Extract from herniaria hirsuta coats calcium oxalate monohydrate crystals and blocks their adhesion to renal epithelial cells

Purpose: The interaction of calcium oxalate crystals with renal epithelial cells is a critical event in kidney stone formation. In this study we assessed the effect of aqueous extract from Herniaria hirsuta on the adhesion of calcium oxalate monohydrate (COM) crystals to cultured renal cells. Materials and Methods: Madin Darby canine kidney cells were used as a model for studying the adhesion of radioactive COM crystals in the presence and absence of plant extract. Results: COM crystal binding to cells was inhibited by extract in a concentration dependent manner. Prior exposure of crystals but not cells to extract blocked crystal binding, suggesting that plant molecules can coat and exert their effect at the crystal surface. Crystal attachment appeared related to membrane fluidity since crystal adhesion increased at higher vs lower temperatures (37C vs 0C) and Herniaria extract altered crystal adhesion only under conditions of increased fluidity (increased temperature). Extract also displaced a significant portion of prebound crystals without apparent effects on cell function or the morphology of preexisting calcium oxalate crystals. Herniaria extract exerted no adverse or toxic effect on cells, which proliferated normally in its presence even at relatively high concentrations. Conclusions: Our current data suggest a mechanism whereby Herniaria hirsuta extract used in traditional characterization of the active compound(s) could identify a new candidate drug for patients with nephrolithiasis.