The liver’s architecture is zonally demarcated, with periportal regions near the portal vein, interzonal regions, and pericentral regions near the central vein, each harboring hepatocytes exhibiting distinct gene expression profiles and metabolic capabilities. This zonation governs critical pathways such as the urea cycle, glutathione synthesis, and glucose metabolism, and it profoundly influences how the liver responds to injury. Reza et al. took on the formidable task of recreating this spatial diversity by pioneering a self-assembling organoid system derived from human induced pluripotent stem cells (hiPSCs). Through carefully designed preconditioning strategies involving well-known bioactive molecules—namely ascorbate and bilirubin—they were able to coax hepatic progenitors into zone-specific phenotypes that spontaneously organized into a spatially ordered microtissue.

This method hinges on the concept that ascorbate and bilirubin, previously implicated in directing zonal hepatic fates in vivo, can be harnessed to steer the differentiation and spatial arrangement of hepatocyte-like cells in culture. By enriching distinct hepatic progenitor populations with these molecules prior to co-culture, the resulting three-dimensional organoids established clear gradients and spatial segregation resembling the portal-central axis of the liver. This represents the first in vitro human model that authentically recapitulates the multi-zonal hepatic architecture, opening new avenues for more physiologically relevant studies in liver biology, toxicity testing, and regenerative medicine.

To deeply characterize the cellular identities within these organoids, the researchers employed single-nucleus RNA sequencing (snRNA-seq), enabling high-resolution dissection of the gene expression landscapes across individual nuclei. This approach elucidated a hepatoblast differentiation trajectory that aligns with known periportal, interzonal, and pericentral hepatocyte populations in the human liver. The transcriptomic data demonstrated that not only do these cells exhibit hallmark gene expression signatures unique to their zonal identity, but they also organize coherently within the organoid, reinforcing the spatial and functional authenticity of the model.

Complementing the transcriptomic insights, epigenetic analyses revealed sophisticated regulatory mechanisms underpinning the establishment and maintenance of zonal identity. The study uncovered that ascorbate and bilirubin influence the binding of the histone acetyltransferase EP300 to distinct partners—TET1 or HIF1α respectively—modulating chromatin accessibility and gene expression patterns specific to each zonal phenotype. This discovery highlights a finely tuned molecular interplay where bioactive molecules dynamically shape the epigenetic landscape to direct hepatic zonation.

The functional validation of the zonally patterned hepatic organoids was equally compelling. Cells exhibited zone-specific metabolic activities—such as those related to the urea cycle and glutathione metabolism—corroborating their molecular zonation profiles. This level of functional fidelity is unprecedented in human organoid models and paves the way for more accurate modeling of liver metabolism and disease states that traditionally depend on zonal vulnerability.

Crucially, the translational potential of this technology was demonstrated through transplantation experiments in immunodeficient rats subjected to bile duct ligation, a model of liver injury and cholestasis. The multi-zonal human organoids improved survival outcomes in these animals by mitigating hyperammonaemia and hyperbilirubinaemia—two key pathological hallmarks of liver dysfunction. This proof-of-concept suggests that zone-specific organoids could form the basis of novel cell therapies or bioengineered grafts aimed at restoring liver function in patients with chronic liver diseases.

The implications of this work extend beyond regenerative medicine applications. The study provides an unprecedented platform to dissect the molecular mechanisms governing liver development, zonal specification, and disease pathogenesis. Researchers can now investigate how distinct hepatocyte subpopulations respond differently to toxins, infections, or metabolic stressors within a controlled human system, something that has been historically constrained by species differences and limitations of traditional cell culture systems.

Moreover, the establishment of a robust human multi-zonal organoid model heralds transformative possibilities in drug discovery. Pharmaceutical compounds often have zone-dependent hepatotoxicity profiles, which have been exceedingly difficult to predict in vitro. These organoids offer a sophisticated assay platform to screen for such liabilities early in the drug development pipeline, potentially reducing late-stage drug failures and enhancing safety assessments.

From a developmental biology perspective, the revealed interaction between small molecules like ascorbate and bilirubin with key epigenetic regulators uncovers new dimensions of hepatic zonation control. The dual role of EP300 partnering with either TET1 or HIF1α in the context of distinct metabolic milieus reflects a novel layer of metabolic-epigenetic crosstalk critical for cellular specialization along physiological gradients.

Looking ahead, the ability to engineer spatially complex human liver tissues opens exciting prospects for the study of hepatic diseases characterized by zonal dysfunction—such as non-alcoholic fatty liver disease, fibrosis, and viral hepatitis. Understanding how zone-specific injury and repair mechanisms unfold offers hope for developing targeted therapeutics that precisely modulate dysfunctional hepatocyte subsets.

In addition to advancing scientific understanding, this study exemplifies the power of integrating stem cell biology, single-cell genomics, and epigenetics to recapitulate human organ complexity in vitro. The self-assembling, multi-zonal liver organoid represents a major step toward fully functional bioartificial livers, with scalability and human relevance that surpass existing models.

By delivering an in vitro system that authentically mirrors the liver’s division of labor and spatial heterogeneity, Reza and colleagues have created a versatile platform with profound impact across multiple biomedical disciplines. This accomplishment not only deepens insight into liver biology but also spotlights the translational potential of pluripotent stem cell-derived organoids in tackling complex organ-level phenomena.

As organoid technology continues to evolve, these innovations underscore a future where human liver diseases can be modeled with unprecedented accuracy and where personalized medicine strategies may harness patient-specific, zonally organized liver tissues for therapeutic intervention. The confluence of stem cell engineering, molecular biology, and regenerative therapy embodied in this study is poised to accelerate the journey from bench to bedside in liver health and disease.

Subject of Research:
Human liver zonal architecture and hepatic progenitor differentiation using pluripotent stem cell-derived liver organoids

Article Title:
Multi-zonal liver organoids from human pluripotent stem cells

Article References:
Reza, H.A., Santangelo, C., Iwasawa, K. et al. Multi-zonal liver organoids from human pluripotent stem cells. Nature (2025). https://doi.org/10.1038/s41586-025-08850-1

Image Credits:
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The liver, a versatile organ, is integral in processing carbohydrates, proteins, and detoxifying harmful substances. It possesses a remarkable ability to regenerate, particularly important given its multifaceted roles in metabolism. Hepatocytes, which constitute around 60% of liver cells, execute these critical metabolic functions, while other cell types, such as endothelial cells, cholangiocytes, and Kupffer cells, participate in various supportive roles that ensure the liver’s functionality.

Hallmarked by their unique position in the specialized blood capillaries known as sinusoids, hepatic stellate cells contribute to liver architecture and function. Historically, their primary association with fibrosis, particularly in chronic liver diseases, has overshadowed their potential physiological roles. Recent investigations, however, have shifted this narrative, as researchers now appreciate that stellate cells are pivotal to hepatic regeneration and metabolic regulation.

In a groundbreaking experiment, researchers crafted genetically modified mice devoid of hepatic stellate cells. The absence of these cells led to significant impairments in liver detoxification processes and regenerative capabilities following injury. Intriguingly, the intricate design of liver lobules, which consists of hepatocytes organized according to metabolic demand and function, was drastically altered in the absence of stellate cells. This disruption underscores the essential structural and functional contributions of HSCs to liver health.

Central to this new understanding is the protein Rspondin 3 (RSPO3). Produced predominantly by hepatic stellate cells, RSPO3 is instrumental in modulating the WNT signaling pathway that governs various functions in liver cells. The research team elucidated that the specific knockout of RSPO3 in stellate cells mirrored the effects observed with the complete elimination of these cells, emphasizing the critical role of this protein in orchestrating liver functionality.

These findings reveal not only the involvement of hepatic stellate cells in liver pathology but also their active engagement in protective and regulatory functions essential for maintaining liver health. As highlighted by Hellmut Augustin, one of the leading researchers, the repercussions of silencing RSPO3 parallel those of totally removing stellate cells, with dire ramifications for liver viability. This new perspective is imperative, as it reshapes how researchers and clinicians could approach liver diseases.

Clinical observations from patient data further substantiate the importance of RSPO3 in liver health. Low levels of this protein correlate with poor disease outcomes in individuals suffering from alcohol-associated and metabolic liver diseases. These findings open up exciting avenues for therapeutic strategies—rather than attempting solely to inhibit the actions of stellate cells to prevent fibrosis, future treatment approaches may seek to enhance their protective and metabolically supportive roles.

The ability of the liver to regenerate is not just a consequence of hepatocyte function but is intricately linked with the activities of stellate cells. The architecture of the liver lobules, as well as the regeneration following injury, rely heavily on the intact and functional nature of these cells. This intricate relationship highlights the need for an integrated understanding of liver cellular dynamics to develop effective interventions for liver-related ailments.

Moreover, the research presents a paradigm shift in how liver diseases are perceived and addressed in clinical settings. There is a growing recognition that fostering the beneficial aspects of hepatic stellate cells could revolutionize treatment methodologies. It promotes the idea that rather than pursuing a one-dimensional strategy focused on fibrosis prevention, a multi-faceted approach celebrating the regenerative and protective attributes of these cells could yield more positive outcomes for patients.

As we glean deeper insights into the multifarious roles of hepatic stellate cells, developing a nuanced understanding of their functions will be paramount in advancing therapeutic options for liver diseases. This newfound knowledge not only enriches our understanding of liver biology but might also transform clinical practice, yielding hope for more effective treatment paradigms in the future.

In summary, the burgeoning evidence surrounding hepatic stellate cells and their influence on liver metabolism and regeneration underscores the complexity of liver pathology. The acknowledgment that HSCs play a dual role—contributing to both fibrosis and liver health—paves the way for innovative avenues in liver research. This research could significantly alter the landscape of hepatology, challenging preconceived notions and offering fresh possibilities for patient care and treatment strategies.

As we look forward, exploration into the regenerative pathways influenced by hepatic stellate cells could illuminate new biotechnological applications and therapeutic interventions aimed at preserving liver health and enhancing recovery from liver injuries. Given the organ’s essential functions and the implications of liver diseases on overall health, such advancements are profoundly critical and eagerly anticipated by the medical and scientific communities.

Understanding these mechanisms presents a critical opportunity not only for biologists and medical researchers but also for clinicians seeking to implement more effective treatments in practice. The journey of hepatic stellate cells from mere fibrosis drivers to key players in liver function epitomizes the dynamic nature of scientific discovery and the continually evolving comprehension of our body’s organ systems.

Subject of Research: Hepatic Stellate Cells and Liver Metabolism
Article Title: Hepatic Stellate Cells Play Pivotal Role in Regulating Liver Function and Size
News Publication Date: October 2023
Web References: DOI link
References: Augustin, Hellmut G., and Schwabe, Robert F. (2023). Hepatic stellate cells control liver zonation, size, and functions via Rspondin 3. Nature. DOI: 10.1038/s41586-025-08735-3
Image Credits: Augustin / DKFZ

Keywords: Hepatic Stellate Cells, Liver Metabolism, Liver Regeneration, Rspondin 3, Liver Health