Exosome-mediated crosstalk between epithelial cells amplifies the cell injury cascade in CaOx stone formation

Calcium oxalate (CaOx) stone disease is found worldwide. To explore the role of exosomes as a mediator of intercellular crosstalk during CaOx stone formation, we conducted this study, which may provide a new insight into the treatment and prevention of CaOx stones.

Exosomes derived from HK2 cells with (EXO(S)) or without (EXO(C))CaOx crystal stimulation were cocultured with normal tubular epithelial cells and subcapsularly injected into rat kidneys. Then, oxidative stress levels, the MAPK signalling pathway and osteogenic changes were detected via qPCR, Western blotting, immunofluorescence and immunohistochemical staining. In vivo fluorescence imaging and exosome internalization assays showed the absorption and utilization of exosomes.

EXO(S) increased the reactive oxygen species (ROS) level and activated the expression of BMP2, OPN and OCN via the MAPK/P-38 pathway both in vivo and in vitro. In vivo experiments showed that preinjection of EXO(S) aggravated, while preinjection of EXO(C) ameliorated, these effects. Crystal depositions were significantly increased in SD rats injected with GAM when they were preinjected with EXO(S), and these effects could be reversed after preinjection with EXO(C).

Our study revealed that exosome-mediated intercellular crosstalk could accelerate the formation of CaOx stones by promoting oxidative stress and the osteogenic cascade in normal tubular epithelial cells. HK2 cells stimulated with CaOx crystals released more exosomal miR-223-3p and S100A8 comparing with normal HK2 cells. These exosomes derived from HK2 cells stimulated with CaOx (EXO(S)) could amplify the oxidative stress and osteogenic changes via MAPK/P-38 pathway, which finally led to the formation of Randall's plaque.