HISTOLOGICAL OBSERVATIONS OF THE ADHESION AND ENDOCYTOSIS OF CALCIUM-OXALATE CRYSTALS IN MDCK CELLS AND IN RAT AND HUMAN KIDNEY

Adhesion and/or endocytosis of calcium oxalate crystals to the three k inds of tubular cells (Madin-Darby canine kidney (MDCK) cells, rat and human kidney) were demonstrated morphologically to presume the initia l formation of kidney stone. After removal of the nonadhesion crystals , the cells were subsequently recultured in the vertical position. At various times thereafter, the interactions between COM crystals and MD CK cells were evaluated morphologically by SEM. COM crystals adhered t o the surface of MDCK cells immediately, and the crystals were then en docytosed. The microvilli of the cells appeared to play an important r ole in these processes, At later times, some complexes that consist of aggregated calcium oxalate crystals and cell debris were observed spo radically, Kidney tissues were obtained from male Sprague-Dawley rats which were injected with sodium oxalate intraperitoneally. Experimenta lly induced calcium oxalate crystals were evaluated histologically usi ng polarized light microscopy. Some crystals in the cortical portion w ere attached to the tubular epithelium or internalized into the lumina l membrane. Whereas in the papilla, the aggregated crystals were obser ved lying free from the degenerated tubular lumen along with the cell debris. Human kidney tissues were obtained from 38 patients with calci um oxalate nephrolithiasis who underwent nephrolithotomy or partial ne phrectomy before the era of ESWL. The specimens were examined for calc ium crystals within the tubular lumen, attached to the tubular walls o r internalized into the tubular cells, by polarized light microscopy. Approximately 50% of the specimens observed crystals attached to the t ubular cell epithelium and some of them were seen inside the tubular c ells. In conclusion, crystal-cell interaction resulted in movement of crystals from the lumen into the cells by an action of microvilli from the results of MDCK cells. However, it was not clear from the results in rats or human kidney tissue that crystal adhesion and/or endocytos is might be vital in the crystal growth in the kidney.