Beyond the blood-brain barrier: humanised mice, the missing link in glioblastoma research.

Glioblastoma (GBM) remains a major challenge in neuro-oncology, associated with a high rate of mortality despite decades of intensive research and therapeutic advancements, underscoring the urgent need for innovative preclinical platforms that can more accurately recapitulate the biological and pathological features of human disease. While conventional animal models have contributed to our understanding of GBM biology and the evaluation of treatment efficacy, they fail to capture the full complexity and heterogeneity of the tumour microenvironment (TME). Ex vivo models are associated with certain advantages in this context; however, they can not mirror the complex dynamic and multicellular interactions present in living organisms, particularly the critical treatment barriers unique to the central nervous system: the blood-brain barrier (BBB), blood-cerebrospinal fluid barrier (BCSFB) and blood-meningeal barrier (BMB). In response to these limitations, humanised mouse models have emerged as an advanced platform capable of faithfully mimicking the molecular, pathological and immunological features of human GBM. These models enable the replication of complex in vivo crosstalk between the immune system and the TME, while preserving the relevant treatment barriers that govern drug delivery to the brain. Accumulating evidence indicates that humanised mouse models closely reproduce the infiltration of human immune components into the TME, enabling the study of clinically relevant interactions that contribute to therapeutic resistance and treatment failure in GBM. This review aims to provide a comprehensive and systematic overview of the currently employed humanised mouse models in GBM research, highlighting their applications and comparative advantages. Finally, we evaluate the opportunities and challenges associated with each model and discuss future directions to increase the translational relevance and predictive power of preclinical GBM research. Humanised mouse models provide a valuable translational platform combining the human immune system and PDX orthotopic engraftment. Compared to conventional models and ex vivo models, these models can reproduce the complex cross-talk between tumour cells and the immune system, tumour heterogeneity, immunosuppressive TME, as well as complex in vivo interactions such as brain-specific barriers, including BBB, BCSFB and BMB. Future implementation of the human gut microbiome in these models has the potential to further increase translational relevance and precision in GBM research. Created in BioRender.com.