Pleural Fibrosis Research Articles

Thoracic aortic coarctation with asbestos-induced pleural fibrosis presenting as lower limb claudication

Asbestos exposure is a well-documented cause of pulmonary diseases. However, its systemic effects, particularly on the cardiovascular system, are less understood. We expose a case that highlights an unusual cardiovascular manifestation in a patient with a history of pleural asbestosis compressing the aorta and clinically manifested as lower limb claudication. A 65-year-old individual presented with bilateral short-distance lower extremity claudication. The patient’s clinical presentation prompted advanced imaging studies, including CT angiography, to assess the extent of vascular involvement. The imaging confirmed the presence of substantial calcification and narrowing of the thoracic aorta. The patient had a documented history of pleural asbestosis. This case underscores the potential for asbestos-related diseases to extend beyond pulmonary manifestations, affecting cardiovascular health. The observed aortic calcification and coarctation represent an atypical progression of asbestosis related pathology.

Epigallocatechin-3-gallate (EGCG) reduced expression of Signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3) and Transforming Growth Factor-β1 (TGF-β1) in visceral pleural tissue cultures of patients with empyema

Abstract* Background Increased expression of signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3) and Transforming Growth Factor-β1 (TGF-β1) has been thought to influence the fibrosis process in many tissues. However, increased expression of these two factors has never been assessed in pleural fibrosis. Pleural fibrosis is a disease that usually results from various infectious processes, such as empyema. Fibrosis formation is recently known to be prevented by Epigallocatechin-3-gallate (EGCG), which is the most potent active substance found in Gambir (Uncaria gambir Roxb) leaves. Thus, further research is needed to determine the potential of EGCG to inhibit the process of pleural fibrosis caused by empyema. Methods An in vitro experimental study with post test-only controlled group was conducted on the pleural tissue of all patients who underwent decortication surgery due to empyema at Dr. M. Djamil Hospital, Padang, Indonesia between March 1st and April 30, 2024. Case samples were obtained by consecutive sampling, and three patients who met the inclusion criteria were obtained. Pleural tissue in each patient was then divided into several groups based on the treatment, namely the control group, 50 μg EGCG administration group, and 100 μg EGCG administration group. We used to determine SCUBE3 and TGF-β1 genes expression. Data were tested using ANOVA and Least Significant Difference (LSD) tests. Results There were significant differences in the SCUBE3 and TGF-β1 genes expression of 50 μg and 100 μg EGCG administration groups and the control groups in the 2 × 2 cm sample preparation (p=0.002) (p=0.014, respectively). Significant differences in TGF-β1 expression were also found between the groups treated with EGCG 50 μg and 100 μg and the control group in the 1 × 1 cm preparation (p=0.019). Conclusion EGCG can potentially decrease SCUBE3 and TGF-β1 expression in patients with pleural empyema.

Epigallocatechin-3-gallate (EGCG) reduced expression of Signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3) and Transforming Growth Factor-β1 (TGF-β1) in visceral pleural tissue cultures of patients with empyema

Abstract* Background Increased expression of signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3) and Transforming Growth Factor-β1 (TGF-β1) has been thought to influence the fibrosis process in many tissues. However, increased expression of these two factors has never been assessed in pleural fibrosis. Pleural fibrosis is a disease that usually results from various infectious processes, such as empyema. Fibrosis formation is recently known to be prevented by Epigallocatechin-3-gallate (EGCG), which is the most potent active substance found in Gambir (Uncaria gambir Roxb) leaves. Thus, further research is needed to determine the potential of EGCG to inhibit the process of pleural fibrosis caused by empyema. Methods An in vitro experimental study with post test-only controlled group was conducted on the pleural tissue of all patients who underwent decortication surgery due to empyema at Dr. M. Djamil Hospital, Padang, Indonesia between March 1st and April 30, 2024. Case samples were obtained by consecutive sampling, and three patients who met the inclusion criteria were obtained. Pleural tissue in each patient was then divided into several groups based on the treatment, namely the control group, 50 μg EGCG administration group, and 100 μg EGCG administration group. We used to determine SCUBE3 and TGF-β1 genes expression. Data were tested using ANOVA and Least Significant Difference (LSD) tests. Results There were significant differences in the SCUBE3 and TGF-β1 genes expression of 50 μg and 100 μg EGCG administration groups and the control groups in the 2 × 2 cm sample preparation (p=0.002) (p=0.014, respectively). Significant differences in TGF-β1 expression were also found between the groups treated with EGCG 50 μg and 100 μg and the control group in the 1 × 1 cm preparation (p=0.019). Conclusion EGCG can potentially decrease SCUBE3 and TGF-β1 expression in patients with pleural empyema.

Brazilian Thoracic Society recommendations for the diagnosis and monitoring of asbestos-exposed individuals.

Asbestos was largely used in Brazil. It is a mineral that induces pleural and pulmonary fibrosis, and it is a potent carcinogen. Our objective was to develop recommendations for the performance of adequate imaging tests for screening asbestos-related diseases. We searched peer-reviewed publications, national and international technical documents, and specialists' opinions on the theme. Based on that, the major recommendations are: Individuals exposed to asbestos at the workplace for ≥ 1 year or those with a history of environmental exposure for at least 5 years, all of those with a latency period > 20 years from the date of initial exposure, should initially undego HRCT of the chest for investigation. Individuals with pleural disease and/or asbestosis should be considered for regular lung cancer monitoring. Risk calculators should be adopted for lung cancer screening, with a risk estimate of 1.5%.

Tuberculous pleural effusion-induced Arg-1+ macrophage polarization contributes to lung cancer progression via autophagy signaling

BackgroundThe association between tuberculous fibrosis and lung cancer development has been reported by some epidemiological and experimental studies; however, its underlying mechanisms remain unclear, and the role of macrophage (MФ) polarization in cancer progression is unknown. The aim of the present study was to investigate the role of M2 Arg-1+ MФ in tuberculous pleurisy-assisted tumorigenicity in vitro and in vivo.MethodsThe interactions between tuberculous pleural effusion (TPE)-induced M2 Arg-1+ MФ and A549 lung cancer cells were evaluated. A murine model injected with cancer cells 2 weeks after Mycobacterium bovis bacillus Calmette–Guérin pleural infection was used to validate the involvement of tuberculous fibrosis to tumor invasion.ResultsIncreased CXCL9 and CXCL10 levels of TPE induced M2 Arg-1+ MФ polarization of murine bone marrow-derived MФ. TPE-induced M2 Arg-1+ MФ polarization facilitated lung cancer proliferation via autophagy signaling and E-cadherin signaling in vitro. An inhibitor of arginase-1 targeting M2 Arg-1+ MФ both in vitro and in vivo significantly reduced tuberculous fibrosis-induced metastatic potential of lung cancer and decreased autophagy signaling and E-cadherin expression.ConclusionTuberculous pleural fibrosis induces M2 Arg-1+ polarization, and M2 Arg-1+ MФ contribute to lung cancer metastasis via autophagy and E-cadherin signaling. Therefore, M2 Arg-1+ tumor associated MФ may be a novel therapeutic target for tuberculous fibrosis-induced lung cancer progression.

Spectrum of chronic lung allograft dysfunction pathology in human lung transplantation

BackgroundLong-term survival after lung transplantation (LTx) remains limited by Chronic Lung Allograft Dysfunction (CLAD), which includes two main phenotypes: bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS), with possible overlap. We aimed to detail and quantify pathological features of these CLAD sub-types. MethodsPeripheral and central paraffin-embedded explanted lung samples were obtained from 20 consecutive patients undergoing a second LTx for CLAD, from 3 lobes. Thirteen lung samples, collected from non-transplant lobectomies or donor lungs, were used as controls. Blinded semi-quantitative grading was performed to assess airway fibrotic changes, parenchymal and pleural fibrosis, as well as epithelial and vascular abnormalities. ResultsCLAD lung samples had higher scores for all airway- and lung-related parameters compared to controls. There was a notable overlap in pathological scores between BOS and RAS, with a wide range of scores in both conditions. Parenchymal and vascular fibrosis scores were significantly higher in RAS compared to BOS (p=0.003 for both). We observed a significant positive correlation between the degree of inflammation around each airway, the severity of epithelial changes and airway fibrosis. Immunofluorescence staining demonstrated a trend towards a lower frequency of club cells in CLAD, and a higher frequency of apoptotic club cells in BOS samples (p=0.01). ConclusionsCLAD is a spectrum of airway, parenchymal, and pleural fibrosis, as well as epithelial, vascular, and inflammatory pathological changes, where BOS and RAS overlap significantly. Our semi-quantitative grading score showed a generally high inter-reader reliability and may be useful for future CLAD pathological assessments.

Pediatric pulmonary Langerhans cell histiocytosis complicated by recurrent hemopneumothoraces

Langerhans cell histiocytosis is a rare disease of clonal proliferation and deposition of immature dendritic cells in various tissues, including the lungs, causing inflammation and organ destruction. We report a case of a 4-year-old girl with refractory multisystem Langerhans cell histiocytosis complicated by recurrent bilateral hemopneumothoraces in a pediatric tertiary hospital in Cape Town, South Africa. Video-assisted thoracoscopy revealed chronic inflammation of her pleura, with pleural fibrosis seen on histology. Despite pleurodesis, she continued to have recurrent hemopneumothoraces until she was started on a hydroxyurea-containing regimen with a good response.

Fibrotic progression from acute cellular rejection is dependent on secondary lymphoid organs in a mouse model of chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) remains one of the major limitations to long-term survival after lung transplantation. We modified a murine model of CLAD and transplanted left lungs from BALB/c donors into B6 recipients that were treated with intermittent cyclosporine and methylprednisolone postoperatively. In this model, the lung allograft developed acute cellular rejection on day 15 which, by day 30 after transplantation, progressed to severe pleural and peribronchovascular fibrosis, reminiscent of changes observed in restrictive allograft syndrome. Lung transplantation into splenectomized B6 alymphoplastic (aly/aly) or splenectomized B6 lymphotoxin-β receptor–deficient mice demonstrated that recipient secondary lymphoid organs, such as spleen and lymph nodes, are necessary for progression from acute cellular rejection to allograft fibrosis in this model. Our work uncovered a critical role for recipient secondary lymphoid organs in the development of CLAD after pulmonary transplantation and may provide mechanistic insights into the pathogenesis of this complication.

Myocardin regulates fibronectin expression and secretion from human pleural mesothelial cells.

During the progression of pleural fibrosis, pleural mesothelial cells (PMCs) undergo a phenotype switching process known as mesothelial-mesenchymal transition (MesoMT). During MesoMT, transformed PMCs become myofibroblasts that produce increased extracellular matrix (ECM) proteins, including collagen and fibronectin (FN1) that is critical to develop fibrosis. Here, we studied the mechanism that regulates FN1 expression in myofibroblasts derived from human pleural mesothelial cells (HPMCs). We found that myocardin (Myocd), a transcriptional coactivator of serum response factor (SRF) and a master regulator of smooth muscle and cardiac muscle differentiation, strongly controls FN1 gene expression. Myocd gene silencing markedly inhibited FN1 expression. FN1 promoter analysis revealed that deletion of the Smad3-binding element diminished FN1 promoter activity, whereas deletion of the putative SRF-binding element increased FN1 promoter activity. Smad3 gene silencing decreased FN1 expression, whereas SRF gene silencing increased FN1 expression. Moreover, SRF competes with Smad3 for binding to Myocd. These results indicate that Myocd activates FN1 expression through Smad3, whereas SRF inhibits FN1 expression in HPMCs. In HPMCs, TGF-β induced Smad3 nuclear localization, and the proximity ligation signal between Myocd and Smad3 was markedly increased after TGF-β stimulation at nucleus, suggesting that TGF-β facilitates nuclear translocation of Smad3 and interaction between Smad3 and Myocd. Moreover, Myocd and Smad3 were coimmunoprecipitated and isolated Myocd and Smad3 proteins directly bound each other. Chromatin immunoprecipitation assays revealed that Myocd interacts with the FN1 promoter at the Smad3-binding consensus sequence. The results indicate that Myocd regulates FN1 gene activation through interaction and activation of the Smad3 transcription factor.NEW & NOTEWORTHY During phenotype switching from mesothelial to mesenchymal, pleural mesothelial cells (PMCs) produce extracellular matrix (ECM) proteins, including collagen and fibronectin (FN1), critical components in the development of fibrosis. Here, we found that myocardin, a transcriptional coactivator of serum response factor (SRF), strongly activates FN1 expression through Smad3, whereas SRF inhibits FN1 expression. This study provides insights about the regulation of FN1 that could lead to the development of novel interventional approaches to prevent pleural fibrosis.

Role of ZIP kinase in development of myofibroblast differentiation from HPMCs.

During the development of pleural fibrosis, pleural mesothelial cells (PMCs) undergo phenotypic switching from differentiated mesothelial cells to mesenchymal cells (MesoMT). Here, we investigated how external stimuli such as TGF-β induce HPMC-derived myofibroblast differentiation to facilitate the development of pleural fibrosis. TGF-β significantly increased di-phosphorylation but not mono-phosphorylation of myosin II regulatory light chain (RLC) in HPMCs. An increase in RLC di-phosphorylation was also found at the pleural layer of our carbon black bleomycin (CBB) pleural fibrosis mouse model, where it showed filamentous localization that coincided with alpha smooth muscle actin (αSMA) in the cells in the pleura. Among the protein kinases that can phosphorylate myosin II RLC, ZIPK (zipper-interacting kinase) protein expression was significantly augmented after TGF-β stimulation. Furthermore, ZIPK gene silencing attenuated RLC di-phosphorylation, suggesting that ZIPK is responsible for di-phosphorylation of myosin II in HPMCs. Although TGF-β significantly increased the expression of ZIP kinase protein, the change in ZIP kinase mRNA was marginal, suggesting a posttranscriptional mechanism for the regulation of ZIP kinase expression by TGF-β. ZIPK gene knockdown (KD) also significantly reduced TGF-β-induced upregulation of αSMA expression. This finding suggests that siZIPK attenuates myofibroblast differentiation of HPMCs. siZIPK diminished TGF-β-induced contractility of HPMCs consistent with siZIPK-induced decrease in the di-phosphorylation of myosin II RLC. The present results implicate ZIPK in the regulation of the contractility of HPMC-derived myofibroblasts, phenotype switching, and myofibroblast differentiation of HPMCs.NEW & NOTEWORTHY Here, we highlight that ZIP kinase is responsible for di-phosphorylation of myosin light chain, which facilitates stress fiber formation and actomyosin-based cell contraction during mesothelial to mesenchymal transition in human pleural mesothelial cells. This transition has a significant impact on tissue remodeling and subsequent stiffness of the pleura. This study provides insight into a new therapeutic strategy for the treatment of pleural fibrosis.

Recognizing the pleura in asbestos-related pleuropulmonary disease: Known and new manifestations of pleural fibrosis.

Pleural thickening (PT) is a major consequence of exposure to all fiber types of asbestos. In recent decades, it is more prevalent than parenchymal asbestosis. Its manifestations occupy a full clinical and radiographic spectrum. Six major manifestations can be identified: (a) acute pleuritis generally with effusion; (b) diffuse PT or fibrous pleuritis; (c) rounded atelectasis; (d) circumscribed PT or plaques; (e) chronic pleuritic pain; and (f) mesothelioma. Review of the experience of workers and community members in Libby, MT to asbestiform fibers in vermiculite has confirmed the appearance of these previously known benign and malignant asbestos-related diseases as well as a unique pleuropulmonary disease characterized as lamellar PT and associated with progressive decline in pulmonary function and pleuritic pain. Despite previous literature asserting that PT represents a marker for asbestos exposure without significant effect on pulmonary function and physiology, the experience of Libby amphibole (LA) disease, along with other studies, indicates that PT plays a role in declining vital capacity in those with prolonged or unusual exposures such as those arising from LA.

The effects of etiological factors on timing of decortication

Aim: Tube drainage is the primary method in the treatment of empyema with 80-90% cure rates. In patients with empyema who have not received adequate treatment, the result is pleural fibrosis. Decortication is the only treatment option for chronic empyema that has caused fibrothorax that prevents lung expansion. In our study, we aimed to determine the relations between etiological base of the disease, the consequences and the decision of decortication timing. Methods: The patients who were admitted and hospitalized with pleural effusion between 1994 and 2000 were included in the study. We examined the duration of pretreatment, pleural thickness and the duration of postoperative hospital stay of these cases, with who have undergone decortication surgery. Results: A total of 82 cases of decortication were enrolled, which consisted of 61 male (74.3%) and 21 female (25.6%). The cases were examined in two groups: tuberculosis [12 (25%) empyema, 27 (56.3%) tuberculous pachypleuritis, 9 (18.8%) pleurisy + parenchymal involvement] and non-tuberculosis [2 (5.9%) trauma, 5 (14.7%) pneumonia + empyema, 23 (%) 67.6% empyema, 4 (11.8%) hydatid cyst]. The effects of preoperative treatment durations on the thickness of the decortication materials and the duration of postoperative hospital stay were investigated. The preoperative treatment period of the tuberculosis group was significantly higher, the decortication pleural thicknesses were found to be greater. (p<0.01) There was no statistically significant difference in the duration of postoperative hospital stay between the tuberculosis and other group (p>0.05). Conclusion: In cases that do not respond to closed tube drainage and appropriate antibiotic therapy, decortication should be performed without delay considering the etiological factors. If decortication is performed earlier than 2 weeks, the visceral pleura can be easily separated; parietal decortication is rarely needed which might be an advantage of the procedure.

239 Novel alternative polyadenylation as a post-transcriptional mechanism in C5ar1 signaling-dependent pleural hypertrophy and fibrosis in collagen-induced arthritic mice

239 Novel alternative polyadenylation as a post-transcriptional mechanism in C5ar1 signaling-dependent pleural hypertrophy and fibrosis in collagen-induced arthritic mice

The mTORC2/SGK1/NDRG1 Signaling Axis Is Critical for the Mesomesenchymal Transition of Pleural Mesothelial Cells and the Progression of Pleural Fibrosis.

Progressive lung scarring because of persistent pleural organization often results in pleural fibrosis (PF). This process affects patients with complicated parapneumonic pleural effusions, empyema, and other pleural diseases prone to loculation. In PF, pleural mesothelial cells undergo mesomesenchymal transition (MesoMT) to become profibrotic, characterized by increased expression of α-smooth muscle actin and matrix proteins, including collagen-1. In our previous study, we showed that blocking PI3K/Akt signaling inhibits MesoMT induction in human pleural mesothelial cells (HPMCs) (1). However, the downstream signaling pathways leading to MesoMT induction remain obscure. Here, we investigated the role of mTOR complexes (mTORC1/2) in MesoMT induction. Our studies show that activation of the downstream mediator mTORC1/2 complex is, likewise, a critical component of MesoMT. Specific targeting of mTORC1/2 complex using pharmacological inhibitors such as INK128 and AZD8055 significantly inhibited transforming growth factor β (TGF-β)-induced MesoMT markers in HPMCs. We further identified the mTORC2/Rictor complex as the principal contributor to MesoMT progression induced by TGF-β. Knockdown of Rictor, but not Raptor, attenuated TGF-β-induced MesoMT in these cells. In these studies, we further show that concomitant activation of the SGK1/NDRG1 signaling cascade is essential for inducing MesoMT. Targeting SGK1 and NDRG1 with siRNA and small molecular inhibitors attenuated TGF-β-induced MesoMT in HPMCs. Additionally, preclinical studies in our Streptococcus pneumoniae-mediated mouse model of PF showed that inhibition of mTORC1/2 with INK128 significantly attenuated the progression of PF in subacute and chronic injury. In conclusion, our studies demonstrate that mTORC2/Rictor-mediated activation of SGK1/NDRG1 is critical for MesoMT induction and that targeting this pathway could inhibit or even reverse the progression of MesoMT and PF.

Immunohistochemical expression of DnaJ homolog subfamily B member 9 in immunoglobulin G4-related disease: a pilot study.

DnaJ homolog subfamily B member 9 (DNAJB9) is a co-chaperone protein that governs the functions and integrity of cells. In immunoglobulin G4-related disease (IgG4-RD), DNAJB9 was shown to be upregulated in plasma cells, but its immunohistochemical expression has never been explored. This pilot study aims to investigate the immunohistochemical distribution and intensity of DNAJB9 in IgG4-RD tissue specimens. Patients with definite IgG4-RD and normal tissue controls were selected for anti-DNAJB9 immunohistochemistry, applying a semi-quantitative staining intensity score. We studied the tissue slides of 9 IgG4-RD patients and 15 controls, including salivary gland, pancreatic, pulmonary, pleural, and retroperitoneal fibrosis tissue. Median immunohistochemical intensity was 0 for IgG4-RD patients vs. 2 for controls for endothelial cells (ES=1.58, p<0.01), 2 in each group for glandular epithelial cells (ES 0.70, p=0.26), and 2 for IgG4-RD vs. 3 for controls for inflammatory cells regarding salivary glands alone (ES=0.90, p=0.11). Endothelial staining intensity was negatively correlated with serum IgG4 concentrations (r= -0.72, p=0.03) and the number of treatments required to achieve disease remission (r= -0.70, p=0.04). Our findings evidenced reduced immunohistochemical expression of DNAJB9 in IgG4-RD endothelial cells, and suggested loss of expression in other cell types, possibly correlating with disease severity and risk of relapse. Although DNAJB9 may not serve as a marker for IgG4-RD, it may be part of a pathophysiological pathway involved in the disease and the onset of fibrosis.

Circulating FGF18 is decreased in pleural mesothelioma but not correlated with disease prognosis.

Pleural mesothelioma (PM) is a relatively rare malignancy with limited treatment options and dismal prognosis. We have previously found elevated FGF18 expression in PM tissue specimens compared with normal mesothelium. The objective of the current study was to further explore the role of FGF18 in PM and evaluate its suitability as a circulating biomarker. FGF18 mRNA expression was analyzed by real-time PCR in cell lines and in silico in datasets from the Cancer Genome Atlas (TCGA). Cell lines overexpressing FGF18 were generated by retroviral transduction and cell behavior was investigated by clonogenic growth and transwell assays. Plasma was collected from 40 PM patients, six patients with pleural fibrosis, and 40 healthy controls. Circulating FGF18 was measured by ELISA and correlated to clinicopathological parameters. FGF18 showed high mRNA expression in PM and PM-derived cell lines. PM patients with high FGF18 mRNA expression showed a trend toward longer overall survival (OS) in the TCGA dataset. In PM cells with low endogenous FGF18 expression, forced overexpression of FGF18 resulted in reduced growth but increased migration. Surprisingly, despite the high FGF18 mRNA levels observed in PM, circulating FGF18 protein was significantly lower in PM patients and patients with pleural fibrosis than in healthy controls. No significant association of circulating FGF18 with OS or other disease parameters of PM patients was observed. FGF18 is not a prognostic biomarker in PM. Its role in PM tumor biology and the clinical significance of decreased plasma FGF18 in PM patients warrant further investigation.

Autopsy findings in a case of idiopathic pleuroparenchymal fibroelastosis: A rare entity with review of literature

Idiopathic pleuroparenchymal fibroelastosis is a rare idiopathic interstitial pneumonia which mainly affects the upper lobe of lungs resulting in intra alveolar fibrosis, elastosis and visceral pleural fibrosis. For definite diagnosis, radiographic findings as well as histopathology findings are required. The overlap with interstitial lung diseases seen usually, makes it challenging to diagnose. There are no guidelines available for the diagnosis and appropriate management of this disease and only a few cases reported in the literature. We report a case of pleuroparenchymal fibroelastosis in autopsy in a 32-year-old female who allegedly died of heart failure with review of literature.

Postmortem Identification of Vascular Ehlers-Danlos Syndrome in a Lung Transplant Recipient.

Postmortem Identification of Vascular Ehlers-Danlos Syndrome in a Lung Transplant Recipient.

Silymarin ameliorates peritoneal fibrosis by inhibiting the TGF-β/Smad signaling pathway.

Peritoneal dialysis (PD) is the mainstay of treatment for renal failure replacement therapy. Although PD has greatly improved the quality of life of end-stage renal disease (ESRD) patients, long-term PD can lead to ultrafiltration failure, which in turn causes peritoneal fibrosis (PF). Silymarin (SM) is a polyphenolic flavonoid isolated from the milk thistle (Silybum marianum) species that has a variety of pharmacological actions, including antioxidant, anti-inflammatory, antiviral, and anti-fibrotic pharmacological activities. However, the effect of SM on PF and its potential mechanisms have not been clarified. The aim of this study was to investigate the preventive effect of SM on PF in vitro and in vivo as well as elucidate the underlying mechanisms. We established PF mouse models and human pleural mesothelial cell fibrosis in vitro by intraperitoneal injection of high-glucose peritoneal dialysis solution (PDS) or transforming growth factor-β1 (TGF-β1), and evaluated the effect of SM on peritoneal fibrosis in vivo and in vitro. We found that SM alleviated peritoneal dysfunction. Meanwhile, SM inhibited the expression of fibrotic markers (TGF-β1, collagen I, fibronectin) and restored the expression of E-cadherin, BMP-7 in PF mice and TGF-β1-treated Met-5A cells. Furthermore, SM markedly down-regulated the expression of TGF-β1, p-Smad2, and p-Smad3 and up-regulated the expression of smad7. In conclusion, these findings suggested that SM may be an efficient and novel therapy for the prevention of PF through inhibition of TGF-β/Smad signaling.

Clinical Diagnosis of Pleuroparenchymal Fibroelastosis

Pleuroparenchymal fibroelastosis (PPFE) is an extremely rare interstitial lung disease (ILD) characterised by fibroelastotic changes predominating in the subpleural lung parenchyma with visceral pleural fibrosis involving the upper lobes. It has distinctive clinical, radiological, and pathological manifestations. Diagnosis constitutes literally a stalemate because of its rarity, unavailability of an agreed diagnostic consensus, and requirement of tissue biopsy for an accurate final diagnosis that can not be performed in most of the patients owing to the comorbid complications of the disease itself. Identification of PPFE may also pose great difficulties due to the coexistence of other interstitial lung diseases. PPFE usually exhibits a persistently deteriorating prognostic course culminating in fatal complications including respiratory failure, pulmonary hypertension, cor pulmonale, or pneumothorax. Presence of disease relevant complications frequently preclude invasive tissue biopsy interventions in these patients leading to a diagnostic challenge for clinicians. This review aims to provide a definitive diagnosis based on entirely the clinical manifestatins of PPFE by shedding light on the pathogenesis, clinical, and radiologic findings of the disease. Histopathological tissue evaluation was also included in the diagnostic approach for patients whose condition was suitable for an invasive biopsy intervention. With this review, it is concluded that an approach consisting of exclusively clinical manifestations will ensure adequate support for an accurate PPFE diagnosis without any requirement for histopathological tissue examination.