Mechanisms and Targeted Therapy of Airway Basal Cell Dysfunction in Bronchiolitis Obliterans Syndrome

The collected samples are digested with tissue collagenase for the culture of airway basal cells (BCs).

After primary BCs are expanded in the P1 passage, single-cell cloning libraries are established by planting them into 384-well cell culture plates in a single-cell per well format using a flow chamber cell sorter. Ten samples are selected from the expandable clones for the identification of differentiation and proliferation capabilities, while the remaining clones are cryopreserved.

For single-cell samples of each patient, in vitro expansion culture is performed to observe the morphology of cells at each passage and calculate the clonogenic rate. Immunofluorescence technique is used to detect the expression of the cell proliferation marker Ki67, and the proliferation capacity is evaluated by combining with the CCK8 assay. Cells at passages P3-P5 are seeded on the permeable membrane of cell culture inserts at a density of (10^6) cells/cm², and after 21 days of culture, the differentiated structures are collected. The expression of ciliated cell marker Ace-Tubulin and goblet cell marker MUC5AC is detected to assess the differentiation capacity. Meanwhile, cells are injected subcutaneously into NSG mice at (10^6) cells/injection site for in vivo differentiation for 28 days, and the differentiated structures are collected for pathological analysis.

The air-liquid interface (ALI) differentiation culture medium is collected, and cell debris is removed by high-speed centrifugation. The supernatant is then collected to extract proteins. Target proteins are purified via immunoprecipitation or affinity chromatography, followed by desalting and concentration for mass spectrometry analysis to detect inflammatory cytokines and extracellular matrix (ECM). Real-time PCR and Western blot techniques are used to measure the expression levels of epithelial markers, mesenchymal markers, and ECM in cells across all groups, thereby evaluating changes in the local microenvironment around small airways.

After plasmid construction, based on gene function, the CRISPR-Cas9-sgRNA (all-in-one) plasmid is transiently transfected into expanded single-cell strains via Nucleofection to knockout the target gene, or the CRISPR-dCas9 fusion-sgRNA plasmid is transiently transfected to activate or inhibit the target gene. After 3-5 days of culture, viable cells are sorted by FACS, and single cells are seeded into 96-well plates for two additional passages of expansion. Samples are collected for Sanger sequencing to screen successfully constructed cell lines.

Before surgery, basal cells (BCs) of recipient ferrets are collected by bronchoscopic brushing, followed by in vitro culture and identification. Prior to the onset of BOS, the cells are injected into recipient ferrets via bronchoscopy. Outcomes including ferret survival rate, body weight, CT imaging, and lung tissue pathology are collected to evaluate the preventive effect of BCs on BOS.

Stable cell lines with target gene knockdown are established in ferret basal cells (BCs). After ferrets develop bronchiolitis obliterans syndrome (BOS), the constructed cell lines are transplanted into recipient ferrets to validate the therapeutic effect of gene-corrected BCs on the disease.