The immortalization of AT2 cell

Our life under the SARs-CoV-2 pandemic has not been what people probably imagine before. Since last December 2019 until now, around 101 million cases with approximately 2% have been confirmed (1). This widespread viral disease did not only impact the healthcare sector negatively but the global economy has also been plummeted owing to the outbreak of this novel coronavirus strain. But keeping the economic aspects aside, SARs-CoV-2 mainly ravages along the respiratory tract, which may lastly result in Acute Respiratory Distress Syndrome (ARDS). Researchers hypothesized that the inflammatory responses between type 2 alveolar epithelial lung cells (AT2) might answered the clinical manifestation (2). Apart from SARs-CoV-2 or other pulmonary infection, there are various lung diseases involving abnormal AT2 cell function including asthma, chronic obstructive pulmonary disease (COPD), or any other diseases affecting the distal pulmonary region even lung cancer, which is the most life-devastated type of cancer (3). Thereupon, what is type 2 alveolar epithelial cell? Briefly, the distal lung part comprises two distinct-functional epithelial cells: 1. alveolar type 1 (AT1) and 2. alveolar type 2 cells (AT2) as mentioned before. 0. 2-micron Flattened shape of AT1 cells plays a major role in gas exchanging with the blood capillary network covering around 95% of the alveolar surface area, while the cuboidal-shaped AT2 cells have been perceived as the pulmonary nursemaid or the lung stem cell. Following lung cells damaged, AT2 cells can redouble and transdifferentiate into AT1 (4, 5) for the regenerating of gaseous alveolar surfaces. Furthermore, AT2 cells are mainly responsible for various types of lung surface surfactant production to prevent the alveolar collapsing by decreasing the surface tension upon the respiration. Even then, AT1 cells also, at least in some subpopulations, have the plasticity ability by reciprocally re-transdifferentiate themselves into AT2 cells as referring to some recent reports (6-9). Regardless of delicate studies on the biomolecular characteristics of AT2 cells, researchers still used other resemble cell lines instead such as A549 (ATCC® CCL-185™), and RLE-6TN (ATCC® CRL-2300™). However, these available example cell lines were isolated from cancerous resources carrying mutations or even came from the murine sample (RLE-6TN) (10), thus these cell lines could not recapitulate the same characteristics as normal AT2 cells in human because of significant lower phospholipid synthesis from lamellar bodies (11). And unfortunately, there have no known AT2 cell lines commercially available. Therefore, this review will provide specific detail upon immortalization of AT2 cell from the past up to date, comprehensively discusses the advantages and limitation, comes to a pondering end with the prospect that may successfully achieve AT2 cell lines as desired.