Glioblastomas are malignant tumors of the central nervous system hallmarked by subclonal diversity and dynamic adaptation amid developmental hierarchies. The source of dynamic reorganization within the spatial context of these tumors remains elusive. Here, we characterized glioblastomas by spatially resolved transcriptomics, metabolomics, and proteomics. By deciphering regionally shared transcriptional programs across patients, we infer that glioblastoma is organized by spatial segregation of lineage states and adapts to inflammatory and/or metabolic stimuli, reminiscent of the reactive transformation in mature astrocytes. Integration of metabolic imaging and imaging mass cytometry uncovered locoregional tumor-host interdependence, resulting in spatially exclusive adaptive transcriptional programs. Inferring copy-number alterations emphasizes a spatially cohesive organization of subclones associated with reactive transcriptional programs, confirming that environmental stress gives rise to selection pressure. A model of glioblastoma stem cells implanted into human and rodent neocortical tissue mimicking various environments confirmed that transcriptional states originate from dynamic adaptation to various environments.

Reactive astrocytes evolve after brain injury, inflammatory and degenerative diseases, whereby they undergo transcriptomic re-programming. In malignant brain tumors, their function and crosstalk to other components of the environment is poorly understood. Here we report a distinct transcriptional phenotype of reactive astrocytes from glioblastoma linked to JAK/STAT pathway activation. Subsequently, we investigate the origin of astrocytic transformation by a microglia loss-of-function model in a human organotypic slice model with injected tumor cells. RNA-seq based gene expression analysis of astrocytes reveals a distinct astrocytic phenotype caused by the coexistence of microglia and astrocytes in the tumor environment, which leads to a large release of anti-inflammatory cytokines such as TGFβ, IL10 and G-CSF. Inhibition of the JAK/STAT pathway shifts the balance of pro- and anti-inflammatory cytokines towards a pro-inflammatory environment. The complex interaction of astrocytes and microglia cells promotes an immunosuppressive environment, suggesting that tumor-associated astrocytes contribute to anti-inflammatory responses.

Stable interconnection to neurons in vivo over long time-periods is critical for the success of future advanced neuroelectronic applications. The inevitable foreign body reaction towards implanted materials challenges the stability and an active intervention strategy would be desirable to treat inflammation locally. Here, we investigate whether controlled release of the anti-inflammatory drug Dexamethasone from flexible neural microelectrodes in the rat hippocampus has an impact on probe-tissue integration over 12 weeks of implantation. The drug was stored in a conducting polymer coating (PEDOT/Dex), selectively deposited on the electrode sites of neural probes, and released on weekly basis by applying a cyclic voltammetry signal in three electrode configuration in fully awake animals. Dex-functionalized probes provided stable recordings and impedance characteristics over the entire chronic study. Histological evaluation after 12 weeks of implantation revealed an overall low degree of inflammation around all flexible probes whereas electrodes exposed to active drug release protocols did have neurons closer to the electrode sites compared to controls. The combination of flexible probe technology with anti-inflammatory coatings accordingly offers a promising approach for enabling long-term stable neural interfaces.

The mechanical behavior of an electrode during implantation into neural tissue can have a profound effect on the neural connections and signaling that takes place within the tissue. The objective of the present work was to investigate the in vivo implant mechanics of flexible, silicon-based ACREO microelectrode arrays recently developed by the VSAMUEL consortium (European Union, grant #IST-1999-10073). We have previously reported on both the electrical [1]-[3] and mechanical [4], [5] properties of the ACREO electrodes. In this paper, the tensile and compression forces were measured during a series of in vivo electrode insertions into the cerebral cortex of rats (7 acute experiments, 2-mm implant depth, 2-mm/s insertion velocity). We compared the ACREO silicon electrodes (4' opening angle, 1-8 shafts) to single-shaft tungsten electrodes (3' and 10' opening angles). The penetration force and dimpling increased with the cross-sectional area (statistical difference between the largest and the smallest electrode) and with the number of shafts (no statistical difference). We consistently observed tensile (drag) forces during the retraction phase, which indicates the brain tissue sticks to the electrode within a short time period. Treating the electrodes prior to insertion with silane (hydrophobic) or piranha (hydrophilic) significantly decreased the penetration force. In conclusion, our findings suggest that reusable electrodes for acute animal experiments must not only be strong enough to survive a maximal force that exceeded the penetration force, but must also be able to withstand high tension forces during retraction. Careful cleaning is not only important to avoid foreign body response, but can also reduce the stress applied to the electrode while penetrating the brain tissue