The structure⁻activity relationships and repair mechanism of six low-molecular-weight seaweed polysaccharides (SPSs) on oxalate-induced damaged human kidney proximal tubular epithelial cells (HK-2) were investigated. These SPSs included Laminaria japonica polysaccharide, degraded Porphyra yezoensis polysaccharide, degraded Gracilaria lemaneiformis polysaccharide, degraded Sargassum fusiforme polysaccharide, Eucheuma gelatinae polysaccharide, and degraded Undaria pinnatifida polysaccharide. These SPSs have a narrow difference of molecular weight (from 1968 to 4020 Da) after degradation by controlling H₂O₂ concentration. The sulfate group (⁻SO₃H) content of the six SPSs was 21.7%, 17.9%, 13.3%, 8.2%, 7.0%, and 5.5%, respectively, and the ⁻COOH contents varied between 1.0% to 1.7%. After degradation, no significant difference was observed in the contents of characteristic ⁻SO₃H and ⁻COOH groups of polysaccharides. The repair effect of polysaccharides was determined using cell-viability test by CCK-8 assay and cell-morphology test by hematoxylin-eosin staining. The results revealed that these SPSs within 0.1⁻100 μg/mL did not express cytotoxicity in HK-2 cells, and each polysaccharide had a repair effect on oxalate-induced damaged HK-2 cells. Simultaneously, the content of polysaccharide ⁻SO₃H was positively correlated with repair ability. Furthermore, the low-molecular-weight degraded polysaccharides showed better repair activity on damaged HK-2 cells than their undegraded counterpart. Our results can provide reference for inhibiting the formation of kidney stones and for developing original anti-stone polysaccharide drugs.
Keywords: cell repair activity; cytotoxicity; molecular weight; polysaccharide degradation; seaweed.