Role of heparan sulfate proteoglycan (syndecan-1) on the renal epithelial cells during calcium oxalate monohydrate crystal attachment.

We have reported that heparan sulfate (HS)/heparan sulfate proteoglycan (HSPG, syndecan-1) expression significantly increased in the rat kidney during calcium oxalate (CaOx) nephrolithiasis. Although the exact role of syndecan still remains unclear, HS/syndecan-1 is thought to have some important role in the CaOx crystal formation. Mardin-Darby canine kidney (MDCK) cells are most commonly used in kidney stone research. It was reported that MDCK cells do not express syndecan-1. In the present study, we established a novel MDCK cell line (KIC-synd-1) that expressed the human syndecan-1 gene. In this cell line, we confirmed stable expression of both sndecan-1 gene and core protein. Immunohistochemical study revealed positive staining of syndecan-1 monoclonal antibody in the basolateral and cytosolic area of the KIC-synd-1 cells. We also investigated the composition of glycosaminoglycans (GAGs) side chains in MDCK cells and KIC-synd-1 cells by using high-performance liquid chromatography (HPLC). Four types of HS chains were identified in both cells as follows; delta diHS-NS, delta diHS-6S, delta diHS-diS1, delta diHS-diS2. Increased production of delta diHS-NS and delta diHS-diS2 were shown in KIC-synd-1 cells compared with production in MDCK cells (p < 0.05). In contrast, only a small amount of delta diHS-6S and delta diHS-diS1 was contained in both cell lines. Total amount of HS was significantly increased in the KIC-synd-1 cells compare with that in the wild type MDCK cells (p < 0.05). Scanning electron microscopy revealed no significant difference between cell surface of wild type MDCK cells and that of KIC-synd-1 cells in normal conditions. However, calcium oxalate crystal attachment was apparently decreased in the KIC-synd-1 cells. These results suggested that cell surface HS/syndecan-1 has preventive role for calcium oxalate nephrolithiasis via creation of a charge barrier against COM crystal attachment.