Selective regulation of RANKL/RANK/OPG pathway by heparan sulfate through the binding with estrogen receptor β in MC3T3-E1 cells

Abstract

Heparan sulfate (HS) is a linear anionic polysaccharide with repeating sulfated disaccharide units, which has been proven with various regulatory osteogenesis effects through multi-pathway signaling, but its impacts on receptor-activator of nuclear factor kappa beta ligand/receptor-activator of nuclear factor kappa beta/osteoprotegerin (RANKL/RANK/OPG) pathway is still poorly understood. In this study, the binding affinity between HS and estrogen receptor beta (ER-β) was virtually analyzed using computer simulative docking method and experimentally studied by surface plasmon resonance (SPR). Thereafter, short interfering RNAs (siRNAs) were constructed to deliberately down-regulate the level of ER-β in MC3T3-E1 cell line, and the transfected and non-transfected osteoblasts displaying good growth conditions were subsequently treated with HS. The results indicated that HS significantly reduced the expression level of RANKL without markedly affecting the expression of decoy receptor OPG during osteoblast differentiation, which can be partially owing to the interaction between HS and ER-β. Meanwhile, the expression of RANKL in MC3T3-E1 cells was obviously increased after the transfection, demonstrating ER-β as the key biomarker that regulates RANKL expression. The current work provided important supplementary information on the regulation mechanism of RANKL/RANK/OPG axis by HS.