Biology of glomerular cells in culture.

The glomerulus is a complex structure including four cell types, namely mesangial, visceral epithelial, parietal epithelial and endothelial cells. Mesangial cells resemble smooth muscle cells and play a major role in the synthesis of the components of the glomerular basement membrane and in the vasoreactivity of the glomerular tuft. In particular, they express receptors for angiotensin II which mediate mesangial cell contraction, this effect resulting in the decrease of the filtration area. They are also the site of synthesis of a variety of inflammatory agents which are involved in the development of glomerular injury in glomerulonephritis. Visceral epithelial cells, also referred to a podocytes, also participate in the synthesis of the normal constituents of the glomerular basement membrane. They express receptors for atrial natriuretic factor and possess on their surface a number of ectoenzymes. They also, in concert with mesangial cells, release metalloproteases which contribute to the degradation of the extracellular matrix. Parietal epithelial cells have been little studied. They represent the main constituent of the crescents observed in extracapillary proliferative glomerulonephritis. Endothelial cells secrete vasodilatory agents such as nitric oxide and prostacyclin and vasoconstrictor agents such as endothelin which act on the adjacent mesangial cells. New methods of culture of glomerular cells are in progress. Their aim is to keep as long as possible the physiological phenotype of these cells. Another progress is the availability of stable transformed cell lines which represent an abundant source of material for biochemical studies.