THE CLARA CELL: FROM DISCOVERY TO CLINICAL IMPLICATIONS Muhammad Atteya Department of Anatomy, College of Medicine, King Saud University, Riyadh, Saudi Arabia
This review presents the history of Clara cells, their number and ultrastructure, their location in the respiratory tract, and their functions. The author discusses the proteins released by Clara cells and the role they play in maintaining the integrity and renewal of the airway lining epithelium. Their importance in the degradation of inhaled hazardous xenobiotics is underlined and their role as progenitor/stem cells for the bronchiolar epithelium is emphasized. The clinical implications of Clara cells are then discussed, including evidence that measuring Clara cell-secreted proteins serum levels can aid in the diagnosis of several lung diseases. Finally, recommendations are made for the use of proteins released by Clara cells in the treatment of major respiratory diseases. Keywords: non-ciliated secretory cell; progenitor cell; stem cell; adenocarcinoma; biomarker; Clara cell; Clara cell secretory protein; lung; regeneration; stem cells; club cells; xenobiotic detoxification.