Medical progress: Stem cells as a new therapeutic strategy for COVID-19.

Currently, the world is facing the SARS-CoV-2 pandemic, coronavirus of acute respiratory distress syndrome 2, causes of COVID-19. Coronaviruses are RNA single-stranded viruses that have an envelope. In addition, coronaviruses are classified into four subfamilies: alpha, beta, gamma and delta coronaviruses. The first of them, cause mildly symptomatic or asymptomatic infections, while beta-coronaviruses are responsible for severe diseases. SARS-CoV-2 belongs to the group of beta-coronaviruses. Current available therapies use corticosteroids to reduce inflammation, non-specific antiviral drugs or antibiotics in the treatment of secondary bacterial infections. In addition, therapies based on the use of hydroxychloroquine, chloroquine, remdesvir, ribavirin, interferon or lopinavir-ritonavir were also initially used. Mesenchemical stem cells (MSCs) are widely used in cell therapies, which include both basic research and clinical trials. Their exceptional effectiveness and safety have been confirmed and documented in many clinical studies, which include a number of inflammatory diseases involving the immune system - one of them is systemic lupus erythematosus. Available data indicate the ability to differentiate MSCs and their immunomodulatory effects. In addition, through interactions with immune cells, which include, but are not limited to, macrophages and dendritic cells, or paracrine secretion, MSCs are able to secrete a number of types of cytokines. MSCs are also characterized by tissue regeneration and regulation of inflammation. Due to their properties, researchers turned to determine whether MSC transplantation is able to improve the outcome of patients with COVID-19 viral pneumonia. The presented review provides not only new knowledge in the field of molecular mechanisms of pro-regenerative action of stem cells, but also have the potential to open up new prospects of action to improve lung tissue regeneration in COVID-19 patients. In addition, in review mentioned about clinical trials using MSCs with a complete status, as well as the latest discoveries in molecular biology, a platform model of pluripotent stem cells in the SARS-CoV-2 study on 3D animal models and nanoconjugates based on stem cells.