Recent advances in airway imaging using micro-computed tomography and computed tomography for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a complex lung disease characterized by a combination of airway disease and emphysema. Emphysema is classified as centrilobular emphysema (CLE), paraseptal emphysema (PSE), or panlobular emphysema (PLE), and airway disease extends from the respiratory, terminal, and preterminal bronchioles to the central segmental airways. Although clinical computed tomography (CT) cannot be used to visualize the small airways, micro-CT has shown that terminal bronchiole disease is more severe in CLE than in PSE and PLE, and micro-CT findings suggest that the loss and luminal narrowing of terminal bronchioles is an early pathological change in CLE. Furthermore, the introduction of ultra-high-resolution CT has enabled direct evaluation of the proximal small (1 to 2-mm diameter) airways, and new CT analytical methods have enabled estimation of small airway disease and prediction of future COPD onset and lung function decline in smokers with and without COPD. This review discusses the literature on micro-CT and the technical advancements in clinical CT analysis for COPD. Hopefully, novel micro-CT findings will improve our understanding of the distinct pathogeneses of the emphysema subtypes to enable exploration of new therapeutic targets, and sophisticated CT imaging methods will be integrated into clinical practice to achieve more personalized management

Associations of CT evaluations of antigravity muscles, emphysema and airway disease with longitudinal outcomes in patients with COPD

Multiple CT indices are associated with disease progression and mortality in patients with COPD, but which indices have the strongest association remain unestablished. This longitudinal 10-year observational study (n=247) showed that the emphysema severity on CT is more closely associated with the progression of airflow limitation and that a reduction in the cross-sectional area of erector spinae muscles (ESMCSA) on CT is more closely associated with mortality than the other CT indices, independent of patient demographics and pulmonary function. ESMCSA is a useful CT index that is more closely associated with long-term mortality than emphysema and airway disease in patients with COPD

Modeling of lung phenotype of Hermansky–Pudlak syndrome type I using patient-specific iPSCs

iPS細胞を用いてヘルマンスキー・パドラック症候群の肺病態の解析に成功 --研究が困難な遺伝性疾患の治療薬開発の足がかりに--. 京都大学プレスリリース. 2021-11-15.[Background] Somatic cells differentiated from patient-specific human induced pluripotent stem cells (iPSCs) could be a useful tool in human cell-based disease research. Hermansky–Pudlak syndrome (HPS) is an autosomal recessive genetic disorder characterized by oculocutaneous albinism and a platelet dysfunction. HPS patients often suffer from lethal HPS associated interstitial pneumonia (HPSIP). Lung transplantation has been the only treatment for HPSIP. Lysosome-related organelles are impaired in HPS, thereby disrupting alveolar type 2 (AT2) cells with lamellar bodies. HPSIP lungs are characterized by enlarged lamellar bodies. Despite species differences between human and mouse in HPSIP, most studies have been conducted in mice since culturing human AT2 cells is difficult. [Methods] We generated patient-specific iPSCs from patient-derived fibroblasts with the most common bi-allelic variant, c.1472_1487dup16, in HPS1 for modeling severe phenotypes of HPSIP. We then corrected the variant of patient-specific iPSCs using CRISPR-based microhomology-mediated end joining to obtain isogenic controls. The iPSCs were then differentiated into lung epithelial cells using two different lung organoid models, lung bud organoids (LBOs) and alveolar organoids (AOs), and explored the phenotypes contributing to the pathogenesis of HPSIP using transcriptomic and proteomic analyses. [Results] The LBOs derived from patient-specific iPSCs successfully recapitulated the abnormalities in morphology and size. Proteomic analysis of AOs involving iPSC-derived AT2 cells and primary lung fibroblasts revealed mitochondrial dysfunction in HPS1 patient-specific alveolar epithelial cells. Further, giant lamellar bodies were recapitulated in patient-specific AT2 cells. [Conclusions] The HPS1 patient-specific iPSCs and their gene-corrected counterparts generated in this study could be a new research tool for understanding the pathogenesis of HPSIP caused by HPS1 deficiency in humans

A homological approach to a mathematical definition of pulmonary fibrosis and emphysema on computed tomography

Three-dimensional imaging is essential to evaluate local abnormalities and understand structure-function relationships in an organ. However, quantifiable and interpretable methods to localize abnormalities remain unestablished. Visual assessments are prone to bias, machine learning methods depend on training images, and the underlying decision principle is usually difficult to interpret. Here, we developed a homological approach to mathematically define emphysema and fibrosis in the lungs on computed tomography (CT). Using persistent homology, the density of homological features, including connected components, tunnels, and voids, was extracted from the volumetric CT scans of lung diseases. A pair of CT values at which each homological feature appeared (birth) and disappeared (death) was computed by sweeping the threshold levels from higher to lower CT values. Consequently, fibrosis and emphysema were defined as voxels with dense voids having a longer lifetime (birth-death difference) and voxels with dense connected components having a lower birth, respectively. In an independent dataset including subjects with idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), and combined pulmonary fibrosis and emphysema (CPFE), the proposed definition enabled accurate segmentation with comparable quality to deep learning in terms of Dice coefficients. Persistent homology-defined fibrosis was closely associated with physiological abnormalities such as impaired diffusion capacity and long-term mortality in subjects with IPF and CPFE, and persistent homology-defined emphysema was associated with impaired diffusion capacity in subjects with COPD. The present persistent homology-based evaluation of structural abnormalities could help explore the clinical and physiological impacts of structural changes and morphological mechanisms of disease progression

Physiological Impairments on Respiratory Oscillometry and Future Exacerbations in Chronic Obstructive Pulmonary Disease Patients without a History of Frequent Exacerbations

Respiratory oscillometry allows measuring respiratory resistance and reactance during tidal breathing and may predict exacerbations in patients with chronic obstructive pulmonary disease (COPD). While the Global Initiative for Chronic Obstructive Lung Disease (GOLD) advocates the ABCD classification tool to determine therapeutic approach based on symptom and exacerbation history, we hypothesized that in addition to spirometry, respiratory oscillometry complemented the ABCD tool to identify patients with a high risk of exacerbations. This study enrolled male outpatients with stable COPD who were prospectively followed-up over 5 years after completing mMRC scale and COPD assessment test (CAT) questionnaires, post-bronchodilator spirometry and respiratory oscillometry to measure resistance, reactance, and resonant frequency (Fres), and emphysema quantitation on computed tomography. Total 134 patients were classified into the GOLD A, B, C, and D groups (n = 48, 71, 5, and 9) based on symptoms on mMRC and CAT and a history of exacerbations in the previous year. In univariable analysis, higher Fres was associated with an increased risk of exacerbation more strongly than other respiratory oscillometry indices. Fres was closely associated with forced expiratory volume in 1 sec (FEV1). In multivariable Cox-proportional hazard models of the GOLD A and B groups, either lower FEV1 group or higher Fres group was associated with a shorter time to the first exacerbation independent of the GOLD group (A vs B) and emphysema severity. Adding respiratory oscillometry to the ABCD tool may be useful for risk estimation of future exacerbations in COPD patients without frequent exacerbation history

p38 mitogen-activated protein kinase determines the susceptibility to cigarette smoke-induced emphysema in mice

BACKGROUND: There is a need for agents that suppress inflammation and progression of chronic obstructive pulmonary disease. p38 mitogen-activated protein kinase (p38 MAPK) has been associated with this disorder, and several inhibitors of this cascade are in clinical trials for its treatment, but their efficacy and utility are unknown. This study evaluated the relationship between p38 MAPK activation and susceptibility to cigarette smoke (CS)-induced emphysema, and whether its inhibition ameliorated the lung inflammation and injury in murine models of cigarette smoke exposure. METHODS: In acute and chronic CS exposure, the activation and expression of p38 MAPK in the lungs, as well as lung inflammation and injury (proteinase production, apoptosis, and oxidative DNA damage), were compared between two mouse strains: C57BL/6 (emphysema-susceptible) and NZW (emphysema-resistant). The selective p38 MAPK inhibitor SB203580 (45 mg/kg) was administrated intra-peritoneally to C57BL/6 mice, to examine whether it ameliorated cigarette smoke-induced lung inflammation and injury. RESULTS: Acute CS-induced lung inflammation (neutrophil infiltration, mRNA expressions of TNF-α and MIP-2), proteinase expression (MMP-12 mRNA), apoptosis, and oxidative DNA damage were significantly lower in NZW than C57BL/6 mice. p38 MAPK was significantly activated and up-regulated by both acute and chronic CS exposure in C57BL/6 but not NZW mice. mRNA expression of p38 MAPK was also upregulated in C57BL/6 by chronic CS exposure and tended to be constitutively suppressed in NZW mice. SB203580 significantly attenuated lung inflammation (neutrophil infiltration, mRNA expressions of TNF-α and MIP-2, protein levels of KC, MIP-1α, IL-1β, and IL-6), proteinase expression (MMP-12 mRNA), oxidative DNA damage, and apoptosis caused by acute CS exposure. CONCLUSIONS: Cigarette smoke activated p38 MAPK only in mice that were susceptible to cigarette smoke-induced emphysema. Its selective inhibition ameliorated lung inflammation and injury in a murine model of cigarette smoke exposure. p38 MAPK pathways are a possible molecular target for the treatment of chronic obstructive pulmonary disease

Directed induction of alveolar type I cells derived from pluripotent stem cells via Wnt signaling inhibition

iPS細胞を用いて肺胞上皮細胞の分化評価に成功 --肺の障害研究への足がかりに--. 京都大学プレスリリース. 2020-12-14.Alveologenesis is a developmental step involving the expansion of the lung surface area which is essential for gas exchange. The gas exchange process is mediated by alveolar type I (AT1) cells, which are known to be differentiated from alveolar type II (AT2) or bipotent cells. Due to the difficulty of isolating and culturing primary AT1 cells, the mechanism underlying their differentiation is not completely understood. We performed single‐cell RNA sequencing (scRNA‐seq) of fibroblast‐dependent alveolar organoids (FD‐AOs), including human induced pluripotent stem cell (hiPSC)‐derived epithelial cells and fetal lung fibroblasts, and identified hiPSC‐derived AT1 (iAT1) cells. A comparison of the FD‐AOs and fibroblast‐free alveolar organoids showed that iAT1 cells were mainly present in the FD‐AOs. Importantly, the transcriptomes of iAT1 cells were remarkably similar to those of primary AT1 cells. Additionally, XAV‐939, a tankyrase inhibitor, increased iAT1 cells in passaged FD‐AOs, suggesting that these cells were differentiated from hiPSC‐derived AT2 (iAT2) cells through the inhibition of canonical Wnt signaling. Consequently, our scRNA‐seq data allowed us to define iAT1 cells and identify FD‐AOs as a useful model for investigating the mechanism underlying human AT1 cell differentiation from AT2 cells in vitro

Low serum free light chain is associated with risk of COPD exacerbation

Background: Most exacerbations of chronic obstructive pulmonary disease (COPD) are triggered by respiratory tract infections. Adaptive immunity via antibody production is important in preventing infections. Impaired antibody production is reported to be associated with an increased risk of exacerbations of COPD. In the present study, we elucidated whether reduced free light chains (FLCs), which are excessive amounts of light chains produced during antibody synthesis and can be used to estimate systemic antibody production, may be a promising biomarker to predict the risk of exacerbations of COPD. Methods: We enrolled stable male patients with COPD and prospectively observed them for 2 years. At baseline, serum combined FLC (cFLC; sum of kappa and lambda values) and pulmonary function were evaluated. Exacerbation was defined as a worsening of symptoms requiring treatments with antibiotics, corticosteroids or both. Results: 63 patients with stable COPD were enrolled (72.8±8.1 years, GOLD A/B/C/D=24/28/6/5), and 51 patients completed the 2-year follow-up. Serum cFLC was 31.1 mg·L−1 on average and ranged widely (1.4 to 89.9 mg·L−1). The patients with low cFLC (below the mean−sd, n=6) experienced a significantly shorter time to the first exacerbation of COPD (p<0.0001 by the log-rank test). A multivariate Cox proportional hazard model, including the COPD assessment test score, % predicted forced expiratory volume in 1 s (FEV1 % pred), and number of previous exacerbations demonstrated that low cFLC and low FEV1 % pred were independently and significantly correlated with the risk for exacerbations of COPD. Conclusion: Low cFLC may be a B-cell-associated novel biomarker associated with risk of COPD exacerbation

Core-shell hydrogel microfiber-expanded pluripotent stem cell-derived lung progenitors applicable to lung reconstruction in vivo

ヒトiPS細胞由来肺前駆細胞の拡大培養とマウス肺への移植・生着に成功 --肺再生医療の実現へ大きな一歩--. 京都大学プレスリリース. 2021-07-30.Lung transplantation is the only treatment available for end-stage lung diseases; however, donor shortage is a global issue. The use of human pluripotent stem cells (hPSCs) for organ regeneration is a promising approach. Nevertheless, methods for the expansion of isolated hPSC-derived lung progenitors (hLPs) for transplantation purposes have not yet been reported. Herein, we established an expansion system of hLPs based on their three-dimensional culture in core-shell hydrogel microfibers, that ensures the maintenance of their bipotency for differentiation into alveolar and airway epithelial cells including alveolar type II (AT2) cells. Further, we developed an efficient in vivo transplantation method using an endoscope-assisted transtracheal administration system; the successful engraftment and in vivo differentiation of hLPs into alveolar epithelial cells (incorporated into the alveoli) was observed. Importantly, expanded hLPs in the context of microfibers were successfully transplanted into the murine lungs, opening avenues for cell-based therapies of lung diseases. Therefore, our novel method has potential regenerative medicine applications; additionally, the high-quality hLPs and AT2 cells generated via the microfiber-based technology are valuable for drug discovery purposes

Disproportionally Impaired Diffusion Capacity Relative to Airflow Limitation in COPD

Forced expiratory volume in 1 s (FEV₁) is a standard physiological index of chronic obstructive pulmonary disease (COPD), but reflects emphysema and vascular abnormalities less sensitively than diffusion capacity for carbon monoxide (D_LCO). This study tested whether a disproportionally impaired D_LCO relative to FEV₁ (FEV₁ z-score>-3 and D_LCO z-score≤-3) is a common functional COPD phenotype associated with distinct clinical and structural features and the prognosis of two cohorts. The cross-sectional analyses of the Korea COPD Subgroup Study (KOCOSS) cohort (multicenter study in Korea) included 743 males with COPD whose D_LCO was available. The cross-sectional and longitudinal analyses of the Kyoto University Cohort (single-center study in Japan) included 195 males with COPD who were prospectively followed for 10 years. A disproportionally impaired D_LCO relative to FEV₁ was observed in 29% and 31% of patients in the KOCOSS and Kyoto University cohorts, respectively. In the multivariable analysis, the disproportionally impaired D_LCO was associated with worse symptoms, shorter 6-minute walking distance, paraseptal and centrilobular emphysema on computed tomography, and reduced arterial oxygen and carbon dioxide pressures compared to the reference (FEV₁ z-score>-3 and D_LCO z-score>-3). In the multivariable Cox proportional hazard model, a higher long-term mortality was observed in the disproportionally impaired D_LCO group than in the reference group (hazard ratio [95% confidence interval] = 3.09 [1.52–6.29]) and similar to the D_LCO z-score≤-3 and FEV₁ z-score≤-3 group. The disproportionally impaired D_LCO relative to FEV₁ is common and associated with increased symptoms, emphysema, arterial blood gas abnormalities, and increased long-term mortality in patients with COPD