Pulmonary fibrosis in the aftermath of the COVID-19 era (Review)

Exploring Prognostically Significant Factors in COVID-19-Associated Pulmonary Fibrosis after Adaptive Lung Ventilation

Background

Research data on hospitalized coronavirus 2019 (COVID-19) survivors indicate the persistence of symptoms, radiological abnormalities, and physiological disorders months after the initial infection. Given the scale of the ongoing pandemic, a substantial number of patients with severe residual pulmonary fibrosis (PF) and oxygen dependence are anticipated. Currently, the search for risk factors associated with the development of fibrotic radiological abnormalities after moderate to severe COVID-19 is underway. Furthermore, the extent to which computed tomography (CT) data correlate with postdischarge symptoms and physical functions remains unclear. This study aimed to characterize patients experiencing persistent pulmonary consequences after hospital discharge. We examined clinical, radiological, and laboratory predictors of pulmonary fibrosis after COVID-19 infection.

Methods

We retrospectively evaluated fibrosis-like lung changes and their prognostic factors in COVID-19 survivors. Our study included 77 patients with laboratory-confirmed COVID-19 who received inpatient treatment at City Clinical Hospital No. 1 in Almaty between November and December 2020. We assessed patients during the acute phase of the disease and again 6 to 8 months after discharge using high-resolution computed tomography (CT). Patients were classified into 2 cohorts based on semi-quantitative analysis of subsequently added tomograms-those with radiological fibrosis-like abnormalities (main group) and those who had recovered (control group).

Results

Parenchymal cords, irregular interfaces, reticulation, and traction bronchiectasis were common CT findings among all COVID-19 patients. Our study focused on patients who developed pulmonary fibrosis within 1 month after the onset of the disease. After 6 to 8 months, fibrosis-like lung changes persisted in 49.35% of patients (leading group), while 50.65% showed disease resolution (control group). Age, body mass index, high interleukin-6 (IL-6) levels, low IO levels, and the need for mechanical ventilation were identified as prognostic indicators for the persistence of pulmonary fibrosis.

Conclusion

Our study revealed that pulmonary function can return to normal in over half of COVID-19 patients 8 months after infection onset. Despite advancements in COVID-19 treatment, there remains a significant knowledge gap in managing long-term effects, especially pulmonary fibrosis. Continued clinical trials and research on post COVID-19 fibrosis are essential to prevent early mortality due to the long-term impacts on these patients.

Post-COVID-19 Pulmonary Fibrosis: Facts-Challenges and Futures: A Narrative Review

Patients with coronavirus disease 2019 (COVID-19) usually suffer from post-acute sequelae of coronavirus disease 2019 (PASC). Pulmonary fibrosis (PF) has the most significant long-term impact on patients' respiratory health, called post-COVID-19 pulmonary fibrosis (PC19-PF). PC19- PF can be caused by acute respiratory distress syndrome (ARDS) or pneumonia due to COVID-19. The risk factors of PC19-PF, such as older age, chronic comorbidities, the use of mechanical ventilation during the acute phase, and female sex, should be considered. Individuals with COVID-19 pneumonia symptoms lasting at least 12 weeks following diagnosis, including cough, dyspnea, exertional dyspnea, and poor saturation, accounted for nearly all disease occurrences. PC19-PF is characterized by persistent fibrotic tomographic sequelae associated with functional impairment throughout follow-up. Thus, clinical examination, radiology, pulmonary function tests, and pathological findings should be done to diagnose PC19-PF patients. PFT indicated persistent limitations in diffusion capacity and restrictive physiology, despite the absence of previous testing and inconsistency in the timeliness of assessments following acute illness. It has been hypothesized that PC19-PF patients may benefit from idiopathic pulmonary fibrosis treatment to prevent continued infection-related disorders, enhance the healing phase, and manage fibroproliferative processes. Immunomodulatory agents might reduce inflammation and the length of mechanical ventilation during the acute phase of COVID-19 infection, and the risk of the PC19-PF stage. Pulmonary rehabilitation, incorporating exercise training, physical education, and behavioral modifications, can improve the physical and psychological conditions of patients with PC19-PF.

Molecular mechanisms of COVID-19-induced pulmonary fibrosis and epithelial-mesenchymal transition

As the outbreak of COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first broke out in Hubei Province, China, at the end of 2019. It has brought great challenges and harms to global public health. SARS-CoV-2 mainly affects the lungs and is mainly manifested as pulmonary disease. However, one of the biggest crises arises from the emergence of COVID-19-induced fibrosis. At present, there are still many questions about how COVID-19 induced pulmonary fibrosis (PF) occurs and how to treat and regulate its long-term effects. In addition, as an important process of fibrosis, the effect of COVID-19 on epithelial-mesenchymal transition (EMT) may be an important factor driving PF. This review summarizes the main pathogenesis and treatment mechanisms of COVID-19 related to PF. Starting with the basic mechanisms of PF, such as EMT, transforming growth factor-β (TGF-β), fibroblasts and myofibroblasts, inflammation, macrophages, innate lymphoid cells, matrix metalloproteinases and tissue inhibitors of metalloproteinases, hedgehog pathway as well as Notch signaling. Further, we highlight the importance of COVID-19-induced EMT in the process of PF and provide an overview of the related molecular mechanisms, which will facilitate future research to propose new clinical therapeutic solutions for the treatment of COVID-19-induced PF.

Pulmonary fibrosis: A short- or long-term sequelae of severe COVID-19?

The pandemic of coronavirus disease 2019 (COVID‑19), caused by a novel severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2), has caused an enormous impact on the global healthcare. SARS-CoV-2 infection primarily targets the respiratory system. Although most individuals testing positive for SARS-CoV-2 present mild or no upper respiratory tract symptoms, patients with severe COVID-19 can rapidly progress to acute respiratory distress syndrome (ARDS). ARDS-related pulmonary fibrosis is a recognized sequelae of COVID-19. Whether post-COVID-19 lung fibrosis is resolvable, persistent, or even becomes progressive as seen in human idiopathic pulmonary fibrosis (IPF) is currently not known and remains a matter of debate. With the emergence of effective vaccines and treatments against COVID-19, it is now important to build our understanding of the long-term sequela of SARS-CoV-2 infection, to identify COVID-19 survivors who are at risk of developing chronic pulmonary fibrosis, and to develop effective anti-fibrotic therapies. The current review aims to summarize the pathogenesis of COVID-19 in the respiratory system and highlights ARDS-related lung fibrosis in severe COVID-19 and the potential mechanisms. It envisions the long-term fibrotic lung complication in COVID-19 survivors, in particular in the aged population. The early identification of patients at risk of developing chronic lung fibrosis and the development of anti-fibrotic therapies are discussed.

Lung mesenchymal cells from patients with COVID-19 driven lung fibrosis: Several features with CTD-ILD derived cells but with higher response to fibrogenic signals and might be more pro-inflammatory

A subset of severe COVID19 patients develop pulmonary fibrosis, but the pathophysiology of this complication is still unclear. We previously described the possibility to isolate lung mesenchymal cells (LMC) by culturing broncho-alveolar lavage (BAL) cells from patients with pulmonary fibrosis or chronic lung allograft dysfunction. Aim of this study was to investigate the possibility to isolate and characterize LMC from BAL of patients that, two months after discharge for severe COVID19, show CT signs of post-COVID19 fibrosis (Post-COVID) and in some cases has been considered transplant indication. Results were compared with those from BAL of patients with collagen tissue disease-associated interstitial fibrosis (CTD-ILD). BAL fluid levels of TGFβ, VEGF, TIMP2, RANTES, IL6, IL8, and PAI1 were assessed. LMC were cultured and expanded, phenotyped by flow cytometry, and tested for osteogenic and adipogenic differentiation. Finally, we tested immunomodulatory and proliferative capabilities, collagen I production + /- TGF-beta stimulation. BAL cytokine and growth factor levels were comparable in the two groups. Efficiency of isolation from BAL was 100% in post-COVID compared to 63% in CTD-ILD. LMC from post-COVID were positive for CD105, CD73, CD90, and negative for CD45, CD34, CD19 and HLA-DR as in CTD-ILD samples. Post-COVID LMC displayed higher collagen production with respect to CTD-ILD LMC. Immunomodulatory capacity towards lymphocytes was very low, while Post-COVID LMC significantly upregulated pro-inflammatory cytokine production by healthy PBMCs. Our preliminary data suggest that LMC from post-COVID19 fibrosis patients share several features with CTD-ILD ones but might have a higher response to fibrogenic signals and pro-inflammatory profile.

Post-intensive care syndrome and pulmonary fibrosis in patients surviving ARDS-pneumonia of COVID-19 and non-COVID-19 etiologies

The purpose was to examine patient-centered outcomes and the occurrence of lung fibrotic changes on Chest computed tomography (CT) imaging following pneumonia-related acute respiratory distress syndrome (ARDS). We sought to investigate outpatient clinic chest CT imaging in survivors of COVID19-related ARDS and non-COVID-related ARDS, to determine group differences and explore relationships between lung fibrotic changes and functional outcomes. A retrospective practice analysis of electronic health records at an ICU Recovery Clinic in a tertiary academic medical center was performed in adult patients surviving ARDS due to COVID-19 and non-COVID etiologies. Ninety-four patients with mean age 53 ± 13 and 51% male were included (n = 64 COVID-19 and n = 30 non-COVID groups). There were no differences for age, sex, hospital length of stay, ICU length of stay, mechanical ventilation duration, or sequential organ failure assessment (SOFA) scores between the two groups. Fibrotic changes visualized on CT imaging occurred in a higher proportion of COVID-19 survivors (70%) compared to the non-COVID group (43%, p < 0.001). Across both groups, patients with fibrotic changes (n = 58) were older, had a lower BMI, longer hospital and ICU LOS, lower mean RASS scores, longer total duration of supplemental oxygen. While not statistically different, patients with fibrotic changes did have reduced respiratory function, worse performance on the six-minute walk test, and had high occurrences of anxiety, depression, emotional distress, and mild cognitive impairment regardless of initial presenting diagnosis. Patients surviving pneumonia-ARDS are at high risk of impairments in physical, emotional, and cognitive health related to Post-Intensive Care Syndrome. Of clinical importance, pulmonary fibrotic changes on chest CT occurred in a higher proportion in COVID-ARDS group; however, no functional differences were measured in spirometry or physical assessments at ICU follow-up. Whether COVID infection imparts a unique recovery is not evident from these data but suggest that long-term follow up is necessary for all survivors of ARDS.

Evaluation of the interaction between tumor growth factor-β and interferon type I pathways in patients with COVID-19: focusing on ages 1 to 90 years

BACKGROUND

Evidence revealed that age could affect immune responses in patients with the acute respiratory syndrome of coronavirus 2 (SARS-CoV-2) infection. This study investigated the impact of age on immune responses, especially on the interaction between the tumor growth factor-β (TGF-β) and interferon type-I (IFN-I) axes in the pathogenesis of novel coronavirus disease 2019 (COVID-19).

METHODS

This age-matched case-control investigation enrolled 41 COVID-19 patients and 40 healthy controls categorized into four groups, including group 1 (up to 20 years), group 2 (20-40 years), group 3 (40-60 years), and group 4 (over 60 years). Blood samples were collected at the time of admission. The expression of TGF-βRI, TGF-βRII, IFNARI, IFNARII, interferon regulatory factor 9 (IRF9), and SMAD family member 3 (SMAD3) was measured using the real-time PCR technique. In addition, serum levels of TGF-β, IFN-α, and SERPINE1 were measured by the enzyme-linked immunosorbent assay (ELISA) technique. All biomarkers were measured and analyzed in the four age studies groups.

RESULTS

The expression of TGF-βRI, TGF-βRII, IFNARI, IFNARII, IRF9, and SMAD3 was markedly upregulated in all age groups of patients compared with the matched control groups. Serum levels of IFN-α and SERPINE1 were significantly higher in patient groups than in control groups. While TGF-β serum levels were only significantly elevated in the 20 to 40 and over 60 years patient group than in matched control groups.

CONCLUSIONS

These data showed that the age of patients, at least at the time of admission, may not significantly affect TGF-β- and IFN-I-associated immune responses. However, it is possible that the severity of the disease affects these pathway-mediated responses, and more studies with a larger sample size are needed to verify it.

Computed tomography chest findings in post-acute COVID-19 lung disease at a South African regional hospital - a descriptive study

Introduction

whilst many studies have focused on acute and chronic complications of COVID-19, few studies have been performed on the immediate post-acute COVID-19 phase complications. The objective of the study was to describe computed tomography (CT) imaging findings in patients from a South African (SA) cohort during the post-acute COVID-19 phase. To describe the findings using existing CT description systems and, if present, pulmonary imaging findings unique to our cohort.

Methods

a review of CT chest examinations performed over the second wave of COVID-19 in SA for post-acute COVID-19 cardiorespiratory complaints at Worcester Hospital. The CT findings were described using a modified semi-quantitative tabulation method.

Results

eight males and 12 females met the inclusion criteria with a mean age of 56 years. Half had hypertension, 11 had diabetes, two had human immunodeficiency virus (HIV), half had raised D-dimers and six had pre-existing lung disease. The predominant parenchymal pattern was mixed ground glass and reticular changes in a diffuse/peripheral multilobar distribution with relative sparing of the left upper lobe. Four cases demonstrated pulmonary emboli, 50% pulmonary hypertension, three pleural effusions and nine lymphadenopathy. None of the cases had evidence of active pulmonary tuberculosis.

Conclusion

CT lung findings appear to mirror global findings with expected evolutionary differences. An interesting observation was the relative sparing of the left upper lobe. Reporting using the modified table proved efficient. Real-world extrapolation of our findings is limited by low-case numbers.

Hyaluronan in the pathogenesis of acute and post-acute COVID-19 infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) recently emerged as the cause of a global pandemic. Infection with SARS-CoV-2 can result in COVID-19 with both acute and chronic disease manifestations that continue to impact many patients long after the resolution of viral replication. There is therefore great interest in understanding the host factors that contribute to COVID-19 pathogenesis. In this review, we address the role of hyaluronan (HA), an extracellular matrix polymer with roles in inflammation and cellular metabolism, in COVID-19 and critically evaluate the hypothesis that HA promotes COVID-19 pathogenesis. We first provide a brief overview of COVID-19 infection. Then we briefly summarize the known roles of HA in airway inflammation and immunity. We then address what is known about HA and the pathogenesis of COVID-19 acute respiratory distress syndrome (COVID-19 ARDS). Next, we examine potential roles for HA in post-acute SARS-CoV-2 infection (PASC), also known as "long COVID" as well as in COVID-associated fibrosis. Finally, we discuss the potential therapeutics that target HA as a means to treat COVID-19, including the repurposed drug hymecromone (4-methylumbelliferone). We conclude that HA is a promising potential therapeutic target for the treatment of COVID-19.

Cardiopulmonary disease as sequelae of long-term COVID-19: Current perspectives and challenges

COVID-19 infection primarily targets the lungs, which in severe cases progresses to cytokine storm, acute respiratory distress syndrome, multiorgan dysfunction, and shock. Survivors are now presenting evidence of cardiopulmonary sequelae such as persistent right ventricular dysfunction, chronic thrombosis, lung fibrosis, and pulmonary hypertension. This review will summarize the current knowledge on long-term cardiopulmonary sequelae of COVID-19 and provide a framework for approaching the diagnosis and management of these entities. We will also identify research priorities to address areas of uncertainty and improve the quality of care provided to these patients.

The effect of Pirfenidone on pulmonary function parameters in post recovery COVID-19 patients with pulmonary fibrosis compared to placebo in a Government Medical College, West Bengal

Introduction and Aim: The recent COVID 19 pandemic has created an unprecedented challenge to the entire global healthcare system by affecting many people worldwide. Post COVID complications are multi-systemic, but pulmonary post COVID complications are most common. Involvement of the lung parenchyma ultimately leads to pulmonary fibrosis in many of the patients. Pirfenidone is a widely used antifibrotic medication in the field of idiopathic pulmonary fibrosis (IPF) management. Our study has assessed the effect of Pirfenidone on spirometry parameters in post recovery COVID 19 patients with diagnosed pulmonary fibrosis as compared to those that received placebo.   Materials and Methods: After obtaining approval from Institutional Ethics Committee, 70 adult patients of COVID-19 with established pulmonary fibrosis in the post recovery phase were chosen and allocated into two groups by randomization in 1:1 ratio. All other factors remaining same, one group was administered the recommended dose of Pirfenidone and the other group received a placebo. Spirometry parameters such as FEV1, FEV1 /FVC ratio, FVC, PEFR of both the groups were recorded on Day 0 and Day 90 and compared using standard statistical tests.   Results: It was found that on Day 0, PFT parameters of the two groups was comparable (P value>0.05). PFT parameters of the group receiving Pirfenidone showed significant improvement on day 90 (P value<0.05). In addition, on day 90, the PFT parameters of the group receiving Pirfenidone showed significantly better values than the group receiving placebo, P value <0.05.   Conclusion: As there is a significant improvement in the PFT parameters of post recovery COVID-19 patients suffering from pulmonary fibrosis, we conclude that Pirfenidone is helpful to improve the pulmonary function parameters in post recovery COVID -19 patients with established lung fibrosis as compared to placebo.

Lung Transplantation in Patients With COVID-19-The Early National Experience

Lung transplant (LT) has become a viable option for COVID-19 patients suffering from end-stage Acute Respiratory Distress Syndrome (ARDS). This analysis sought to describe the early national experience of COVID-19 patients who received LT and compare transplant characteristics and short-term outcomes of COVID-19 and non-COVID-19 ARDS LT recipients. We queried the Organ Procurement and Transplantation database for adults (≥18 years old) receiving LT from January 2009 to March 31, 2022 with diagnoses of COVID-19 or ARDS. We identified 353 COVID-19 and 64 non-COVID-19 ARDS LT recipients. COVID-19 recipients were older (median age: 51, interquartile range [40-57] years vs 41 [26-52]; P < 0.001), more predominantly male (78% (n = 274) vs 55% (n = 35), P < 0.001), and had higher body mass indices (median 27.2 interquartile range [24.5-30.9] vs 25.4 [22.1-28.6]; P < 0.01) than non-COVID-19 ARDS recipients. COVID-19 LT recipients were less frequently reliant on extra-corporeal membrane oxygenation at 72 hours after transplant (26% (n = 80) vs 31% (n = 15), P < 0.001), and were less frequently dependent on dialysis post-transplant than non-COVID-19 ARDS LT recipients (14% (n = 43) vs 23% (n = 14); P = 0.01). Survival at 90 days post-transplant was comparable for the non-COVID ARDS (90%, n = 54) and COVID-19 (94%, n = 202) LT recipients with available follow-up (P = 0.17). LT appears to be a viable therapy for COVID-19 patients with end-stage lung disease. COVID-19 LT and non-COVID-19 ARDS LT recipients have comparable 90 days post-transplant survival.

Interstitial Lung Fibrosis Following COVID-19 Pneumonia

Background and Objectives: Pulmonary fibrosis represents a stage of normal physiologic response to inflammatory aggression, mostly self-limiting and reversible; however, numerous patients treated for SARS-CoV-2 pneumonia present after release from hospital residual lung fibrosis. In this article, we aim to present an optimization method for evaluating pulmonary fibrosis by quantitative analysis, to identify the risk factors/predictors for pulmonary fibrosis in patients with SARS-CoV-2 infection, and to characterize the impact of pulmonary fibrosis on the symptomatology of patients after release from the hospital. Materials and Methods: We performed a prospective observational study on 100 patients with severe forms of pneumonia, with a control group of 61 non-COVID normal patients. Results: We found persistent interstitial changes consistent with fibrotic changes in 69% of patients. The risk of fibrosis was proportional to the values of erythrocyte sedimentation rate (ESR), C reactive protein (CRP), and lactate dehydrogenase (LDH), and to the duration of hospitalization. The imaging parameters correlated with increased risk for interstitial fibrosis were the number of affected pulmonary lobes and the percent of interstitial pulmonary fibrosis. Conclusions: The main risk factors for pulmonary fibrosis post-COVID-19 identified in our study are increased ESR, CRP, LDH, duration of hospitalization and the severity of pneumonia.

Mortality and Its Predictors in COVID-19 Patients With Pre-existing Interstitial Lung Disease

Background

The data on the impact of coronavirus disease 2019 (COVID-19) on interstitial lung disease (ILD) is still limited. To the best of our knowledge, there has been no study from India to date to assess the impact of COVID-19 in patients with preexisting ILD. We undertook this study to assess the clinical outcome of ILD patients admitted to our hospital with COVID-19.

Methods

In this retrospective observational study, records of reverse transcription polymerase chain reaction (RT-PCR)-confirmed COVID-19 patients with preexisting ILD who were admitted to the hospital in the period from May 1, 2020, to April 30, 2021, were obtained from the hospital database. The clinical outcomes of the patients were recorded. Univariate analysis was performed to find relation between various predetermined risk factors for mortality and those with significant p values (p<0.05) were subjected to multiple logistic regression to determine independent risk factors.

Results

In our study of 28 patients, the overall mortality was 35.7%. On comparing the parameters associated with increased mortality, there was no effect of age, gender, comorbidities, type of ILD, CT thorax findings on diagnosis, use of corticosteroids and antifibrotics in the past, spirometric findings on mortality. On multivariate analysis, the significant parameters were interleukin 6 (IL-6), p=0.02, OR=1.020 (1.006-1.043) and D-dimer, p=0.04, OR=2.14 (5.55-1.14).

Conclusion

COVID-19 in patients with pre-existing ILD has a comparatively higher mortality. D-dimer and IL-6 are significant predictors of mortality in ILD patients infected with COVID-19.

β-Carboline Alkaloids From the Deep-Sea Fungus Trichoderma sp. MCCC 3A01244 as a New Type of Anti-pulmonary Fibrosis Agent That Inhibits TGF-β/Smad Signaling Pathway

Pulmonary fibrosis is a scarring disease of lung tissue, which seriously threatens human health. Treatment options are currently limited, and effective strategies are still lacking. In the present study, 25 compounds were isolated from the deep-sea fungus Trichoderma sp. MCCC 3A01244. Among them, two β-carboline alkaloids, trichocarbolines A (1) and C (4) are new compounds. The chemical structures of these compounds were elucidated based on their HRESIMS, 1D and 2D NMR spectra, optical rotation calculation, and comparisons with data reported in the literature. Trichocarboline B [(+)- and (–)-enantiomers] had previously been synthesized, and this is its first report as a natural product. Their anti-pulmonary fibrosis (PF) activity and cytotoxicity were investigated. Compounds 1, 11, and 13 strongly inhibited TGF-β1-induced total collagen accumulation and showed low cytotoxicity against the HFL1 cell line. Further studies revealed compound 1 inhibited extracellular matrix (ECM) deposition by downregulating the expression of protein fibronectin (FN), proliferating cell nuclear antigen (PCNA), and α-smooth muscle actin (α-SMA). Mechanistic study revealed that compound 1 decreased pulmonary fibrosis by inhibiting the TGF-β/Smad signaling pathway. As a newly identified β-carboline alkaloid, compound 1 may be used as a lead compound for developing more efficient anti-pulmonary fibrosis agents.

TRPM7 restrains plasmin activity and promotes transforming growth factor-β1 signaling in primary human lung fibroblasts

Sustained exposure of the lung to various environmental or occupational toxins may eventually lead to pulmonary fibrosis, a devastating disease with no cure. Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix (ECM) proteins such as fibronectin and collagens. The peptidase plasmin degrades the ECM, but protein levels of the plasmin activator inhibitor-1 (PAI-1) are increased in fibrotic lung tissue, thereby dampening plasmin activity. Transforming growth factor-β1 (TGF-β1)-induced activation of SMAD transcription factors promotes ECM deposition by enhancing collagen, fibronectin and PAI-1 levels in pulmonary fibroblasts. Hence, counteracting TGF-β1-induced signaling is a promising approach for the therapy of pulmonary fibrosis. Transient receptor potential cation channel subfamily M Member 7 (TRPM7) supports TGF-β1-promoted SMAD signaling in T-lymphocytes and the progression of fibrosis in kidney and heart. Thus, we investigated possible effects of TRPM7 on plasmin activity, ECM levels and TGF-β1 signaling in primary human pulmonary fibroblasts (pHPF). We found that two structurally unrelated TRPM7 blockers enhanced plasmin activity and reduced fibronectin or PAI-1 protein levels in pHPF under basal conditions. Further, TRPM7 blockade strongly inhibited fibronectin and collagen deposition induced by sustained TGF-β1 stimulation. In line with these data, inhibition of TRPM7 activity diminished TGF-β1-triggered phosphorylation of SMAD-2, SMAD-3/4-dependent reporter activation and PAI-1 mRNA levels. Overall, we uncover TRPM7 as a novel supporter of TGF-β1 signaling in pHPF and propose TRPM7 blockers as new candidates to control excessive ECM levels under pathophysiological conditions conducive to pulmonary fibrosis.

The Atrium in Atrial Fibrillation - A Clinical Review on How to Manage Atrial Fibrotic Substrates

Atrial fibrillation (AF) is the most common sustained arrhythmia in the population and is associated with a significant clinical and economic burden. Rigorous assessment of the presence and degree of an atrial arrhythmic substrate is essential for determining treatment options, predicting long-term success after catheter ablation, and as a substrate critical in the pathophysiology of atrial thrombogenesis. Catheter ablation of AF has developed into an essential rhythm-control strategy. Nowadays is one of the most common cardiac ablation procedures performed worldwide, with its success inversely related to the extent of atrial structural disease. Although atrial substrate evaluation remains complex, several diagnostic resources allow for a more comprehensive assessment and quantification of the extent of left atrial structural remodeling and the presence of atrial fibrosis. In this review, we summarize the current knowledge on the pathophysiology, etiology, and electrophysiological aspects of atrial substrates promoting the development of AF. We also describe the risk factors for its development and how to diagnose its presence using imaging, electrocardiograms, and electroanatomic voltage mapping. Finally, we discuss recent data regarding fibrosis biomarkers that could help diagnose atrial fibrotic substrates.

Impact of the COVID-19 Pandemic on Trends in Cardiothoracic Imaging

Introduction

Here, we evaluate the effect of the COVID-19 pandemic on utilization of cardiothoracic imaging studies.

Methods

We queried our radiology record system to retrospectively identify numbers of specific key cardiothoracic imaging studies for five years prior and during the COVID-19 pandemic. Statistical analysis was performed to evaluate changes in the number of exams in 2020 and 2021 compared to 2019.

Results

Five-year retrospective analysis demonstrated progressive increases in nearly all cross-sectional studies. In 2020, daily chest radiograph utilization decreased with an overall number of daily radiographs of 406 (SD = 73.1) compared to 480 per day in 2019 (SD = 82.6) (p < 0.0001). Portable radiograph utilization was increased in 2020 averaging 320 (SD = 68.2) films daily in 2020 compared to 266 (SD = 29.1) in 2019 (p < 0.0001). Utilization of thoracic CT was decreased during the pandemic, with 21.8 (SD = 12.9) studies daily compared to 52.0 (SD = 21.4) (p < 0.0001) studies daily in 2019. Cardiac imaging utilization was also substantially decreased in 2020 compared to 2019, averaging a total of 3.8 (SD = 3.2) versus 10.8 (SD = 6.6) studies daily and 0.88 (SD = 1.7) versus 2.5 (SD = 2.3) studies daily for CT and MRI, respectively. Evaluation of cardiothoracic imaging for the subsequent 18 months after New York's entry to phase I recovery in June 2020 demonstrated that by one year after the emergence of COVID-19 imaging utilization had recovered to prepandemic levels. Cardiac imaging continued to increase throughout the chronic phase of the COVID-19 pandemic, reaching almost twice the prepandemic levels by the end of 2021.

Conclusion

COVID-19 has had far-reaching effects on medicine and public health. Here, we demonstrate decreases in all cross-sectional cardiothoracic imaging studies, closely mirroring findings in other fields during the height of the pandemic, which have since rebounded.

PTPα Promotes Fibroproliferative Responses After Acute Lung Injury

The Acute Respiratory Distress Syndrome (ARDS) is a major healthcare problem, accounting for significant mortality and long-term disability. Approximately 25% of patients with ARDS will develop an over-exuberant fibrotic response, termed fibroproliferative ARDS (FP-ARDS) that portends a poor prognosis and increased mortality. The cellular pathologic processes that drive FP-ARDS remain incompletely understood. We have previously shown that the transmembrane receptor-type tyrosine phosphatase Protein Tyrosine Phosphatase-a (PTPa) promotes pulmonary fibrosis in preclinical murine models through regulation of TGF-b signaling. In this study, we examine the role of PTPa in the pathogenesis of FP-ARDS in a preclinical murine model of acid (HCl)-induced acute lung injury. We demonstrate that while mice genetically deficient in PTPa (Ptpra^-/-) are susceptible to early HCl-induced lung injury, they exhibit markedly attenuated fibroproliferative responses. Additionally, early pro-fibrotic gene expression is reduced in lung tissue after acute lung injury in Ptpra^-/- mice, and stimulation of naïve lung fibroblasts with the BAL fluid from these mice results in attenuated fibrotic outcomes compared to wild type littermate controls. Transcriptomic analyses demonstrates reduced Extracellular Matrix (ECM) deposition and remodeling in mice genetically deficient in PTPa. Importantly, human lung fibroblasts modified with a CRISPR-targeted deletion of PTPRA exhibit reduced expression of profibrotic genes in response to TGF-β stimulation, demonstrating the importance of PTPa in human lung fibroblasts. Together, these findings demonstrate that PTPa is a key regulator of fibroproliferative processes following acute lung injury and could serve as a therapeutic target for patients at risk for poor long-term outcomes in ARDS.

Histopathological and molecular links of COVID-19 with novel clinical manifestations for the management of coronavirus-like complications

Coronavirus disease 2019 (COVID-19) causes transmissible viral illness of the respiratory tract prompted by the SARS-CoV-2 virus. COVID-19 is one of the worst global pandemics affecting a large population worldwide and causing catastrophic loss of life. Patients having pre-existing chronic disorders are more susceptible to contracting this viral infection. This pandemic virus is known to cause notable respiratory pathology. Besides, it can also cause extra-pulmonary manifestations. Multiple extra-pulmonary tissues express the SARS-CoV-2 entry receptor, hence causing direct viral tissue damage. This insightful review gives a brief description of the impact of coronavirus on the pulmonary system, extra-pulmonary systems, histopathology, multiorgan consequences, the possible mechanisms associated with the disease, and various potential therapeutic approaches to tackle the manifestations.

An interpretable deep learning workflow for discovering subvisual abnormalities in CT scans of COVID-19 inpatients and survivors

Tremendous efforts have been made to improve diagnosis and treatment of COVID-19, but knowledge on long-term complications is limited. In particular, a large portion of survivors has respiratory complications, but currently, experienced radiologists and state-of-the-art artificial intelligence systems are not able to detect many abnormalities from follow-up computerized tomography (CT) scans of COVID-19 survivors. Here we propose Deep-LungParenchyma-Enhancing (DLPE), a computer-aided detection (CAD) method for detecting and quantifying pulmonary parenchyma lesions on chest CT. Through proposing a number of deep-learning-based segmentation models and assembling them in an interpretable manner, DLPE removes irrelevant tissues from the perspective of pulmonary parenchyma, and calculates the scan-level optimal window, which considerably enhances parenchyma lesions relative to the lung window. Aided by DLPE, radiologists discovered novel and interpretable lesions from COVID-19 inpatients and survivors, which were previously invisible under the lung window. Based on DLPE, we removed the scan-level bias of CT scans, and then extracted precise radiomics from such novel lesions. We further demonstrated that these radiomics have strong predictive power for key COVID-19 clinical metrics on an inpatient cohort of 1,193 CT scans and for sequelae on a survivor cohort of 219 CT scans. Our work sheds light on the development of interpretable medical artificial intelligence and showcases how artificial intelligence can discover medical findings that are beyond sight.

Radiologically suspected COVID‑19‑associated organizing pneumonia responding well to corticosteroids: A report of two cases and a review of the literature

Organizing pneumonia (OP) is a type of diffuse interstitial lung disease, which may be induced in the context of several clinical conditions, such as drug reactions, infections, autoimmune diseases and cancer. Coronavirus disease 2019 (COVID-19)-associated OP has been reported as a late-stage consequence of the infection or a histological form of COVID-19-associated pneumonia. Autopsies and postmortem lung biopsies have demonstrated that the majority of patients with COVID-19-associated pneumonia develop secondary OP, and COVID-19-associated pneumonia and OP have common radiological features. The diagnosis of COVID-19-associated OP should be suspected in patients with severe acute respiratory syndrome coronavirus 2 infection who exhibit clinical deterioration despite optimal care, or who have aggravating symptoms following an initial recovery. The use of corticosteroids is a typical treatment for OP. However, to date, at least to the best of our knowledge, there are a few reports regarding the role of corticosteroids in COVID-19-associated pneumonia; thus, the optimal time for administration, the dose and treatment duration have not yet been determined. The present study presents two cases of patients with COVID-19, who exhibited clinical deterioration following the initial phase of infection and with radiological characteristics of OP who received corticosteroids and had a favorable outcome. The early diagnosis of COVID-19-associated OP may lead to targeted treatment, decreased requirements for ventilatory support and an improved survival rate.

The Role of Cytokines and Chemokines in Severe Acute Respiratory Syndrome Coronavirus 2 Infections

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in countless infections and caused millions of deaths since its emergence in 2019. Coronavirus disease 2019 (COVID-19)-associated mortality is caused by uncontrolled inflammation, aberrant immune response, cytokine storm, and an imbalanced hyperactive immune system. The cytokine storm further results in multiple organ failure and lung immunopathology. Therefore, any potential treatments should focus on the direct elimination of viral particles, prevention strategies, and mitigation of the imbalanced (hyperactive) immune system. This review focuses on cytokine secretions of innate and adaptive immune responses against COVID-19, including interleukins, interferons, tumor necrosis factor-alpha, and other chemokines. In addition to the review focus, we discuss potential immunotherapeutic approaches based on relevant pathophysiological features, the systemic immune response against SARS-CoV-2, and data from recent clinical trials and experiments on the COVID-19-associated cytokine storm. Prompt use of these cytokines as diagnostic markers and aggressive prevention and management of the cytokine storm can help determine COVID-19-associated morbidity and mortality. The prophylaxis and rapid management of the cytokine storm appear to significantly improve disease outcomes. For these reasons, this study aims to provide advanced information to facilitate innovative strategies to survive in the COVID-19 pandemic.

Bioavailability Enhancement of Cepharanthine via Pulmonary Administration in Rats and Its Therapeutic Potential for Pulmonary Fibrosis Associated with COVID-19 Infection

Cepharanthine (CEP) has excellent anti-SARS-CoV-2 properties, indicating its favorable potential for COVID-19 treatment. However, its application is challenged by its poor dissolubility and oral bioavailability. The present study aimed to improve the bioavailability of CEP by optimizing its solubility and through a pulmonary delivery method, which improved its bioavailability by five times when compared to that through the oral delivery method (68.07% vs. 13.15%). An ultra-performance liquid chromatography tandem-mass spectrometry (UPLC-MS/MS) method for quantification of CEP in rat plasma was developed and validated to support the bioavailability and pharmacokinetic studies. In addition, pulmonary fibrosis was recognized as a sequela of COVID-19 infection, warranting further evaluation of the therapeutic potential of CEP on a rat lung fibrosis model. The antifibrotic effect was assessed by analysis of lung index and histopathological examination, detection of transforming growth factor (TGF)-β1, interleukin-6 (IL-6), α-smooth muscle actin (α-SMA), and hydroxyproline level in serum or lung tissues. Our data demonstrated that CEP could significantly alleviate bleomycin (BLM)-induced collagen accumulation and inflammation, thereby exerting protective effects against pulmonary fibrosis. Our results provide evidence supporting the hypothesis that pulmonary delivery CEP may be a promising therapy for pulmonary fibrosis associated with COVID-19 infection.

Mesenchymal Stromal/Stem Cells and Their Extracellular Vesicles Application in Acute and Chronic Inflammatory Liver Diseases: Emphasizing on the Anti-Fibrotic and Immunomodulatory Mechanisms

Various factors, including viral and bacterial infections, autoimmune responses, diabetes, drugs, alcohol abuse, and fat deposition, can damage liver tissue and impair its function. These factors affect the liver tissue and lead to acute and chronic liver damage, and if left untreated, can eventually lead to cirrhosis, fibrosis, and liver carcinoma. The main treatment for these disorders is liver transplantation. Still, given the few tissue donors, problems with tissue rejection, immunosuppression caused by medications taken while receiving tissue, and the high cost of transplantation, liver transplantation have been limited. Therefore, finding alternative treatments that do not have the mentioned problems is significant. Cell therapy is one of the treatments that has received a lot of attention today. Hepatocytes and mesenchymal stromal/stem cells (MSCs) are used in many patients to treat liver-related diseases. In the meantime, the use of mesenchymal stem cells has been studied more than other cells due to their favourable characteristics and has reduced the need for liver transplantation. These cells increase the regeneration and repair of liver tissue through various mechanisms, including migration to the site of liver injury, differentiation into liver cells, production of extracellular vesicles (EVs), secretion of various growth factors, and regulation of the immune system. Notably, cell therapy is not entirely excellent and has problems such as cell rejection, undesirable differentiation, accumulation in unwanted locations, and potential tumorigenesis. Therefore, the application of MSCs derived EVs, including exosomes, can help treat liver disease and prevent its progression. Exosomes can prevent apoptosis and induce proliferation by transferring different cargos to the target cell. In addition, these vesicles have been shown to transport hepatocyte growth factor (HGF) and can promote the hepatocytes'(one of the most important cells in the liver parenchyma) growths.

Post-COVID-19 Pulmonary Fibrosis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected millions worldwide with a high mortality rate due to a lack of definitive treatment. Despite having a wide range of clinical features, acute respiratory distress syndrome (ARDS) has emerged as the primary cause of mortality in these patients. Risk factors and comorbidities like advanced age with limited lung function, pre-existing diabetes, hypertension, cardiovascular diseases, and obesity have increased the risk for severe COVID-19 infection. Rise in inflammatory markers like transforming growth factor β (TGF-β), interleukin-6 (IL-6), and expression of matrix metalloproteinase 1 and 7 (MMP-1, MMP-7), along with collagen deposition at the site of lung injury, results in extensive lung scarring and fibrosis. Anti-fibrotic drugs, such as Pirfenidone and Nintedanib, have emerged as potential treatment options for post-COVID-19 pulmonary fibrosis. A lung transplant might be the only life-saving treatment. Despite the current advances in the management of COVID-19, there is still a considerable knowledge gap in the management of long-term sequelae in such patients, especially concerning pulmonary fibrosis. Follow up on the current clinical trials and research to test the efficacy of various anti-inflammatory drugs is needed to prevent long-term sequelae early mortality in these patients.

Natural Product-Based Potential Therapeutic Interventions of Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a disease-refractive lung condition with an increased rate of mortality. The potential factors causing PF include viral infections, radiation exposure, and toxic airborne chemicals. Idiopathic PF (IPF) is related to pneumonia affecting the elderly and is characterized by recurring scar formation in the lungs. An impaired wound healing process, defined by the dysregulated aggregation of extracellular matrix components, triggers fibrotic scar formation in the lungs. The potential pathogenesis includes oxidative stress, altered cell signaling, inflammation, etc. Nintedanib and pirfenidone have been approved with a conditional endorsement for the management of IPF. In addition, natural product-based treatment strategies have shown promising results in treating PF. In this study, we reviewed the recently published literature and discussed the potential uses of natural products, classified into three types—isolated active compounds, crude extracts of plants, and traditional medicine, consisting of mixtures of different plant products—in treating PF. These natural products are promising in the treatment of PF via inhibiting inflammation, oxidative stress, and endothelial mesenchymal transition, as well as affecting TGF-β-mediated cell signaling, etc. Based on the current review, we have revealed the signaling mechanisms of PF pathogenesis and the potential opportunities offered by natural product-based medicine in treating PF.

Dihydroartemisinin attenuates pulmonary inflammation and fibrosis in rats by suppressing JAK2/STAT3 signaling

Coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has induced a worldwide pandemic since early 2020. COVID-19 causes pulmonary inflammation, secondary pulmonary fibrosis (PF); however, there are still no effective treatments for PF. The present study aimed to explore the inhibitory effect of dihydroartemisinin (DHA) on pulmonary inflammation and PF, and its molecular mechanism. Morphological changes and collagen deposition were analyzed using hematoxylin-eosin staining, Masson staining, and the hydroxyproline content. DHA attenuated early alveolar inflammation and later PF in a bleomycin-induced rat PF model, and inhibited the expression of interleukin (IL)-1β, IL-6, tumor necrosis factor α (TNFα), and chemokine (C-C Motif) Ligand 3 (CCL3) in model rat serum. Further molecular analysis revealed that both pulmonary inflammation and PF were associated with increased transforming growth factor-β1 (TGF-β1), Janus activated kinase 2 (JAK2), and signal transducer and activator 3(STAT3) expression in the lung tissues of model rats. DHA reduced the inflammatory response and PF in the lungs by suppressing TGF-β1, JAK2, phosphorylated (p)-JAK2, STAT3, and p-STAT3. Thus, DHA exerts therapeutic effects against bleomycin-induced pulmonary inflammation and PF by inhibiting JAK2-STAT3 activation. DHA inhibits alveolar inflammation, and attenuates lung injury and fibrosis, possibly representing a therapeutic candidate to treat PF associated with COVID-19.

The state of complement in COVID-19

Hyperactivation of the complement and coagulation systems is recognized as part of the clinical syndrome of COVID-19. Here we review systemic complement activation and local complement activation in response to the causative virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and their currently known relationships to hyperinflammation and thrombosis. We also provide an update on early clinical findings and emerging clinical trial evidence that suggest potential therapeutic benefit of complement inhibition in severe COVID-19.

The "Elastic Perspective" of SARS-CoV-2 Infection and the Role of Intrinsic and Extrinsic Factors

Elastin represents the structural component of the extracellular matrix providing elastic recoil to tissues such as skin, blood vessels and lungs. Elastogenic cells secrete soluble tropoelastin monomers into the extracellular space where these monomers associate with other matrix proteins (e.g., microfibrils and glycoproteins) and are crosslinked by lysyl oxidase to form insoluble fibres. Once elastic fibres are formed, they are very stable, highly resistant to degradation and have an almost negligible turnover. However, there are circumstances, mainly related to inflammatory conditions, where increased proteolytic degradation of elastic fibres may lead to consequences of major clinical relevance. In severely affected COVID-19 patients, for instance, the massive recruitment and activation of neutrophils is responsible for the profuse release of elastases and other proteolytic enzymes which cause the irreversible degradation of elastic fibres. Within the lungs, destruction of the elastic network may lead to the permanent impairment of pulmonary function, thus suggesting that elastases can be a promising target to preserve the elastic component in COVID-19 patients. Moreover, intrinsic and extrinsic factors additionally contributing to damaging the elastic component and to increasing the spread and severity of SARS-CoV-2 infection are reviewed.

Recovering from a pandemic: pulmonary fibrosis after SARS-CoV-2 infection

Acute manifestations of SARS-CoV-2 infection continue to impact the lives of many across the world. Post-acute sequelae of coronavirus disease 2019 (COVID-19) may affect 10–30% of survivors of COVID-19, and post-acute sequelae of COVID-19 (PASC)-pulmonary fibrosis is a long-term outcome associated with major morbidity. Data from prior coronavirus outbreaks (severe acute respiratory syndrome and Middle East respiratory syndrome) suggest that pulmonary fibrosis will contribute to long-term respiratory morbidity, suggesting that PASC-pulmonary fibrosis should be thoroughly screened for through pulmonary function testing and cross-sectional imaging. As data accumulates on the unique pathobiologic mechanisms underlying critical COVID-19, a focus on corollaries to the subacute and chronic profibrotic phenotype must be sought as well. Key aspects of acute COVID-19 pathobiology that may account for increased rates of pulmonary fibrosis include monocyte/macrophage–T-cell circuits, profibrotic RNA transcriptomics, protracted elevated levels of inflammatory cytokines, and duration of illness and ventilation. Mechanistic understanding of PASC-pulmonary fibrosis will be central in determining therapeutic options and will ultimately play a role in transplant considerations. Well-designed cohort studies and prospective clinical registries are needed. Clinicians, researchers and healthcare systems must actively address this complication of PASC to minimise disability, maximise quality of life and confront a post-COVID-19 global health crisis.

A complication of COVID-19, PASC-pulmonary fibrosis, has the potential to become a global respiratory health crisis. Dedicated surveillance, mechanistic understanding and clinical and research efforts are needed to confront this emerging sequela of COVID-19.https://bit.ly/3GEyB04

Temporal Patterns of COVID-19-Associated Pulmonary Pathology: An Autopsy Study

Introduction

The novel coronavirus variant - severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) and the disease it causes clinically (novel coronavirus disease 2019 or COVID-19) have placed medical science into a frenzy due to the significant morbidity and mortality, as well as the myriad of clinical complications developing as a direct result of infection. The most notable and one of the most severe changes in COVID-19 develops in the lungs.

Materials and methods

All cases of real-time polymerase chain reaction (rtPCR)-proved COVID-19 subjected to autopsy were withdrawn from the central histopathology archive of a single tertiary medical institution - St. Marina University Hospital - Varna, Varna, Bulgaria. Pulmonary gross and histopathology changes observed on light microscopy with hematoxylin and eosin as well with other histochemical and immunohistochemical stains were compared with the time from patient-reported symptom onset to expiration, to compare the extent and type of changes based on disease duration.

Results

A total of 27 autopsy cases fit the established criteria. All cases clinically manifested with severe COVID-19. From the selected 27 cases, n=14 were male and n=13 were female. The mean age in the cohort was 67.44 years (range 18-91 years), with the mean age for males being 68.29 (range 38-80 years) and the mean age for females being 66.54 (range 18-91 years). Gross changes in patients who expired in the first 10 days after disease onset showed a significantly increased mean weight - 1050g, compared to a relatively lower weight in patients expiring more than 10 days after symptom onset - 940g. Histopathology changes were identified as intermittent (developing independent from symptom onset and persisting) - diffuse alveolar damage with hyaline membranes - acute respiratory distress syndrome, endothelitis with vascular degeneration and fibrin thrombi; early (developing within the first week, but persisting) - type II pneumocyte hyperplasia, alveolar cell multinucleation and scant interstitial mononuclear inflammation; intermediate (developing within the late first and second weeks) - Clara cell hyperplasia and late (developing after the second week of symptom onset) - respiratory tract and alveolar squamous cell metaplasia and fibrosis.

Conclusion

COVID-19-associated pulmonary pathology, both gross and histopathology, show a time-related dynamic with persistent early and a myriad of later developing dynamic changes in patients with severe disease. These changes underline both the severity of the condition, as well as the mechanisms and the probability of long-lasting severe complications in patients with post-COVID syndrome.

Acute Respiratory Distress Syndrome: Focus on Viral Origin and Role of Pulmonary Lymphatics

Acute respiratory distress syndrome (ARDS) is a serious affection of the lung caused by a variety of pathologies. Great interest is currently focused on ARDS induced by viruses (pandemic influenza and corona viruses). The review describes pulmonary changes in ARDS and specific effects of the pandemic viruses in ARDS, and summarizes treatment options. Because the known pathogenic mechanisms cannot explain all aspects of the syndrome, the contribution of pulmonary lymphatics to the pathology is discussed. Organization and function of lymphatics in a healthy lung and in resorption of pulmonary edema are described. A future clinical trial may provide more insight into the role of hyaluronan in ARDS but the development of promising pharmacological treatments is unlikely because drugs play no important role in lymphedema therapy.

The pathogenesis, epidemiology and biomarkers of susceptibility of pulmonary fibrosis in COVID-19 survivors

Pulmonary fibrosis (PF), a pathological outcome of chronic and acute interstitial lung diseases associated to compromised wound healing, is a key component of the "post-acute COVID-19 syndrome" that may severely complicate patients' clinical course. Although inconclusive, available data suggest that more than a third of hospitalized COVID-19 patients develop lung fibrotic abnormalities after their discharge from hospital. The pathogenesis of PF in patients recovering from a severe acute case of COVID-19 is complex, and several hypotheses have been formulated to explain its development. An analysis of the data that is presently available suggests that biomarkers of susceptibility could help to identify subjects with increased probability of developing PF and may represent a means to personalize the management of COVID-19's long-term effects. Our review highlights the importance of both patient-related and disease-related contributing risk factors for PF in COVID-19 survivors and makes it definitely clear the possible use of acute phase and follow-up biomarkers for identifying the patients at greatest risk of developing this disease.

Gamma Delta T Cells and Their Involvement in COVID-19 Virus Infections

The global outbreak of the SARS-Cov-2 virus in 2020 has killed millions of people worldwide and forced large parts of the world into lockdowns. While multiple vaccine programs are starting to immunize the global population, there is no direct cure for COVID-19, the disease caused by the SARS-Cov-2 infection. A common symptom in patients is a decrease in T cells, called lymphopenia. It is as of yet unclear what the exact role of T cells are in the immune response to COVID-19. The research so far has mainly focused on the involvement of classical αβ T cells. However, another subset of T cells called γδ T cells could have an important role to play. As part of the innate immune system, γδ T cells respond to inflammation and stressed or infected cells. The γδ T cell subset appears to be particularly affected by lymphopenia in COVID-19 patients and commonly express activation and exhaustion markers. Particularly in children, this subset of T cells seems to be most affected. This is interesting and relevant because γδ T cells are more prominent and active in early life. Their specific involvement in this group of patients could indicate a significant role for γδ T cells in this disease. Furthermore, they seem to be involved in other viral infections and were able to kill SARS infected cells in vitro. γδ T cells can take up, process and present antigens from microbes and human cells. As e.g. tumour-associated antigens are presented by MHC on γδ T cells to classical T-cells, we argue here that it stands to reason that also viral antigens, such as SARS-Cov-2-derived peptides, can be presented in the same way. γδ T cells are already used for medical purposes in oncology and have potential in cancer therapy. As γδ T cells are not necessarily able to distinguish between a transformed and a virally infected cell it could therefore be of great interest to investigate further the relationship between COVID-19 and γδ T cells.

Alveolar Regeneration in COVID-19 Patients: A Network Perspective

A viral infection involves entry and replication of viral nucleic acid in a host organism, subsequently leading to biochemical and structural alterations in the host cell. In the case of SARS-CoV-2 viral infection, over-activation of the host immune system may lead to lung damage. Albeit the regeneration and fibrotic repair processes being the two protective host responses, prolonged injury may lead to excessive fibrosis, a pathological state that can result in lung collapse. In this review, we discuss regeneration and fibrosis processes in response to SARS-CoV-2 and provide our viewpoint on the triggering of alveolar regeneration in coronavirus disease 2019 (COVID-19) patients.

Commonalities Between ARDS, Pulmonary Fibrosis and COVID-19: The Potential of Autotaxin as a Therapeutic Target

Severe COVID-19 is characterized by acute respiratory distress syndrome (ARDS)-like hyperinflammation and endothelial dysfunction, that can lead to respiratory and multi organ failure and death. Interstitial lung diseases (ILD) and pulmonary fibrosis confer an increased risk for severe disease, while a subset of COVID-19-related ARDS surviving patients will develop a fibroproliferative response that can persist post hospitalization. Autotaxin (ATX) is a secreted lysophospholipase D, largely responsible for the extracellular production of lysophosphatidic acid (LPA), a pleiotropic signaling lysophospholipid with multiple effects in pulmonary and immune cells. In this review, we discuss the similarities of COVID-19, ARDS and ILDs, and suggest ATX as a possible pathologic link and a potential common therapeutic target.

Iron oxide nanoparticles augment the intercellular mitochondrial transfer-mediated therapy

The transfer of mitochondria between cells has recently been revealed as a spontaneous way to protect the injured cells. However, the utilization of this natural transfer process for disease treatment is so far limited by its unsatisfactory transfer efficiency and selectivity. Here, we demonstrate that iron oxide nanoparticles (IONPs) can augment the intercellular mitochondrial transfer from human mesenchymal stem cells (hMSCs) selectively to diseased cells, owing to the enhanced formation of connexin 43–containing gap junctional channels triggered by ionized IONPs. In a mouse model of pulmonary fibrosis, the IONP-engineered hMSCs achieve a remarkable mitigation of fibrotic progression because of the promoted intercellular mitochondrial transfer, with no serious safety issues identified. The present study reports a potential method of using IONPs to enable hMSCs for efficient and safe transfer of mitochondria to diseased cells to restore mitochondrial bioenergetics.

Increased Autotaxin Levels in Severe COVID-19, Correlating with IL-6 Levels, Endothelial Dysfunction Biomarkers, and Impaired Functions of Dendritic Cells

Autotaxin (ATX; ENPP2) is a secreted lysophospholipase D catalyzing the extracellular production of lysophosphatidic acid (LPA), a pleiotropic signaling phospholipid. Genetic and pharmacologic studies have previously established a pathologic role for ATX and LPA signaling in pulmonary injury, inflammation, and fibrosis. Here, increased ENPP2 mRNA levels were detected in immune cells from nasopharyngeal swab samples of COVID-19 patients, and increased ATX serum levels were found in severe COVID-19 patients. ATX serum levels correlated with the corresponding increased serum levels of IL-6 and endothelial damage biomarkers, suggesting an interplay of the ATX/LPA axis with hyperinflammation and the associated vascular dysfunction in COVID-19. Accordingly, dexamethasone (Dex) treatment of mechanically ventilated patients reduced ATX levels, as shown in two independent cohorts, indicating that the therapeutic benefits of Dex include the suppression of ATX. Moreover, large scale analysis of multiple single cell RNA sequencing datasets revealed the expression landscape of ENPP2 in COVID-19 and further suggested a role for ATX in the homeostasis of dendritic cells, which exhibit both numerical and functional deficits in COVID-19. Therefore, ATX has likely a multifunctional role in COVID-19 pathogenesis, suggesting that its pharmacological targeting might represent an additional therapeutic option, both during and after hospitalization.

Cell Properties of Lung Tissue-Resident Macrophages Propagated by Co-Culture with Lung Fibroblastic Cells from C57BL/6 and BALB/c Mice

Tissue-resident macrophages (Mø) originating from foetal precursors are maintained by self-renewal under tissue/organ-specific microenvironments (niches). We recently developed a simple propagation method applicable to tissue-resident Mø by co-culturing. Here, we examined the properties of lung tissue-resident Mø propagated by co-culturing with lung interstitial cells. The intracardially and intratracheally perfused lung from BALB/c and C57BL/6 mice could minimise the contamination of alveolar Mø and lung monocytes. Lung tissue-resident Mø could be largely propagated under standard culture media along with the propagation of lung interstitial cells demonstrating a fibroblastic morphology. Propagated lung Mø showed characteristic expression properties for Mø/monocyte markers: high expressions of CD11b, CD64 and CD206; substantial expressions of Mertk; and negative expressions of Ly6C, MHC II and Siglec-F. These properties fit with those of lung interstitial Mø of a certain population that can undergo self-renewal. Propagated fibroblastic cells by co-culturing with lung Mø possessed niche properties such as Csf1 and Tgfb1 expression. Propagated lung Mø from both the mouse types were polarised to an M2 phenotype highly expressing arginase 1 without M2 inducer treatment, whereas the M1 inducers significantly increased the iNOS-positive cell percentages in C57BL/6 mice relative to those in BALB/c mice. This is the first study to demonstrate fundamental properties of lung tissue-resident Mø propagated by co-culturing. Propagated lung Mø showing features of lung interstitial Mø can serve as an indispensable tool for investigating SARS-CoV-2 diseases, although lung interstitial Mø have gained little attention in terms of their involvement in SARS-CoV-2 disease pathology, in contrast to alveolar and recruited Mø.

mTOR-Inhibition and COVID-19 in Kidney Transplant Recipients: Focus on Pulmonary Fibrosis

Kidney transplant recipients are at high risk of developing severe COVID-19 due to the coexistence of several transplant-related comorbidities (e.g., cardiovascular disease, diabetes) and chronic immunosuppression. As a consequence, a large part of SARS-CoV-2 infected patients have been managed with a reduction of immunosuppression. The mTOR-I, together with antimetabolites, have been often discontinued in order to minimize the risk of pulmonary toxicity and to antagonize pharmacological interaction with antiviral/anti-inflammatory drugs. However, at our opinion, this therapeutic strategy, although justified in kidney transplant recipients with severe COVID-19, should be carefully evaluated in asymptomatic/paucisymptomatic patients in order to avoid the onset of acute allograft rejections, to potentially exploit the mTOR-I antiviral properties, to reduce proliferation of conventional T lymphocytes (which could mitigate the cytokine storm) and to preserve Treg growth/activity which could reduce the risk of progression to severe disease. In this review, we discuss the current literature regarding the therapeutic potential of mTOR-Is in kidney transplant recipients with COVID-19 with a focus on pulmonary fibrosis.

Overview of the pathogenesis of COVID-19 (Review)

At present, the pathogenesis of the novel coronavirus disease 2019 (COVID-19) has not been fully elucidated. Clinical and experimental findings from studies investigating COVID-19 have suggested that the immune-inflammatory response has a crucial role in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The present article aimed to systematically review the available literature on the pathogenesis of COVID-19. Severe COVID-19 is characterized by organ dysfunction, hypercytokinemia and lymphopenia. It is assumed that the direct cytopathological damage of host cells and the dysregulated immune response caused by SARS-CoV-2 may be the primary underlying mechanisms of COVID-19. Based on the published literature, this review attempts to provide an integrated view of the immunological mechanisms and the potential pathogenesis of COVID-19, providing an in-depth summary of the host-pathogen interaction and host immune responses. It is of great importance to elucidate the possible pathogenesis of COVID-19 to determine the direction of future research.

Pharmacological Interactions of Nintedanib and Pirfenidone in Patients with Idiopathic Pulmonary Fibrosis in Times of COVID-19 Pandemic

The discovery of antifibrotic agents have resulted in advances in the therapeutic management of idiopathic pulmonary fibrosis (IPF). Currently, nintedanib and pirfenidone have become the basis of IPF therapy based on the results of large randomized clinical trials showing their safety and efficacy in reducing disease advancement. However, the goal of completely halting disease progress has not been reached yet. Administering nintedanib with add-on pirfenidone is supposed to enhance the therapeutic benefit by simultaneously acting on two different pathogenic pathways. All this becomes more important in the context of the ongoing global pandemic of coronavirus disease 2019 (COVID-19) because of the fibrotic consequences following SARS-CoV-2 infection in some patients. However, little information is available about their drug–drug interaction, which is important mainly in polymedicated patients. The aim of this review is to describe the current management of progressive fibrosing interstitial lung diseases (PF-ILDs) in general and of IPF in particular, focusing on the pharmacokinetic drug-drug interactions between these two drugs and their relationship with other medications in patients with IPF.

Lung Fibrosis after COVID-19: Treatment Prospects

At the end of 2019, a highly contagious infection began its ominous conquest of the world. It was soon discovered that the disease was caused by a novel coronavirus designated as SARS-CoV-2, and the disease was thus abbreviated to COVID-19 (COVID). The global medical community has directed its efforts not only to find effective therapies against the deadly pathogen but also to combat the concomitant complications. Two of the most common respiratory manifestations of COVID are a significant reduction in the diffusing capacity of the lungs (DLCO) and the associated pulmonary interstitial damage. One year after moderate COVID, the incidence rate of impaired DLCO and persistent lung damage still exceeds 30%, and one-third of the patients have severe DLCO impairment and fibrotic lung damage. The persistent respiratory complications may cause substantial population morbidity, long-term disability, and even death due to the lung fibrosis progression. The incidence of COVID-induced pulmonary fibrosis caused by COVID can be estimated based on a 15-year observational study of lung pathology after SARS. Most SARS patients with fibrotic lung damage recovered within the first year and then remained healthy; however, in 20% of the cases, significant fibrosis progression was found in 5-10 years. Based on these data, the incidence rate of post-COVID lung fibrosis can be estimated at 2-6% after moderate illness. What is worse, there are reasons to believe that fibrosis may become one of the major long-term complications of COVID, even in asymptomatic individuals. Currently, despite the best efforts of the global medical community, there are no treatments for COVID-induced pulmonary fibrosis. In this review, we analyze the latest data from ongoing clinical trials aimed at treating post-COVID lung fibrosis and analyze the rationale for the current drug candidates. We discuss the use of antifibrotic therapy for idiopathic pulmonary fibrosis, the IN01 vaccine, glucocorticosteroids as well as the stromal vascular fraction for the treatment and rehabilitation of patients with COVID-associated pulmonary damage.

The Impact of the COVID-19 Pandemic on Dementia Risk: Potential Pathways to Cognitive Decline

BACKGROUND

Coronavirus disease 2019 (COVID-19), the far-reaching pandemic, has infected approximately 185 million of the world's population to date. After infection, certain groups, including older adults, men, and people of color, are more likely to have adverse medical outcomes. COVID-19 can affect multiple organ systems, even among asymptomatic/mild severity individuals, with progressively worse damage for those with higher severity infections.

SUMMARY

The COVID-19 virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), primarily attaches to cells through the angiotensin-converting enzyme 2 (ACE2) receptor, a universal receptor present in most major organ systems. As SARS-CoV-2 binds to the ACE2 receptor, its bioavailability becomes limited, thus disrupting homeostatic organ function and inducing an injury cascade. Organ damage can then arise from multiple sources including direct cellular infection, overactive detrimental systemic immune response, and ischemia/hypoxia through thromboembolisms or disruption of perfusion. In the brain, SARS-CoV-2 has neuroinvasive and neurotropic characteristics with acute and chronic neurovirulent potential. In the cardiovascular system, COVID-19 can induce myocardial and systemic vascular damage along with thrombosis. Other organ systems such as the lungs, kidney, and liver are all at risk for infection damage. Key Messages: Our hypothesis is that each injury consequence has the independent potential to contribute to long-term cognitive deficits with the possibility of progressing to or worsening pre-existing dementia. Already, reports from recovered COVID-19 patients indicate that cognitive alterations and long-term symptoms are prevalent. This critical review highlights the injury pathways possible through SARS-CoV-2 infection that have the potential to increase and contribute to cognitive impairment and dementia.

SARS-CoV-2 diagnosis: a single-centre experience

The coronavirus disease 2019 (COVID-19) was declared a pandemic by the World Health Organization (WHO) on the 11^th of March 2020. In Romania, there have been 983,217 confirmed cases and 24,386 deaths. We aim to show our experience at the Fundeni Clinical Institute in the diagnosis of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection in both patients and health care personnel. Swab samples were collected for extraction of the SARS-CoV-2 RNA from 29380 patients and health care personnel. We have combined three real-time reverse transcription-polymerase chain reaction (RT-PCR) assays for the qualitative detection of SARS-CoV-2. Also, the presence of IgG against SARS-CoV-2 nucleoprotein was analyzed in 1068 patients and clinical staff using the chemiluminescence method. Other 50 people were screened post-vaccination for the presence of SARS-CoV-2 antibodies against the spike (S) protein, using the chemiluminescence method as well. The majority of confirmed cases were in adults, 71.3% of cases being registered in people aged 30-69 years. Most patients diagnosed with SARS-CoV-2 infection (83%) were admitted to the gastroenterology, hematology, and surgery wards. Our study showed that one-third of people developed antibodies against the nucleocapsid of SARS-CoV-2. SARS-CoV-2 IgG seroprevalence does not vary by gender or age. Also, we noticed the presence of antibodies against the SARS-CoV-2 spike protein in all 50 people post-vaccination that were tested two weeks after the second dose. Due to the increasing number of infected patients with SARS-CoV-2, the new coronavirus pandemic involves a sustained testing effort for an accurate virological diagnosis in both direct and indirect diagnosis.

Characterising the long-term clinical outcomes of 1190 hospitalised patients with COVID-19 in New York City: a retrospective case series

OBJECTIVE

To characterise the long-term outcomes of patients with COVID-19 admitted to a large New York City medical centre at 3 and 6 months after hospitalisation and describe their healthcare usage, symptoms, morbidity and mortality.

DESIGN

Retrospective cohort through manual chart review of the electronic medical record.

SETTING

NewYork-Presbyterian/Columbia University Irving Medical Center, a quaternary care academic medical centre in New York City.

PARTICIPANTS

The first 1190 consecutive patients with symptoms of COVID-19 who presented to the hospital for care between 1 March and 8 April 2020 and tested positive for SARS-CoV-2 on reverse transcriptase PCR assay.

MAIN OUTCOME MEASURES

Type and frequency of follow-up encounters, self-reported symptoms, morbidity and mortality at 3 and 6 months after presentation, respectively; patient disposition information prior to admission, at discharge, and at 3 and 6 months after hospital presentation.

RESULTS

Of the 1190 reviewed patients, 929 survived their initial hospitalisation and 261 died. Among survivors, 570 had follow-up encounters (488 at 3 months and 364 at 6 months). An additional 33 patients died in the follow-up period. In the first 3 months after admission, most encounters were telehealth visits (59%). Cardiopulmonary symptoms (35.7% and 28%), especially dyspnoea (22.1% and 15.9%), were the most common reported symptoms at 3-month and 6-month encounters, respectively. Additionally, a large number of patients reported generalised (26.4%) or neuropsychiatric (24.2%) symptoms 6 months after hospitalisation. Patients with severe COVID-19 were more likely to have reduced mobility, reduced independence or a new dialysis requirement in the 6 months after hospitalisation.

CONCLUSIONS

Patients hospitalised with SARS-CoV-2 infection reported persistent symptoms up to 6 months after diagnosis. These results highlight the long-term morbidity of COVID-19 and its burden on patients and healthcare resources.

Post-COVID-19 Pulmonary Fibrosis: Novel Sequelae of the Current Pandemic

Since the initial identification of the novel coronavirus SARS-CoV-2 in December 2019, the COVID-19 pandemic has become a leading cause of morbidity and mortality worldwide. As effective vaccines and treatments begin to emerge, it will become increasingly important to identify and proactively manage the long-term respiratory complications of severe disease. The patterns of imaging abnormalities coupled with data from prior coronavirus outbreaks suggest that patients with severe COVID-19 pneumonia are likely at an increased risk of progression to interstitial lung disease (ILD) and chronic pulmonary vascular disease. In this paper, we briefly review the definition, classification, and underlying pathophysiology of interstitial lung disease (ILD). We then review the current literature on the proposed mechanisms of lung injury in severe COVID-19 infection, and outline potential viral- and immune-mediated processes implicated in the development of post-COVID-19 pulmonary fibrosis (PCPF). Finally, we address patient-specific and iatrogenic risk factors that could lead to PCPF and discuss strategies for reducing risk of pulmonary complications/sequelae.

Dynamic role of LMW-hyaluronan fragments and Toll-like receptors 2,4 in progression of bleomycin induced lung parenchymal injury to fibrosis

Background

Pulmonary fibrosis (PF) is a progressive and lethal lung disease of elderly whose incidence has been increasing following the Covid-19 pandemic caused by severe acute respiratory syndrome corona virus 2 (SARS-CoV-2). PF immunopathogenesis involves progressive alveolar epithelial cell damage, release of damage-associated molecular patterns (DAMPs), and extracellular matrix (ECM) injury. We assessed the dynamic role of LMW-hyaluronan (LMW-HA) as DAMP in initiation of host immune TLR-2,4 responses and as determinant in progression of ECM injury to fibrosis. Male Wistar rats were divided into Group I (saline control, n = 24) and Group II (intratracheal bleomycin, 7 U/kg/animal, n = 24). Animals were euthanized on 0, 7, 14, and 28 days. The time course of release of LMW-HA, TLR-2,4 mRNA and protein levels, and NF-κB-p65 levels after bleomycin injury were correlated with the development of parenchymal inflammation, remodelling, and fibrosis.

Results

Acute lung injury caused by bleomycin significantly increases the pro-inflammatory LMW-HA levels and elevates TLR-2,4 levels on day 7. Subsequently, TLR-2 upregulation, TLR-4 downregulation, and NF-κB signalling follow on days 14 and 28. This results in progressive tissue inflammation, alveolar and interstitial macrophage accumulation, and fibrosis.

Conclusions

LMW-HA significantly increases in PF caused by non-infectious and infectious (Covid-19) etiologies. The accumulating HA fragments function as endogenous DAMPs and trigger inflammatory responses, through differential TLR2 and TLR4 signalling, thus promoting inflammation and macrophage influx. LMW-HA are reflective of the state of ongoing tissue inflammation and may be considered as a natural biosensor for fibrotic lung diseases and as potential therapeutic targets.