Alveolar type II (ATII) cells are a key structure of the distal lung epithelium, where they exert their innate immune response and serve as progenitors of alveolar type I (ATI) cells, contributing to alveolar epithelial repair and regeneration. In the healthy lung, ATII cells coordinate the host defense mechanisms, not only generating a restrictive alveolar epithelial barrier, but also orchestrating host defense mechanisms and secreting surfactant proteins, which are important in lung protection against pathogen exposure. Moreover, surfactant proteins help to maintain homeostasis in the distal lung and reduce surface tension at the pulmonary air–liquid interface, thereby preventing atelectasis and reducing the work of breathing. ATII cells may also contribute to the fibroproliferative reaction by secreting growth factors and proinflammatory molecules after damage. Indeed, various acute and chronic diseases are associated with intensive inflammation. These include oedema, acute respiratory distress syndrome, fibrosis and numerous interstitial lung diseases, and are characterized by hyperplastic ATII cells which are considered an essential part of the epithelialization process and, consequently, wound healing. The aim of this review is that of revising the physiologic and pathologic role ATII cells play in pulmonary diseases, as, despite what has been learnt in the last few decades of research, the origin, phenotypic regulation and crosstalk of these cells still remain, in part, a mystery.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease (ILD) with unknown etiology in which gradual fibrotic scarring of the lungs leads to usual interstitial pneumonia (UIP) and, ultimately, to death. IPF affects three million people worldwide, and the only currently available treatments include the antifibrotic drugs nintedanib and pirfenidone, which effectively reduce fibrosis progression are, unfortunately, not effective in curing the disease. In recent years, the paradigm of IPF pathogenesis has shifted from a fibroblast-driven disease to an epithelium-driven disease, wherein, upon recurrent microinjuries, dysfunctional alveolar type II epithelial cells (ATII) are not only unable to sustain physiological lung regeneration but also promote aberrant epithelial–mesenchymal crosstalk. This creates a drift towards fibrosis rather than regeneration. In the context of this review article, we discuss the most relevant mechanisms involved in IPF pathogenesis with a specific focus on the role of dysfunctional ATII cells in promoting disease progression. In particular, we summarize the main causes of ATII cell dysfunction, such as aging, environmental factors, and genetic determinants. Next, we describe the known mechanisms of physiological lung regeneration by drawing a parallel between embryonic lung development and the known pathways involved in ATII-driven alveolar re-epithelization after injury. Finally, we review the most relevant interventional clinical trials performed in the last 20 years with the aim of underlining the urgency of developing new therapies against IPF that are not only aimed at reducing disease progression by hampering ECM deposition but also boost the physiological processes of ATII-driven alveolar regeneration.

Pirfenidone and Nintedanib are specific drugs used against idiopathic pulmonary fibrosis (IPF) that showed efficacy in non-IPF fibrosing interstitial lung diseases (ILD). Both drugs have side effects that affect patients in different ways and have different levels of severity, making treatment even more challenging for patients and clinicians. The present review aims to assess the effectiveness and potential complications of Pirfenidone and Nintedanib treatment regimens across various ILD diseases. A detailed search was performed in relevant articles published between 2018 and 2023 listed in PubMed, UpToDate, Google Scholar, and ResearchGate, supplemented with manual research. The following keywords were searched in the databases in all possible combinations: Nintedanib; Pirfenidone, interstitial lung disease, and idiopathic pulmonary fibrosis. The most widely accepted method for evaluating the progression of ILD is through the decline in forced vital capacity (FVC), as determined by respiratory function tests. Specifically, a decrease in FVC over a 6–12-month period correlates directly with increased mortality rates. Antifibrotic drugs Pirfenidone and Nintedanib have been extensively validated; however, some patients reported several side effects, predominantly gastrointestinal symptoms (such as diarrhea, dyspepsia, and vomiting), as well as photosensitivity and skin rashes, particularly associated with Pirfenidone. In cases where the side effects are extremely severe and are more threatening than the disease itself, the treatment has to be discontinued. However, further research is needed to optimize the use of antifibrotic agents in patients with PF-ILDs, which could slow disease progression and decrease all-cause mortality. Finally, other studies are requested to establish the treatments that can stop ILD progression.

The latest guidelines for the hospital care of patients affected by coronavirus disease 2019 (COVID-19)-related acute respiratory failure have moved towards the widely accepted use of noninvasive respiratory support (NIRS) as opposed to early intubation at the pandemic onset. The establishment of severe COVID-19 pneumonia goes through different pathophysiological phases that partially resemble typical acute respiratory distress syndrome (ARDS) and have been categorized into different clinical–radiological phenotypes. These can variably benefit on the application of external positive end-expiratory pressure (PEEP) during noninvasive mechanical ventilation, mainly due to variable levels of lung recruitment ability and lung compliance during different phases of the disease. A growing body of evidence suggests that intense respiratory effort producing excessive negative pleural pressure swings (P_pl) plays a critical role in the onset and progression of lung and diaphragm damage in patients treated with noninvasive respiratory support. Routine respiratory monitoring is mandatory to avoid the nasty continuation of NIRS in patients who are at higher risk for respiratory deterioration and could benefit from early initiation of invasive mechanical ventilation instead. Here we propose different monitoring methods both in the clinical and experimental settings adapted for this purpose, although further research is required to allow their extensive application in clinical practice. We reviewed the needs and available tools for clinical–physiological monitoring that aims at optimizing the ventilatory management of patients affected by acute respiratory distress syndrome due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection.

Background. Glucocorticoids (GCs) have been shown to reduce mortality and the need for invasive mechanical ventilation (IMV) in SARS-CoV-2-induced acute respiratory distress syndrome (ARDS). It has been suggested that serum cytokines levels are markers of disease severity in ARDS, although there is only limited evidence of a relationship between the longitudinal cytokine profile and clinical outcomes in patients with SARS-CoV-2-induced ARDS treated with GC. Methods. We conducted a single-center observational study to investigate serial plasma cytokine levels in 17 patients supported with non-invasive ventilation (NIV) in order to compare the response in five patients who progressed to IMV versus 12 patients who continued with NIV alone. All patients received methylprednisolone 80 mg/day continuous infusion until clinical improvement. Results. The study groups were comparable at baseline. All patients survived. Although IL-6 was higher in the NIV group at baseline, several cytokines were significantly higher in the IMV group on day 7 (IL-6, IL-8, IL-9, G-CSF, IP-10, MCP-1, MIP-1α) and 14 (IL-6, IL-8, IL-17, G-CSF, MIP-1α, RANTES). No significant differences were observed between groups on day 28. Conclusions. Patients in the IMV group had higher inflammation levels at intubation than the NIV group, which may indicate a higher resistance to glucocorticoids. Higher GC doses or a longer treatment duration in these patients might have allowed for a better control of inflammation and a better outcome. Further studies are required to define the prognostic value of cytokine patterns, in terms of both GC treatment tailoring and timely initiation of IMV.

Background: Idiopathic pulmonary fibrosis (IPF) is a rare and severe disease with a median survival of ∼3 years. Several risk factors have been identified, such as age, genetic predisposition, tobacco exposure, and gastro-oesophageal reflux disease (GERD). Prevalence of GERD in IPF is high and may affect 87% of patients, of whom only half (47%) report symptoms. Objective: The aim of this study is to review current evidence regarding the correlation between GERD and IPF and to evaluate the current studies regarding treatments for GERD-IPF. Methods: A review to identify research papers documenting an association between GERD and IPF was performed. Results: We identified several studies that have confirmed the association between GERD and IPF, with an increased acid exposure, risk of gastric aspiration and bile acids levels in these patients. Few studies focused their attention on GERD treatment, showing how antiacid therapy was not able to change IPF evolution. Conclusions: This review investigating the correlation between GERD and IPF has confirmed the hypothesized association. However, further large prospective studies are needed to corroborate and elucidate these findings with a focus on preventative and treatment strategies.