INTRODUCTION: As life expectancy increases , age-related diseases such as neurodegenerative disorders are becoming increasingly relevant. To study these diseases, patient-derived induced pluripotent stem cells (iPSCs) can be used to generate brain organoids: small, three-dimensional tissues that mimic important features of the human brain. However, these organoids generally remain developmentally young, making it difficult to study ageing. Previous research suggests that physical culture conditions, including simulated microgravity, can influence cellular maturation and ageing. We therefore investigated whether dynamic culture conditions could promote an older, more mature phenotype in brain organoids. Platform for drug discovery

METHODS: Mature brain organoids were cultured either under standard static conditions or in a 2D-clinostat bioreactor, which continuously rotates the organoids and creates a simulated microgravity environment. We compared their growth, cellular composition, protein and gene expression, and changes in the extracellular matrix (ECM), the structural environment surrounding the cells.

RESULTS: Organoids grown under dynamic conditions developed mature astrocytes, an important supporting cell type in the brain, which were not detected under static culture conditions. These organoids also showed faster growth. Analysis of gene and protein expression showed increased activity of biological processes related to neuronal maturation. In addition, the gene-expression profile of dynamically cultured organoids more closely resembled that of chronologically older human brain tissue than organoids grown under static conditions.

CONCLUSION: Dynamic culture conditions promoted several characteristics associated with brain tissue maturation, including the development of mature astrocytes, changes in ECM composition, and molecular profiles associated with neuronal maturation. Importantly, their gene-expression patterns also showed greater similarity to older human brain tissue. These findings suggest that dynamic culture may provide a useful approach for generating more mature brain organoids and potentially modelling aspects of human brain ageing.