Characterization of Chondroitin-4-Sulfate extracted from Tilapia viscera (Oreochromis niloticus) and evaluation of its effect on the crystallization of Calcium Oxalate

Abstract

Glycosaminoglycans (GAGs) are sulfated polysaccharides that are naturally present in urine and have been identified as modulators of urinary stone formation. Among GAGs, chondroitin sulfate (CS) has shown promise as a possible modulator of crystal growth. Studies have revealed that aquatic organisms are alternative sources of CS with therapeutic potential. The fish Oreochromis niloticus, also known as Nile tilapia, was chosen for this study due to its high production and potential for environmental damage. The objective of this study was to isolate CS from O. niloticus viscera and evaluate its modulating effect on calcium oxalate (OxCa) crystal growth. The tilapia culture residues were subjected to an enzymatic proteolysis process, followed by complexation and decomplexation with Lewatit cationic resin to obtain a mixture of GAGs. The GAGs were then purified using fractionation with acetone and ion exchange chromatography. The purified CS was identified as chondroitin-4-sulfate (CSA) and named tilapia chondroitin sulfate (CST). CST (0.01 mg/mL) was found to decrease the size of OxCa crystals and increase the number of crystals formed by 15 times. Fluorescence microscopy assays revealed that CST interacts with the faces of the CaOx monohydrate (COM) crystal, but not with dihydrate crystals. Scanning electron microscopy indicated that CST alters the morphology of COM crystals, making them assume a more elongated shape. Additionally, the study showed that CST does not present cytotoxicity under the evaluated conditions (0.01 – 0.2 mg/mL) in MadinDarby canine renal cell (MDCK) cells. These findings suggest that CST has potential as an anti-kidney stone agent, but further in vivo studies are needed to confirm its efficacy.