Table_6_Progression to lung fibrosis in severe COVID-19 patients: A morphological and transcriptomic study in postmortem samples.XLSX

The development of lung fibrosis is a major concern in patients recovered from severe COVID-19 pneumonia. This study aimed to document the evolution of diffuse alveolar damage (DAD) to the fibrosing pattern and define the transcriptional programs involved. Morphological, immunohistochemical and transcriptional analysis were performed in lung samples obtained from autopsy of 33 severe COVID-19 patients (median illness duration: 36 days). Normal lung and idiopathic pulmonary fibrosis (IPF) were used for comparison. Twenty-seven patients with DAD and disease evolution of more than 2 weeks had fibrosis. Pathways and genes related with collagen biosynthesis and extracellular matrix (ECM) biosynthesis and degradation, myofibroblastic differentiation and epithelial to mesenchymal transition (EMT) were overexpressed in COVID-19. This pattern had similarities with that observed in IPF. By immunohistochemistry, pathological fibroblasts (pFBs), with CTHRC1 and SPARC expression, increased in areas of proliferative DAD and decreased in areas of mature fibrosis. Immunohistochemical analysis demonstrated constitutive expression of cadherin-11 in normal epithelial cells and a similar pattern of cadherin and catenin expression in epithelial cells from both normal and COVID-19 samples. Transcriptomic analysis revealed downregulation of the Hippo pathway, concordant with the observation of YAP overexpression in hyperplastic alveolar epithelial cells. Progression to fibrosis in severe COVID-19 is associated with overexpression of fibrogenic pathways and increased in CTHRC1- and SPARC-positive pFBs. Whereas the Hippo pathway seemed to be implicated in the response to epithelial cell damage, EMT was not a major process implicated in COVID-19 mediated lung fibrosis.

肺部纤维化的发生是严重COVID-19肺炎康复患者的一大关注焦点。本研究旨在记录弥漫性肺泡损伤（DAD）向纤维化模式的演变过程，并定义其中涉及的转录程序。通过对33例严重COVID-19患者（中位病程：36天）的尸检肺样本进行形态学、免疫组化和转录组分析，并与正常肺组织和特发性肺纤维化（IPF）进行比较。在27例DAD病程超过2周的患者中，出现纤维化。在COVID-19患者中，与胶原蛋白生物合成和细胞外基质（ECM）生物合成及降解、肌成纤维细胞分化以及上皮间质转化（EMT）相关的通路和基因表达上调。这种模式与IPF中观察到的模式相似。通过免疫组化分析，病理成纤维细胞（pFBs）在增殖性DAD区域表达CTHRC1和SPARC，而在成熟纤维化区域表达下降。免疫组化分析还显示，在正常上皮细胞中存在cadherin-11的构成性表达，以及正常和COVID-19样本上皮细胞中cadherin和catenin表达的相似模式。转录组分析揭示了Hippo通路的下调，这与在增生性肺泡上皮细胞中观察到的YAP过表达相一致。严重COVID-19患者纤维化进展与成纤维通路的上调和CTHRC1-及SPARC阳性pFBs的增加相关。而Hippo通路似乎在应对上皮细胞损伤中发挥作用，但EMT并非COVID-19介导的肺纤维化的主要过程。