The blood-brain barrier is a specialized, semipermeable barrier composed primarily of endothelial cells, pericytes, astrocytes, and extracellular matrix components. It critically regulates the exchange of molecules between the bloodstream and the neural tissue, maintaining central nervous system (CNS) homeostasis. Disruptions in BBB integrity are implicated in numerous neurological disorders, including Alzheimer’s disease, stroke, multiple sclerosis, and brain tumors. Traditional in vitro BBB models, often using primary cells or immortalized lines in two-dimensional cultures, have struggled to recapitulate the multifaceted in vivo environment, limiting their utility in disease modeling and pharmacological testing.

Addressing these limitations, González-Gallego and colleagues constructed their 3D model entirely from iPSCs, which are capable of differentiating into virtually any cell type. The use of iPSCs circumvents ethical issues associated with embryonic stem cells and enables patient-specific disease modeling by generating cells with matched genetic backgrounds. By carefully directing the differentiation of iPSCs into various neurovascular cell types, the researchers integrated endothelial cells, pericytes, and astrocytes into a biomimetic 3D scaffold that reproduces the intricate spatial organization and cellular interactions of the BBB.

Central to the model’s success was the meticulous orchestration of cellular differentiation cues and microenvironmental conditions. The researchers employed a stepwise protocol involving the application of specific growth factors and signaling molecules that mirror embryonic development pathways, guiding iPSCs toward BBB-relevant cell fates. This approach yielded cells exhibiting hallmark functional markers, such as tight junction proteins (claudin-5, occludin) in endothelial cells and the characteristic end-foot structures of astrocytes. Electrophysiological assessments and permeability assays confirmed that the model exhibited robust barrier properties, comparable to those seen in vivo, demonstrating physiological relevance.

What sets this model apart is its three-dimensional architecture. Unlike conventional flat cultures, the 3D scaffold provides a more physiologically accurate representation of the BBB microenvironment, which is pivotal for maintaining functional cell-to-cell communication and proper polarization of endothelial cells. The extracellular matrix composition was carefully tailored to afford mechanical cues and biochemical signals crucial for barrier integrity and cellular vitality. Confocal microscopy revealed a sophisticated network of cellular interactions resembling in vivo neurovascular units, underscoring the model’s fidelity.

The implications of this 3D iPSC-derived BBB model for neuroscience and pharmacology are profound. It presents an unparalleled platform to investigate how pathological conditions disrupt BBB function. Using this system, researchers can model diseases such as neuroinflammation, cerebral ischemia, and neurodegeneration under controlled, reproducible conditions, bypassing the ethical and practical constraints associated with human brain tissue studies. Moreover, the ability to create patient-specific BBB models from iPSCs opens avenues for personalized medicine, allowing evaluation of individual responses to therapeutic compounds and toxicants.

One of the notable applications demonstrated by González-Gallego and colleagues involved subjecting the model to inflammatory stimuli that mimic pathologic states, leading to characteristic BBB breakdown and altered neurovascular signaling. This capability enables detailed mechanistic studies of disease progression and identification of molecular targets for intervention. The platform also proved amenable to high-throughput drug screening, revealing both the protective and deleterious effects of candidate molecules on barrier integrity with remarkable sensitivity.

In addition to disease modeling, the researchers highlighted the model’s potential in facilitating the development of CNS-targeted therapeutics. Historically, one of the substantial hurdles in drug discovery has been the blood-brain barrier itself, which blocks over 98% of small molecule drugs and virtually all large molecules from entering the brain. Screening novel compounds in this physiologically relevant 3D system can accelerate the identification of molecules capable of crossing the BBB safely and effectively, reducing reliance on animal models that often poorly recapitulate human neurovascular physiology.

The model’s incorporation of pericytes and astrocytes alongside endothelial cells is a critical advance. Both pericytes and astrocytes play indispensable roles in regulating BBB function, from controlling tight junction assembly to modulating vascular tone and immune responses. Prior models that neglected these supporting cell types failed to replicate critical dynamics of barrier physiology. This fully integrated cellular milieu provides a realistic environment to dissect intercellular signaling pathways and understand their contributions to barrier maintenance or dysfunction under various conditions.

Another crucial technical achievement was the long-term stability of the model. Maintaining BBB properties over extended periods is essential for chronic disease modeling and repeated drug exposure studies. The 3D system sustained tight barrier function and cellular viability for weeks, offering an experimental window previously unattainable in culture systems. Such longevity also permits time-course investigations of chronic neurovascular insults and therapeutic regimens.

From a translational perspective, this human BBB model aligns with the growing emphasis on reducing animal experimentation and enhancing preclinical model predictivity. It supports the concept of “disease-in-a-dish,” where patient-derived iPSCs can faithfully recapitulate the unique pathophysiology of neurovascular diseases. Furthermore, it fosters collaboration between basic scientists, clinicians, and pharmaceutical developers, creating a nexus for accelerated innovation in neurological therapeutics.

Looking forward, this breakthrough opens multiple avenues for refinement and application. Integration with microfluidic systems to simulate blood flow shear stress, incorporation of immune cells to mimic neuroinflammation faithfully, and coupling with neural organoids to study neurovascular coupling more comprehensively represent exciting frontiers. Additionally, expanding the model’s use to study BBB aging, genetic disorders, and tumor metastasis promises to deepen understanding and treatment of a broad spectrum of CNS conditions.

In summary, the fully iPSC-derived 3D human blood-brain barrier model from González-Gallego et al. constitutes a monumental advance in neurovascular research. By deftly combining stem cell biology, biomaterials engineering, and neurobiology, this study has delivered a versatile, physiologically relevant in vitro tool that captures the complexity of the human BBB. It ushers in a new era of possibility for deciphering disease mechanisms, testing therapeutics, and ultimately improving neurological health outcomes through precision medicine and innovative drug development.

As neurological disorders continue to impose profound societal and economic burdens worldwide, the ability to better model the BBB’s role represents a beacon of hope. This study propels the field toward a future where laboratory models not only mimic human physiology with unprecedented accuracy but also accelerate the journey from bench to bedside. The convergence of stem cell technology and bioengineering demonstrated here exemplifies how interdisciplinary innovation can unlock mysteries of the brain’s protective barriers and spearhead new strategies for combating devastating CNS diseases.

For the neuroscience community and beyond, this fully human 3D BBB model stands as a testament to the power of modern biomedical science and a harbinger of transformative advances in understanding and treating brain disorders. As this platform gains traction and evolves, it promises to become an indispensable asset not only for scientific discovery but also for the development of safer, more effective therapies that cross the elusive blood-brain barrier and improve patients’ lives.

Subject of Research: Development of a fully iPSC-derived 3D model of the human blood-brain barrier for neurovascular disease modeling and therapeutic testing.

Article Title: A fully iPS-cell-derived 3D model of the human blood–brain barrier for exploring neurovascular disease mechanisms and therapeutic interventions.

Article References:
González-Gallego, J., Todorov-Völgyi, K., Müller, S.A. et al. A fully iPS-cell-derived 3D model of the human blood–brain barrier for exploring neurovascular disease mechanisms and therapeutic interventions. Nat Neurosci (2025). https://doi.org/10.1038/s41593-025-02123-w

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41593-025-02123-w

The liver’s ability to regenerate after injury is among the most remarkable feats of human biology. Yet, chronic injuries such as those caused by alcohol abuse, metabolic syndromes, and drug-induced toxicity trigger maladaptive repair mechanisms. Hepatic stellate cells, typically quiescent and vitamin A-rich in a healthy environment, become activated upon injury, transforming into myofibroblast-like cells that secrete extracellular matrix (ECM) components excessively. The resulting fibrotic scar tissue stiffens the liver, disrupting its intricate architecture and culminating in irreversible cirrhosis. Although liver transplantation remains the definitive treatment at late disease stages, it is plagued by donor shortages and complex complications, underscoring the urgent need for alternative therapeutic strategies.

Addressing this critical gap, the team at Science Tokyo devised an organoid system, termed iPSC-derived hepatocyte–stellate cell surrounding organoid (iHSO), which recapitulates native liver microenvironments more accurately than previous in vitro models. By differentiating human iPSCs into hepatocyte-like cells (iPS-Heps) and hepatic stellate-like cells (iPS-HSCs), then co-culturing them to form spheroids where stellate cells envelop hepatocytes, the system mimics the liver’s architectural and functional anatomy. This configuration allows direct observation of cellular signaling pathways governing repair and fibrogenesis, a feat impossible in monotypic cultures or animal surrogates.

A pivotal revelation from this model is the dualistic communication between stellate cells and hepatocytes mediated by the adhesion molecule ICAM-1 and cytokine interleukin-1β (IL-1β). The iHSO demonstrated that quiescent iPS-HSCs sustain a cytokine-rich environment that promotes hepatocyte proliferation via the ICAM-1–IL-1β axis, highlighting a supportive stellate cell phenotype in liver regeneration. This intricate signaling relationship elucidates how HSCs can act both as protectors during tissue repair and as drivers of fibrosis when dysregulated, providing critical insights into temporal therapeutic targeting.

Moreover, the iHSO exhibited robust responses to hepatotoxic insult, exemplified by exposure to acetaminophen, a common analgesic known to induce liver injury at high doses. The organoids mirrored pathophysiological injuries seen in vivo, including hepatocyte damage and subsequent stellate cell activation. This injury modeling capacity validates the iHSO as a valuable experimental platform for investigating drug-induced liver injury mechanisms and screening potential hepatoprotective agents, bridging a vital translational gap.

Chronic liver disease constitutes a burgeoning global health crisis, with over four million adults afflicted in the United States alone, and rising incidence rates documented in countries like Japan due to lifestyle and metabolic factors. Despite increased awareness, therapeutic options capable of halting or reversing fibrosis before catastrophic liver failure remain elusive. The human-based iHSO organoid presents a paradigm shift by offering a scalable, physiologically relevant tool for dissecting fibrosis evolution and for accelerating the discovery of anti-fibrotic drugs with greater predictive validity than existing animal models.

Beyond pathological applications, the organoid system opens new avenues in regenerative medicine. Understanding stellate cell heterogeneity — from quiescence to activation states — and their influence on hepatocyte survival and proliferation sets the stage for engineering next-generation bioartificial livers. Such constructs could one day supplement or replace conventional transplants, mitigating immunological rejection risks and donor scarcity.

The research team, led by Professors Sei Kakinuma and Yasuhiro Asahina alongside Assistant Professor Masato Miyoshi and graduate student Tomohiro Mochida, showcases how sophisticated in vitro models can powerfully simulate in vivo biology. Their findings, published in September 2025’s issue of Stem Cell Reports, underscore the transformative potential of organoid platforms in resolving complex cell-to-cell communication pathways essential to liver homeostasis and pathology.

This study not only validates the iHSO as a human-relevant model for liver fibrosis research but also spotlights ICAM-1 and IL-1β as promising molecular targets. Future therapeutic strategies might exploit these pathways to modulate stellate cell behavior, fine-tuning the balance between repair and fibrosis. Such interventions could forestall progression to cirrhosis, reducing the global burden of liver disease and diminishing the reliance on transplantation.

The Institute of Science Tokyo, born from the union of Tokyo Medical and Dental University and Tokyo Institute of Technology, reflects a forward-looking mission to harness fundamental and translational science in advancing human health. With the iHSO model, they have laid a solid foundation for future exploration of hepatic diseases, offering hope that one day, chronic liver injuries will be manageable and even reversible.

In sum, this pioneering organoid system provides a vital, human-based window into the cellular dynamics underlying chronic liver diseases. It redefines experimental possibilities in fibrosis research, opening pathways to innovative drug development and regenerative therapies. As the global community grapples with the rising incidence of liver pathologies, such scientific innovations stand to chart a new course toward addressing one of medicine’s most daunting challenges.

Subject of Research: Cells

Article Title: Crosstalk via ICAM-1 enhances supportive phenotype of stellate cells and drives hepatocyte proliferation in iPSC-derived hepatic organoids

News Publication Date: 18-Sep-2025

Web References:
https://www.cell.com/stem-cell-reports/fulltext/S2213-6711(25)00246-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2213671125002462%3Fshowall%3Dtrue

References:
Kakinuma S, Asahina Y, Miyoshi M, Mochida T, et al. Crosstalk via ICAM-1 enhances supportive phenotype of stellate cells and drives hepatocyte proliferation in iPSC-derived hepatic organoids. Stem Cell Reports. 2025 Sep 18. DOI: 10.1016/j.stemcr.2025.102642

Image Credits: Institute of Science Tokyo

Keywords: Liver damage, Diseases and disorders, Medical treatments, Clinical medicine, Health and medicine