The mechanism underlying extrapulmonary complications of the coronavirus disease 2019 and its therapeutic implication.

The coronavirus disease 2019 (COVID-19) is a highly transmissible disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that poses a major threat to global public health. Although COVID-19 primarily affects the respiratory system, causing severe pneumonia and acute respiratory distress syndrome in severe cases, it can also result in multiple extrapulmonary complications. The pathogenesis of extrapulmonary damage in patients with COVID-19 is probably multifactorial, involving both the direct effects of SARS-CoV-2 and the indirect mechanisms associated with the host inflammatory response. Recognition of features and pathogenesis of extrapulmonary complications has clinical implications for identifying disease progression and designing therapeutic strategies. This review provides an overview of the extrapulmonary complications of COVID-19 from immunological and pathophysiologic perspectives and focuses on the pathogenesis and potential therapeutic targets for the management of COVID-19.

A Review of Pathophysiology, Clinical Features, and Management Options of COVID-19 Associated Coagulopathy.

ABSTRACT: There is increasing evidence that novel coronavirus disease 2019 (COVID-19) leads to a significant coagulopathy, a phenomenon termed "COVID-19 associated coagulopathy." COVID-19 has been associated with increased rates of both venous and arterial thromboembolic events, a source of significant morbidity and mortality in this disease. Further evidence suggests a link between the inflammatory response and coagulopathy associated with COVID-19. This presents a unique set of challenges for diagnosis, prevention, and treatment of thrombotic complications. In this review, we summarize and discuss the current literature on laboratory coagulation disruptions associated with COVID-19 and the clinical effects of thromboembolic events including pulmonary embolism, deep vein thrombosis, peripheral arterial thrombosis, and acute ischemic stroke in COVID-19. Endothelial injury and augmented innate immune response are implicated in the development of diffuse macro- and microvascular thrombosis in COVID-19. The pathophysiology of COVID-19 associated coagulopathy is an important determinant of appropriate treatment and monitoring of these complications. We highlight the importance of diagnosis and management of dysregulated coagulation in COVID-19 to improve outcomes in COVID-19 patients with thromboembolic complications.

Alveolar cells under mechanical stressed niche: critical contributors to pulmonary fibrosis.

Pulmonary fibrosis arises from the repeated epithelial mild injuries and insufficient repair lead to over activation of fibroblasts and excessive deposition of extracellular matrix, which result in a mechanical stretched niche. However, increasing mechanical stress likely exists before the establishment of fibrosis since early micro injuries increase local vascular permeability and prompt cytoskeletal remodeling which alter cellular mechanical forces. It is noteworthy that COVID-19 patients with severe hypoxemia will receive mechanical ventilation as supportive treatment and subsequent pathology studies indicate lung fibrosis pattern. At advanced stages, mechanical stress originates mainly from the stiff matrix since boundaries between stiff and compliant parts of the tissue could generate mechanical stress. Therefore, mechanical stress has a significant role in the whole development process of pulmonary fibrosis. The alveoli are covered by abundant capillaries and function as the main gas exchange unit. Constantly subject to variety of damages, the alveolar epithelium injuries were recently recognized to play a vital role in the onset and development of idiopathic pulmonary fibrosis. In this review, we summarize the literature regarding the effects of mechanical stress on the fundamental cells constituting the alveoli in the process of pulmonary fibrosis, particularly on epithelial cells, capillary endothelial cells, fibroblasts, mast cells, macrophages and stem cells. Finally, we briefly review this issue from a more comprehensive perspective: the metabolic and epigenetic regulation.

Cardiovascular Manifestations and Mechanisms in Patients with COVID-19.

Coronavirus disease 2019 (COVID-19) patients with pre-existing cardiovascular disease (CVD) or with cardiovascular complications have a higher risk of mortality. The main cardiovascular complications of COVID-19 include acute cardiac injury, acute myocardial infarction (AMI), myocarditis, arrhythmia, heart failure, shock, and venous thromboembolism (VTE)/pulmonary embolism (PE). COVID-19 can cause cardiovascular complications or deterioration of coexisting CVD through direct or indirect mechanisms, including viral toxicity, dysregulation of the renin-angiotensin-aldosterone system (RAAS), endothelial cell damage and thromboinflammation, cytokine storm, and oxygen supply-demand mismatch. We systematically review cardiovascular manifestations, histopathology, and mechanisms of COVID-19, to help to formulate future research goals and facilitate the development of therapeutic management strategies.

Neurological injuries in COVID-19 patients: direct viral invasion or a bystander injury after infection of epithelial/endothelial cells.

A subset of patients with coronavirus 2 disease (COVID-19) experience neurological complications. These complications include loss of sense of taste and smell, stroke, delirium, and neuromuscular signs and symptoms. The etiological agent of COVID-19 is SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), an RNA virus with a glycoprotein-studded viral envelope that uses ACE2 (angiotensin-converting enzyme 2) as a functional receptor for infecting the host cells. Thus, the interaction of the envelope spike proteins with ACE2 on host cells determines the tropism and virulence of SARS-CoV-2. Loss of sense of taste and smell is an initial symptom of COVID-19 because the virus enters the nasal and oral cavities first and the epithelial cells are the receptors for these senses. Stroke in COVID-19 patients is likely a consequence of coagulopathy and injury to cerebral vascular endothelial cells that cause thrombo-embolism and stroke. Delirium and encephalopathy in acute and post COVID-19 patients are likely multifactorial and secondary to hypoxia, metabolic abnormalities, and immunological abnormalities. Thus far, there is no clear evidence that coronaviruses cause inflammatory neuromuscular diseases via direct invasion of peripheral nerves or muscles or via molecular mimicry. It appears that most of neurologic complications in COVID-19 patients are indirect and as a result of a bystander injury to neurons.

Thromboinflammation in COVID-19 acute lung injury.

Since the initial description in 2019, the novel coronavirus SARS-Cov-2 infection (COVID-19) pandemic has swept the globe. The most severe form of the disease presents with fever and shortness of breath, which rapidly deteriorates to respiratory failure and acute lung injury (ALI). COVID-19 also presents with a severe coagulopathy with a high rate of venous thromboembiolism. In addition, autopsy studies have revealed co-localized thrombosis and inflammation, which is the signature of thromboinflammation, within the pulmonary capillary vasculature. While the majority of published data is on adult patients, there are parallels to pediatric patients. In our experience as a COVID-19 epicenter, children and young adults do develop both the coagulopathy and the ALI of COVID-19. This review will discuss COVID-19 ALI from a hematological perspective with discussion of the distinct aspects of coagulation that are apparent in COVID-19. Current and potential interventions targeting the multiple thromboinflammatory mechanisms will be discussed.