The medial prefrontal cortex (mPFC) is important for cognitive flexibility, the ability to switch between two task-relevant dimensions. Changes in neuronal oscillations and alterations in the coupling across frequency ranges have been correlated with attention and cognitive flexibility. Here we show that astrocytes in the mPFC of adult male Sprague Dawley rats, participate in cognitive flexibility through the astrocyte-specific Ca²⁺ binding protein S100β, which improves cognitive flexibility and increases phase amplitude coupling between theta and gamma oscillations. We further show that reduction of astrocyte number in the mPFC impairs cognitive flexibility and diminishes delta, alpha and gamma power. Conversely, chemogenetic activation of astrocytic intracellular Ca²⁺ signaling in the mPFC enhances cognitive flexibility, while inactivation of endogenous S100β among chemogenetically activated astrocytes in the mPFC prevents this improvement. Collectively, our work suggests that astrocytes make important contributions to cognitive flexibility and that they do so by releasing a Ca²⁺ binding protein which in turn enhances coordinated neuronal oscillations.

There is an urgent need for predictive in vitro models to improve disease modeling and drug target identification and validation, especially for neurological disorders. Cerebral organoids, as alternative methods to in vivo studies, appear now as powerful tools to decipher complex biological processes thanks to their ability to recapitulate many features of the human brain. Combining these innovative models with microfluidic technologies, referred to as brain organoids-on-chips, allows us to model the microenvironment of several neuronal cell types in 3D. Thus, this platform opens new avenues to create a relevant in vitro approach for preclinical applications in neuroscience. The transfer to the pharmaceutical industry in drug discovery stages and the adoption of this approach by the scientific community requires the proposition of innovative microphysiological systems allowing the generation of reproducible cerebral organoids of high quality in terms of structural and functional maturation, and compatibility with automation processes and high-throughput screening. In this review, we will focus on the promising advantages of cerebral organoids for disease modeling and how their combination with microfluidic systems can enhance the reproducibility and quality of these in vitro models. Then, we will finish by explaining why brain organoids-on-chips could be considered promising platforms for pharmacological applications.

Autism spectrum disorder (ASD) is often associated with cognitive deficits and excessive anxiety. Neuroimaging studies have shown atypical structure and neural connectivity in the hippocampus, medial prefrontal cortex (mPFC), and striatum, regions associated with cognitive function and anxiety regulation. Adult hippocampal neurogenesis is involved in many behaviors that are disrupted in ASD, including cognition, anxiety, and social behaviors. Additionally, glial cells, such as astrocytes and microglia, are important for modulating neural connectivity during development, and glial dysfunction has been hypothesized to be a key contributor to the development of ASD. Cells with astroglial characteristics are known to serve as progenitor cells in the developing and adult brain. Here, we examined adult neurogenesis in the hippocampus, as well as astroglia and microglia in the hippocampus, mPFC, and striatum of two models that display autism-like phenotypes, Cntnap2^−/−and Shank3^+/ΔCtransgenic mice. We found a substantial decrease in the number of immature neurons and radial glial progenitor cells in the ventral hippocampus of both transgenic models compared with wild-type controls. No consistent differences were detected in the number or size of astrocytes or microglia in any other brain region examined. Future work is needed to explore the functional contribution of adult neurogenesis to autism-related behaviors as well as to temporally characterize glial plasticity as it is associated with ASD.

Cerebral organoids offer significant potential for neuroscience research as complex in vitro models that mimic human brain development. However, challenges related to their quality and reproducibility hinder their reliability. Discrepancies in morphology, size, cellular composition, and cytoarchitectural organization limit their applications, particularly in disease modeling, drug screening, and neurotoxicity testing. Critically, current methods for organoid characterization often lack standardization, restricting their broader applicability. To address the need for standardized quality assessment of cerebral organoids, we developed a Quality Control (QC) methodology for 60-day cortical organoids, evaluating five key criteria using a scoring system: morphology, size and growth profile, cellular composition, cytoarchitectural organization, and cytotoxicity. We implemented a hierarchical approach, beginning with non-invasive assessments to exclude low-quality organoids, while reserving in-depth analyses for those that passed the initial evaluation. To validate this framework, we exposed 60-day cortical organoids to graded doses of hydrogen peroxide (H ₂ O ₂ ), inducing a range of quality outcomes. The QC system demonstrated its robustness by accurately discriminating organoid qualities. Our proposed QC framework is designed to be user-friendly, flexible, and broadly applicable, making it suitable for routine assessment of cerebral organoid quality. Additionally, its scalability enables industrial applications, offering a valuable tool for advancing both fundamental and pre-clinical research.