Different Faces of Idiopathic Pulmonary Fibrosis With Preserved Forced Vital Capacity

Role of telomere dysfunction and immune infiltration in idiopathic pulmonary fibrosis: new insights from bioinformatics analysis

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease characterized by unexplained irreversible pulmonary fibrosis. Although the etiology of IPF is unclear, studies have shown that it is related to telomere length shortening. However, the prognostic value of telomere-related genes in IPF has not been investigated.

Methods

We utilized the GSE10667 and GSE110147 datasets as the training set, employing differential expression analysis and weighted gene co-expression network analysis (WGCNA) to screen for disease candidate genes. Then, we used consensus clustering analysis to identify different telomere patterns. Next, we used summary data-based mendelian randomization (SMR) analysis to screen core genes. We further evaluated the relationship between core genes and overall survival and lung function in IPF patients. Finally, we performed immune infiltration analysis to reveal the changes in the immune microenvironment of IPF.

Results

Through differential expression analysis and WGCNA, we identified 35 significant telomere regulatory factors. Consensus clustering analysis revealed two distinct telomere patterns, consisting of cluster A (n = 26) and cluster B (n = 19). Immune infiltration analysis revealed that cluster B had a more active immune microenvironment, suggesting its potential association with IPF. Using GTEx eQTL data, our SMR analysis identified two genes with potential causal associations with IPF, including GPA33 (PSMR = 0.0013; PHEIDI = 0.0741) and MICA (PSMR = 0.0112; PHEIDI = 0.9712). We further revealed that the expression of core genes is associated with survival time and lung function in IPF patients. Finally, immune infiltration analysis revealed that NK cells were downregulated and plasma cells and memory B cells were upregulated in IPF. Further correlation analysis showed that GPA33 expression was positively correlated with NK cells and negatively correlated with plasma cells and memory B cells.

Conclusion

Our study provides a new perspective for the role of telomere dysfunction and immune infiltration in IPF and identifies potential therapeutic targets. Further research may reveal how core genes affect cell function and disease progression, providing new insights into the complex mechanisms of IPF.

The immunoregulatory role of IL-35 in patients with interstitial lung disease

Pulmonary fibrosis involves various types of immune cells and soluble mediators, including TGF-β and IL-35, a recently identified heterodimeric cytokine that belongs to the IL-12 cytokine family. However, the effect of regulatory IL-35 may play an important role in fibrotic diseases. The aim of this paper is to explore the immunoregulatory role of IL-35 in the development of fibrosis in interstitial lung disease (ILD). To gain a better understanding of this issue, the concentrations of IL-35 and different profibrotic cytokines in fibrotic (F-ILD) and non-fibrotic (NF-ILD) patients by ELISA were compared to that of intracellular IL-35 and IL-17 on CD4+ T cells stimulated in the presence of BAL or with different ratios of recombinant IL-35 (rIL-35) and TGF-β (rTGF-β), which were evaluated by flow cytometry. We observed that BAL concentration of IL-35 was lower in F patients (p < 0.001) and was negatively correlated with concentrations of TGF-β (p < 0.001) and IL-17 (p < 0.001). In supplemented cell cultures, BAL from NF but not F patients enhanced the percentage of IL-35 + CD4+ T (p < 0.001) cells and decreased the percentage of IL-17 + CD4+ T cells (p < 0.001). The percentage of IL-35 + CD4+ T cells correlated positively with BAL concentration of IL-35 (p = 0.02), but correlated negatively with BAL concentrations of IL-17 (p = 0.007) and TGF-β (p = 0.01). After adjusting the concentrations of recombinant cytokines to establish a TGF-β: IL-35 ratio of 1:4, an enhanced percentage of IL-35 + CD4+ T cells (p < 0.001) but a decreased percentage of IL-17 + CD4+ T cells (p < 0.001) was observed. After adding recombinant IL-35 to the BAL from F patients until a 1:4 ratio of TGF-β: IL-35 was reached, a significantly increased percentage of IL-35 + CD4+ T cells (p < 0.001) and a decreased percentage of IL-17 + CD4+ T cells (p = 0.003) was found. These results suggest that IL-35 may induce an anti-fibrotic response, regulating the effect of TGF-β and the inflammatory response on CD4+ T cells. In addition, the TGF-β: IL-35 ratio in BAL has been shown to be a potential biomarker to predict the outcome of F patients with ILD.

Physiological underpinnings of exertional dyspnoea in mild fibrosing interstitial lung disease

The functional disturbances driving "out-of-proportion" dyspnoea in patients with fibrosing interstitial lung disease (f-ILD) showing only mild restrictive abnormalities remain poorly understood. Eighteen patients (10 with idiopathic pulmonary fibrosis) showing preserved spirometry and mildly reduced total lung capacity (≥70% predicted) and 18 controls underwent an incremental cardiopulmonary exercise test with measurements of operating lung volumes and Borg dyspnoea scores. Patients' lower exercise tolerance was associated with higher ventilation (V̇_E)/carbon dioxide (V̇CO₂) compared with controls (V̇_E/V̇CO₂ nadir=35 ± 3 versus 29 ± 2; p < 0.001). Patients showed higher tidal volume/inspiratory capacity and lower inspiratory reserve volume at a given exercise intensity, reporting higher dyspnoea scores as a function of both work rate and V̇_E. Steeper dyspnoea-work rate slopes were associated with lower lung diffusing capacity, higher V̇_E/V̇CO₂, and lower peak O₂ uptake (p < 0.05). Heightened ventilatory demands in the setting of progressively lower capacity for tidal volume expansion on exertion largely explain higher-than-expected dyspnoea in f-ILD patients with largely preserved dynamic and "static" lung volumes at rest.

Radiological and Physiological Predictors of IPF Mortality

Background and Objectives: Idiopathic pulmonary fibrosis (IPF) has a variable clinical course, which ranges from being asymptomatic to progressive respiratory failure. The purpose of this study was to evaluate the novel clinical parameters of IPF patients who receive an anti-fibrotic agent. Materials and Methods: From January 2011 to January 2021, we identified 39 IPF patients at Okinawa Chubu Hospital. Clinical information was obtained, such as laboratory data, pulmonary function test (PFT) results, and chest images, including of soft tissue thickness and the high-resolution computed tomography (HRCT) pattern at diagnosis. Results: The mean age was 72.9 ± 7.0 (53–85); 27 patients were men and 12 were women. The mean body mass index was 25.1 ± 3.9 (17.3–35). Twenty-four were active smokers and the median number of packs per year was 20. Regarding laboratory findings, mean white blood cell (WBC), lactate dehydrogenase (LDH), and Krebs Von den Lungen-6 (KL-6) values were 7816 ± 1859, 248 ± 47, and 1615 ± 1503, respectively. In PFT, the mean percent predicted FVC, percent predicted total lung capacity, percent predicted functional residual capacity (FRC), and percent predicted diffusion capacity of the lung for carbon monoxide (DLco) were 66.8 ± 14.9%, 71.8 ± 13.7%, 65 ± 39.6%, and 64.6 ± 27.9%, respectively. In chest radiological findings, soft tissue thickness at the right 9th rib was 26.4 ± 8.8 mm. Regarding chest HRCT patterns, 15 showed the definite usual interstitial pneumonia (UIP) pattern, 16 showed the probable UIP pattern, and eight showed the indeterminate for UIP pattern. In the treatment, 24 patients received pirfenidone and 15 patients took nintedanib. The mean observation period was 38.6 ± 30.6 months and 24 patients died. The median survival time was 32.4 months (0.9–142.5). Multivariate analysis adjusted for age showed that both soft tissue thickness [Hazard ratio (HR): 0.912, 95% confidence interval (CI): 0.859–0.979, p-value: 0.009] and percent FRC [HR: 0.980, 95% CI: 0.967–0.992, p-value: 0.002] were robust predictors of IPF mortality. Conclusions: In IPF patients treated with anti-fibrotic agents, both soft tissue thickness at the right 9th rib shown on the chest radiograph and %FRC can be novel predictors of IPF mortality.