An Exopolysaccharide Produced by Bifidobacterium longum 35624® Inhibits Osteoclast Formation via a TLR2-Dependent Mechanism

Calcif Tissue Int. 2021 May;108(5):654-666. doi: 10.1007/s00223-020-00790-4. Epub 2021 Jan 3.

Abstract

The probiotic Bifidobacterium longum subsp. longum 35624® (B. longum 35624®), with its surface exopolysaccharide (EPS624), has previously been demonstrated to induce immunoregulatory responses in the host and may, therefore, be a novel approach to prevent bone loss in inflammatory conditions such as post-menopausal osteoporosis (PMO). The aim of this study was to investigate the effect of EPS624 on osteoclast and osteoblast differentiation and to assess the potential of B. longum 35624® to prevent bone loss in vivo. In vitro cell assays were used to assess the impact of EPS624 on osteoclast and osteoblast differentiation. The potential of two probiotic B. longum 35624® strains, including an EPS-deficient strain, for preventing ovariectomy (Ovx)-induced bone loss was assessed in a murine model. EPS624 prevented osteoclast formation from murine bone marrow precursors under both normal and TNFα-induced inflammatory conditions and modestly increased mineralized matrix deposition in osteogenic cell cultures. However, in the presence of an anti-TLR2 blocking antibody, or in MyD88-/- osteoclast precursors, the inhibitory effect of EPS624 on osteoclast formation was diminished or completely prevented, respectively. Moreover, EPS624 induced IL-10 production in osteoclast precursors in a TLR2-dependent manner, although IL-10 was dispensable in the EPS624-mediated inhibition of osteoclast formation. In addition, EPS624-producing B. longum 35624® partially prevented bone loss in Ovx mice when administered by oral gavage. This study introduced EPS624 as a potential anti-resorptive therapy, although optimal in vivo delivery of the probiotic strain for treating low-grade inflammatory diseases such as PMO remains to be determined.

Keywords: Bifidobacterium; Exopolysaccharide; Osteoclast; Ovariectomy; Probiotics; TLR2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bifidobacterium
  • Bifidobacterium longum*
  • Female
  • Mice
  • Osteoclasts
  • Toll-Like Receptor 2

Substances

  • Tlr2 protein, mouse
  • Toll-Like Receptor 2

Supplementary concepts

  • Bifidobacterium longum subsp. longum