The complex role of fibrin in acute lung injury

Pathophysiological Role of Vimentin Intermediate Filaments in Lung Diseases

Vimentin intermediate filaments, a type III intermediate filament, are among the most widely studied IFs and are found abundantly in mesenchymal cells. Vimentin intermediate filaments localize primarily in the cytoplasm but can also be found on the cell surface and extracellular space. The cytoplasmic vimentin is well-recognized for its role in providing mechanical strength and regulating cell migration, adhesion, and division. The post-translationally modified forms of Vimentin intermediate filaments have several implications in host-pathogen interactions, cancers, and non-malignant lung diseases. This review will analyze the role of vimentin beyond just the epithelial to mesenchymal transition (EMT) marker highlighting its role as a regulator of host-pathogen interactions and signaling pathways for the pathophysiology of various lung diseases. In addition, we will also examine the clinically relevant anti-vimentin compounds and antibodies that could potentially interfere with the pathogenic role of Vimentin intermediate filaments in lung disease.

Pulmonary histopathology in fatal paraquat poisoning

Paraquat is a potent herbicide widely used in the Indian agriculture industry. Human fatality due to paraquat poisoning is not uncommon in this country. The primary effect of paraquat is on the lungs, and the resultant pulmonary damage leads to the patient's demise. There is a high mortality rate in paraquat poisoning as the treatment is usually supportive with no known antidote. There are limited human studies that have observed the histopathological changes in lungs in paraquat poisoning. The authors have discussed the time-related histopathological changes in lungs in paraquat poisoning on autopsy subjects. The role of anticoagulants and fibrinolytic agents in the treatment of this poisoning has also been discussed.

The Contribution of the Urokinase Plasminogen Activator and the Urokinase Receptor to Pleural and Parenchymal Lung Injury and Repair: A Narrative Review

Pleural and parenchymal lung injury have long been characterized by acute inflammation and pathologic tissue reorganization, when severe. Although transitional matrix deposition is a normal part of the injury response, unresolved fibrin deposition can lead to pleural loculation and scarification of affected areas. Within this review, we present a brief discussion of the fibrinolytic pathway, its components, and their contribution to injury progression. We review how local derangements of fibrinolysis, resulting from increased coagulation and reduced plasminogen activator activity, promote extravascular fibrin deposition. Further, we describe how pleural mesothelial cells contribute to lung scarring via the acquisition of a profibrotic phenotype. We also discuss soluble uPAR, a recently identified biomarker of pleural injury, and its diagnostic value in the grading of pleural effusions. Finally, we provide an in-depth discussion on the clinical importance of single-chain urokinase plasminogen activator (uPA) for the treatment of loculated pleural collections.

Extracellular vesicles in lung health, disease, and therapy

Both physiological homeostasis and pathological disease processes in the lung typically result from complex, yet coordinated multicellular responses that are synchronized via paracrine and endocrine intercellular communication pathways. Of late, extracellular vesicles have emerged as important information shuttles that can coordinate and disseminate homeostatic and disease signals. In parallel, extracellular vesicles in biological fluids such as sputum, mucus, epithelial lining fluid, edema fluid, the pulmonary circulation, pleural fluid, and lymphatics have emerged as promising candidate biomarkers for diagnosis and prognosis in lung disease. Extracellular vesicles are small, subcellular, membrane-bound vesicles containing cargos from parent cells such as lipids, proteins, genetic information, or entire organelles. These cargos endow extracellular vesicles with biologically active information or functions by which they can reprogram their respective target cells. Recent studies show that extracellular vesicles found in lung-associated biological fluids play key roles as biomarkers and effectors of disease. Conversely, administration of naïve or engineered extracellular vesicles with homeostatic or reparative effects may provide a promising novel protective and regenerative strategy to treat lung disease. To highlight this rapidly developing field, the American Journal of Physiology-Lung Cellular and Molecular Physiology is now launching a special Call for Papers on extracellular vesicles in lung health, disease, and therapy. This review aims to set the stage for this call by introducing extracellular vesicles and their emerging roles in lung physiology and pathobiology.

Clinicopathologic features associated with relapse in cryptogenic organizing pneumonia

Organizing pneumonia (OP) is a histopathologic pattern of response to lung injury. Fibrin is a marker of acute microvascular injury, and variable amounts of intraalveolar fibrin are seen in OP; however, its relevance to clinical outcomes is unclear. We examined lung wedge biopsies of 26 patients with cryptogenic organizing pneumonia (COP), assessed the amount of fibrin associated with airspace organization, and correlated fibrin levels with other histologic, clinical, and radiographic findings. Seven patients with COP had disease relapse. Patients with multifocal fibrin deposits or acute fibrinous and organizing pneumonia (collectively, "high fibrin") showed a higher rate of OP relapse compared to those with no or focal fibrin (60% versus 6%, P < .05). Patients with radiographic evidence of disease involving all three lung zones (upper, middle, and lower) also showed higher rates of relapse compared to those in whom disease was limited to one or two zones (41% versus 0%, P = .055). In patients with both pathologic evidence of high fibrin and radiographic evidence of three-zone disease, OP relapse could be predicted with a sensitivity of 86% and specificity of 84% (positive predictive value of 67% and negative predictive value of 94%). The presence of high levels of intraalveolar fibrin in lung biopsies and radiographic evidence of disease involving all three lung zones is associated with increased risk of relapse in patients with COP, and these features may help identify patients who may benefit from more intensive steroid therapy.

Stem cell and biomaterials research in dental tissue engineering and regeneration

This review summarizes approaches used in tissue engineering and regenerative medicine, with a focus on dental applications. Dental caries and periodontal disease are the most common diseases resulting in tissue loss. To replace or regenerate new tissues, various sources of stem cells have been identified such as somatic stem cells from teeth and peridontium. Advances in biomaterial sciences including microfabrication, self-assembled biomimetic peptides, and 3-dimensional printing hold great promise for whole-organ or partial tissue regeneration to replace teeth and periodontium.