What Role do Alveolar Epithelial Cells Play in COVID-19 Disease Progression?

Alveolus model

SARS-CoV-2 is the seventh known coronavirus that causes the human disease known as COVID-19. The virus can grow in cells lining the conducting airways and in alveolar epithelial cells. First, the virus generally enters the body through the nose or mouth. From there, the virus travels down into the alveoli which are located in the lungs. Once in the alveoli, the virus “hijacks” cells to make new copies of the virus. The infected cell is then killed, releasing new viruses to infect neighboring cells in the alveolus. Each sac of air, or alveolus, is wrapped with capillaries where red blood cells release carbon dioxide (CO2) and pick up oxygen (O2). Two alveolar epithelial cells (type I and II) facilitate gas exchange. Type I cells are squamous alveolar cells with thin membranes that perform gas exchange. Type II cells are known as progenitor cells in the alveoli and proliferate and differentiate into type I cells. In addition, Type II cells secrete the pulmonary surfactant that lines the alveolus and prevent it from collapsing.

After the outbreak of COVID-19, a group of scientists from China quickly determined that SARS-CoV-2 utilizes ACE2 receptor as a gateway to infect alveolar epithelial cells. Following infection, type II cells recruit immune cells to clear out the virus and any infected cells. At the same time the immune cells also end up killing healthy alveolar cells. Ultimately, the death of type I and II cells lead to alveolar collapse and impaired gas exchange, causing Acute Respiratory Distress Syndrome (ARDS) and requiring a patient to be placed on a ventilator for breathing assistance.

In order to combat the novel coronavirus, researchers are working around the clock to discover antiviral drugs and other inhibitors. For testing the effects of antiviral drugs, human primary cell cultures present a great model system since they express many of the key functional markers that are found in vivo. ScienCell is the unique provider of human primary alveolar epithelial cells (Cat #3200), the cell types which are PRIMARILY targeted by the SARS-CoV-2 virus. ScienCell’s human primary alveolar epithelial cells are cryopreserved at passage 0, and contain a mixture of both type I and II cells.

Ready-To-Use 3D Human Pulmonary Alveolar Epithelial Cell Spheroids

Cells post thawing
Immunostaining of the human pulmonary alveolar epithelial cell spheroids with the epithelial cell marker CK18 and the specific alveolar epithelial cell type II marker SP-C.

ScienCell also offers the ready-to-use 3D human alveolar epithelial spheroids (Cat #SP3D-3200). Studies have shown that type II lung cells lose their functional markers within a few days of cultivation in 2D cell culture. When alveolar epithelial cells are cultured in three-dimensional (3D) cell culture, they better maintain their epithelial functional markers, and express the surfactant proteins such as SP-A, -B, -C, and –D. These ready-to-use spheroids are cryopreserved and delivered frozen. Upon receiving, our customers can store the spheroids in liquid nitrogen or can directly thaw and plate them into the ultra-low binding culture plates. Next, the spheroids will be ready for experiments at 24 hours post thawing, and are an excellent in vitro model for studying the contribution of the alveolar epithelial cells to alveolar maintenance and repair. In sum, we believe that the use of physiologically relevant cells and in vitro models will more accurately reflect the effects of antiviral drugs for COVID-19.

 

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