail to induce or capture these dynamic changes as they develop. In glioblastoma (GBM; WHO grade IV), the most malignant primary brain tumor, vascular pathology and central necrosis precedes rapid, radial expansion resulting in patient mortality. While genetic alterations in GBM have been highly characterized, biological adaptations arising from sustained hypoxia/anoxia require further mechanistic investigation. This sustained nutrient deprivation leads to necrosis which dramatically changes the tumor microenvironment (TME). To reveal the dynamic temporal and spatial changes promoting expansive progression, we are generating mouse models that more appropriately capture events found in human gliomas, accounting for unique microenvironmental stressors often lacking in GBM animal models, specifically central necrosis. Combining hypoxia-induced focal necrosis within high grade gliomas with intravital microscopy captures TME restructuring to understand its impact on glioma progression. Our studies use both genetically characterized patient-derived orthotopic GBM xenografts, alongside an immunocompetent RCAS/tv-a model, to determine how antagonizing these processes impacts disease progression and outcomes across multiple GBM subtypes. Complementary to this, we are investigating how increasing hypoxia and necrosis-driven signaling events promotes tumor-associated macrophages (TAMs) influx and reprogramming during glioma progression. Our preliminary data indicate substantial differences pre- and post-necrosis regarding TAM enrichment, immunosuppressive phenotypic conversion and their biological impact, however these mechanisms have not yet been elucidated. Our models capture glioma growth dynamics, reactive neuroinflammation and therapeutic resistance, facilitating innovative pre-clinical interventions to improve patient outcome.

Hyperbaric oxygen therapy reduces neuroinflammation and expression of matrix metalloproteinase‐9 in the rat model of traumatic brain injury

The acute inflammatory response plays an important role in secondary brain damage after traumatic brain injury (TBI). Neutrophils provide the main source of matrix metalloproteinases (MMPs) which also play a deleterious role in TBI. Numerous preclinical studies have suggested that hyperbaric oxygen therapy (HBOT) may by beneficial in various noncerebral and cerebral inflammatory diseases. The goal of this study was to evaluate the effects of HBOT on inflammatory infiltration and the expression of MMPs in correlation with secondary cell death in the rat model of dynamic cortical deformation (DCD). Twenty animals underwent DCD with subsequent HBOT (2.8 ATA, two sessions of 45 min each); 10 animals: DCD and normobaric oxygenation (1 ATA), 10 animals: not treated after DCD. Cell death was evaluated by TUNEL. Neutrophils were revealed by myeloperoxidase staining. Immunohistochemical staining for MMP-2 and -9 and tissue inhibitors of MMP-1 (TIMP-1) and -2 was also performed and the results were quantitatively evaluated by image analysis. In the animals treated by HBOT, a significant decrease in the number of TUNEL-positive cells and neutrophilic inflammatory infiltration was seen in comparison with nontreated animals and those treated by normobaric oxygen. The expression of MMP-9 was also significantly lower in the treated group. Staining for MMP-2 and TIMP-2 did not change significantly. Our results demonstrate that HBOT decreased the extent of secondary cell death and reactive neuroinflammation in the TBI model. The decline of MMP-9 expression after HBOT may also contribute to protection of brain tissue in the perilesional area. Further research should be centred on the evaluation of long-term functional and morphological results of HBOT.