Pulmonary Fibrosis in COVID-19 Survivors: Predictive Factors and Risk Reduction Strategies

Interstitial lung abnormalities and pulmonary fibrosis in COVID-19 patients: a short-term follow-up case series

Fibrotic lung changes are well-known complications of SARS, MERS, and ARDS from other causes and are anticipated in recovered COVID patients. However, there is limited data so far showing a temporal relationship between lung changes on imaging in the acute phase and follow-up imaging after recovery from the infection. We present 12 patients who demonstrate the development of interstitial lung changes and pulmonary fibrosis in the same distribution and pattern as the acute phase findings, up to 6 months after the acute infection, demonstrating a direct relationship between these changes and COVID-19 pneumonia.

Strengthening CoViD-19 therapy via combinations of RAS modulators

Evidence has accumulated that the pathology of CoViD-19 is strongly related to the renin-angiotensin system (RAS). The blockage of the angiotensin converting enzyme 2 (ACE2) by the SARS-CoV-2 virus leads to downstream consequences such as increased vascular tone, extensive fibrosis and pronounced immune reactions. Different approaches to tackle the adverse viral effects by compensating the lost ACE2 function have been suggested. Here, we use an unequal-arm lever model to describe a simplified version of the biased regulation exercised by the angiotensin II and angiotensin-(1-7) hormones, which are the substrate and the product of ACE2, respectively. We reason upon the lever dynamics and its disruptions caused by the virus, and propose that a combination of RAS modulators will most efficiently compensate the imbalance due to the excess of angiotensin II and the scarcity of angiotensin-(1-7). Specifically, we focus on the possible benefits of the simultaneous application of two agents, a MAS-receptor agonist and an angiotensin-II-type-2-receptor agonist. We conjecture that this combination has the potential to introduce a beneficial synergistic action that promotes anti-hypoxic, anti-fibrotic and anti-proliferative effects, thereby improving the clinical management of acute and chronic CoViD-19 pathologies.

Efficacy of the combination of modern medicine and traditional Chinese medicine in pulmonary fibrosis arising as a sequelae in convalescent COVID-19 patients: a randomized multicenter trial

Background

The coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to a significant number of mortalities worldwide. COVID-19 poses a serious threat to human life. The clinical manifestations of COVID-19 are diverse and severe and 20% of infected patients are reported to be in a critical condition. A loss in lung function and pulmonary fibrosis are the main manifestations of patients with the severe form of the disease. The lung function is affected, even after recovery, thereby greatly affecting the psychology and well-being of patients, and significantly reducing their quality of life.

Methods

Participants must meet the following simultaneous inclusion criteria: over 18 years of age, should have recovered from severe or critical COVID-19 cases, should exhibit pulmonary fibrosis after recovery, and should exhibit Qi-Yin deficiency syndrome as indicated in the system of traditional Chinese medicine (TCM). The eligible candidates will be randomized into treatment or control groups. The treatment group will receive modern medicine (pirfenidone) plus TCM whereas the control group will be administered modern medicine plus TCM placebo. The lung function index will be continuously surveyed and recorded. By comparing the treatment effect between the two groups, the study intend to explore whether TCM can improve the effectiveness of modern medicine in patients with pulmonary fibrosis arising as a sequelae after SARS-CoV-2 infection.

Discussion

Pulmonary fibrosis is one of fatal sequelae for some severe or critical COVID-19 cases, some studies reveal that pirfenidone lead to a delay in the decline of forced expiratory vital capacity, thereby reducing the mortality partly. Additionally, although TCM has been proven to be efficacious in treating pulmonary fibrosis, its role in treating pulmonary fibrosis related COVID-19 has not been explored. Hence, a multicenter, parallel-group, randomized controlled, interventional, prospective clinical trial has been designed and will be conducted to determine if a new comprehensive treatment for pulmonary fibrosis related to COVID-19 is feasible and if it can improve the quality of life of patients.

Trial registration: This multicenter, parallel-group, randomized controlled, interventional, prospective trial was registered at the Chinese Clinical Trial Registry (ChiCTR2000033284) on 26th May 2020 (prospective registered).

Corticosteroids and pulmonary rehabilitation reducing long-term morbidity in a patient with post-COVID-19 pneumonitis: A case study

Background

Whilst research efforts have focussed on treatment during the acute phase, little work has focussed on the long‐term sequelae of COVID‐19 infection. This case described a patient who remained symptomatic several weeks after discharge from hospital with what was diagnosed as a COVID‐19 infection. There were significant deficits shown in his functional exercise testing, his pulmonary functions testing and there was evidence of fibrotic changes on his radiology.

Methods

As part of a multidisciplinary clinic, he was started on steroids and a tailored pulmonary rehabilitation course over a course of 6–8 weeks. Thereafter, his exercise testing, pulmonary function tests and radiology were all repeated to see progress.

Results

On completing the course of corticosteroids and concurrent personalised pulmonary rehabilitation, there was a dramatic improvement in the patient's symptom severity, radiology and pulmonary function. The most significant improvement noted was in his exercise testing, namely a 6‐min walk test and 1 min of sit‐to‐stands. Before treatment, he had a Medical Reserch Council (MRC) score of 2, and after it returned to his baseline of 0.

Discussion

Using corticosteroids and exercise training that allowed quantitative evaluation throughout the stages of recovery was a valuable tool to gauge progress and response to treatment. These therapies present opportunity to prevent the development of irreversible pulmonary fibrosis that could prove to be a major breakthrough in reducing long‐term morbidity and improving the quality of life of those affected.

A novel multi-omics-based highly accurate prediction of symptoms, comorbid conditions, and possible long-term complications of COVID-19

Comprehensive clinical pictures, comorbid conditions, and long-term complications of COVID-19 are still unknown. Recently, using a multi-omics-based strategy, we predicted potential drugs for COVID-19 with ∼70% accuracy. Herein, using a novel multi-omics-based bioinformatic approach and three ways of analysis, we identified the symptoms, comorbid conditions, and short-, mid-, and possible long-term complications of COVID-19 with >90% precision including 27 parent, 170 child, and 403 specific conditions. Among the specific conditions, 36 viral, 53 short-term, 62 short-mid-long-term, 194 mid-long-term, and 57 congenital conditions are identified. At a threshold "count of occurrence" of 4, we found that 83-100% (average 92.67%) of enriched conditions are associated with COVID-19. Except for dry cough and loss of taste, all the other COVID-19-associated mild and severe symptoms are enriched. CVDs, and pulmonary, metabolic, musculoskeletal, neuropsychiatric, kidney, liver, and immune system disorders are top comorbid conditions. Specific diseases like myocardial infarction, hypertension, COPD, lung injury, diabetes, cirrhosis, mood disorders, dementia, macular degeneration, chronic kidney disease, lupus, arthritis, etc. along with several other NCDs were found to be top candidates. Interestingly, many cancers and congenital disorders associated with COVID-19 severity are also identified. Arthritis, gliomas, diabetes, psychiatric disorders, and CVDs having a bidirectional relationship with COVID-19 are also identified as top conditions. Based on our accuracy (>90%), the long-term presence of SARS-CoV-2 RNA in human, and our "genetic remittance" assumption, we hypothesize that all the identified top-ranked conditions could be potential long-term consequences in COVID-19 survivors, warranting long-term observational studies.

Stem cells and COVID-19: are the human amniotic cells a new hope for therapies against the SARS-CoV-2 virus?

A new coronavirus respiratory disease (COVID-19) caused by the SARS-CoV-2 virus, surprised the entire world, producing social, economic, and health problems. The COVID-19 triggers a lung infection with a multiple proinflammatory cytokine storm in severe patients. Without effective and safe treatments, COVID-19 has killed thousands of people, becoming a pandemic. Stem cells have been suggested as a therapy for lung-related diseases. In particular, mesenchymal stem cells (MSCs) have been successfully tested in some clinical trials in patients with COVID-19. The encouraging results positioned MSCs as a possible cell therapy for COVID-19. The amniotic membrane from the human placenta at term is a valuable stem cell source, including human amniotic epithelial cells (hAECs) and human mesenchymal stromal cells (hAMSCs). Interestingly, amnion cells have immunoregulatory, regenerative, and anti-inflammatory properties. Moreover, hAECs and hAMSCs have been used both in preclinical studies and in clinical trials against respiratory diseases. They have reduced the inflammatory response and restored the pulmonary tissue architecture in lung injury in vivo models. Here, we review the existing data about the stem cells use for COVID-19 treatment, including the ongoing clinical trials. We also consider the non-cellular therapies that are being applied. Finally, we discuss the human amniotic membrane cells use in patients who suffer from immune/inflammatory lung diseases and hypothesize their possible use as a successful treatment against COVID-19.

Ultrasound assessment of pulmonary fibroproliferative changes in severe COVID-19: a quantitative correlation study with histopathological findings

PURPOSE

This study was designed to evaluate the usefulness of lung ultrasound (LUS) imaging to characterize the progression and severity of lung damage in cases of COVID-19.

METHODS

We employed a set of combined ultrasound parameters and histopathological images obtained simultaneously in 28 patients (15 women, 0.6-83 years) with fatal COVID-19 submitted to minimally invasive autopsies, with different times of disease evolution from initial symptoms to death (3-37 days, median 18 days). For each patient, we analysed eight post-mortem LUS parameters and the proportion of three histological patterns (normal lung, exudative diffuse alveolar damage [DAD] and fibroproliferative DAD) in eight different lung regions. The relationship between histopathological and post-mortem ultrasonographic findings was assessed using various statistical approaches.

RESULTS

Statistically significant positive correlations were observed between fibroproliferative DAD and peripheral consolidation (coefficient 0.43, p = 0.02) and pulmonary consolidation (coefficient 0.51, p = 0.005). A model combining age, time of evolution, sex and ultrasound score predicted reasonably well (r = 0.66) the proportion of pulmonary parenchyma with fibroproliferative DAD.

CONCLUSION

The present study adds information to previous studies related to the use of LUS as a tool to assess the severity of acute pulmonary damage. We provide a histological background that supports the concept that LUS can be used to characterize the progression and severity of lung damage in severe COVID-19.

Healing after COVID-19: are survivors at risk for pulmonary fibrosis?

The novel SARS-CoV-2 coronavirus, which is responsible for COVID-19 disease, was first reported in Wuhan, China, in December of 2019. The virus rapidly spread, and the World Health Organization declared a pandemic by March 2020. With millions of confirmed cases worldwide, there is growing concern and considerable debate regarding the potential for coronavirus infection to contribute to an appreciable burden of chronic respiratory symptoms or fibrotic disease among recovered individuals. Because the first case of COVID-19 was documented less than one year ago, data regarding long-term clinical outcomes are not yet available, and predictions for long-term outcome are speculative at best. However, due to the staggering number of cases and the severity of disease in many individuals, there is a critical need to consider the potential long-term implications of COVID-19. This review examines current basic and clinical data regarding fibrogenic mechanisms of viral injury in the context of SARS-CoV-2. Several intersecting mechanisms between coronavirus infection and fibrotic pathways are discussed to highlight factors and processes that may be targetable to improve patient outcome. Reports of post-infection sequelae from previous coronavirus outbreaks are presented toward the goal of improved recognition of potential contributing risk factors for fibrotic disease.

Mesenchymal Stem Cell-Derived Extracellular Vesicles Carrying miRNA as a Potential Multi Target Therapy to COVID-19: an In Silico Analysis

In the end of 2019 COVID-19 emerged as a new threat worldwide and this disease present impaired immune system, exacerbated production of inflammatory cytokines, and coagulation disturbs. Mesenchymal stem cell (MSC) derived extracellular vesicles (EVs) have emerged as a therapeutic option due to its intrinsic properties to alleviate inflammatory responses, capable to promote the restoring of injured tissue. EVs contain heterogeneous cargo, including active microRNAs, small noncoding sequences involved in post-transcriptional gene repression or degradation and can attach in multiple targets. This study investigated whether the MSC-EVs miRNA cargo has the capacity to modulate the exacerbated cytokines, cell death and coagulation disturbs present in severe COVID-19. Through bioinformatics analysis, four datasets of miRNA, using different stem cell tissue sources (bone marrow, umbilical cord and adipose tissue), and one dataset of mRNA (bone marrow) were analyzed. 58 miRNAs overlap in the four miRNA datasets analyzed. Sequentially, those miRNAs present in at least two datasets, were analyzed using miRWalk for the 3’UTR binding target mRNA. The result predicted 258 miRNAs for exacerbated cytokines and chemokines, 266 miRNAs for cell death genes and 148 miRNAs for coagulation cascades. Some miRNAs may simultaneously attenuate inflammatory agents, inhibit cell death genes and key factors of coagulation cascade, consequently preventing tissue damage and coagulation disturbs. Therefore, the MSC-derived EVs due to their heterogeneous cargo are a potential multitarget approach able to improve the survival rates of severe COVID-19 patients.

Chest Imaging of Patients with Sarcoidosis and SARS-CoV-2 Infection. Current Evidence and Clinical Perspectives

The recent COVID-19 pandemic has dramatically changed the world in the last months, leading to a serious global emergency related to a novel coronavirus infection that affects both sexes of all ages ubiquitously. Advanced age, cardiovascular comorbidity, and viral load have been hypothesized as some of the risk factors for severity, but their role in patients affected with other diseases, in particular immune disorders, such as sarcoidosis, and the specific interaction between these two diseases remains unclear. The two conditions might share similar imaging findings but have distinctive features that are here described. The recent development of complex imaging softwares, called deep learning techniques, opens new scenarios for the diagnosis and management.

Restrictive Lung Disease in Patients With Subclinical Coronavirus Infection: Are We Bracing Ourselves for Devastating Sequelae?

The coronavirus disease 2019 (COVID-19) pandemic has affected millions of people worldwide. The manifestations of COVID-19 infection can range from being asymptomatic to developing severe acute respiratory distress syndrome (ARDS). Here, we present a case series of five patients who were either asymptomatic or had very mild symptoms of COVID-19 infection upon diagnosis. These patients neither required a visit to the emergency department (ED) nor did they need to be hospitalized but became symptomatic and were found to have interstitial lung disease four to eight weeks after a COVID-19 diagnosis. Thus, it is imperative that we routinely follow up patients with a subclinical COVID 19 infection besides those who were symptomatic. We may be witnessing a silent surge and new-onset interstitial lung disease (ILD) as sequelae of COVID 19 infection.

Comorbidities in rheumatic diseases need special consideration during the COVID-19 pandemic

Comorbidities in rheumatic and musculoskeletal diseases (RMDs) not only increase morbidity and mortality but also confound disease activity, limit drug usage and increase chances of severe infections or drug-associated adverse effects. Most RMDs lead to accelerated atherosclerosis and variable manifestations of the metabolic syndrome. Literature on COVID-19 in patients with RMDs, and the effects of various comorbidities on COVID-19 was reviewed. The initial data of COVID-19 infections in RMDs have not shown an increased risk for severe disease or the use of different immunosuppression. However, there are some emerging data that patients with RMDs and comorbidities may fare worse. Various meta-analyses have reiterated that pre-existing hypertension, cardiovascular disease, stroke, diabetes, chronic kidney disease, heart failure, lung disease or obesity predispose to increased COVID-19 mortality. All these comorbidities are commonly encountered in the various RMDs. Presence of comorbidities in RMDs pose a greater risk than the RMDs themselves. A risk score based on comorbidities in RMDs should be developed to predict severe COVID-19 and death. Additionally, there should be active management of such comorbidities to mitigate these risks. The pandemic must draw our attention towards, and not away from, comorbidities.

A Study on the Safety of Percutaneous Tracheostomy in Patients with Severe Acute Respiratory Syndrome Novel Corona Virus 2 (SARS-nCoV2) Infection: A Single-Center Observational Cohort Study in a CoVID Intensive Care Unit

BACKGROUND

We studied the safety of percutaneous dilatational tracheostomy (PCDT) in severe acute respiratory syndrome novel coronavirus 2 (SARS-nCoV2).

PATIENTS AND METHODS

From 01 March 20 to 30 November 2020, 1635 required hospital admission of which 145 (9%) required intensive (ICU) care. The primary outcomes are mortality and secondary outcomes were duration of invasive mechanical ventilation (IMV), length of stay (LOS) in ICU and hospital, and days required for decannulation.

RESULTS

Out of the 145 (9%), 107 (73.7%) were males (mean 61.4 years, median body mass index (BMI) of 28.2 kg/m²), and 38 (26.2%) were females (mean 58.10 years, median BMI of 31.2 kg/m²). In the cohort of 80 (55.17%) requiring IMV, 19 (23.7%) died within 72 hours and were not included in the study, 37 (group "NT") and 24 (group "T") had a median duration of ventilation of 9 d (IQR, 6-11) and 12 d (IQR, 11-17.25) respectively. Patients in group "T" underwent PCDT based on clinical criteria (fraction of inspired oxygen (FiO₂) of ≤ 50% with positive end-expiratory pressure (PEEP) of ≤ 10 cms of H₂O with stable hemodynamics), and 16 (66.7%) had survived. The reverse transcription-polymerase chain reaction (RT-PCR) does not need to be negative, and none of the health care workers (HCW's) were infected. The Cox-hazard ratio [HR] is 0.19, 95% confidence interval [CI] (0.09, 0.41) with a P-value of <0.001, 83 (57.2%) were discharged with a mortality of 42.8%.

CONCLUSIONS

PCDT is safe and effective in patients anticipated in need of prolonged mechanical ventilation.

The Effect of Intravenous Autologous Activated Platelet-Rich Plasma Therapy on "Profibrotic Cytokine" IL-1β Levels in Severe and Critical COVID-19 Patients: A Preliminary Study

INTRODUCTION

Elevated concentration of proinflammatory cytokines followed by hyperinflammation is one of the hallmarks of severe and critical COVID-19. In the short term, this may result in ARDS and lung injury; subsequently, this may cause pulmonary fibrosis-a disease with poor prognosis-in the long run. Among the cytokines, interleukin-1β (IL-1β) is one of the most overexpressed in COVID-19. We speculate that administration of intravenous activated autologous platelet-rich plasma (aaPRP), which contains interleukin-1 receptor antagonist (IL-1RA), would lower IL-1β levels and benefit the severe and critical COVID-19 patients.

METHODS

After acquiring ethical clearance, we recruited 12 adult COVID-19 patients of both sexes from the Koja Regional Hospital (Jakarta, Indonesia) ICU. After selection, seven patients were included and divided into two groups, severe and critical. In addition to three doses of aaPRP, both groups received the same treatment of antiviral, steroid, and antibiotics. Quantification of plasma IL-1β levels was performed by beads multiplex assay a day before the first aaPRP administration and a day after the second and third aaPRP administration. PaO₂/FiO₂ ratio and lung injury scores were evaluated a day before and a day after each aaPRP administration.

RESULTS

Severe and critical patients' initial plasma IL-1β concentration was 4.71 pg/mL and 3.095 pg/mL, respectively. After 2 treatments with aaPRP, severe patients' plasma IL-1β concentration decreased 12.48 pg/mL, while critical patients' plasma IL-1β concentration increased to 18.77 pg/mL. Furthermore, after 3 aaPRP treatments, significant amelioration of patients' PaO₂/FiO₂ ratio from 71.33 mmHg at baseline to 144.97 mmHg was observed (p < 0.05). However, no significant improvement in lung injury score was observed in severe and critical groups. All severe patients and one critical patient recovered.

CONCLUSION

The use of aaPRP may prevent pulmonary fibrosis in severe COVID-19 patients through the reduction of patients' plasma IL-1β concentration and the amelioration of PaO₂/FiO₂ ratio.

Post-COVID lung fibrosis: The tsunami that will follow the earthquake

The SARS-CoV-2 pandemic has already infected in excess of 50 million people worldwide and resulted in 1.2 million deaths. While the majority of those infected will not have long-term pulmonary sequelae, 5%–10% will develop severe COVID-19 pneumonia and acute respiratory distress syndrome (ARDS). The natural history of these severely affected patients is unclear at present, but using our knowledge of closely related coronavirus outbreaks like severe acute respiratory distress syndrome (SARS) and middle east respiratory syndrome (MERS), we would hypothesize that the majority will stabilize or improve over time although some patients will progress to advanced lung fibrosis or post-COVID interstitial lung disease (PC-ILD). Unlike the SARS and MERS outbreaks which affected only a few thousands, the sheer scale of the present pandemic suggests that physicians are likely to encounter large numbers of patients (potentially hundreds of thousands) with PC-ILD. In this review, we discuss the pathogenesis, natural history, and radiology of such patients and touch on clinical, laboratory, and radiographic clues at presentation which might help predict the future development of lung fibrosis. Finally, we discuss the responsible use of antifibrotic drugs such as pirfenidone, nintedanib, and some newer antifibrotics, still in the pipeline. The biological rationale of these drugs and the patient groups where they may have a plausible role will be discussed. We conclude by stressing the importance of careful longitudinal follow-up of multiple cohorts of post-COVID survivors with serial lung function and imaging. This will eventually help to determine the natural history, course, and response to therapy of these patients.

An atlas connecting shared genetic architecture of human diseases and molecular phenotypes provides insight into COVID-19 susceptibility

While genome-wide associations studies (GWAS) have successfully elucidated the genetic architecture of complex human traits and diseases, understanding mechanisms that lead from genetic variation to pathophysiology remains an important challenge. Methods are needed to systematically bridge this crucial gap to facilitate experimental testing of hypotheses and translation to clinical utility. Here, we leveraged cross-phenotype associations to identify traits with shared genetic architecture, using linkage disequilibrium (LD) information to accurately capture shared SNPs by proxy, and calculate significance of enrichment. This shared genetic architecture was examined across differing biological scales through incorporating data from catalogs of clinical, cellular, and molecular GWAS. We have created an interactive web database (interactive Cross-Phenotype Analysis of GWAS database (iCPAGdb); http://cpag.oit.duke.edu) to facilitate exploration and allow rapid analysis of user-uploaded GWAS summary statistics. This database revealed well-known relationships among phenotypes, as well as the generation of novel hypotheses to explain the pathophysiology of common diseases. Application of iCPAGdb to a recent GWAS of severe COVID-19 demonstrated unexpected overlap of GWAS signals between COVID-19 and human diseases, including with idiopathic pulmonary fibrosis driven by the DPP9 locus. Transcriptomics from peripheral blood of COVID-19 patients demonstrated that DPP9 was induced in SARS-CoV-2 compared to healthy controls or those with bacterial infection. Further investigation of cross-phenotype SNPs with severe COVID-19 demonstrated colocalization of the GWAS signal of the ABO locus with plasma protein levels of a reported receptor of SARS-CoV-2, CD209 (DC-SIGN), pointing to a possible mechanism whereby glycosylation of CD209 by ABO may regulate COVID-19 disease severity. Thus, connecting genetically related traits across phenotypic scales links human diseases to molecular and cellular measurements that can reveal mechanisms and lead to novel biomarkers and therapeutic approaches.

Effect of COVID-19 on Lungs: Focusing on Prospective Malignant Phenotypes

Currently, the healthcare management systems are shattered throughout the world, even in the developed nations due to the COVID-19 viral outbreak. A substantial number of patients infected with SARS-CoV2 develop acute respiratory distress syndrome (ARDS) and need advanced healthcare facilities, including invasive mechanical ventilation. Intracellular infiltration of the SARS-CoV2 virus particles into the epithelial cells in lungs are facilitated by the spike glycoprotein (S Protein) on the outer side of the virus envelope, a membrane protein ACE2 (angiotensin-converting enzyme 2) and two proteases (TMPRSS2 and Furin) in the host cell. This virus has unprecedented effects on the immune system and induces a sudden upregulation of the levels of different pro-inflammatory cytokines. This can be a cause for the onset of pulmonary fibrosis in the lungs. Existence of a high concentration of inflammatory cytokines and viral load can also lead to numerous pathophysiological conditions. Although it is well established that cancer patients are among the high-risk population due to COVID-19-associated mortality, it is still unknown whether survivors of COVID-19-infected subjects are at high-risk population for developing cancer and whether any biologic and clinical features exist in post-COVID-19 individuals that might be related to carcinogenesis.

Repurposing of histone deacetylase inhibitors: A promising strategy to combat pulmonary fibrosis promoted by TGF-β signalling in COVID-19 survivors

Coronavirus disease 2019 (COVID-19) has rapidly spread around the world causing global public health emergency. In the last twenty years, we have witnessed several viral epidemics such as severe acute respiratory syndrome coronavirus (SARS-CoV), Influenza A virus subtype H1N1 and most recently Middle East respiratory syndrome coronavirus (MERS-CoV). There were tremendous efforts endeavoured globally by scientists to combat these viral diseases and now for SARS-CoV-2. Several drugs such as chloroquine, arbidol, remdesivir, favipiravir and dexamethasone are adopted for use against COVID-19 and currently clinical studies are underway to test their safety and efficacy for treating COVID-19 patients. As per World Health Organization reports, so far more than 16 million people are affected by COVID-19 with a recovery of close to 10 million and deaths at 600,000 globally.

SARS-CoV-2 infection is reported to cause extensive pulmonary damages in affected people. Given the large number of recoveries, it is important to follow-up the recovered patients for apparent lung function abnormalities. In this review, we discuss our understanding about the development of long-term pulmonary abnormalities such as lung fibrosis observed in patients recovered from coronavirus infections (SARS-CoV and MERS-CoV) and probable epigenetic therapeutic strategy to prevent the development of similar pulmonary abnormalities in SARS-CoV-2 recovered patients. In this regard, we address the use of U.S. Food and Drug Administration (FDA) approved histone deacetylase (HDAC) inhibitors therapy to manage pulmonary fibrosis and their underlying molecular mechanisms in managing the pathologic processes in COVID-19 recovered patients.

Stabilizing mast cells by commonly used drugs: a novel therapeutic target to relieve post-COVID syndrome?

Regardless of the severity of coronavirus disease 2019 (COVID-19), a high proportion of patients struggle with persistent respiratory or systemic symptoms after recovery. This is called "postCOVID syndrome", for which pulmonary fibrosis is one of the pathogenesis. Besides T-lymphocytes and macrophages, mast cells also contribute to the development of cytokine storm and thus stimulate the activity of fibroblasts. Additionally, by the exocytotic release of fibroblast-activating factors, mast cells directly facilitate the progression of pulmonary fibrosis. In our previous basic studies, anti-allergic drugs (olopatadine, ketotifen), antibiotics (clarithromycin) and corticosteroids (hydrocortisone, dexamethasone) inhibited the process of exocytosis and showed their potency as highly effective mast cell stabilizers. Given such pharmacological properties of these commonly used drugs, they may be useful in the treatment of post-COVID-19 pulmonary fibrosis and in relieving the symptoms of post-COVID syndrome.