Mesothelial primary cilia of peritoneal and other serosal surfaces

The conspicuous presence of primary cilia, a small immotile cilium present on most cell types, left researchers with little doubt of their functional relevance. Recently mechanosensitive functional significance was established and a link with the pathogenesis of polycystic kidney disease. Together these discoveries have raised the profile of this, previously considered "vestigial", organelle. Primary cilia are expressed on the apical surface of serosal mesothelium and display regional variation but are more abundant on biosynthetically active cells. Adult mesothelial cells are highly biosynthetic producing a phospholipid rich surfactant that lubricates and protects the visceral organs. The mesothelium is utilized as a semipermeable membrane during peritoneal dialysis for patients with end stage renal failure. However, little is known about the functional role of primary cilia on this highly specialized cell type. The present review, examines the significance of the primary cilium in serosal mesothelial cell biology with an emphasis on ciliary location, structure, form and function. Future research is identified and discussed in view of the emerging role cilia have in other cells and the established function of the serosal mesothelium in development, normal function, peritoneal dialysis and pathology of the serosal membranes.