The modulatory effects of large and small extracellular vesicles from normal human urine on calcium oxalate crystallization, growth, aggregation, adhesion on renal cells, and invasion through extracellular matrix: An in vitro study

Abstract

Urinary extracellular vesicles (uEVs) play important roles in physiologic condition and various renal/urological disorders. However, their roles in kidney stone disease remain unclear. This study aimed to examine modulatory effects of large and small uEVs derived from normal human urine on calcium oxalate (CaOx) crystals (the main component in kidney stones). After isolation, large uEVs, small uEVs and total urinary proteins (TUPs) with equal (protein equivalent) concentration were added into various crystal assays to compare with the control (without uEVs or TUPs). TUPs strongly inhibited CaOx crystallization, growth, aggregation and crystal-cell adhesion. Large uEVs had lesser degree of inhibition against crystallization, growth and crystal-cell adhesion, and comparable degree of aggregation inhibition compared with TUPs. Small uEVs had comparable inhibitory effects as of TUPs for all these crystal assays. However, TUPs and large uEVs slightly promoted CaOx invasion through extracellular matrix, whereas small uEVs did not affect this. Matching of the proteins reported in six uEVs datasets with those in the kidney stone modulator (StoneMod) database revealed that uEVs contained 18 known CaOx stone modulators (mainly inhibitors). These findings suggest that uEVs derived from normal human urine serve as CaOx stone inhibitors to prevent healthy individuals from kidney stone formation.