Pericellular Matrix Formation by Renal Tubule Epithelial Cells in Relation to Crystal Binding

Abstract

Background/Aim: Retention of crystals in the kidney ultimately leads to renal stone formation. Hyaluronan (HA) has been identified as binding molecule for calcium oxalate monohydrate crystals. The association of high molecular mass (M_r) HA with cell surface receptors such as CD44 gives rise to pericellular matrix (PCM) formation by many eukaryotic cells in culture. Here, we study the ability of several renal tubular cell lines to assemble PCMs and to synthesize high-M_r HA during proliferation in relation to crystal retention. Methods: PCM assembly by MDCK-I, MDCK-II, and LLC-PK₁ cells was visualized by particle exclusion assay. Metabolic labeling studies were performed to estimate the cellular production of HA. The expression of CD44 and HA was studied using fluorescent probes, and crystal binding was quantified with radiolabeled calcium oxalate monohydrate. Results: PCMs were formed, and HA was expressed by most MDCK-I and some MDCK-II, but not by LLC-PK₁ cells. All cell types expressed CD44 at their apical surface. MDCK-I and MDCK-II cells secreted, respectively, 14.7 ± 1.6 and 0.5 ± 0.2 pmol [³H]glucosamine incorporated in high-M_r HA, whereas LLC-PK₁ cells did not secrete HA. Streptomyces hyaluronidase treatment significantly decreased crystal binding (µg/cm²) to MDCK-I cells (from 8.6 ± 0.4 to 3.9 ± 0.9), but hardly to MDCK-II cells (from 10.2 ± 0.2 to 9.6 ± 0.1) or LLC-PK₁ cells (from 10.2 ± 0.8 to 9.9 ± 0.3). Conclusions: There are various forms of crystal binding to renal tubular cells in culture. Crystal attachment to MDCK-I and some MDCK-II cells involves PCM assembly that requires high-M_r HA synthesis. HA production and PCM formation do not play a role in crystal binding to LLC-PK₁ and the majority of MDCK-II cells. It remains to be determined which form of binding is involved in renal stone disease.