Epithelial-mesenchymal transition and membrane microparticles: Potential implications for bronchiolitis obliterans syndrome after lung transplantation

Periostin in Bronchiolitis Obliterans Syndrome after Lung Transplant

The utility of measuring serum periostin levels for predicting the occurrence of bronchiolitis obliterans syndrome (BOS) after lung transplantation remains underexplored. We analyzed differentially expressed genes (DEGs) between initially transplanted lung tissue and lung tissue with BOS from four patients. Periostin levels were assessed in 97 patients who had undergone lung transplantation 1 year post-transplantation and at the onset of BOS. The association between periostin levels and BOS, as well as their correlation with the decline in forced expiratory volume in one second (FEV1), was evaluated. Periostin levels in the BOS group were significantly higher than those in the control group (p < 0.001) and the stable group (p < 0.001). Periostin levels at the onset of BOS were significantly higher than those 1 year post-transplantation in the BOS group (p < 0.001). The serum periostin levels at the time of BOS diagnosis showed a positive correlation with the reduction in FEV1 (%) (r = 0.745, p < 0.001). The increase in the serum periostin levels at the time of BOS diagnosis compared with those 1 year post-transplantation was positively correlated with reduction in FEV1 (%) (r = 0.753, p < 0.001). Thus, serum periostin levels may serve as biomarkers for predicting a decline in lung function in patients with BOS after lung transplantation.

RNA Sequencing of Idiopathic Subglottic Stenosis Tissues Uncovers Putative Profibrotic Mechanisms and Identifies a Prognostic Biomarker

Idiopathic subglottic stenosis (iSGS) is a localized airway disease that almost exclusively affects females. Understanding the molecular mechanisms involved may provide insights leading to therapeutic interventions. Next-generation sequencing was performed on tissue sections from patients with iSGS (n = 22), antineutrophil cytoplasmic antibody-associated vasculitis (AAV; n = 5), and matched controls (n = 9) to explore candidate genes and mechanisms of disease. Gene expression changes were validated, and selected markers were identified by immunofluorescence staining. Epithelial-mesenchymal transition (EMT) and leukocyte extravasation pathways were the biological mechanisms most relevant to iSGS pathogenesis. Alternatively activated macrophages (M2) were abundant in the subepithelium and perisubmucosal glands of the airway in iSGS and AAV. Increased expression of the mesenchymal marker S100A4 and decreased expression of the epithelial marker epithelial cell adhesion molecule (EPCAM) further supported a role for EMT, but to different extents, in iSGS and antineutrophil cytoplasmic antibody-associated subglottic stenosis. In patients with iSGS, high expression of prostate transmembrane protein, androgen induced 1 (PMEPA1), an EMT regulator, was associated with a shorter recurrence interval (25 versus 116 months: hazard ratio = 4.16; P = 0.041; 95% CI, 1.056-15.60). Thus, EMT is a key pathogenetic mechanism of subglottic stenosis in iSGS and AAV. M2 macrophages contribute to the pathogenesis of both diseases, suggesting a shared profibrotic mechanism, and PMEPA1 may be a biomarker for predicting disease recurrence in iSGS.

siRNA: Mechanism of action, challenges, and therapeutic approaches

Owing to specific and compelling gene silencing, RNA interference (RNAi) is expected to become an essential approach in treating a variety of infectious, hemato-oncological, cardiovascular, and neurodegenerative conditions. The mechanism of action of small interfering RNA (siRNA) is based on post-transcriptional gene silencing. siRNA molecules are usually specific and efficient in the knockdown of disease-related genes. However, they are characterized by low cellular uptake and are susceptible to nuclease-mediated degradation. Therefore, siRNAs require a carrier for their protection and efficient delivery into target cells. The current review highlights the siRNA-based mechanism of action, challanges, and recent advances in clinical applications.

N-myc-interactor mediates microbiome induced epithelial to mesenchymal transition and is associated with chronic lung allograft dysfunction

BACKGROUND

Recent evidence suggests a role for lung microbiome in occurrence of chronic lung allograft dysfunction (CLAD). However, the mechanisms linking the microbiome to CLAD are poorly delineated. We investigated a possible mechanism involved in microbial modulation of mucosal response leading to CLAD with the hypothesis that a Proteobacteria dominant lung microbiome would inhibit N-myc-interactor (NMI) expression and induce epithelial to mesenchymal transition (EMT).

METHODS

Explant CLAD, non-CLAD, and healthy nontransplant lung tissue were collected, as well as bronchoalveolar lavage from 14 CLAD and matched non-CLAD subjects, which were followed by 16S rRNA amplicon sequencing and quantitative polymerase chain reaction (PCR) analysis. Pseudomonas aeruginosa (PsA) or PsA-lipopolysaccharide was cocultured with primary human bronchial epithelial cells (PBEC). Western blot analysis and quantitative reverse transcription (qRT) PCR was performed to evaluate NMI expression and EMT in explants and in PsA-exposed PBECs. These experiments were repeated after siRNA silencing and upregulation (plasmid vector) of EMT regulator NMI.

RESULTS

16S rRNA amplicon analyses revealed that CLAD patients have a higher abundance of phyla Proteobacteria and reduced abundance of the phyla Bacteroidetes. At the genera level, CLAD subjects had an increased abundance of genera Pseudomonas and reduced Prevotella. Human CLAD airway cells showed a downregulation of the N-myc-interactor gene and presence of EMT. Furthermore, exposure of human primary bronchial epithelial cells to PsA resulted in downregulation of NMI and induction of an EMT phenotype while NMI upregulation resulted in attenuation of this PsA-induced EMT response.

CONCLUSIONS

CLAD is associated with increased bacterial biomass and a Proteobacteria enriched airway microbiome and EMT. Proteobacteria such as PsA induces EMT in human bronchial epithelial cells via NMI, demonstrating a newly uncovered mechanism by which the microbiome induces cellular metaplasia.