Non-myeloablative busulfan chimeric mouse models are less pro-inflammatory than head-shielded irradiation for studying immune cell interactions in brain tumours.

BACKGROUND: Chimeric mouse models generated via adoptive bone marrow transfer are the foundation for immune cell tracking in neuroinflammation. Chimeras that exhibit low chimerism levels, blood-brain barrier disruption and pro-inflammatory effects prior to the progression of the pathological phenotype, make it difficult to distinguish the role of immune cells in neuroinflammatory conditions. Head-shielded irradiation overcomes many of the issues described and replaces the recipient bone marrow system with donor haematopoietic cells expressing a reporter gene or different pan-leukocyte antigen, whilst leaving the blood-brain barrier intact. However, our previous work with full body irradiation suggests that this may generate a pro-inflammatory peripheral environment which could impact on the brain's immune microenvironment. Our aim was to compare non-myeloablative busulfan conditioning against head-shielded irradiation bone marrow chimeras prior to implantation of glioblastoma, a malignant brain tumour with a pro-inflammatory phenotype. METHODS: Recipient wild-type/CD45.1 mice received non-myeloablative busulfan conditioning (25 mg/kg), full intensity head-shielded irradiation, full intensity busulfan conditioning (125 mg/kg) prior to transplant with whole bone marrow from CD45.2 donors and were compared against untransplanted controls. Half the mice from each group were orthotopically implanted with syngeneic GL-261 glioblastoma cells. We assessed peripheral blood, bone marrow and spleen chimerism, multi-organ pro-inflammatory cytokine profiles at 12 weeks and brain chimerism and immune cell infiltration by whole brain flow cytometry before and after implantation of glioblastoma at 12 and 14 weeks respectively. RESULTS: Both non-myeloablative conditioning and head-shielded irradiation achieve equivalent blood and spleen chimerism of approximately 80%, although bone marrow engraftment is higher in the head-shielded irradiation group and highest in the fully conditioned group. Head-shielded irradiation stimulated pro-inflammatory cytokines in the blood and spleen but not in the brain, suggesting a systemic response to irradiation, whilst non-myeloablative conditioning showed no cytokine elevation. Non-myeloablative conditioning achieved higher donor chimerism in the brain after glioblastoma implantation than head-shielded irradiation with an altered immune cell profile. CONCLUSION: Our data suggest that non-myeloablative conditioning generates a more homeostatic peripheral inflammatory environment than head-shielded irradiation to allow a more consistent evaluation of immune cells in glioblastoma and can be used to investigate the roles of peripheral immune cells and bone marrow-derived subsets in other neurological diseases.

Safety and feasibility of posterior fossa neurosurgery in the supine position - A UK series from a large centre.

BACKGROUND: Posterior fossa surgery in the supine position remains a relatively underutilised approach, compared to the routinely performed prone, park-bench or sitting positions. This surgical approach may confer additional advantages over other modalities commonly restricted by patient co-morbidity and anaesthetic concerns. The purpose of this article is to highlight this approach as a potential viable, safe and alternative approach. METHODS: We retrospectively collected data of all supine infra-tentorial/posterior fossa surgery by one surgeon between 2015 and the present via our electronic patient record system. Demographic data alongside duration of surgery, ASA grading, location of lesions, length of stay, presence of post-operative infections, presence of post-operative CSF leak/pseudomeningocele and post-operative mortality were assessed. RESULTS: A total of 64 procedures on 58 patients were identified. Of the procedures, 60 were performed for neoplasms (93.8%). Mean overall surgical time was 176 min. Median ASA grade for tumour surgery was 3. Median length of stay was 3 days. Of the non-emergency tumour cases (n = 53), 43 (81.1%) lesions were located in the cerebellar hemisphere, the remainder were in the vermis and tentorium. There were 6 documented post-operative infections (9.4%). The rates of CSF-related complications were: CSF Leak 1.6% (1/64) and Pseudomeningocele 1.6% (1/64). 30-day mortality was 1.6% (1/64). CONCLUSION: This study suggests that supine positioning is a safe alternative to be considered when operating upon posterior fossa lesions. Further studies are warranted to assess efficacy of this approach, but it can be considered for wider use in the UK and further afield.