Pirfenidone Reduces Fibrosis-Associated Transcripts in Irradiated Human Lung Organoids
Repeated irradiation produced epithelial injury and fibrosis-like changes in H9-derived lung organoids. Pirfenidone given after each irradiation reduced TGFβ, α-SMA and COL1A2 transcripts; the drug experiment assessed an early epithelial response rather than recovery of established lung fibrosis.
An Epithelial Model Linked Radiation Injury to a Drug Test
Researchers at the Korea Atomic Energy Research Institute and collaborating Korean institutions developed a human lung organoid assay for radiation-associated injury and antifibrotic testing. The Scientific Reports study examined how repeated irradiation changed epithelial composition and matrix-associated signals, then used pirfenidone as a benchmark intervention. A parallel mouse experiment supplied a separate comparison with delayed whole-lung pathology.
The organoids were differentiated from the H9 human embryonic stem cell line, with passages 3–8 used experimentally. Marker staining and single-cell analysis identified alveolar type 1 and type 2 cells, proliferating type 2 cells, and airway-associated goblet, club, basal and ciliated populations. The culture was established without a fibroblast compartment, and immune cells were absent. Its biological coverage was therefore epithelial, even when the measured response involved fibrotic mediators.
Repeated Exposure Altered Proliferation and Cell Composition
The researchers compared 2, 4 and 8 Gy exposures and selected two 4-Gy irradiations for the subsequent model. Organoids became smaller and failed to regenerate normally. Ki-67-positive cells fell from approximately 30 per control organoid to fewer than five after irradiation. The organoid size comparison included 60 organoids per condition, while molecular measurements generally used three assay repetitions.
Single-cell sequencing recovered 10,265 control cells and 6,890 irradiated cells. Proliferating type 2 alveolar cells were particularly depleted, accounting for 13.1% of the irradiated population. Relative increases in other lineages described the remaining cell mixture; they did not establish that all those populations expanded in absolute number.
Radiation reduced E-cadherin and occludin and increased N-cadherin, vimentin, α-SMA and collagen-associated markers. The authors described this as an epithelial-to-mesenchymal-transition-like response. Collagen I and III staining and increased COL1A1, COL1A2 and COL3A1 transcripts provided additional evidence of matrix-related remodeling. These marker changes did not trace individual epithelial cells into a definitive fibroblast lineage.
The Drug Experiment Measured Early Transcriptional Effects
TGFβ, GDF15 and PDGFA transcripts increased after repeated irradiation. A single exposure did not significantly raise TGFβ, even at higher doses. The repeated-exposure requirement therefore distinguished the profibrotic transcriptional program from a general response to any irradiation. The TGFβ increase in organoids was modest, approximately twofold, which the authors related to the absence of macrophages.
Pirfenidone was administered at 0.5 mg/mL immediately after each irradiation. RNA measurements in the drug experiment showed lower TGFβ, α-SMA and COL1A2 expression than in irradiated PBS-treated controls. The Figure 7 experiment reports day 5 analysis and n = 3. It establishes a compound-responsive molecular endpoint within the injury assay; organoid growth recovery, restored epithelial function and reversal of established fibrosis were not measured in this drug comparison.
The Mouse Comparison Supplied a Different Scale of Pathology
In the separate animal arm, female C57BL/6 mice received a single 14-Gy thoracic exposure. Four- and six-month assessments showed inflammatory pathology, collagen accumulation and increased profibrotic signals. Histological comparisons used five mice per group. The organoid response developed over days and captured selected epithelial and matrix-associated features, while the mouse experiment included the broader tissue environment over months.
The rapid organoid assay is useful for testing whether a compound changes early radiation-associated signaling under defined exposure conditions. Its lack of immune and stromal compartments is particularly relevant to the modest TGFβ response and to the incomplete representation of sustained fibrotic remodeling. The current evidence supports pirfenidone-responsive transcriptional testing in human epithelial organoids, with cellular complexity and longer-term functional outcomes left for subsequent experiments.