The researchers, led by corresponding authors Seok Chung of Korea University and Hyun Jik Kim of Seoul National University College of Medicine, obtained primary nasal mucosal tissue from healthy donors undergoing nasal surgery, with institutional ethical approval and written informed consent. From these samples they isolated nasal epithelial cells and embedded them in a Matrigel-based three-dimensional culture system, a matrix-rich environment that allows epithelial stem and progenitor cells to self-organize into hollow, polarized structures. Over successive culture cycles, the organoids expanded and could be maintained through multiple passages, a property that distinguishes them from conventional two-dimensional nasal epithelial cultures, which the team found could not be carried reliably beyond passage two. The organoids, by contrast, sustained successful expansion up to passage five, giving laboratories a substantially longer working window from each donor sample.

Characterizing what the organoids actually contained was a central task of the study. The team applied a battery of complementary techniques: histological staining to examine tissue architecture, immunostaining to identify specific cell populations, scanning and transmission electron microscopy to resolve surface features and ultrastructure, and quantitative real-time polymerase chain reaction to measure gene expression. Together these analyses showed that the organoids recapitulated the structural characteristics of the human nasal epithelium and harbored seven distinct cell types. Single-cell RNA sequencing, which profiles gene expression in individual cells, confirmed this cellular diversity and allowed the researchers to map differentiation trajectories, tracing how progenitor populations give rise to the mature cell types that populate the nasal lining.

The cellular composition was not, however, a perfect mirror of the tissue in situ. The organoids contained a markedly higher proportion of basal progenitor cells, the self-renewing population from which the epithelium regenerates, while ciliated cells, the hair-like projections that sweep mucus and trapped pathogens along the airway, were less dominant than in native tissue. This skew toward a progenitor-rich state is a common feature of organoid systems, which favor proliferative cells under culture conditions. It also reflects the biology of the source: basal cells are the engine of epithelial renewal, and their enrichment is precisely what allows the organoids to be passaged repeatedly. For infection studies, the presence of the relevant target cells matters more than an exact census, and the organoids retained the differentiated lineages needed to model virus-host interaction.

To test whether the platform could support respiratory virology, the team exposed the organoids to influenza A virus, using the H1N1 strain A/WS/33. Infection assays measured viral nucleoprotein, a structural component of the virus whose detection marks infected cells, and tracked the course of infection over days post-infection. The organoids proved permissive to influenza A virus, supporting viral entry and replication in a way that made them, in the authors’ assessment, an adequate in vitro model for influenza infection. This is a nontrivial result: many epithelial culture systems either fail to support productive infection or do so inconsistently, undermining their usefulness for reproducible experiments on viral pathogenesis.

The most consequential findings concerned the innate immune response. Following infection, the organoids showed a sharp induction of messenger RNA for interferons, the signaling proteins that constitute the body’s first molecular alarm against viral invaders, and for interferon-stimulated genes, the downstream antiviral effectors that interferons switch on. This interferon-driven cascade is the epithelium’s principal intrinsic defense, and its faithful reproduction in vitro is what turns a static model of tissue architecture into a dynamic model of virus-host biology. With the organoids, the researchers could observe both halves of the interaction: the virus exploiting host cells for replication, and the host cells responding with a coordinated antiviral transcriptional program.

Methodologically, the study also compared the organoid system with air-liquid interface culture, a widely used technique in which epithelial cells are grown on a permeable membrane with their apical surface exposed to air, encouraging differentiation into the full repertoire of airway cell types. Air-liquid interface cultures remain valuable, but the passage limitation the team observed, with quality degrading after passage two, constrains how many experiments a single donor’s cells can support. The organoids’ ability to reach passage five while sustaining differentiation potential addresses a practical constraint that has limited sample throughput in airway epithelial research, particularly for studies requiring paired comparisons across multiple donors or repeated infection experiments from the same genetic background.

The single-cell RNA sequencing component adds a layer of analytical depth that extends beyond simple characterization. By resolving cellular heterogeneity within the organoids and reconstructing differentiation trajectories, the technique allows researchers to ask which cell populations are infected, which respond with interferon production, and how progenitor cells mature along defined pathways. This kind of resolution matters for influenza biology, because the virus shows preferences for particular cell types within the airway, and the strength of the interferon response can vary with the infected population. A model whose cellular composition is mapped at single-cell resolution gives virologists a framework for interpreting such differences rather than treating the epithelium as a uniform sheet of cells.

The broader significance of the work lies in the gap it fills. Respiratory viral research has relied heavily on immortalized cell lines, such as the Madin-Darby canine kidney cells that remain a standard substrate for propagating influenza viruses, and on animal models whose airway biology differs from that of humans in ways that complicate translation. Human airway organoids, including those derived from nasal tissue, have emerged over the past decade as an intermediate option, closer to native physiology than cell lines and more ethically tractable than animal experimentation. The Korean team’s contribution is to demonstrate that nasal organoids specifically can be established reproducibly from surgical specimens, expanded through multiple passages, differentiated into the major epithelial lineages, and used to study influenza infection with a quantifiable innate immune readout.

There are, of course, limits to what any in vitro system can claim. The organoid composition, with its basal-cell enrichment and reduced ciliated fraction, differs from native nasal epithelium, and the study used a single laboratory strain of influenza A virus, H1N1 A/WS/33, rather than the circulating or avian strains that drive public health concern. The authors frame the platform as a tool for exploring interferon-related innate immune responses following influenza infection, a scope that future work can broaden to other respiratory pathogens, including SARS-CoV-2 and respiratory syncytial virus, and to patient-derived samples from individuals with allergic rhinitis, chronic rhinosinusitis, or other conditions that alter nasal epithelial biology. As such extensions accumulate, the nasal organoid system described here could become a standard bridge between donor tissue and antiviral research, allowing the first hours of a respiratory infection to be watched, measured, and manipulated entirely within the walls of a laboratory dish.

Subject of Research: Human nasal epithelial organoids as an in vitro model for airway differentiation and influenza virus innate immune responses

Article Title: Human nasal organoids sustain reproducible airway epithelial differentiation and influenza virus-host innate immune interaction

Article References: Jin, S., Kim, S., Kim, M., Cha, H., Chung, S., & Kim, H. J. (2026). Human nasal organoids sustain reproducible airway epithelial differentiation and influenza virus-host innate immune interaction. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08908-2

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08908-2

Keywords: organoids, nasal epithelium, influenza A virus, innate immunity, interferon, air-liquid interface, single-cell RNA sequencing, 3D cell culture, respiratory virology, basal progenitor cells, ciliated cells, in vitro model