Since the outbreak of the COVID-19 pandemic, much has been learned regarding its clinical course, prognostic inflammatory markers, disease complications, and mechanical ventilation strategy. Clinically, three stages have been identified based on viral infection, pulmonary involvement with inflammation, and fibrosis. Moreover, low and high elastance phenotypes can be distinguished in mechanically ventilated patients, based on lung mechanics, ventilation-to-perfusion ratio, and CT scans; these two phenotypes have presumed differences in their underlying pathophysiology. Although essential for therapeutic guidance, the pathophysiology of COVID-19 is poorly understood. Here, we systematically reviewed published case reports and case series in order to increase our understanding of COVID-19 pathophysiology by constructing a timeline and correlating histopathological findings with clinical stages of COVID-19. Using PRISMA-IPD guidelines, 42 articles reporting 198 individual cases were included in our analysis. In lung samples (n = 131 cases), we identified three main histological patterns: epithelial (n = 110, 85%), with reactive epithelial changes and DAD; vascular (n = 76, 59%) with microvascular damage, (micro)thrombi, and acute fibrinous and organizing pneumonia; and fibrotic (n = 28, 22%) with interstitial fibrosis. The epithelial and vascular patterns can present in all stages of symptomatic COVID-19, whereas the fibrotic pattern presents starting at~3 weeks. Moreover, patients can present with more than one pattern, either simultaneously or consecutively. These findings are consistent with knowledge regarding clinical patterns of viral infection, development of hyperinflammation and hypercoagulability, and fibrosis. Close collaboration among medical staff is necessary in order to translate this knowledge and classification of pathophysiological mechanisms into clinical stages of disease in individual patients. Moreover, further research, including histopathological studies, is warranted in order to develop reliable, clinically relevant biomarkers by correlating these pathological findings with laboratory results and radiological findings, thus, increasing our understanding of COVID-19 and facilitating the move to precision medicine for treating patients.

Idiopathic pulmonary fibrosis (IPF) is a progressive, and ultimately fatal, chronic interstitial lung disease characterized by enhanced extracellular matrix deposition. Repetitive alveolar epithelial injury triggers the early development of fibrosis. These injuries, in combination with dysregulated wound repair and fibroblast dysfunction, lead to ongoing tissue remodelling and fibrosis seen in end-stage pulmonary fibrosis. Although the exact etiology in IPF is unknown and probably diverse, all stages of fibrosis are accompanied by innate and adaptive immune responses. The role of inflammation as an important component in IPF etiology is controversial and sometimes seen as an epiphenomenon of fibrosis. This view is partly the result of negative multicenter trials of anti-inflammatory drugs for IPF treatment. However, new insights on the role of macrophages, the loss of Tcell and B-cell tolerance leading auto-immune responses in IPF, and the interaction of immune cells with (myo) fibroblasts have led to a slow change of this opinion. Clearly, more insight is needed to integrate basic immune mechanisms into translational research and finally new IPF therapies.In this concise review, we will focus on the role of our innate and adaptive immune system in the initiation and perpetuation of IPF pathobiology. Next, we will discuss how immune responses are influenced by current anti-fibrotic treatments, such as pirfenidone and nintedanib and end with an overview of recent and upcoming therapeutic trials that target and modulate our immune system in patients with IPF.

We propose that this model of collar-induced acceleration of carotid atherogenesis is of hemodynamic cause. It may serve as a substrate for sequential mechanistic studies concerned with the underlying cause and pathogenesis of atherosclerosis. The rapidity of lesion development will also aid the efficient screening of new potentially antiatherogenic chemical entities and the evaluation of therapies with limited duration of effectiveness, such as adenoviral gene therapy.

Background-The presence of the tumor-suppressor gene p53 in advanced atherosclerotic plaques and the sensitivity to p53-induced cell death of smooth muscle cells isolated from these plaques have fueled speculation about the role of p53 in lesion destabilization and plaque rupture. In this study, we describe a strategy to promote (thrombotic) rupture of preexisting atherosclerotic lesions using p53-induced lesion remodeling. Methods and Results-Carotid atherogenesis was initiated in apolipoprotein E knockout mice by placement of a perivascular silastic collar. The resulting plaques were incubated transluminally with recombinant adenovirus carrying either a p53 or ␤-galactosidase (lacZ) transgene. p53 transfection was restricted to the smooth muscle cell-rich cap of the plaque and led to an increase in cap cell apoptosis 1 day after transfer. p53 overexpression resulted in a marked decrease in the cellular and extracellular content of the cap, reflected by a markedly reduced cap/intima ratio (0.21Ϯ0.04 versus 0.46Ϯ0.03, PϽ0.001). The latter is a characteristic feature of plaque vulnerability to rupture, and whereas spontaneous rupture of p53-treated lesions was rare, it was found in 40% of cases after treatment with the vasopressor compound phenylephrine (Pϭ0.003). Conclusions-We have demonstrated a potential role of p53-induced remodeling in atherosclerotic plaque destabilization.Being the first example of inducible rupture at a predefined location, this model offers a unique opportunity to delineate the processes that precede rupture and to evaluate plaque-stabilizing therapies.

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