Experimental studies of adhesion and endocytosis of calcium oxalate crystals in renal tubular cells.

The present investigation was designed to study the interactions between Madin-Darby canine kidney (MDCK) cells and calcium oxalate monohydrate (COM) crystals, the most abundant constituent of urinary crystals, and to clarify the significance of these crystal-cell interactions in stone pathogenesis. COM crystals adhered to the intact surface of MDCK cells by some biological mechanisms (biological adhesion) and, were then internalized into the cell (endocytosis). The microvilli of the cell appeared to play an important role in this process. In the kidneys of rats with experimentally induced stones, most COM crystals adhered to the tubular cells and some crystals were engulfed, via endocytosis. Thus, these crystal-cell interactions might be one of the earliest processes in the formation of kidney stones. Further elucidation of the mechanism and the regulatory factors of this process may provide new insight into stone pathogenesis.