Infection of Brain Organoids and 2D Cortical Neurons with SARS-CoV-2 Pseudovirus

Abstract

Since the global outbreak of SARS-CoV-2 (COVID-19), infections of diverse human organs along with multiple symptoms continue to be reported. However, the susceptibility of the brain to SARS-CoV-2, and the mechanisms underlying neurological infection are still elusive. Here, we utilized human embryonic stem cell-derived brain organoids and monolayer cortical neurons to investigate infection of brain with pseudotyped SARS-CoV-2 viral particles. Spike-containing SARS-CoV-2 pseudovirus infected neural layers within brain organoids. The expression of ACE2, a host cell receptor for SARS-CoV-2, was sustained during the development of brain organoids, especially in the somas of mature neurons, while remaining rare in neural stem cells. However, pseudotyped SARS-CoV-2 was observed in the axon of neurons, which lack ACE2. Neural infectivity of SARS-CoV-2 pseudovirus did not increase in proportion to viral load, but only 10% of neurons were infected. Our findings demonstrate that brain organoids provide a useful model for investigating SARS-CoV-2 entry into the human brain and elucidating the susceptibility of the brain to SARS-CoV-2.

Expression of Endogenous Angiotensin-Converting Enzyme 2 in Human Induced Pluripotent Stem Cell-Derived Retinal Organoids

“…Consistent with recent studies, our study also demonstrated organoid cultures as a promising approach to model diseases and showed lung and colonic organoid culture effectiveness in being infected by SARS-CoV-2 [ 51 , 52 ]. Organoids for various tissues, intestinal organoids, blood vessel organoids, and brain organoids have been used to better understand the pathological mechanism of SARS-CoV-2 viral tropism [ 7 , 47 , 53 ]. This study successfully established human iPSC-derived retinal organoids and monolayer cultures as the in vitro model for SARS-CoV-2 pseudovirus infection.…”

“…Hao et al also identified ACE2 expression in oral cavity mucosa, especially in the tongue’s epithelial cells compared to other oral sites [ 6 ]. Sang et al and Jacob et al demonstrated that the SARS-CoV-2 pseudovirus can successfully infect the nervous system, induced pluripotent stem cell (iPSC)-derived neural cells, and brain organoids [ 7 , 8 ]. Another group reported ACE2 expression in the human cornea and conjunctiva [ 2 ].…”

“…Given that the SARS-CoV-2 pseudovirus contains the S protein of SARS-CoV-2, it is widely accepted that the entry process of the SARS-CoV-2 pseudovirus highly resembles that of SARS-CoV-2. Using the SARS-CoV-2 pseudovirus for investigating the viral entry process allows experiments to be performed in biosafety level 2 facilities instead of biosafety level 3 [ 7 ]. Here, we utilized both human iPSC-derived retinal organoids and retinal monolayer cultures as in vitro platforms to investigate the viral entry of the SARS-CoV-2 pseudovirus and the expression of ACE2 and TMPRSS2.…”

SARS-CoV-2 Infection and Disease Modelling Using Stem Cell Technology and Organoids

“…In particular, it still remains to be elucidated whether these symptoms are a direct consequence of the replication of the virus in neural cells, are due to post-infectious immune-mediated disease, or are the result of systemic disease [ 112 , 113 ]. Conflicting preliminary data have been reported on SARS-CoV-2 neurotropism in in vitro systems derived from hPSCs, including data on expression of the entry receptor ACE2 in neural stem cells/NPCs and in mature neurons [ 96 , 114 , 115 , 116 , 117 , 118 , 119 , 120 ]. ACE2 expression has been also reported in 3D brain spheres and in brain organoids [ 117 , 118 ], whereas other researchers detected the presence of the receptor confined in choroid plexus (ChP) epithelial cells of brain organoids, but not in neurons and NPCs [ 119 , 120 ].…”

“…Conflicting preliminary data have been reported on SARS-CoV-2 neurotropism in in vitro systems derived from hPSCs, including data on expression of the entry receptor ACE2 in neural stem cells/NPCs and in mature neurons [ 96 , 114 , 115 , 116 , 117 , 118 , 119 , 120 ]. ACE2 expression has been also reported in 3D brain spheres and in brain organoids [ 117 , 118 ], whereas other researchers detected the presence of the receptor confined in choroid plexus (ChP) epithelial cells of brain organoids, but not in neurons and NPCs [ 119 , 120 ]. Although these conflicting data may be ascribable to the different sensitivity of the methods employed, in line with this varying pattern of ACE2 expression, susceptibility and permissiveness of neural cells to SARS-CoV-2 was also investigated with conflicting results in 2D cultures of neural cells, i.e., NPCs, neurons, and astrocytes.…”