Post-COVID-19 lung pathogenesis and pathomorphology

The article describes the main pathogenetic and pathomorphological aspects of pulmonary fibrosis onset and development in patients with COVID-19 in anamnesis. The authors analyzed open access articles in Russian and English from eLibrary and Pubmed archives. The key aspect of the pulmonary fibrosis pathogenesis is fibroblast and myofibroblast activation. In response to the lung parenchyma damage, it leads to fibroblast and myofibroblast proliferation and differentiation and triggers a cascade of cytokine reactions. T-helper cells are responsible for the regulation of the inflam-matory-reparative process in the lungs. T-helper cells directly or indirectly trigger the remodeling of the pulmonary parenchyma in favor of the fibrous component. Literature shows that the role of cytokines is assessed differently, and currently there is no consensus on their influence on pulmonary fibrosis formation. However, studies showing the possibility to prevent and treat fibrosis with anti-cytokine drugs place the development of a cytokine storm at the forefront. Growth factors, especially TGF, FGF, PDGF, are important not only in understanding pathogenesis, but also in finding new, promising therapeutic modalities. Due to external factors, many authors refrain from quantitative assessments of long-term consequences. Data on the persistence and regression of post-Covid pulmonary fibrosis are also contradictory. Despite much information on issues related to COVID-19 pathogenesis and pulmonary fibrosis development, many molecular mechanisms remain hidden from researchers. Thus, there are new prospects in diagnosis, prevention and treatment of the disease.