Lung structure and function relation in systemic sclerosis: Application of lung densitometry

Network pharmacology and experimental verification to decode the action of Qing Fei Hua Xian Decotion against pulmonary fibrosis

BACKGROUND

Pulmonary fibrosis (PF) is a common interstitial pneumonia disease, also occurred in post-COVID-19 survivors. The mechanism underlying the anti-PF effect of Qing Fei Hua Xian Decotion (QFHXD), a traditional Chinese medicine formula applied for treating PF in COVID-19 survivors, is unclear. This study aimed to uncover the mechanisms related to the anti-PF effect of QFHXD through analysis of network pharmacology and experimental verification.

METHODS

The candidate chemical compounds of QFHXD and its putative targets for treating PF were achieved from public databases, thereby we established the corresponding "herb-compound-target" network of QFHXD. The protein-protein interaction network of potential targets was also constructed to screen the core targets. Furthermore, Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to predict targets, and pathways, then validated by in vivo experiments.

RESULTS

A total of 188 active compounds in QFHXD and 50 target genes were identified from databases. The key therapeutic targets of QFHXD, such as PI3K/Akt, IL-6, TNF, IL-1β, STAT3, MMP-9, and TGF-β1 were identified by KEGG and GO analysis. Anti-PF effects of QFHXD (in a dose-dependent manner) and prednisone were confirmed by HE, Masson staining, and Sirius red staining as well as in vivo Micro-CT and immunohistochemical analysis in a rat model of bleomycin-induced PF. Besides, QFXHD remarkably inhibits the activity of PI3K/Akt/NF-κB and TGF-β1/Smad2/3.

CONCLUSIONS

QFXHD significantly attenuated bleomycin-induced PF via inhibiting inflammation and epithelial-mesenchymal transition. PI3K/Akt/NF-κB and TGF-β1/Smad2/3 pathways might be the potential therapeutic effects of QFHXD for treating PF.

Skin and lung fibrosis induced by bleomycin in mice: a systematic review

OBJECTIVE

Scleroderma, or systemic sclerosis (SSc), is a chronic autoimmune connective disease with an unknown etiology and poorly understood pathogenesis. The striking array of autoimmune, vascular, and fibrotic changes that develop in almost all patients makes SSc unique among connective tissue diseases. Although no animal model developed for SSc to date fully represents all features of human disease, some animal models that demonstrate features of SSc may help to better understand the pathogenesis of the disease and to develop new therapeutic options. In this review, we aimed to evaluate skin fibrosis and lung involvement in a bleomycin (BLM)-induced mouse model and to evaluate the differences between studies.

METHODS

A systematic literature review (PRISMA guideline) on PubMed and EMBASE (until May 2023, without limits) was performed. A primary literature search was conducted using the PubMed and EMBASE databases for all articles published from 1990 to May 2023. Review articles, human studies, and non-dermatological studies were excluded. Of the 38 non-duplicated studies, 20 articles were included.

RESULTS

Among inducible animal models, the BLM-induced SSc is still the most widely used. In recent years, the measurement of tissue thickness between the epidermal-dermal junction and the dermal-adipose tissue junction (dermal layer) has become more widely accepted.

CONCLUSIONS

In animal studies, it is important to simultaneously evaluate lung tissues in addition to skin fibrosis induced in mice by subcutaneous BLM application, following the 3R (replacement, reduction, and refinement) principle to avoid cruelty to animals.

Histogram-Based Densitometry Index to Assess the Severity of Interstitial Lung Disease in Systemic Sclerosis in Standard and Low-Dose Computed Tomography

OBJECTIVE

Mean lung attenuation, skewness, and kurtosis are histogram-based densitometry variables that quantify systemic sclerosis-associated interstitial lung disease (SSc-ILD) and were recently merged into a computerized integrated index (CII). Our work tested the CII in low-dose 9-slice (reduced) and standard high-resolution computed tomography (CT) scans to evaluate extensive SSc-ILD and predict mortality.

METHODS

CT scans from patients with SSc-ILD were assessed using the software Horos to compute standard and reduced CIIs. Extensive ILD was determined following the Goh staging system. The association between CIIs and extensive ILD was analyzed with a generalized estimating equation regression model, the predictive ability of CIIs by the area under the receiver-operation characteristic curve (AUC), and the association between CIIs and death by Kaplan-Meier analysis.

RESULTS

Among 243 patients with standard and reduced CT scans available, 157 CT scans from 119 patients with SSc-ILD constituted the derivation cohort. The validation cohort included 116 standard and 175 reduced CT scans. Both CIIs from standard (odds ratio [OR] 0.53, 95% CI 0.37-0.75; AUC 0.77, 95% CI 0.68-0.87) and reduced CT scans (OR 0.54, 95% CI 0.35-0.82; AUC 0.78, 95% CI 0.70-0.87) were significantly associated with extensive ILD. A threshold of CII ≤ -0.96 for standard CT scans and CII ≤ -1.85 for reduced CT scans detected extensive ILD with high sensitivity in both derivation and validation cohorts. Extensive ILD according to Goh staging (OR 2.94, 95% CI 1.10-7.82) and standard CII ≤ -0.96 (OR 1.78, 95% CI 1.24-2.56) significantly predicted mortality; a marginal P value was observed for reduced CII ≤ -1.85 (OR 1.27, 95% CI 0.93-1.75).

CONCLUSION

Thresholds for both standard and reduced CII to identify extensive ILD were developed and validated, with an additional association with mortality. CIIs might help in clinical practice when radiology expertise is missing.

High-Resolution Computed Tomography and Lung Ultrasound in Patients with Systemic Sclerosis: Which One to Choose?

Imaging plays a pivotal role in systemic sclerosis for both diagnosis management of pulmonary complications, and high-resolution computed tomography (HRCT) is the most sensitive technique for the evaluation of systemic sclerosis-associated interstitial lung disease (SSc-ILD). Indeed, several studies have demonstrated that HRCT helps radiologists and clinicians to make a correct diagnosis on the basis of recognised typical patterns for SSc-ILD. Most SSc patients affected by ILD have a non-specific interstitial pneumonia pattern (NISP) on HRCT scan, whilst a minority of cases fulfil the criteria for usual interstitial pneumonia (UIP). Moreover, several recent studies have demonstrated that lung ultrasound (LUS) is an emergent tool in SSc diagnosis and follow-up, although its role is still to be confirmed. Therefore, this article aims at evaluating the role of LUS in SSc screening, aimed at limiting the use of CT to selected cases.

Combination therapy of tanshinone IIA and puerarin for pulmonary fibrosis via targeting IL6-JAK2-STAT3/STAT1 signaling pathways

Efficient therapy of idiopathic pulmonary fibrosis (IPF) is still a major challenge. The current studies with single-target drug therapy are the pessimistic approaches due to the complex characteristics of IPF. Here, a combination therapy of Tanshinone IIA and Puerarin for IPF was proposed to alleviate IPF due to their antiinflammatory and anti-fibrotic effects. In vivo, the combination therapy could significantly attenuate the area of ground glass opacification that was presented by 85% percentile density score of the micro-CT images when compared to single conditions. In addition, the combination therapy enormously improved the survival rate and alleviated pathological changes in bleomycin (BLM)-induced IPF mice. By using a wide spectrum of infiltration biomarkers in immunofluorescence assay in pathological sections, we demonstrate that fewer IL6 related macrophage infiltration and fibrosis area after this combination therapy, and further proved that IL6-JAK2-STAT3/STAT1 is the key mechanism of the combination therapy. In vitro, combination therapy markedly inhibited the fibroblasts activation and migration which was induced by TGF-β1 or/and IL6 through JAK2-STAT3/STAT1 signaling pathway. This study demonstrated that combination therapeutic effect of TanIIA and Pue on IPF may be related to the reduced inflammatory response targeting IL6, which could be an optimistic and effective approach for IPF.

In-vivo lung fibrosis staging in a bleomycin-mouse model: a new micro-CT guided densitometric approach

Although increasing used in the preclinical testing of new anti-fibrotic drugs, a thorough validation of micro-computed tomography (CT) in pulmonary fibrosis models has not been performed. Moreover, no attempts have been made so far to define density thresholds to discriminate between aeration levels in lung parenchyma. In the present study, a histogram-based analysis was performed in a mouse model of bleomycin (BLM)-induced pulmonary fibrosis by micro-CT, evaluating longitudinal density changes from 7 to 21 days after BLM challenge, a period representing the progression of fibrosis. Two discriminative densitometric indices (i.e. 40th and 70th percentiles) were extracted from Hounsfield Unit density distributions and selected for lung fibrosis staging. The strong correlation with histological findings (r_Spearman = 0.76, p < 0.01) confirmed that variations in 70th percentile could reflect a pathological lung condition and estimate the effect of antifibrotic treatments. This index was therefore used to define lung aeration levels in mice distinguishing in hyper-inflated, normo-, hypo- and non-aerated pulmonary compartments. A retrospective analysis performed on a large cohort of mice confirmed the correlation between the proposed preclinical density thresholds and the histological outcomes (r_Spearman = 0.6, p < 0.01), strengthening their suitability for tracking disease progression and evaluating antifibrotic drug candidates.

Reduced vitamin K status as a potentially modifiable risk factor of severe COVID-19

BACKGROUND

Respiratory failure and thromboembolism are frequent in SARS-CoV-2-infected patients. Vitamin K activates both hepatic coagulation factors and extrahepatic endothelial anticoagulant protein S, required for thrombosis prevention. In times of vitamin K insufficiency, hepatic procoagulant factors are preferentially activated over extrahepatic proteins. Vitamin K also activates matrix Gla protein (MGP), which protects against pulmonary and vascular elastic fiber damage. We hypothesized that vitamin K may be implicated in coronavirus disease 2019 (COVID-19), linking pulmonary and thromboembolic disease.

METHODS

135 hospitalized COVID-19 patients were compared with 184 historical controls. Poor outcome was defined as invasive ventilation and/or death. Inactive vitamin K-dependent MGP (dp-ucMGP) and prothrombin (PIVKA-II) were measured, inversely related to extrahepatic and hepatic vitamin K status, respectively. Desmosine was measured to quantify the rate of elastic fiber degradation. Arterial calcification severity was assessed by computed tomography.

RESULTS

Dp-ucMGP was elevated in COVID-19 patients compared to controls (p<0.001), with even higher dp-ucMGP in patients with poor outcomes (p<0.001). PIVKA-II was normal in 82.1% of patients. Dp-ucMGP was correlated with desmosine (p<0.001), and coronary artery (p=0.002) and thoracic aortic (p<0.001) calcification scores.

CONCLUSIONS

Dp-ucMGP was severely increased in COVID-19 patients, indicating extrahepatic vitamin K insufficiency, which was related to poor outcome while hepatic procoagulant factor II remained unaffected. These data suggest a mechanism of pneumonia-induced extrahepatic vitamin K depletion leading to accelerated elastic fiber damage and thrombosis in severe COVID-19 due to impaired activation of MGP and endothelial protein S, respectively. A clinical trial could assess whether vitamin K administration improves COVID-19 outcomes.

Pulmonary Vascular Morphology Associated With Gas Exchange in Systemic Sclerosis Without Lung Fibrosis

PURPOSE

Gas exchange in systemic sclerosis (SSc) is known to be affected by fibrotic changes in the pulmonary parenchyma. However, SSc patients without detectable fibrosis can still have impaired gas transfer. We aim to investigate whether pulmonary vascular changes could partly explain a reduction in gas transfer of SSc patients without fibrosis.

MATERIALS AND METHODS

We selected 77 patients whose visual computed tomography (CT) scoring showed no fibrosis. Pulmonary vessels were detected automatically in CT images, and their local radii were calculated. The frequency of occurrence for each radius was calculated, and, from this radius histogram, 2 imaging biomarkers (α and β) were extracted, wherein α reflects the relative contribution of small vessels compared with large vessels, and β represents the vessel tree capacity. Correlations between imaging biomarkers and gas transfer [single-breath diffusion capacity for carbon monoxide corrected for hemoglobin concentration (DLCOc) %predicted] were evaluated with Spearman correlation. Multivariable stepwise linear regression was performed with DLCOc %predicted as the dependent variable and age, BMI, sPAP, FEV1 %predicted, TLC %predicted, FVC %predicted, α, β, voxel size, and CT-derived lung volume as independent variables.

RESULTS

Both α and β were significantly correlated with gas transfer (R=-0.29, P-value=0.011 and R=0.32, P-value=0.004, respectively). The multivariable stepwise linear regression analysis selected sPAP [coefficient=-0.78; 95% confidence interval (CI)=-1.07, -0.49; P-value<0.001], β (coefficient=8.6; 95% CI=4.07, 13.1; P-value<0.001), and FEV1% predicted (coefficient=0.3; 95% CI=0.12, 0.48; P-value=0.001) as significant independent predictors of DLCOc %predicted (R=0.71, P-value<0.001).

CONCLUSIONS

In SSc patients without detectable pulmonary fibrosis, impaired gas exchange is associated with alterations in pulmonary vascular morphology.

Quantitative computed tomography assessment for systemic sclerosis-related interstitial lung disease: comparison of different methods

OBJECTIVES

To compare the previously defined six different histogram-based quantitative lung assessment (QLA) methods on high-resolution CT (HRCT) in patients with systemic sclerosis (SSc)-related interstitial lung disease (ILD).

METHODS

The HRCT images of SSc patients with ILD were reviewed, and the visual ILD score (semiquantitative) and the severity of ILD (limited or extensive) were calculated. The QLA score of ILD was evaluated using the previously defined six different methods and parameters (different lung attenuation ranges, skewness, kurtosis, mean lung attenuation, and standard deviation [SD]). Pulmonary function tests (PFTs) were also performed on all patients. Relationships among variables were evaluated using Spearman's correlation coefficient (r). Diagnostic performance of quantitative methods for the ability to differentiate the limited from extensive ILD was calculated using ROC analysis.

RESULTS

Fifty-five patients were included in the study. There was a significant correlation between all quantitative and semiquantitative measurement results (p < 0.0001). The QLA scores revealed a significant correlation with PFT results. The kurtosis value of the voxels between - 200 and - 1024 Hounsfield unit (HU) (Method-5) showed the best correlation with semiquantitative evaluation (r = - 0.740, p < 0.0001). The ROC analysis demonstrated the best performance of SD of the voxels between - 400 and - 950 HU (Method-6) for histogram analysis method and Method-3 (voxels between - 260 and - 600 HU were calculated as ILD) for CT density cutoff methods.

CONCLUSIONS

All the QLA methods are applicable in assessing the ILD score in SSc patients and have potential importance to differentiate limited from extensive ILD.

KEY POINTS

• Quantitative interstitial lung disease assessment helps clinicians to assess systemic sclerosis patients with interstitial lung disease. • Quantitative lung assessment methods are applicable in assessing the interstitial lung disease score in systemic sclerosis patients. • Quantitative lung assessment methods have potential importance in the management of patients.

Use of artificial intelligence in imaging in rheumatology - current status and future perspectives

After decades of basic research with many setbacks, artificial intelligence (AI) has recently obtained significant breakthroughs, enabling computer programs to outperform human interpretation of medical images in very specific areas. After this shock wave that probably exceeds the impact of the first AI victory of defeating the world chess champion in 1997, some reflection may be appropriate on the consequences for clinical imaging in rheumatology. In this narrative review, a short explanation is given about the various AI techniques, including 'deep learning', and how these have been applied to rheumatological imaging, focussing on rheumatoid arthritis and systemic sclerosis as examples. By discussing the principle limitations of AI and deep learning, this review aims to give insight into possible future perspectives of AI applications in rheumatology.

Automatic quantitative analysis of pulmonary vascular morphology in CT images

PURPOSE

Vascular remodeling is a significant pathological feature of various pulmonary diseases, which may be assessed by quantitative computed tomography (CT) imaging. The purpose of this study was therefore to develop and validate an automatic method for quantifying pulmonary vascular morphology in CT images.

METHODS

The proposed method consists of pulmonary vessel extraction and quantification. For extracting pulmonary vessels, a graph-cuts-based method is proposed which considers appearance (CT intensity) and shape (vesselness from a Hessian-based filter) features, and incorporates distance to the airways into the cost function to prevent false detection of airway walls. For quantifying the extracted pulmonary vessels, a radius histogram is generated by counting the occurrence of vessel radii, calculated from a distance transform-based method. Subsequently, two biomarkers, slope α and intercept β, are calculated by linear regression on the radius histogram. A public data set from the VESSEL12 challenge was used to independently evaluate the vessel extraction. The quantitative analysis method was validated using images of a three-dimensional (3D) printed vessel phantom, scanned by a clinical CT scanner and a micro-CT scanner (to obtain a gold standard). To confirm the association between imaging biomarkers and pulmonary function, 77 scleroderma patients were investigated with the proposed method.

RESULTS

In the independent evaluation with the public data set, our vessel segmentation method obtained an area under the receiver operating characteristic (ROC) curve of 0.976. The median radius difference between clinical and micro-CT scans of a 3D printed vessel phantom was 0.062 ± 0.020 mm, with interquartile range of 0.199 ± 0.050 mm. In the studied patient group, a significant correlation between diffusion capacity for carbon monoxide and the biomarkers, α (R = -0.27, P = 0.018) and β (R = 0.321, P = 0.004), was obtained.

CONCLUSION

In conclusion, the proposed method was validated independently using a public data set resulting in an area under the ROC curve of 0.976 and using a 3D printed vessel phantom data set, showing a vessel sizing error of 0.062 mm (0.16 in-plane pixel units). The correlation between imaging biomarkers and diffusion capacity in a clinical data set confirmed an association between lung structure and function. This quantification of pulmonary vascular morphology may be helpful in understanding the pathophysiology of pulmonary vascular diseases.

Automated CT quantification methods for the assessment of interstitial lung disease in collagen vascular diseases: A systematic review

Interstitial lung disease (ILD) is highly prevalent in collagen vascular diseases and reduction of ILD is an important therapeutic target. To that end, reliable quantification of pulmonary disease severity is of great significance. This study systematically reviewed the literature on automated computed tomography (CT) quantification methods for assessing ILD in collagen vascular diseases. PRISMA-DTA guidelines for systematic reviews were used and 19 original research articles up to January 2018 were included based on a MEDLINE/Pubmed and Embase search. Quantitative CT methods were categorized as histogram assessment (12 studies) or pattern/texture recognition (7 studies). R² for correlation with visual ILD scoring ranged from 0.143 (p < 0.01) to 0.687 (p < 0.0001), for FVC from 0.048 (p < 0.0001) to 0.504 (p < 0.0001) and for DLCO from 0.015 (p = 0.61) to 0.449 (p < 0.0001). Automated CT methods are independent of reader's expertise and are a promising tool in the quantification of ILD in collagen vascular disease patients.

Pulmonary function tests as outcomes for systemic sclerosis interstitial lung disease

Interstitial lung disease (ILD) is the leading cause of morbidity and mortality in systemic sclerosis (SSc). We performed a systematic review to characterise the use and validation of pulmonary function tests (PFTs) as surrogate markers for systemic sclerosis-associated interstitial lung disease (SSc-ILD) progression.Five electronic databases were searched to identify all relevant studies. Included studies either used at least one PFT measure as a longitudinal outcome for SSc-ILD progression (i.e. outcome studies) and/or reported at least one classical measure of validity for the PFTs in SSc-ILD (i.e. validation studies).This systematic review included 169 outcome studies and 50 validation studies. Diffusing capacity of the lung for carbon monoxide (DLCO) was cumulatively the most commonly used outcome until 2010 when it was surpassed by forced vital capacity (FVC). FVC (% predicted) was the primary endpoint in 70.4% of studies, compared to 11.3% for % predicted DLCO Only five studies specifically aimed to validate the PFTs: two concluded that DLCO was the best measure of SSc-ILD extent, while the others did not favour any PFT. These studies also showed respectable validity measures for total lung capacity (TLC).Despite the current preference for FVC, available evidence suggests that DLCO and TLC should not yet be discounted as potential surrogate markers for SSc-ILD progression.

Lung densitometry: why, how and when

Lung densitometry assesses with computed tomography (CT) the X-ray attenuation of the pulmonary tissue which reflects both the degree of inflation and the structural lung abnormalities implying decreased attenuation, as in emphysema and cystic diseases, or increased attenuation, as in fibrosis. Five reasons justify replacement with lung densitometry of semi-quantitative visual scales used to measure extent and severity of diffuse lung diseases: (I) improved reproducibility; (II) complete vs. discrete assessment of the lung tissue; (III) shorter computation times; (IV) better correlation with pathology quantification of pulmonary emphysema; (V) better or equal correlation with pulmonary function tests (PFT). Commercially and open platform software are available for lung densitometry. It requires attention to technical and methodological issues including CT scanner calibration, radiation dose, and selection of thickness and filter to be applied to sections reconstructed from whole-lung CT acquisition. Critical is also the lung volume reached by the subject at scanning that can be measured in post-processing and represent valuable information per se. The measurements of lung density include mean and standard deviation, relative area (RA) at -970, -960 or -950 Hounsfield units (HU) and 1st and 15th percentile for emphysema in inspiratory scans, and RA at -856 HU for air trapping in expiratory scans. Kurtosis and skewness are used for evaluating pulmonary fibrosis in inspiratory scans. The main indication for lung densitometry is assessment of emphysema component in the single patient with chronic obstructive pulmonary diseases (COPD). Additional emerging applications include the evaluation of air trapping in COPD patients and in subjects at risk of emphysema and the staging in patients with lymphangioleiomyomatosis (LAM) and with pulmonary fibrosis. It has also been applied to assess prevalence of smoking-related emphysema and to monitor progression of smoking-related emphysema, alpha1 antitrypsin deficiency emphysema, and pulmonary fibrosis. Finally, it is recommended as end-point in pharmacological trials of emphysema and lung fibrosis.

Interstitial lung disease in systemic sclerosis: where do we stand?

Interstitial lung disease (ILD) is common in systemic sclerosis (SSc) patients and despite recent advances in the treatment is, at present, the major cause of death. Today, an early diagnosis of ILD is possible, and is mandatory to improve the prognosis of the disease. Pulmonary function tests and high-resolution computed tomography remain the mainstay for the diagnosis of SSc-ILD, but there is a growing interest in lung ultrasound. Recently, the correlation between severity of fibrosis and some peripheral blood biomarkers has been described. Nonselective immunosuppressors are still the main treatment for ILD, with cyclophosphamide (CYC) most widely used to obtain remission. Novel therapies towards specific molecular and cellular targets have been suggested; in particular, rituximab (RTX) has shown promising results, but further research is needed. It is of paramount importance to define the severity of the disease and the risk of progression in order to define the need for treatment and the treatment intensity. We propose the division of the treatment strategies at our disposal to induce remission into three categories: high intensity (haematopoietic stem cell transplantation), medium intensity (CYC and RTX) and low intensity (azathioprine (AZA) and mycophenolate mofetil (MMF)). After obtaining remission, maintenance treatment with AZA or MMF should be started. In this review we explore new advances in the pathogenesis, diagnosis and treatment of SSc-ILD.