Abstract
The cytotoxicity of calcium oxalate (CaOx) in renal epithelial cells has been studied extensively, but the cell death mode induced by CaOx with different physical properties, such as crystal size and crystal phase, has not been studied in detail. In this study, we comparatively investigated the differences of cell death mode induced by nano-sized (50 nm) and micron-sized (10 μm) calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) to explore the cell death mechanism. The effect of the exposure of nano-/micron-sized COM and COD crystals toward the African green monkey renal epithelial (Vero) cells were investigated by detecting cell cytoskeleton changes, lysosomal integrity, mitochondrial membrane potential (Δψm), apoptosis and/or necrosis, osteopontin (OPN) expression, and malondialdehyde (MDA) release. Nano-/micron-sized COM and COD crystals could cause apoptosis and necrosis simultaneously. Nano-sized crystals primarily caused apoptotic cell death, leading to cell shrinkage, phosphatidylserine ectropion, and nuclear shrinkage, whereas micron-sized crystals primarily caused necrotic cell death, leading to cell swelling and cell membrane and lysosome rupture. Nano-sized COM and COD crystals induced much greater cell death (sum of apoptosis and necrosis) than micron-sized crystals, and COM crystals showed higher cytotoxicity than the same-sized COD crystals. Both apoptosis and necrosis could lead to mitochondria depolarization and elevate the expression of OPN and the generation of lipid peroxidation product MDA. The amount of expressed OPN and generated MDA was positively related to cell injury degree. The physicochemical properties of crystals could affect the cell death mode. The results of this study may provide a basis for future studies on cell death mechanisms.
Highlights
IntroductionMore than 70% of renal stone patients suffer from urolithiasis caused by calcium oxalate (CaOx) stones, of which calcium oxalate dihydrate (COD) is the most common crystal in healthy human urine, and calcium oxalate monohydrate (COM) is the most common crystal in renal stones.[1,2] In the absence of medical treatment, nephrolithiasis is a recurrent disease, with a prevalence of 50% over 10 years.[1]Many researchers have recently emphasized that the interaction between crystals and renal tubular epithelial cells, including the adhesion or endocytosis of crystals by cells, is an important factor in stone formation.[3,4] These processes could lead to cellular injury, alterations in cellular structure, compositions, physiology and gene expression, initiation of DNA synthesis, and cell death.[5,6] cell death caused by CaOx crystals has been extensively studied, the mode of cell death produced by CaOx has not been defined
calcium oxalate monohydrate (COM)-50 nm and calcium oxalate dihydrate (COD)-50 nm were nearly spherical, COM-10 μm transformed into hexagonal lozenge, whereas COD-10 μm transformed into tetragonal bipyramid
The crystal phase was detected by XRD and FT-IR characterization in our present study,[20] all the prepared samples were pure-phase COM crystals or COD crystals
Summary
More than 70% of renal stone patients suffer from urolithiasis caused by calcium oxalate (CaOx) stones, of which calcium oxalate dihydrate (COD) is the most common crystal in healthy human urine, and calcium oxalate monohydrate (COM) is the most common crystal in renal stones.[1,2] In the absence of medical treatment, nephrolithiasis is a recurrent disease, with a prevalence of 50% over 10 years.[1]Many researchers have recently emphasized that the interaction between crystals and renal tubular epithelial cells, including the adhesion or endocytosis of crystals by cells, is an important factor in stone formation.[3,4] These processes could lead to cellular injury, alterations in cellular structure, compositions, physiology and gene expression, initiation of DNA synthesis, and cell death.[5,6] cell death caused by CaOx crystals has been extensively studied, the mode of cell death produced by CaOx has not been defined. Many researchers have recently emphasized that the interaction between crystals and renal tubular epithelial cells, including the adhesion or endocytosis of crystals by cells, is an important factor in stone formation.[3,4] These processes could lead to cellular injury, alterations in cellular structure, compositions, physiology and gene expression, initiation of DNA synthesis, and cell death.[5,6]. Necrosis has been traditionally thought to be a passive form of cell death with more similarities to a train wreck than a suicide.[12,13] In general, fast-acting metabolic poisons and strong physical stress, such as freezing, boiling, or shearing, rupture cell membranes and cause rapid cell necrosis. A slow-acting form of cell death called apoptosis does not involve membrane damage and inflammation.[14,15] cell death is a complicated pathological process. Cell apoptosis and necrosis caused by CaOx crystal exposure may be related to cell types, crystal concentration, exposure time, and even the unknown physicochemical properties of crystals
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
