The coronavirus disease 2019 (COVID-19) pandemic is caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is spread primary via respiratory droplets and infects the lungs. Currently widely used cell lines and animals are unable to accurately mimic human physiological conditions because of the abnormal status of cell lines (transformed or cancer cells) and species differences between animals and humans. Organoids are stem cell-derived self-organized three-dimensional culture in vitro and model the physiological conditions of natural organs. Here we showed that SARS-CoV-2 infected and extensively replicated in human embryonic stem cells (hESCs)-derived lung organoids, including airway and alveolar organoids which covered the complete infection and spread route for SARS-CoV-2 within lungs. The infected cells were ciliated, club, and alveolar type 2 (AT2) cells, which were sequentially located from the proximal to the distal airway and terminal alveoli, respectively. Additionally, RNA-seq revealed early cell response to virus infection including an unexpected downregulation of the metabolic processes, especially lipid metabolism, in addition to the well-known upregulation of immune response. Further, Remdesivir and a human neutralizing antibody potently inhibited SARS-CoV-2 replication in lung organoids. Therefore, human lung organoids can serve as a pathophysiological model to investigate the underlying mechanism of SARS-CoV-2 infection and to discover and test therapeutic drugs for COVID-19.
Adenosine Monophosphate/therapeutic use* ; Alanine/therapeutic use* ; Alveolar Epithelial Cells/virology* ; Antibodies, Neutralizing/therapeutic use* ; COVID-19/virology* ; Down-Regulation ; Drug Discovery ; Human Embryonic Stem Cells/metabolism* ; Humans ; Immunity ; Lipid Metabolism ; Lung/virology* ; RNA, Viral/metabolism* ; SARS-CoV-2/physiology* ; Virus Replication/drug effects*

【Objective】 To investigate whether 17β-estradiol (βE2) can activate the NF-E2-related factor 2(Nrf2) pathway to resist the downregulation of retinal function induced by light damage. 【Methods】 Two weeks after female SD rats were castrated, they were divided into the following six groups: control group (control), light-damage group (LD), saline group, saline light-damage group (saline-LD), βE2 group, and βE2 light-damage group (βE2-LD). Rats in the light-damage were exposed to 8000-lux fluorescence for 12 h after 18 h of dark adaptation. Then electroretinogram (ERG), immunofluorescence, Real-time PCR and immunohistochemical detection were performed after one day of dark recovery. 【Results】 The results of ERG showed that ERG was lower in LD group than in control group (P<0.05). After light damage, ROS was increased and the mRNA expressions of antioxidant genes, such as Sod1, Sod2, Cat, Glrx1, Glrx2, Txn1, and Txn2 were decreased (all P<0.05). After βE2 administration, compared with those in saline-LD, ROS level was decreased, the levels of Nrf2 protein and antioxidant genes were increased, and ERG was recovered to a certain extent in βE2-LD (P<0.05). 【Conclusion】 βE2 can restore the function of rat retina, and its mechanism might be related to the upregulation of Nrf2 and antioxidant genes.